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Submitted 18 June 2013
Accepted 30 October 2013
Published 21 November 2013
Corresponding author
Naoki Amada,
Amada.Naoki@otsuka.jp,
n.amada@pgr.reading.ac.uk
Academic editor
Ariela Benigni
Additional Information and
Declarations can be found on
page 13
DOI 10.7717/peerj.214
Copyright
2013 Amada et al.
Distributed under
Creative Commons CC-BY 3.0
OPEN ACCESS
Cannabidivarin (CBDV) suppresses
pentylenetetrazole (PTZ)-induced
increases in epilepsy-related gene
expression
Naoki Amada1,2,3 , Yuki Yamasaki1,2 ,3, Claire M. Williams2and
Benjamin J. Whalley1
1School of Chemistry, Food and Nutritional Sciences and Pharmacy, The University of Reading,
Reading, Berkshire, UK
2School of Psychology and Clinical Language Sciences, The University of Reading, Reading,
Berkshire, UK
3Qs’ Research Institute, Otsuka Pharmaceutical, Co. Ltd., Kagasuno, Kawauchi-cho, Tokushima,
Japan
ABSTRACT
To date, anticonvulsant effects of the plant cannabinoid, cannabidivarin (CBDV),
have been reported in several animal models of seizure. However, these behaviourally
observed anticonvulsant effects have not been confirmed at the molecular level. To
examine changes to epilepsy-related gene expression following chemical convulsant
treatment and their subsequent control by phytocannabinoid administration, we
behaviourally evaluated effects of CBDV (400 mg/kg, p.o.) on acute, pentylenetetra-
zole (PTZ: 95 mg/kg, i.p.)-induced seizures, quantified expression levels of several
epilepsy-related genes (Fos, Casp 3, Ccl3, Ccl4, Npy, Arc, Penk, Camk2a, Bdnf and
Egr1) by qPCR using hippocampal, neocortical and prefrontal cortical tissue samples
before examining correlations between expression changes and seizure severity.
PTZ treatment alone produced generalised seizures (median: 5.00) and significantly
increased expression of Fos, Egr1, Arc, Ccl4 and Bdnf. Consistent with previous
findings, CBDV significantly decreased PTZ-induced seizure severity (median: 3.25)
and increased latency to the first sign of seizure. Furthermore, there were correlations
between reductions of seizure severity and mRNA expression of Fos, Egr1, Arc,
Ccl4 and Bdnf in the majority of brain regions in the CBDV+PTZ treated group.
When CBDV treated animals were grouped into CBDV responders (criterion: seizure
severity ≤3.25) and non-responders (criterion: seizure severity >3.25), PTZ-induced
increases of Fos, Egr1, Arc, Ccl4 and Bdnf expression were suppressed in CBDV re-
sponders. These results provide the first molecular confirmation of behaviourally
observed effects of the non-psychoactive, anticonvulsant cannabinoid, CBDV,
upon chemically-induced seizures and serve to underscore its suitability for clinical
development.
Subjects Molecular Biology, Neuroscience, Neurology, Pharmacology
Keywords Cannabinoid, Pentylenetetrazole, Cannabidivarin, qPCR, Seizure, Epilepsy
How to cite this article Amada et al. (2013), Cannabidivarin (CBDV) suppresses pentylenetetrazole (PTZ)-induced increases in
epilepsy-related gene expression. PeerJ 1:e214;DOI 10.7717/peerj.214
INTRODUCTION
Epilepsy affects ∼1% of individuals and is often characterized by recurrent seizures. Many
treatments are available but more effective and better-tolerated antiepileptic drugs (AEDs)
with new mechanisms of actions are needed due to drug resistance (∼35%) and poor AED
side-effect profiles (Kwan & Brodie, 2007).
Several cannabinoids (19-tetrahydrocannabinol: 19-THC, cannabidiol: CBD,
19-tetrahydrocannabivarin: 19-THCV and cannabidivarin: CBDV) are anticonvulsant
in a variety of animal models of seizure and epilepsy (Consroe & Wolkin, 1977;Hill et
al., 2012a;Hill et al., 2010;Jones et al., 2010). Whilst CB1cannabinoid receptor (CB1R)
agonism is anti-epileptiform and anticonvulsant (Chesher & Jackson, 1974;Deshpande et
al., 2007b;Wallace et al., 2003;Wallace et al., 2001), the notable psychoactivity associated
with CB1R activation hinders the prospective clinical utility of this target. However,
many plant cannabinoids do not act at CB1R and the most promising non-psychoactive
anticonvulsant phytocannabinoid studied thus far is CBD, which exerts effects via, as
yet unknown, non-CB1R mechanisms in vitro,in vivo and in humans (Consroe et al.,
1982;Cunha et al., 1980;Jones et al., 2010;Wallace et al., 2001). Because CBD has low
affinity for CB1 and CB2 receptors (Pertwee, 2008), CBD may exert its effects through
different mechanisms. For instance, it is known that CBD can, at a number of different
concentrations in vitro, inhibit adenosine uptake, inhibit FAAH (the enzyme primarily
responsible for degradation of the endocannabinoid, anandamide), inhibit anandamide
reuptake, act as a TRPA1 receptor agonist, a TRPM8 receptor antagonist, a 5-HT1A
receptor agonist, a T-type calcium channel inhibitor and a regulator of intracellular
calcium (Izzo et al., 2009).
Here, we have used molecular methods to further investigate the anticonvulsant
potential of CBD’s propyl analogue, CBDV (Hill et al., 2012a). Although first isolated
in 1969 (Vollner, Bieniek & Korte, 1969), little is known about CBDV’s pharmacological
properties (Izzo et al., 2009). Scutt and Williamson reported CBDV to act via CB2
cannabinoid receptor-dependent mechanisms but direct CB2 receptor effects were not
shown (Scutt & Williamson, 2007). De Petrocellis reported differential CBDV effects at
transient receptor potential (TRP) channels in vitro, noting potent human TRPA1, TRPV1
and TRPV2 agonism and TRPM8 antagonism (De Petrocellis et al., 2011;De Petrocellis
et al., 2012). CBDV has also been reported to inhibit diacylglycerol (DAG) lipase-α,
the primary synthetic enzyme of the endocannabinoid, 2-arachidonoylglycerol (2-AG)
(Bisogno et al., 2003), in vitro (De Petrocellis et al., 2011). However, 2-AG inhibits status
epilepticus-like activity in rat hippocampal neuronal cultures (Deshpande et al., 2007a)
such that diacylglycerol lipase-αinhibition is unlikely to be anticonvulsant. Furthermore,
inhibition of DAG lipase-αby CBDV occurs at high micromolar concentrations (IC50:
16.6 µM) in vitro which are unlikely to have relevance in vivo making it unlikely that CBDV
exerts anticonvulsant effects via this route. Although the pharmacological relevance of
these effects remains unconfirmed in vivo and the targets identified have not yet been
linked to epilepsy, they illustrate an emergent role for multiple, non-CB receptor targets
of phytocannabinoids (Hill et al., 2012b;Pertwee, 2010). Furthermore, unlike 19-THC,
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 2/18
anticonvulsant doses of CBDV exert no detectable effects upon motor function (Hill et al.,
2012a) which further supports the assertion that its effects are not CB1R-mediated.
Despite our earlier report showing significant anticonvulsant effects of CBDV in animal
models of acute seizure (Hill et al., 2012a), molecular validation of these effects has not
yet been undertaken. Here, we evaluated CBDV’s effect (p.o.) on pentylenetetrazole
(PTZ)-induced seizures and quantified expression levels of several epilepsy-related genes
in tissue from hippocampus, neocortex and prefrontal cortex. Genes of interest were
selected on the basis that: (i) their expression was significantly changed in previously
published gene expression microarray results from people with epilepsy (PWE) (Helbig
et al., 2008;Jamali et al., 2006;van Gassen et al., 2008) and animal models of epilepsy
(Elliott, Miles & Lowenstein, 2003;Gorter et al., 2006;Gorter et al., 2007;Okamoto et al.,
2010) and (ii) published results (Johnson et al., 2011;Link et al., 1995;McCarthy et al., 1998;
Nanda & Mack, 2000;Saffen et al., 1988;Sola, Tusell & Serratosa, 1998;Zhu & Inturrisi,
1993) suggested that expression changes were acute (within a few hours of seizure), making
them suitable for study in a model of acute seizure. On this basis, Early growth response 1
(Egr1), Activity-regulated cytoskeleton-associated protein (Arc), Chemokine (C-C motif)
ligand 3 (Ccl3), Chemokine (C-C motif) ligand 4 (Ccl4), Brain derived neurotrophic
factor (Bdnf), Proenkephalin (Penk) and Neuropeptide Y (Npy) and the downregulated
gene, Calcium/calmodulin-dependent protein kinase II alpha (Camk2a) were chosen. FBJ
osteosarcoma oncogene (Fos) and Caspase 3 (Casp3) were also selected due to the former’s
increased expression in brain regions including hippocampus following experimentally
induced seizures (e.g., via PTZ) (Popovici et al., 1990;Saffen et al., 1988) and the latter
as a result of increased expression in resected neocortex from people with temporal lobe
epilepsy (Henshall et al., 2000).
MATERIAL AND METHODS
Animals
Experiments were conducted in accordance with UK Home Office regulations (Animals
(Scientific Procedures) Act, 1986). A total of 51 Wistar-Kyoto rats (Harlan, UK; 3–4 weeks
old) were used in this study and ARRIVE guidelines complied with. Animals were group
housed in cages of five with water and food supplied ad libitum. Temperature and humidity
were maintained at 21◦C and 55 ±10% respectively.
Drug administration
Seizures were induced using PTZ (Sigma, Poole, United Kingdom). After overnight
fasting, rats received either vehicle (20% solutol (Sigma) in 0.9%w/vNaCl) or CBDV
(400 mg kg−1; GW Pharmaceuticals Ltd., Salisbury, UK) in vehicle by oral gavage. Three
and a half hours after vehicle or CBDV administration, rats were challenged (i.p.) with
saline or PTZ (95 mg kg−1) and behaviour monitored for 1 h. Animals were euthanised
by CO2overdose and brains immediately removed. Whole hippocampi, neocortices and
prefrontal cortices were isolated, snap-frozen in liquid nitrogen and stored at −80◦C until
RNA extraction.
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 3/18
Analysis of seizure behaviours
Seizure behaviour was video recorded and responses coded exactly as described previously
(Hill et al., 2012a). Responses were coded using the following modified Racine seizure
severity scale: 0, normal behaviour; 1, isolated myoclonic jerks; 2, atypical clonic seizure;
3, fully developed bilateral forelimb clonus; 3.5, forelimb clonus with tonic component
and body twist; 4, tonic–clonic seizure with suppressed tonic phase; 5, fully developed
tonic–clonic seizure. Latency to the first sign of seizure was also recorded.
Gene expression analysis
Gene expression was quantified in rat hippocampus, prefrontal cortex and neocortex for
four experimental groups: vehicle +saline treated (n=5), vehicle +PTZ treated (n=7),
CBDV +saline treated (n=5) and CBDV +PTZ treated (n=7). Total RNA was extracted
using an miRNeasy Mini kit (Qiagen, West Sussex, UK), following the manufacturer’s
protocol. RNA purity was assessed spectrometrically at 260/280 nm. RNA integrity was
determined by gel electrophoresis. A 28S:18S rRNA ratio of ∼2:1 was taken to indicate
intact RNA.
Total RNA (0.5 µg) was reverse-transcribed into cDNA using High Capacity cDNA
Reverse Transcription Kits (Applied Biosystems). qPCR assays were carried out in a volume
of 14 µl, containing 5 µl cDNA, 2 µl 2.5 µM primer mix (forward and reverse primers) and
7µl QuantiTect SYBR Green QPCR 2×Master Mix (Qiagen, West Sussex, UK). Samples
were processed for 40 cycles on a StepOnePlusTM (Applied Biosystems, Foster City, CA,
USA) as follows: denaturation at 95◦C for 15 min (one cycle), 40 cycles of denaturation
at 95◦C for 15 s and annealing at 60◦C for 1 min. All samples were analysed in the same
plate in a single PCR run and quantification was based on the standard curve method.
Standard curves were constructed using cDNA solution diluted fivefold in series for a total
of five dilutions and consisted of a mixture of cDNA equally from hippocampus, prefrontal
cortex and neocortex of all animals. Sample cDNA concentrations were expressed relative
to the concentration of the standard curves. Normalisation of quantitative data was
based on a housekeeping gene, β-actin. Values are expressed as a percentage of control
(mean of the vehicle +saline group). The following primers were used (parenthesised
values are forward and reverse sequence and amplicon length respectively): Ccl3
(50-TGCCCTTGCTGTTCTTCTCTGC-30, 50-TAGGAGAAGCAGCAGGCAGTCG-30, 96),
Ccl4 (50-CGCCTTCTGCGATTCAGTGC-30, 50-AAGGCTGCTGGTCTCATAGTAATCC-
30, 127), Npy (50-TCGTGTGTTTGGGCATTCTGGC-30, 50-TGTAGTGTCGCAGAGCGG
AGTAG-30, 111), Arc (50-AGGCACTCACGCCTGCTCTTAC-30, 50-TCAGCCCCAGCTC
AATCAAGTCC-30, 146), Bdnf (50-AGCCTCCTCTGCTCTTTCTGCTG-30, 50-TATCTGC
CGCTGTGACCCACTC-30, 150), Egr1 (50-AGCCTTCGCTCACTCCACTATCC-30, 50-GC
GGCTGGGTTTGATGAGTTGG-30, 113), Penk (50-CCAACTCCTCCGACCTGCTGAAA
G-30, 50-AAGCCCCCATACCTCTTGCTCGTG-30, 121) and Camk2a (50-TGAGAGCACC
AACACCACCATCG-30, 50-TGTCATTCCAGGGTCGCACATCTTC-30, 142), Fos (50-TGC
GTTGCAGACCGAGATTGC-30, 50-AGCCCAGGTCATTGGGGATCTTG-30, 104), Casp3
(50-TTGCGCCATGCTGAAACTGTACG-30, 50-AAAGTGGCGTCCAGGGAGAAGG-30,
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 4/18
111) and β-Actin (50-CTCTATCCTGGCCTCACTGTCCACC-30, 50-AAACGCAGCTC
AGTAACAGTCCGC-30, 124). Primers were designed using NCBI/Primer-BLAST
(http://www.ncbi.nlm.nih.gov/tools/primer-blast/).
Statistics
CBDV effects upon seizure severity and onset latency were assessed by comparing
vehicle +PTZ treated and CBDV +PTZ treated groups using a two-tailed Mann-Whitney
test and a two-tailed t-test, respectively. Subsequently, animals in the CBDV +PTZ treated
group were divided according to median seizure severity score into CBDV ‘responders’
(criterion: seizure severity ≤median) and ‘non-responders’ (criterion: seizure severity
>median) to permit a preliminary subgroup analysis of CBDV effects in these two
groups without statistical analysis on subgroups. In qPCR analysis, differences of mRNA
expressions between treatment groups were analysed in each brain region using one-way
analysis of variance (one-way ANOVA) followed by Tukey’s test. Correlations between
seizure severity and mRNA expression in the CBDV +PTZ treated group were analysed
using Spearman’s rank correlation coefficient. A preliminary assessment of gene expression
changes for CBDV ‘responders’ and ‘non-responders’ was performed, in which differences
of mRNA expressions between the vehicle +PTZ treated and the CBDV responder or
non-responder subgroups were analysed in each brain region by two-tailed t-test. Since
samples from each brain region were analysed on physically separate PCR plates, no
comparisons of seizure or drug effects between brain areas were made. Differences were
considered statistically significant when the P≤0.05.
RESULTS
Anticonvulsant effects of CBDV on PTZ-induced acute seizures
400 mg kg−1CBDV significantly decreased seizure severity (vehicle: 5; CBDV: 3.25;
P<0.05) and increased latency to the first seizure sign (vehicle: 60 s; CBDV: 272 s;
P<0.05; Figs. 1A and 1B). Responses of CBDV +PTZ animals sub-grouped into CBDV
responders (criterion: seizure severity ≤3.25; n=10) and non-responders (criterion:
seizure severity >3.25; n=10) showed clear behavioural differences (Figs. 1C and 1D)
where CBDV responders exhibit lower seizure severity and increased onset latency.
Effects of PTZ treatment on mRNA expression of epilepsy-related
genes in the hippocampus, neocortex and prefrontal cortex
PTZ treatment significantly upregulated Fos mRNA expression in neocortex (P=0.0001)
and prefrontal cortex (P=0.0003; Table 1) whilst hippocampal Fos mRNA expression
only showed a trend to increase (P=0.1089). Egr1 mRNA expression was significantly
upregulated by PTZ treatment in the hippocampus (P=0.0244), neocortex (P=0.0001)
and prefrontal cortex (P<0.0001) whilst Arc mRNA expression was also significantly up-
regulated by PTZ treatment in the hippocampus (P=0.0374), neocortex (P=0.0039) and
prefrontal cortex (P=0.0038). Expression of Ccl4 mRNA was significantly upregulated
only in the prefrontal cortex (P=0.0220) by PTZ treatment. Trends toward an increase
of Ccl4 mRNA expression in the hippocampus (P=0.1720) and neocortex (P=0.1093)
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 5/18
Figure 1 Anticonvulsant effects of CBDV on PTZ-induced acute seizures. (A) Plot showing median
seizure severity in the vehicle- and CBDV-treated groups following PTZ administration. (B) Plot showing
latency (seconds) to the first seizure sign in the vehicle- and CBDV-treated groups. (C) Seizure severity
after sub-grouping CBDV treated group animals into CBDV non-responders and CBDV responders.
(D) Latency (seconds) to the first seizure sign after subgrouping CBDV treated group animals into CBDV
non-responders and CBDV responders. In seizure severity plots, median seizure severity is represented
by a thick horizontal line, the 25th and the 75th percentiles are represented by the box and maxima and
minima are represented by ‘whiskers’. Latency to the first seizure sign was presented as mean ±SEM.
∗,P<0.05 by Mann-Whitney Test vs vehicle group; #, P<0.05 by t-test vs vehicle group.
by PTZ treatment were seen. Expression of Bdnf mRNA was significantly upregulated in
the neocortex (P=0.0308) and prefrontal cortex (P=0.0345) but only a trend towards
increased expression in the hippocampus was seen (P=0.0564). mRNA expression of
Casp3, Npy, Penk, Ccl3 and Camk2a were not significantly changed by any treatment.
Effects of CBDV upon PTZ-induced mRNA expression of epilepsy-
related genes in the hippocampus, neocortex and prefrontal
cortex
Fos and Egr1 mRNA expression were significantly upregulated in the neocortex
(P=0.0201 and P=0.0033, respectively) and the prefrontal cortex (P=0.0156 and
P=0.0023, respectively) in the CBDV +PTZ treated group. Although there were no
statistically significant changes in the expression levels of any other genes between the
vehicle +saline and CBDV +PTZ treated groups which suggests an inhibitory effect
of CBDV on PTZ-induced upregulation of gene expression, neither were statistically
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 6/18
Table 1 Relative mRNA expression levels of epilepsy-related genes in the hippocampus (HIP), neocortex (Nctx) and prefrontal cortex (PFC). Ex-
pressions of Fos, Egr1, Arc, Ccl4 and Bdnf were upregulated by PTZ treatment. mRNA levels are presented as a fold change vs mean level of vehicle
+saline treated group (data are expressed as mean ±s.e.m.). Differences between individual groups were assessed by 1-way ANOVA (followed by a
Tukey’s post-hoc test if warranted).
Gene official
name
Gene
symbol
GO biological
processes
Brain
region
Vehicle +
Saline
Vehicle +
PTZ
CBDV +
Saline
CBDV +
PTZ
Fold change
(N=5)
Fold change
(N=7)
Fold change
(N=5)
Fold change
(N=7)
HIP 1.0 ±0.2 55.6 ±22.2 0.8 ±0.1 25.4 ±15.0
Nctx 1.0 ±0.3 21.5 ±3.5** 0.7 ±0.1 13.2 ±2.8*
FBJ osteosarcoma oncogene Fos
Cellular response to calcium ion,
cellular response to extracellular
stimulus, inflammatory response,
nervous system development PFC 1.0 ±0.1 20.0 ±3.8** 0.8 ±0.1 13.5 ±2.3*
HIP 1.0 ±0.1 0.9 ±0.1 0.9 ±0.1 0.9 ±0.1
Nctx 1.0 ±0.1 1.1 ±0.1 1.0 ±0.1 1.1 ±0.1
Caspase 3 Casp3 Apoptosis, intracellular signal
transduction
PFC 1.0 ±0.0 1.1 ±0.1 0.9 ±0.1 0.9 ±0.1
HIP 1.0 ±0.0 6.1±1.5*0.8 ±0.1 3.6 ±1.1
Nctx 1.0 ±0.1 3.0 ±0.4** 0.7 ±0.1 2.5 ±0.2**
Early growth response 1 Egr1
Cellular response to drug, cellular
response to growth factor stimulus,
cellular response to steroid
hormone stimulus, circadian
rhythm, interleukin-1-mediated
signaling pathway
PFC 1.0 ±0.1 2.7 ±0.3** 0.8 ±0.1 2.2 ±0.2**
HIP 1.0 ±0.1 8.6 ±2.5*0.8 ±0.1 4.2 ±1.7
Nctx 1.0 ±0.2 5.0 ±1.1** 0.6 ±0.1 3.4 ±0.5
Activity-regulated
cytoskeleton-associated
protein
Arc Regulation of neuronal synaptic
plasticity, endocytosis
PFC 1.0 ±0.1 4.4 ±0.9** 0.7 ±0.1 3.0 ±0.4
HIP 1.0 ±0.1 0.9 ±0.1 1.0 ±0.1 1.0 ±0.1
Nctx 1.0 ±0.1 1.0 ±0.1 1.0 ±0.1 1.1 ±0.1
Neuropeptide Y Npy
Feeding behavior, negative
regulation of blood pressure,
synaptic transmission PFC 1.0 ±0.1 0.9 ±0.0 1.0 ±0.1 0.9 ±0.0
HIP 1.0 ±0.1 16.7 ±5.9 0.7 ±0.2 7.9 ±6.3
Nctx 1.0 ±0.3 36.0 ±14.8 1.4 ±0.3 15.4 ±8.8
Chemokine (C-C motif)
ligand 4 Ccl4 Chemotaxis, inflammatory
response
PFC 1.0 ±0.2 13.3 ±3.4*1.0 ±0.2 7.9 ±3.0
HIP 1.0 ±0.2 8.8 ±3.7 1.1 ±0.2 5.3 ±3.7
Nctx 1.0 ±0.2 21.1 ±10.5 1.6 ±0.2 13.0 ±6.2
Chemokine (C-C motif)
ligand 3 Ccl3
Chemotaxis, elevation of cytosolic
calcium ion concentration,
inflammatory response PFC 1.0 ±0.1 16.4 ±6.3 1.5 ±0.1 13.5 ±5.9
HIP 1.0 ±0.1 2.6 ±0.6 0.9 ±0.1 1.7 ±0.3
Nctx 1.0 ±0.0 2.5 ±0.4*0.9 ±0.1 2.1 ±0.4
Brain derived
neurotrophic factor Bdnf
Neuron differentiation,
positive regulation of long-term
neuronal synaptic plasticity,
glutamate secretion PFC 1.0 ±0.1 2.1 ±0.4*1.1 ±0.2 1.9 ±0.2
HIP 1.0 ±0.1 1.2 ±0.2 1.1 ±0.1 1.1 ±0.1
Nctx 1.0 ±0.2 1.1 ±0.2 0.8 ±0.1 1.1 ±0.1
Proenkephalin Penk Behavioral fear response,
sensory perception of pain
PFC 1.0 ±0.2 0.9 ±0.2 1.1 ±0.2 0.9 ±0.2
HIP 1.0 ±0.1 0.9 ±0.0 0.9 ±0.1 0.9 ±0.1
Nctx 1.0 ±0.1 0.9 ±0.1 1.0 ±0.1 1.0 ±0.1
Calcium/calmodulin-
dependent protein
kinase II alpha
Camk2a
Calcium ion transport, ionotropic
glutamate receptor signaling
pathway, protein phosphorylation,
regulation of neuronal synaptic
plasticity, regulation of
neurotransmitter secretion PFC 1.0 ±0.1 1.0 ±0.1 1.1 ±0.1 1.0 ±0.1
Notes.
*P<0.05 vs vehicle +saline group.
** P<0.01.
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 7/18
significant differences in gene expression levels between the vehicle +PTZ and
CBDV +PTZ treated groups found. However, when potential correlations between the
behavioural measure of seizure severity and mRNA expression levels of Fos, Egr1, Arc,
Bdnf and Ccl4 in the CBDV +PTZ treated group were examined using Spearman’s rank
correlation coefficient, mRNA expression levels of these genes were highly correlated with
seizure severity in the majority of brain regions examined (Fig. 2: hippocampus, Fig. 3:
neocortex and Fig. 4: prefrontal cortex). Fos mRNA expression correlated with seizure
severity in the hippocampus (R2=0.91, P=0.0008), neocortex (R2=0.91, P=0.0008)
and prefrontal cortex (R2=0.91, P=0.0008) of the CBDV +PTZ treated group.
Egr1 mRNA expression was correlated with seizure severity only in the hippocampus
(R2=0.91, P=0.0008) whilst Arc mRNA expression was correlated with seizure severity
in the hippocampus (R2=0.91, P=0.0008), neocortex (R2=0.91, P=0.0008) and
prefrontal cortex (R2=0.71, P=0.0175). Bdnf mRNA expression was correlated with
seizure severity in the hippocampus (R2=0.71, P=0.0175) and neocortex (R2=0.65,
P=0.0291) whilst Ccl4 mRNA expression was correlated with seizure severity in the
hippocampus (R2=0.91, P=0.0008), neocortex (R2=0.71, P=0.0175) and prefrontal
cortex (R2=0.71, P=0.0175). Together, these suggest a possible contribution of the
anti-convulsant effects of CBDV in reduction of mRNA expression of Fos, Egr1, Arc, Bdnf
and Ccl4.
Effects of CBDV treatment on the PTZ-induced increases of the
epilepsy-related genes in CBDV responders
Consistent with differing behavioural patterns observed between CBDV responder and
non-responder subgroups, alterations in gene expression were also seen. Importantly,
changes in gene expression levels between the vehicle +PTZ and the CBDV responder
subgroups were most obvious, with few changes seen in gene expression levels between
vehicle +PTZ and the CBDV +PTZ non-responder subgroups. Importantly, PTZ-
induced increases in gene expression were most reliably suppressed in the hippocampus
of CBDV responders, with less obvious suppression in prefrontal cortex and neocortex.
The PTZ-induced increase of Fos mRNA expression in CBDV responders was suppressed
in the neocortex (P=0.0274) and the prefrontal cortex (P=0.0337), and there was
a strong trend towards a decrease in the hippocampus (P=0.0579; Fig. 5A). The
PTZ-induced increase of Egr1 mRNA expression was suppressed in the hippocampus
(P=0.0234) of CBDV responders, but less obviously so in the neocortex (P=0.1837)
and the prefrontal cortex (P=0.1038; Fig. 5B). The increase in Arc mRNA expression
induced by PTZ treatment was also suppressed in the hippocampus (P=0.0221) of CBDV
responders, and there were strong trends towards decreases in the neocortex (P=0.0643)
and the prefrontal cortex (P=0.0879; Fig. 5C). The increase of Bdnf mRNA expression
following PTZ treatment was most suppressed in the hippocampus (P=0.0441) of CBDV
responders whilst less decreases were seen in the neocortex (P=0.1099) and prefrontal
cortex (P=0.4128; Fig. 5D). Finally the PTZ-induced increase of Ccl4 mRNA expression
was suppressed in the hippocampus (P=0.0323) and the prefrontal cortex (P=0.0459),
and there was a strong trend towards a decrease in the neocortex (P=0.0942; Fig. 5E). On
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 8/18
Figure 2 Correlation analysis between seizure severity and mRNA expression levels in the hippocam-
pus. Correlations between mRNA expression of Fos (A), Egr1 (B), Arc (C), Bdnf (D) and Ccl4 (E) and
seizure severity were analysed using Spearman’s rank correlation coefficient.
the other hand, neither statistically significant decreases nor trends towards decreases in
the gene expressions were found in the CBDV non-responder subgroup.
DISCUSSION
PTZ treatment upregulated (significant increase or statistically strong trend to increase)
mRNA expression coding for Fos, Egr1, Arc, Ccl4 and Bdnf in all brain regions tested. Clear
correlations between seizure severity and mRNA expression were observed for these genes
in the majority of brain regions of CBDV +PTZ treated animals and mRNA expression
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 9/18
Figure 3 Correlation analysis between seizure severity and mRNA expression levels in the neocor-
tex. Correlations between mRNA expression of Fos (A), Egr1 (B), Arc (C), Bdnf (D) and Ccl4 (E) and
seizure severity were analysed using Spearman’s rank correlation coefficient.
of these genes was suppressed in the majority of brain regions examined from the CBDV
responder subgroup. Upregulation of Fos and Egr1 mRNA expression following PTZ
treatment has previously been reported in rat hippocampi (Saffen et al., 1988) and both Fos
and Egr1 are transcription factors belonging to IEG (immediate early gene) family which
is transiently and rapidly activated following a variety of cellular stimuli. IEGs can identify
activated neurons and brain circuits since seizure activity, and other excitatory stimuli, can
induce rapid and transient Fos expression increases (Herrera & Robertson, 1996), making
it a useful metabolic marker for brain activity (Dragunow & Faull, 1989). Fos expression
level in the brain is typically low under basal conditions and is induced in response to
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 10/18
Figure 4 Correlation analysis between seizure severity and mRNA expression levels in the prefrontal
cortex. Correlations between mRNA expression of Fos (A), Egr1 (B), Arc (C), Bdnf (D) and Ccl4 (E) and
seizure severity were analysed using Spearman’s rank correlation coefficient.
extracellular signals such as ions, neurotransmitters, growth factors and drugs and is
closely linked to the induction of transcription of other genes (Kovacs, 2008). Fos induction
also correlates with the mossy fibre sprouting (Kiessling & Gass, 1993;Popovici et al., 1990)
that occurs during epileptogenesis and may play a role in the subsequent manifestation of
seizure symptoms. Like Fos, Egr1 also activates transcription of other genes (Beckmann
et al., 1997;Christy & Nathans, 1989) and is considered to play an important role in
neuronal plasticity (Knapska & Kaczmarek, 2004). Furthermore, the expression of Fos
and Egr1 in seizure onset regions in PWE strongly correlates with interictal spiking
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 11/18
Figure 5 Subgroup-analysis of mRNA levels of epilepsy-related genes in CBDV responders and nonresponders. Subgrouping CBDV +PTZ
treated animals into responders (criterion: seizure severity ≤3.25) and non-responders (criterion: seizure severity >3.25) revealed that the
PTZ-induced increases of mRNA expression of Fos (A), Egr1 (B), Arc (C), Bdnf (D) and Ccl4 (E) were significantly suppressed in brain regions
examined from the CBDV responder subgroup. mRNA levels are presented as a fold change vs mean level of vehicle +saline treated group (data are
expressed as mean ±s.e.m.). ∗,P<0.05 by t-test vs vehicle +PTZ group.
(Rakhade et al., 2007). Thus, suppression of Fos and Egr1 mRNA expression are consistent
with ameliorative drug effects on seizures, epileptogenesis and/or epilepsy. In addition,
increased Arc mRNA expression in rat hippocampus (0.5–4 h) and cortex (0.5–1 h) after
PTZ treatment has also been reported (Link et al., 1995). It has been reported that newly
synthesised Arc mRNA is selectively localised in active dendritic segments and that Arc
plays a role in activity-dependent plasticity of dendrites (Lyford et al., 1995;Steward et al.,
1998). Arc is induced by hippocampal seizures, and glutamatergic neurons increase Arc
expression in response to increased synaptic activity (Korb & Finkbeiner, 2011), implying
a relationship between seizure activity and Arc expression. Ccl4 is a proinflammatory
chemokine that is known as a chemo-attractant for monocytes and T cells and has been
suggested to play a part in various nervous system pathologies such as inflammation,
trauma, ischemia and multiple sclerosis (Semple, Kossmann & Morganti-Kossmann, 2010).
Although a relationship between CCL4 and epilepsy is unclear, a relationship between
epilepsy and immune response has been suggested (Vezzani & Granata, 2005). Moreover,
increased Ccl4 mRNA expression has been reported in rat hippocampi and temporal
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 12/18
lobe tissue following status epilepticus events triggered by electrical stimulation of the
amygdala (Guzik-Kornacka et al., 2011). In the present study, PTZ-induced increase
of Ccl4 expression was suppressed in CBDV responders, although whether this is a
direct anti-inflammatory effect of CBDV or an indirect effect of reduced seizure severity
remains unknown. Increased expression of mRNA coding for Bdnf was confirmed in
rat hippocampus after PTZ treatment (Nanda & Mack, 2000). BDNF is one of many
neurotrophic factors and is known to promote survival and growth of a variety of neurons
in addition to strengthening excitatory (glutamatergic) synapses (Binder & Scharfman,
2004). BDNF is involved in the control of hippocampal plasticity and is thought to play
an important role in epileptogenesis and in temporal lobe epilepsy (Binder et al., 2001;
Scharfman, 2002), suggesting therapeutic importance for control of Bdnf expression.
CONCLUSIONS
We have confirmed upregulation of mRNA expression coding for Fos, Egr1, Arc, Ccl4
and Bdnf in the brains of rats treated with PTZ and shown that PTZ-induced increases of
mRNA expression for these genes were suppressed in CBDV responders, and not animals
that failed to respond to CBDV treatment. Overall, we provide molecular evidence that
directly supports behavioural evidence that CBDV exerts significant anticonvulsant
effects via oral and other routes of administration (Hill et al., 2012a). Whether gene
expression changes demonstrated here also underlie cellular and molecular mechanisms by
which CBDV exerts its anticonvulsant effect presently remains unknown. However, these
results provide important acute biomarkers for additional investigation in models of the
progressive disorder and following longer term CBDV treatment.
ACKNOWLEDGEMENTS
We thank GW Pharmaceuticals Plc. for providing CBDV.
ADDITIONAL INFORMATION AND DECLARATIONS
Funding
This work was supported by GW Pharmaceuticals Plc. and Otsuka Pharmaceutical Co,
Ltd. The funders gave final approval to submit the prepared manuscript to peer review for
publication.
Grant Disclosures
The following grant information was disclosed by the authors:
GW Pharmaceuticals Plc.
Otsuka Pharmaceutical Co, Ltd.
Competing Interests
GW Pharmaceuticals Plc. and Otsuka Pharmaceutical Co, Ltd. are collaborators on an
epilepsy research project. As an employee of Otsuka Pharmaceutical Co, Ltd., Naoki
Amada is participating in this collaborative project, and Naoki Amada’s PhD project
is funded by this research collaboration. GW Pharmaceuticals Plc. provided materials
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 13/18
(CBDV). Yuki Yamasaki is an employee of Otsuka Pharmaceutical Co, Ltd., and holds
stocks in the company. Benjamin Whalley is an Academic Editor for PeerJ.
Author Contributions
•Naoki Amada and Yuki Yamasaki conceived and designed the experiments, performed
the experiments, analyzed the data, wrote the paper.
•Claire M. Williams and Benjamin J. Whalley conceived and designed the experiments,
wrote the paper.
Animal Ethics
The following information was supplied relating to ethical approvals (i.e., approving body
and any reference numbers):
All work involving the use of animals was reviewed by the University of Reading
Local Ethical Review Panel in addition to being conducted under the authority of UK
Home Office Project Licence 30/2538 issued to Dr Benjamin Whalley under the Animals
(Sceintific Procedures) Act, 1986.
Data Deposition
The following information was supplied regarding the deposition of related data:
CentAUR (Central Archive at the University of Reading)
http://centaur.reading.ac.uk/.
REFERENCES
Beckmann AM, Davidson MS, Goodenough S, Wilce PA. 1997. Differential expression of
Egr-1-like DNA-binding activities in the naive rat brain and after excitatory stimulation. Journal
of Neurochemistry 69:2227–2237 DOI 10.1046/j.1471-4159.1997.69062227.x.
Binder DK, Croll SD, Gall CM, Scharfman HE. 2001. BDNF and epilepsy: too much of a good
thing? Trends in Neurosciences 24:47–53 DOI 10.1016/S0166-2236(00)01682-9.
Binder DK, Scharfman HE. 2004. Brain-derived neurotrophic factor. Growth Factors 22:123–131
DOI 10.1080/08977190410001723308.
Bisogno T, Howell F, Williams G, Minassi A, Cascio MG, Ligresti A, Matias I, Schiano-
Moriello A, Paul P, Williams EJ, Gangadharan U, Hobbs C, Di Marzo V, Doherty P.
2003. Cloning of the first sn1-DAG lipases points to the spatial and temporal
regulation of endocannabinoid signaling in the brain. Journal of Cell Biology 163:463–468
DOI 10.1083/jcb.200305129.
Chesher GB, Jackson DM. 1974. Anticonvulsant effects of cannabinoids in mice: drug interactions
within cannabinoids and cannabinoid interactions with phenytoin. Psychopharmacologia
37:255–264 DOI 10.1007/BF00421539.
Christy B, Nathans D. 1989. DNA binding site of the growth factor-inducible protein Zif268.
Proceedings of the National Academy of Sciences of the United States of America 86:8737–8741
DOI 10.1073/pnas.86.22.8737.
Consroe P, Benedito MA, Leite JR, Carlini EA, Mechoulam R. 1982. Effects of cannabidiol
on behavioral seizures caused by convulsant drugs or current in mice. European Journal of
Pharmacology 83:293–298 DOI 10.1016/0014-2999(82)90264-3.
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 14/18
Consroe P, Wolkin A. 1977. Cannabidiol–antiepileptic drug comparisons and interactions in
experimentally induced seizures in rats. Journal of Pharmacology and Experimental Therapeutics
201:26–32.
Cunha JM, Carlini EA, Pereira AE, Ramos OL, Pimentel C, Gagliardi R, Sanvito WL, Lander N,
Mechoulam R. 1980. Chronic administration of cannabidiol to healthy volunteers and epileptic
patients. Pharmacology 21:175–185 DOI 10.1159/000137430.
De Petrocellis L, Ligresti A, Moriello AS, Allara M, Bisogno T, Petrosino S, Stott CG,
Di Marzo V. 2011. Effects of cannabinoids and cannabinoid-enriched Cannabis extracts on
TRP channels and endocannabinoid metabolic enzymes. British Journal of Pharmacology
163:1479–1494 DOI 10.1111/j.1476-5381.2010.01166.x.
De Petrocellis L, Orlando P, Moriello AS, Aviello G, Stott C, Izzo AA, Di Marzo V. 2012.
Cannabinoid actions at TRPV channels: effects on TRPV3 and TRPV4 and their potential
relevance to gastrointestinal inflammation. Acta Physiologica 204:255–266
DOI 10.1111/j.1748-1716.2011.02338.x.
Deshpande LS, Blair RE, Ziobro JM, Sombati S, Martin BR, DeLorenzo RJ. 2007a.
Endocannabinoids block status epilepticus in cultured hippocampal neurons.
European Journal of Pharmacology 558:52–59 DOI 10.1016/j.ejphar.2006.11.030.
Deshpande LS, Sombati S, Blair RE, Carter DS, Martin BR, DeLorenzo RJ. 2007b.
Cannabinoid CB1 receptor antagonists cause status epilepticus-like activity in the
hippocampal neuronal culture model of acquired epilepsy. Neuroscience Letters 411:11–16
DOI 10.1016/j.neulet.2006.09.046.
Dragunow M, Faull R. 1989. The use of c-fos as a metabolic marker in neuronal pathway tracing.
Journal of Neuroscience Methods 29:261–265 DOI 10.1016/0165-0270(89)90150-7.
Elliott RC, Miles MF, Lowenstein DH. 2003. Overlapping microarray profiles of dentate gyrus
gene expression during development- and epilepsy-associated neurogenesis and axon
outgrowth. Journal of Neuroscience 23:2218–2227.
Gorter JA, van Vliet EA, Aronica E, Breit T, Rauwerda H, Lopes da Silva FH, Wadman WJ. 2006.
Potential new antiepileptogenic targets indicated by microarray analysis in a rat model for
temporal lobe epilepsy. Journal of Neuroscience 26:11083–11110
DOI 10.1523/JNEUROSCI.2766-06.2006.
Gorter JA, Van Vliet EA, Rauwerda H, Breit T, Stad R, van Schaik L, Vreugdenhil E,
Redeker S, Hendriksen E, Aronica E, Lopes da Silva FH, Wadman WJ. 2007. Dynamic
changes of proteases and protease inhibitors revealed by microarray analysis in CA3
and entorhinal cortex during epileptogenesis in the rat. Epilepsia 48(Suppl 5):53–64
DOI 10.1111/j.1528-1167.2007.01290.x.
Guzik-Kornacka A, Sliwa A, Plucinska G, Lukasiuk K. 2011. Status epilepticus evokes prolonged
increase in the expression of CCL3 and CCL4 mRNA and protein in the rat brain.
Acta Neurobiologiae Experimentalis (Warsaw) 71:193–207.
Helbig I, Matigian NA, Vadlamudi L, Lawrence KM, Bayly MA, Bain SM, Diyagama D,
Scheffer IE, Mulley JC, Holloway AJ, Dibbens LM, Berkovic SF, Hayward NK. 2008.
Gene expression analysis in absence epilepsy using a monozygotic twin design.
Epilepsia 49:1546–1554 DOI 10.1111/j.1528-1167.2008.01630.x.
Henshall DC, Clark RS, Adelson PD, Chen M, Watkins SC, Simon RP. 2000. Alterations in bcl-2
and caspase gene family protein expression in human temporal lobe epilepsy. Neurology
55:250–257 DOI 10.1212/WNL.55.2.250.
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 15/18
Herrera DG, Robertson HA. 1996. Activation of c-fos in the brain. Progress in Neurobiology
50:83–107 DOI 10.1016/S0301-0082(96)00021-4.
Hill AJ, Mercier MS, Hill TD, Glyn SE, Jones NA, Yamasaki Y, Futamura T, Duncan M, Stott CG,
Stephens GJ, Williams CM, Whalley BJ. 2012a. Cannabidivarin is anticonvulsant in mouse and
rat. British Journal of Pharmacology 167:1629–1642 DOI 10.1111/j.1476-5381.2012.02207.x.
Hill AJ, Williams CM, Whalley BJ, Stephens GJ. 2012b. Phytocannabinoids as novel therapeutic
agents in CNS disorders. Pharmacology and Therapeutics 133:79–97
DOI 10.1016/j.pharmthera.2011.09.002.
Hill AJ, Weston SE, Jones NA, Smith I, Bevan SA, Williamson EM, Stephens GJ, Williams CM,
Whalley BJ. 2010. Delta-Tetrahydrocannabivarin suppresses in vitro epileptiform and in vivo
seizure activity in adult rats. Epilepsia 51:1522–1532 DOI 10.1111/j.1528-1167.2010.02523.x.
Izzo AA, Borrelli F, Capasso R, Di Marzo V, Mechoulam R. 2009. Non-psychotropic plant
cannabinoids: new therapeutic opportunities from an ancient herb. Trends in Pharmacological
Sciences 30:515–527 DOI 10.1016/j.tips.2009.07.006.
Jamali S, Bartolomei F, Robaglia-Schlupp A, Massacrier A, Peragut JC, R´
egis J, Dufour H,
Ravid R, Roll P, Pereira S, Royer B, Roeckel-Trevisiol N, Fontaine M, Guye M, Boucraut J,
Chauvel P, Cau P, Szepetowski P. 2006. Large-scale expression study of human mesial
temporal lobe epilepsy: evidence for dysregulation of the neurotransmission and complement
systems in the entorhinal cortex. Brain 129:625–641 DOI 10.1093/brain/awl001.
Johnson EA, Dao TL, Guignet MA, Geddes CE, Koemeter-Cox AI, Kan RK. 2011. Increased
expression of the chemokines CXCL1 and MIP-1alpha by resident brain cells precedes
neutrophil infiltration in the brain following prolonged soman-induced status epilepticus
in rats. Journal of Neuroinflammation 8:41 DOI 10.1186/1742-2094-8-41.
Jones NA, Hill AJ, Smith I, Bevan SA, Williams CM, Whalley BJ, Stephens GJ. 2010. Cannabidiol
displays antiepileptiform and antiseizure properties in vitro and in vivo. Journal of
Pharmacology and Experimental Therapeutics 332:569–577 DOI 10.1124/jpet.109.159145.
Kiessling M, Gass P. 1993. Immediate early gene expression in experimental epilepsy. Brain
Pathology 3:381–393 DOI 10.1111/j.1750-3639.1993.tb00766.x.
Knapska E, Kaczmarek L. 2004. A gene for neuronal plasticity in the mammalian brain:
Zif268/Egr-1/NGFI-A/Krox-24/TIS8/ZENK? Progress in Neurobiology 74:183–211
DOI 10.1016/j.pneurobio.2004.05.007.
Korb E, Finkbeiner S. 2011. Arc in synaptic plasticity: from gene to behavior. Trends in
Neurosciences 34:591–598 DOI 10.1016/j.tins.2011.08.007.
Kovacs KJ. 2008. Measurement of immediate-early gene activation- c-fos and beyond. Journal of
Neuroendocrinology 20:665–672 DOI 10.1111/j.1365-2826.2008.01734.x.
Kwan P, Brodie MJ. 2007. Emerging drugs for epilepsy. Expert Opinion on Emerging Drugs
12:407–422 DOI 10.1517/14728214.12.3.407.
Link W, Konietzko U, Kauselmann G, Krug M, Schwanke B, Frey U, Kuhl D. 1995.
Somatodendritic expression of an immediate early gene is regulated by synaptic activity.
Proceedings of the National Academy of Sciences of the United States of America 92:5734–5738
DOI 10.1073/pnas.92.12.5734.
Lyford GL, Yamagata K, Kaufmann WE, Barnes CA, Sanders LK, Copeland NG, Gilbert DJ,
Jenkins NA, Lanahan AA, Worley PF. 1995. Arc, a growth factor and activity-regulated gene,
encodes a novel cytoskeleton-associated protein that is enriched in neuronal dendrites. Neuron
14:433–445 DOI 10.1016/0896-6273(95)90299-6.
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 16/18
McCarthy JB, Walker M, Pierce J, Camp P, White JD. 1998. Biosynthesis and metabolism of
native and oxidized neuropeptide Y in the hippocampal mossy fiber system. Journal of
Neurochemistry 70:1950–1963 DOI 10.1046/j.1471-4159.1998.70051950.x.
Nanda SA, Mack KJ. 2000. Seizures and sensory stimulation result in different patterns of brain
derived neurotrophic factor protein expression in the barrel cortex and hippocampus. Molecular
Brain Research 78:1–14 DOI 10.1016/S0169-328X(00)00054-1.
Okamoto OK, Janjoppi L, Bonone FM, Pansani AP, da Silva AV, Scorza FA, Cavalheiro EA.
2010. Whole transcriptome analysis of the hippocampus: toward a molecular portrait of
epileptogenesis. BMC Genomics 11:230 DOI 10.1186/1471-2164-11-230.
Pertwee RG. 2008. The diverse CB1and CB2receptor pharmacology of three plant cannabinoids:
delta9-tetrahydrocannabinol, cannabidiol and delta9-tetrahydrocannabivarin. British Journal of
Pharmacology 153:199–215 DOI 10.1038/sj.bjp.0707442.
Pertwee RG. 2010. Receptors and channels targeted by synthetic cannabinoid receptor agonists and
antagonists. Current Medicinal Chemistry 17:1360–1381 DOI 10.2174/092986710790980050.
Popovici T, Represa A, Crepel V, Barbin G, Beaudoin M, Ben-Ari Y. 1990. Effects of kainic
acid-induced seizures and ischemia on c-fos-like proteins in rat brain. Brain Research
536:183–194 DOI 10.1016/0006-8993(90)90024-6.
Rakhade SN, Shah AK, Agarwal R, Yao B, Asano E, Loeb JA. 2007. Activity-dependent gene
expression correlates with interictal spiking in human neocortical epilepsy. Epilepsia 48:86–95
DOI 10.1111/j.1528-1167.2007.01294.x.
Saffen DW, Cole AJ, Worley PF, Christy BA, Ryder K, Baraban JM. 1988. Convulsant-induced
increase in transcription factor messenger RNAs in rat brain. Proceedings of the National
Academy of Sciences of the United States of America 85:7795–7799 DOI 10.1073/pnas.85.20.7795.
Scharfman H. 2002. Does BDNF contribute to temporal lobe epilepsy? Epilepsy Current 2:92–94
DOI 10.1046/j.1535-7597.2002.t01-1-00033.x.
Scutt A, Williamson EM. 2007. Cannabinoids stimulate fibroblastic colony formation by bone
marrow cells indirectly via CB2 receptors. Calcified Tissue International 80:50–59
DOI 10.1007/s00223-006-0171-7.
Semple BD, Kossmann T, Morganti-Kossmann MC. 2010. Role of chemokines in CNS health and
pathology: a focus on the CCL2/CCR2 and CXCL8/CXCR2 networks. Journal of Cerebral Blood
Flow & Metabolism 30:459–473 DOI 10.1038/jcbfm.2009.240.
Sola C, Tusell JM, Serratosa J. 1998. Decreased expression of calmodulin kinase II and calcineurin
messenger RNAs in the mouse hippocampus after kainic acid-induced seizures. Journal of
Neurochemistry 70:1600–1608 DOI 10.1046/j.1471-4159.1998.70041600.x.
Steward O, Wallace CS, Lyford GL, Worley PF. 1998. Synaptic activation causes the mRNA for the
IEG Arc to localize selectively near activated postsynaptic sites on dendrites. Neuron 21:741–751
DOI 10.1016/S0896-6273(00)80591-7.
van Gassen KL, de Wit M, Koerkamp MJ, Rensen MG, van Rijen PC, Holstege FC, Lindhout D,
de Graan PN. 2008. Possible role of the innate immunity in temporal lobe epilepsy. Epilepsia
49:1055–1065 DOI 10.1111/j.1528-1167.2007.01470.x.
Vezzani A, Granata T. 2005. Brain inflammation in epilepsy: experimental and clinical evidence.
Epilepsia 46:1724–1743 DOI 10.1111/j.1528-1167.2005.00298.x.
Vollner L, Bieniek D, Korte F. 1969. Hashish. XX. Cannabidivarin, a new hashish constituent.
Tetrahedron Letters 3:145–147 DOI 10.1016/S0040-4039(01)87494-3.
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 17/18
Wallace MJ, Blair RE, Falenski KW, Martin BR, DeLorenzo RJ. 2003. The endogenous
cannabinoid system regulates seizure frequency and duration in a model of temporal lobe
epilepsy. Journal of Pharmacology and Experimental Therapeutics 307:129–137
DOI 10.1124/jpet.103.051920.
Wallace MJ, Wiley JL, Martin BR, DeLorenzo RJ. 2001. Assessment of the role of CB1
receptors in cannabinoid anticonvulsant effects. European Journal of Pharmacology 428:51–57
DOI 10.1016/S0014-2999(01)01243-2.
Zhu YS, Inturrisi CE. 1993. Metrazole induction of c-fos and proenkephalin gene expression in
the rat adrenal and hippocampus: pharmacological characterization. Molecular Brain Research
20:118–124 DOI 10.1016/0169-328X(93)90116-7.
Amada et al. (2013), PeerJ, DOI 10.7717/peerj.214 18/18