Δ9Tetrahydrocannabinol impairs reversal learning but not extra-dimensional shifts in rhesus macaques
Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, La Jolla, CA, USA Neuroscience
(Impact Factor: 3.36).
01/2013; 235:51–58. DOI: 10.1016/j.neuroscience.2013.01.018
Expansion of medical marijuana use in the US and the recently successful decriminalization of recreational marijuana in two States elevates interest in the specific cognitive effects of Δ9tetrahydrocannabinol (Δ9THC), the major psychoactive constituent of marijuana. Controlled laboratory studies in nonhuman primates provide mixed evidence for specific effects of Δ9THC in learning and memory tasks, with a suggestion that frontal-mediated tasks may be the most sensitive. In this study, adult male rhesus monkeys were trained on tasks which assess reversal learning, extradimensional attentional shift learning and spatial delayed-response. Subjects were challenged with 0.1–0.5 mg/kg Δ9THC, i.m., in randomized order and evaluated on the behavioral measures. Peak plasma levels of Δ9THC were observed 30 min after 0.2 mg/kg (69 ± 29 ng/ml) and 60 min after 0.5 mg/kg (121 ± 23 ng/ml) was administered and behavioral effects on a bimanual motor task persisted for up to 2 h after injection. An increase in errors-to-criterion (ETC) associated with reversal learning was further increased by Δ9THC in a dose-dependent manner. The increase in ETC associated with extradimensional shifts was not affected by Δ9THC. Spatial delayed-response performance was impaired by Δ9THC in a retention-interval-dependent manner. Overall the pattern of results suggests a more profound effect of Δ9THC on tasks mediated by orbitofrontal (reversal learning) versus dorsolateral (extradimensional shifts) prefrontal mechanisms.
Available from: Janelle H P van Wel
- "It is a cognitive function that is frequently reported to be affected by drug use. Preclinical research has revealed that cannabis and cocaine are associated with impaired reversal learning (Egerton et al. 2005; Sokolic et al. 2011; Wright et al. 2013; McCracken and Grace 2013; Schoenbaum et al. 2004). Furthermore, chronic cocaine use in human addicted "
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Long-term cannabis and cocaine use has been associated with impairments in reversal learning. However, how acute cannabis and cocaine administration affect reversal learning in humans is not known.
In this study, we aimed to establish the acute effects of administration of cannabis and cocaine on valence-dependent reversal learning as a function of DRD2 Taq1A (rs1800497) and COMT Val108/158Met (rs4680) genotype.
A double-blind placebo-controlled randomized 3-way crossover design was used. Sixty-one regular poly-drug users completed a deterministic reversal learning task under the influence of cocaine, cannabis, and placebo that enabled assessment of both reward- and punishment-based reversal learning.
Proportion correct on the reversal learning task was increased by cocaine, but decreased by cannabis. Effects of cocaine depended on the DRD2 genotype, as increases in proportion correct were seen only in the A1 carriers, and not in the A2/A2 homozygotes. COMT genotype did not modulate drug-induced effects on reversal learning.
These data indicate that acute administration of cannabis and cocaine has opposite effects on reversal learning. The effects of cocaine, but not cannabis, depend on interindividual genetic differences in the dopamine D2 receptor gene.
Available from: Maarten van den Buuse
- "However, similar to Y-maze performance, there was no effect of chronic CP treatment, strengthening the selectivity of its action on PPI. Thus, although previous studies have shown involvement of both the endocannabinoid system and BDNF in memory formation and consolidation (Papaleo et al., 2011; Panlilio et al., 2012; De Bitencourt et al., 2013; Wright et al., 2013), in our protocol including chronic CP treatment followed by a 2-week washout, there were no such effects. Future studies could include the acute effects of cannabinoid receptor stimulation on memory function in BDNF HET mice and controls after chronic pre-treatment with CP, similar to the PPI studies presented here. "
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ABSTRACT: Reduced brain-derived neurotrophic factor (BDNF) signaling has been shown in the frontal cortex and hippocampus in schizophrenia. The aim of the present study was to investigate whether a BDNF deficit would modulate effects of chronic cannabis intake, a well-described risk factor for schizophrenia development. BDNF heterozygous mice (HET) and wild-type controls were chronically treated during weeks 6, 7, and 8 of life with the cannabinoid receptor agonist, CP55,940 (CP). After a 2-week delay, there were no CP-induced deficits in any of the groups in short-term spatial memory in a Y-maze task or novel object recognition memory. Baseline prepulse inhibition (PPI) was lower but average startle was increased in BDNF HET compared to wild-type controls. Acute CP administration before the PPI session caused a marked increase in PPI in male HET mice pre-treated with CP but not in any of the other male groups. In females, there were small increases of PPI in all groups upon acute CP administration. Acute CP administration furthermore reduced startle and this effect was greater in HET mice irrespective of chronic CP pre-treatment. Analysis of the levels of [(3)H]CP55,940 binding by autoradiography revealed a significant increase in the nucleus accumbens of male BDNF HET mice previously treated with CP but not in any of the other groups or in the caudate nucleus. These results show that BDNF deficiency and chronic young-adult cannabinoid receptor stimulation do not interact in this model on learning and memory later in life. In contrast, male "two hit" mice, but not females, were hypersensitive to the effect of acute CP on sensorimotor gating. These effects may be related to a selective increase of [(3)H]CP55,940 binding in the nucleus accumbens, reflecting up-regulation of CB1 receptor density in this region. These data could be of relevance to our understanding of differential "two hit" neurodevelopmental mechanisms in schizophrenia.
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ABSTRACT: Cognition deficits in schizophrenia remain an untreated area, and one in which R&D investment by pharmaceutical companies is high. However, whilst many preclinical assays demonstrate pro-cognitive activity with new drugs, in the main, this has not yet translated successfully to the clinic. In an attempt to address this and reduce the high attrition rate for drugs in the clinic, selected preclinical researchers are re-focusing their efforts on the development and validation of more translational assays. The attentional set-shifting task is an example of such an assay, which has been back-translated from the clinic to a preclinical setting. Here we review its application in schizophrenia research across humans and animals, specifically with regards to the neural basis underlying cognitive performance, the various disease-like or symptom models employed in rodents to mimic cognitive dysfunction in schizophrenia, and the resulting impact of drug treatment on executive function. Using the attentional set-shifting task, we highlight the potential promise a more translational approach can bring, whilst demonstrating the need for closer alignment in the validation and integration of this task to fully realize this promise.
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