[Show abstract][Hide abstract]ABSTRACT: The rate of Neonatal Abstinence Syndrome (NAS) has drastically increased over the past decade. The average hospital expense per NAS patient has tripled, while the number of babies born to opioid-dependent mothers has increased to 5 in 1000 births. Current treatment options are limited to opioid replacement and tapering. Consequently, we examined the efficacy of prenatal, low-dose and short-term vigabatrin (γ-vinyl GABA, GVG) exposure for attenuating these symptoms as well as the metabolic changes observed in the brains of these animals upon reaching adolescence. Pregnant Sprague-Dawley rats were treated in one of four ways: 1) saline; 2) morphine alone; 3) morphine+GVG at 25 mg/kg; 4) morphine+GVG at 50 mg/kg. Morphine was administered throughout gestation, while GVG administration occurred only during the last 5 days of gestation. On post-natal day 1, naloxone-induced withdrawal behaviours were recorded in order to obtain a gross behaviour score. Approximately 28 days following birth, 18 FDG microPET scans were obtained on these same animals (Groups 1, 2, and 4). Morphine-treated neonates demonstrated significantly higher withdrawal scores than saline controls. However, GVG at 50 but not 25 mg/kg/day significantly attenuated them. Upon reaching adolescence, morphine treated animals showed regionally specific changes in 18 FDG uptake. Again, prenatal GVG exposure blocked them. These data demonstrate that low-dose, short-term prenatal GVG administration blocks naloxone-induced withdrawal in neonates. Taken together, these preliminary findings suggest that GVG may provide an alternative and long-lasting pharmacologic approach for the management of neonatal and adolescent symptoms associated with NAS.
Full-text Article · Sep 2016 · Journal of Addiction Research & Therapy
[Show abstract][Hide abstract]ABSTRACT: Dissociation of vasomotor and metabolic responses to levodopa has been observed in human subjects with Parkinson's disease (PD) studied with PET and in autoradiograms from 6-hydroxydopamine (6-OHDA) rat. In both species, acute levodopa administration was associated with increases in basal ganglia cerebral blood flow (CBF) with concurrent reductions in cerebral metabolic rate (CMR) for glucose in the same brain regions. In this study, we used a novel dual-tracer microPET technique to measure CBF and CMR levodopa responses in the same animal. Rats with unilateral 6-OHDA or sham lesion underwent sequential (15)O-water (H2(15)O) and (18)F-fluorodeoxyglucose (FDG) microPET to map CBF and CMR following the injection of levodopa or saline. A subset of animals was separately scanned under ketamine/xylazine and isoflurane to compare the effects of these anesthetics. Regardless of anesthetic agent, 6-OHDA animals exhibited significant dissociation of vasomotor (ΔCBF) and metabolic (ΔCMR) responses to levodopa, with stereotyped increases in CBF and reductions in CMR in the basal ganglia ipsilateral to the dopamine lesion. No significant changes were seen in sham-lesioned animals. These data faithfully recapitulate analogous dissociation effects observed previously in human PD subjects scanned sequentially during levodopa infusion. This approach may have utility in the assessment of new drugs targeting the exaggerated regional vasomotor responses seen in human PD and in experimental models of levodopa-induced dyskinesia.
[Show abstract][Hide abstract]ABSTRACT: Opioid abuse is a major health concern making the clinical management of pain a particularly complex issue. Central modulation of pain requires both inhibitory and excitatory pathways in neocortical and subcortical structures. Additionally, there is a marked difference between males and females in their response to opioid analgesia (Mogil, et al., 2012). In an ongoing effort to better understand how opioid-mediated pain management develops into opioid abuse, we established a reproducible metabolic signature of inflammatory pain using microposi- tron emission tomography (microPET), 18FDG, and two distinct animal models. Specifically, we utilized the acetic acid writhing and the formalin pain assays, the former a measure of visceral pain and the latter a measure of tonic peripheral inflammatory pain. Finally, using the formalin assay, we examined sex differences with respect to behavioral responses and metabolic signatures.
[Show abstract][Hide abstract]ABSTRACT: Extracellular superoxide dismutase (EC-SOD) is an isoform of SOD normally found both intra- and extra-cellularly and accounting for most SOD activity in blood vessels. Here we explored the role of EC-SOD in protecting against brain damage induced by chronic hypoxia. EC-SOD Transgenic mice, were exposed to hypoxia (FiO2.1%) for 10 days (H-KI) and compared to transgenic animals housed in room air (RA-KI), wild type animals exposed to hypoxia (H-WT or wild type mice housed in room air (RA-WT). Overall brain metabolism evaluated by positron emission tomography (PET) showed that H-WT mice had significantly higher uptake of 18FDG in the brain particularly the hippocampus, hypothalamus, and cerebellum. H-KI mice had comparable uptake to the RA-KI and RA-WT groups. To investigate the functional state of the hippocampus, electrophysiological techniques in ex vivo hippocampal slices were performed and showed that H-KI had normal synaptic plasticity, whereas H-WT were severely affected. Markers of oxidative stress, GFAP, IBA1, MIF, and pAMPK showed similar values in the H-KI and RA-WT groups, but were significantly increased in the H-WT group. Caspase-3 assay and histopathological studies showed significant apoptosis/cell damage in the H-WT group, but no significant difference in the H-KI group compared to the RA groups. The data suggest that EC-SOD has potential prophylactic and therapeutic roles in diseases with compromised brain oxygenation.
[Show abstract][Hide abstract]ABSTRACT: Systemic lupus erythematosus (SLE) is characterized by multiorgan inflammation, neuropsychiatric disorders (NPSLE), and anti-nuclear antibodies. We previously identified a subset of anti-DNA antibodies (DNRAb) cross-reactive with the N-methyl-D-aspartate receptor, present in 30% to 40% of patients, able to enhance excitatory post-synaptic potentials and trigger neuronal apoptosis. DNRAb+ mice exhibit memory impairment or altered fear response, depending on whether the antibody penetrates the hippocampus or amygdala. Here, we used 18F-fluorodeoxyglucose (FDG) microPET to plot changes in brain metabolism after regional blood-brain barrier (BBB) breach. In DNRAb+ mice, metabolism declined at the site of BBB breach in the first 2 weeks and increased over the next 2 weeks. In contrast, DNRAb- mice exhibited metabolic increases in these regions over the 4 weeks after the insult. Memory impairment was present in DNRAb+ animals with hippocampal BBB breach and altered fear conditioning in DNRAb+ mice with amygdala BBB breach. In DNRAb+ mice, we observed an inverse relationship between neuron number and regional metabolism, while a positive correlation was observed in DNRAb- mice. These findings suggest that local metabolic alterations in this model take place through different mechanisms with distinct time courses, with important implications for the interpretation of imaging data in SLE subjects.Journal of Cerebral Blood Flow & Metabolism advance online publication, 14 May 2014; doi:10.1038/jcbfm.2014.85.
Full-text Article · May 2014 · Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism
[Show abstract][Hide abstract]ABSTRACT: Introduction: Incidence of Neonatal Abstinence Syndrome (NAS) has significantly increased in past few years. Current approaches designed to treat NAS include replacement therapies with drugs like morphine and methadone. These drugs themselves are associated with significant side effects and have addictive liability. Despite implementation of these treatments, the length of stay has not significantly reduced. Objective: To test a novel prenatal strategy of using low dose GABA transaminase inhibitor vigabatrin (GVG), a non-addictive, non-narcotic GABAergic drug to attenuate naloxone induced withdrawal symptoms in neonatal rats. Method: Pregnant rats, starting from gestation day 2 were divided into morphine and saline groups. They continued to receive this therapy daily throughout gestation. The Morphine group either continued to receive morphine only, or received GVG for last five days of gestation in addition to morphine. GVG was given either at 25 mg/kg/day or 50 mg/kg/day. On post natal day 1, pups received naloxone challenge and withdrawal behaviors were video recorded. Locomotion, rolling, curling, and stretching of each pup were counted to obtain gross behavior scores, which were then compared between treatment groups. Daily weights of pregnant rats and neonates were also measured. Results: • Pups in all the groups had similar scores at baseline. On administration of naloxone, morphine group had markedly higher scores than saline group (p<0.05). In contrast, morphine + GVG50 group had significantly lower (attenuated) scores as compared to morphine alone (p<0.05). This difference was consistent across all time points. • Saline group pups had higher birth weight and better weight gain for first 3 weeks. For all remaining groups, birth weights and weight gain pattern was similar to each other. • Weight gain of pregnant rats in treatment groups were no different than each other. Conclusion: Prenatal administration of GVG to morphine dependent pregnant rats abolishes acute withdrawal behavior in pups. This prenatal GABAergic modulation can be an alternative to current treatment strategies. Objective To test a novel prenatal strategy of using low dose vigabatrin (GVG), a non-addictive, non-narcotic GABAergic drug to attenuate naloxone induced withdrawal symptoms in neonatal rats. Conclusions Prenatal administration of GVG to morphine dependent pregnant rats abolishes acute withdrawal behavior in pups.
[Show abstract][Hide abstract]ABSTRACT: Background: In treatment refractory OCD, anterior cingu-lotomy can be effective for some patients, with pre-operative posterior cingulate cortex metabolism predicting better response (Rauch et al, 2001). Animal work shows the cingulum bundle to include afferent/efferent fibers from rostral anterior, dorsal anterior and posterior subregions of cingulate cortex as well as more distal cortical and subcortical regions. As such, the cingulum bundle is a complex white matter tract, likely comprised of distinct white matter pathways, serving distinct functions (Jones et al, 2013). Fractional anisotropy (FA), measured using DTI, reflectswhite matter coherence, and can be used to measure the integrity of white matter fibers within the cingulum bundle, as well as white matter projections throughout adjacent subregions of cingulate cortex. Given evidence for hyperactive dorsal anterior cingulate gyrus function in pediatric OCD, we hypothesized that, compared to healthy controls, young patients would exhibit increased FA in dorsal anterior cingulum bundle. Methods: A 3 T GE MRI machine was used to collect DTI data from 36 patients with pediatric OCD (20 F; 14.7±3.1 years) and 27 healthy control subjects (16 F; 14.1 ± 2.9 years), ranging in age from 8 to 19 years. 15 diffusion-weighted images (b ¼ 800 s/mm2, two averages) were acquired for 39 slices (thickness ¼ 3 mm, skip ¼ 1 mm, TR ¼ 9000 ms, TE ¼ 82.3 ms, FOV ¼ 22 cm). One non-diffusion weighted image (b ¼ 0 s/mm2) was collected to transform the diffusion-weighted images to a template in MNI space. FA images were created, realigned to the FMRIB standard-space image and transformed into MNI space in FSL. Using tract-based spatial statistics (TBSS), a mean FA skeleton was created and thresholded at .2 for each participant. Regions of interest included the entire anterior to posterior length of right and left cingulum bundles (CB) from the Johns Hopkins University (JHU) White Matter Tractography Atlas, as well as rostral anterior, dorsal anterior and posterior subregions of adjacent cingulate cortex from the Automated Anatomic Labeling Atlas. Mean FA values were extracted from each ROI for each participant and entered into a linear regression to test the effects of group, age and group x age interactions in SPSS. Results: A group x age interaction was observed for FA extracted from the right dorsal anterior cingulate cortex (dACC) (p ¼ 0.001), driven by increases in FA with increasing age in pediatric OCD (r ¼ 0.64, po0.0001), but not healthy controls (r ¼ À0.06, p ¼ 0.76). A trend-level group x age interaction was observed for the right JHU-defined CB (p ¼ 0.12); as with the right dACC, FA in the right JHU-CB increased with age in the OCD (r ¼ 0.39, p ¼ 0.02), but not healthy control (r ¼ 0.08, p ¼ 0.70) group. An inverse effect of age (p ¼ 0.04) and a trend-level group x age interaction (p ¼ 0.09) was also observed for left rostral anterior cingulate but here, in contrast with the right dorsal anterior cingulate ROIs, the interaction was driven by a tendency towards age-related decreases in FA in the healthy (r ¼ À0.36, p ¼ 0.07), but not OCD (r ¼ 0.04, p ¼ 0.83) group. There were no other significant (or trend-level) effects of age, group or group x age interactions in any ROI. Conclusions: Our results suggest atypical development white matter may localize to right dorsal anterior cingulate cortex in youth with OCD, with a pattern of protracted increase in FA in patients compared to healthy controls. Longitudinal work is needed to determine if increasing FA is more associated with persistence or remission of illness as youth with OCD continue to mature.
[Show abstract][Hide abstract]ABSTRACT: Neonatal abstinence syndrome (NAS) is a drug withdrawal disorder caused by chronic maternal opiate use. Recent findings from hospitals across the U.S. suggest that the newborn addiction rate has tripled over the last decade, and that newborns with NAS spent an average of 16 days in the hospital being treated for opiate withdrawal. Symptoms of NAS include seizures, respiratory and feeding difficulties and low birth weight. While the immediate treatment of behavioral changes associated with NAS have been the focus of recent investigations, the longterm consequences remain relatively unknown. Therefore, in an ongoing effort to better understand the lifetime effects of prenatal opiate exposure on the adolescent and adult brain, we treated 4 pregnant SpragueDawley rats from Gestational Day (GD) 2 GD21 (day of parturition) with an escalating dose of morphine (20 60 mg/kg/day). Immediately upon birth, litters were culled to 9 animals and crossed fostered to normal surrogates. Litter sizes were not significantly different between morphine and salinetreated controls. However, birth weights were significantly reduced in morphinetreated animals (p < 0.01). To determine if this treatment paradigm produced pups sensitive to opiate withdrawal, animals were challenged with naloxone (1.0 mg/kg) on Post Natal Day (PND) 1. Behaviors were scored (0 3 with 3 being highest) by 5 individuals blind to the treatment condition. Animals exposed to morphine in utero demonstrated marked withdraw behaviors following an acute naloxone challenge (saline = 1.01 ± 0.22, morphine treated = 4.91 ± 0.34, mean of the summed scores for all behaviors). At PND35 (adolescence), animals received an acute morphine challenge (10 mg/kg) 20 minutes prior to being injected with 2deoxy 2(18F)fluoroDglucose (18FDG). Scanning was performed using a Siemen's Inveon positron emission tomograph. Uptake (45 minutes) occurred in awake and freely moving animals in their home cage. Following this period, animals were anesthetized (ketamine/xylazine) and placed in the gantry. Static images were reconstructed using both filtered back projection (FBP) and maximum a posteriori (MAP) algorithms. Images were coregistered to a standard rat atlas with PMOD. Using a region of interest (ROI) and/or a statistical parametric map (SPM) protocol, data comparing the morphineexposed group to the saline control group were obtained. Using either method of analysis, morphineexposed animals demonstrated marked increases in 18FDG uptake in both the corpus striatum and the thalamus, bilaterally. Marked decreases, however, were noted bilaterally in the superior colliculus of these same animals. These increases and decreases were significantly different from control values (P < 0.001). Ongoing studies are examining whether these alterations remain into adulthood. In summary, the present findings have important implications for the abuse liability of opiates as well as the potential use of narcotic analgesics for adequate pain management in individuals with a gestational history of opiate exposure.
[Show abstract][Hide abstract]ABSTRACT: There is increasing evidence that hyperoxia, particularly at the time of birth, may result in neurological injury, in particular to the susceptible vasculature of these tissues. This study was aimed at determining whether overexpression of extracellular superoxide dismutase (EC-SOD) is protective against brain injury induced by hyperoxia. Transgenic (TG) mice (with an extra copy of the human extracellular superoxide dismutase gene) and wild-type (WT) neonate mice were exposed to hyperoxia (95% of F(i) o(2) ) for 7 days after birth versus the control group in room air. Brain positron emission tomography (PET) scanning with fludeoxyglucose (FDG) isotope uptake was performed after exposure. To assess apoptosis induced by hyperoxia exposure, caspase 3 ELISA and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining were performed. Quantitative western blot for the following inflammatory markers was performed: glial fibrillary acidic protein, ionized calcium-binding adaptor molecule 1, macrophage-inhibiting factor, and phospho-AMP-activated protein kinase. PET scanning with FDG isotope uptake showed significantly higher uptake in the WT hyperoxia neonate brain group (0.14 ± 0.03) than in both the TG group (0.09 ± 0.01) and the control group (0.08 ± 0.02) (P< 0.05). Histopathological investigation showed more apoptosis and dead neurons in hippocampus and cerebellum brain sections of WT neonate mice after exposure to hyperoxia than in TG mice; this finding was also confirmed by TUNEL staining. The caspase 3 assay confirmed the finding of more apoptosis in WT hyperoxia neonates (0.814 ± 0.112) than in the TG hyperoxic group (0.579 ± 0.144) (P < 0.05); this finding was also confirmed by TUNEL staining. Quantitative western blotting for the inflammatory and metabolic markers showed significantly higher expression in the WT group than in the TG and control groups. Thus, overexpression of EC-SOD in the neonate brain offers significant protection against hyperoxia-induced brain damage.
[Show abstract][Hide abstract]ABSTRACT: Vigabatrin, a GABA aminotransferase (GABA-AT) inactivator, is used to treat infantile spasms and refractory complex partial seizures and is in clinical trials to treat addiction. We evaluated a novel GABA-AT inactivator (1S, 3S)-3-amino-4-difluoromethylenyl-1-cyclopentanoic acid (CPP-115, compound 1) and observed that it does not exhibit other GABAergic or off-target activities and is rapidly and completely orally absorbed and eliminated. By use of in vivo microdialysis techniques in freely moving rats and microPET imaging techniques, 1 produced similar inhibition of cocaine-induced increases in extracellular dopamine and in synaptic dopamine in the nucleus accumbens at (1)/(300) to (1)/(600) the dose of vigabatrin. It also blocks expression of cocaine-induced conditioned place preference at a dose (1)/(300) that of vigabatrin. Electroretinographic (ERG) responses in rats treated with 1, at doses 20-40 times higher than those needed to treat addiction in rats, exhibited reductions in ERG responses, which were less than the reductions observed in rats treated with vigabatrin at the same dose needed to treat addiction in rats. In conclusion, 1 can be administered at significantly lower doses than vigabatrin, which suggests a potential new treatment for addiction with a significantly reduced risk of visual field defects.
Full-text Article · Nov 2011 · Journal of Medicinal Chemistry
[Show abstract][Hide abstract]ABSTRACT: The factors that determine symptom penetrance in inherited disease are poorly understood. Increasingly, magnetic resonance diffusion tensor imaging (DTI) and PET are used to separate alterations in brain structure and function that are linked to disease symptomatology from those linked to gene carrier status. One example is DYT1 dystonia, a dominantly inherited movement disorder characterized by sustained muscle contractions, postures, and/or involuntary movements. This form of dystonia is caused by a 3-bp deletion (i.e., ΔE) in the TOR1A gene that encodes torsinA. Carriers of the DYT1 dystonia mutation, even if clinically nonpenetrant, exhibit abnormalities in cerebellothalamocortical (CbTC) motor pathways. However, observations in human gene carriers may be confounded by variability in genetic background and age. To address this problem, we implemented a unique multimodal imaging strategy in a congenic line of DYT1 mutant mice that contain the ΔE mutation in the endogenous mouse torsinA allele (i.e., DYT1 knock-in). Heterozygous knock-in mice and littermate controls underwent microPET followed by ex vivo high-field DTI and tractographic analysis. Mutant mice, which do not display abnormal movements, exhibited significant CbTC tract changes as well as abnormalities in brainstem regions linking cerebellar and basal ganglia motor circuits highly similar to those identified in human nonmanifesting gene carriers. Moreover, metabolic activity in the sensorimotor cortex of these animals was closely correlated with individual measures of CbTC pathway integrity. These findings further link a selective brain circuit abnormality to gene carrier status and demonstrate that DYT1 mutant torsinA has similar effects in mice and humans.
Full-text Article · Apr 2011 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract]ABSTRACT: PET imaging in plants is receiving increased interest as a new strategy to measure plant responses to environmental stimuli and as a tool for phenotyping genetically engineered plants. PET imaging in plants, however, poses new challenges. In particular, the leaves of most plants are so thin that a large fraction of positrons emitted from PET isotopes ((18)F, (11)C, (13)N) escape while even state-of-the-art PET cameras have significant partial-volume errors for such thin objects. Although these limitations are acknowledged by researchers, little data have been published on them.
Here we measured the magnitude and distribution of escaping positrons from the leaf of Nicotiana tabacum for the radionuclides (18)F, (11)C and (13)N using a commercial small-animal PET scanner. Imaging results were compared to radionuclide concentrations measured from dissection and counting and to a Monte Carlo simulation using GATE (Geant4 Application for Tomographic Emission).
Simulated and experimentally determined escape fractions were consistent. The fractions of positrons (mean±S.D.) escaping the leaf parenchyma were measured to be 59±1.1%, 64±4.4% and 67±1.9% for (18)F, (11)C and (13)N, respectively. Escape fractions were lower in thicker leaf areas like the midrib. Partial-volume averaging underestimated activity concentrations in the leaf blade by a factor of 10 to 15.
The foregoing effects combine to yield PET images whose contrast does not reflect the actual activity concentrations. These errors can be largely corrected by integrating activity along the PET axis perpendicular to the leaf surface, including detection of escaped positrons, and calculating concentration using a measured leaf thickness.
[Show abstract][Hide abstract]ABSTRACT: Activated microglia have been associated with neurodegeneration in patients and in animal models of Temporal Lobe Epilepsy (TLE), however their precise functions as neurotoxic or neuroprotective is a topic of significant investigation. To explore this, we examined the effects of pilocarpine-induced seizures in transgenic mice where microglia/macrophages were conditionally ablated. We found that unilateral ablation of microglia from the dorsal hippocampus did not alter acute seizure sensitivity. However, when this procedure was coupled with lipopolysaccharide (LPS) preconditioning (1 mg/kg given 24 h prior to acute seizure), we observed a significant pro-convulsant phenomenon. This effect was associated with lower metabolic activation in the ipsilateral hippocampus during acute seizures, and could be attributed to activity in the mossy fiber pathway. These findings reveal that preconditioning with LPS 24 h prior to seizure induction may have a protective effect which is abolished by unilateral hippocampal microglia/macrophage ablation.
Full-text Article · Apr 2010 · Neurobiology of Disease