GABAA Receptor Alpha Research Articles

An alpha 5-GABAA receptor positive allosteric modulator attenuates social and cognitive deficits without changing dopamine system hyperactivity in rats exposed to valproic acid in utero.

Autism spectrum disorders (ASDs) are characterized by core behavioral symptoms in the domains of sociability, language/communication, and repetitive or stereotyped behaviors. Deficits in the prefrontal and hippocampal excitatory/inhibitory balance due to a functional loss of GABAergic interneurons are proposed to underlie these symptoms. Increasing the postsynaptic effects of GABA with compounds that selectively modulate GABAergic receptors could be a potential target for treating ASD symptoms. In addition, deficits in GABAergic interneurons have been linked to dopamine (DA) system dysregulation, and, despite conflicting evidence, abnormalities in the DA system activity may underly some ASD symptoms. Here, we investigated whether the positive allosteric modulator of α5-containing GABAA receptors (α5-GABAARs) SH-053-2'F-R-CH3 (10 mg/kg) attenuates behavioral abnormalities in rats exposed to valproic acid (VPA) in utero, an established risk factor for autism. We also evaluated if animals exposed to VPA in utero present changes in the ventral tegmental area (VTA) DA system activity using in vivo electrophysiology and if SH-053-2'F-R-CH3 could attenuate these changes. SH-053-2'F-R-CH3 was administered intraperitoneally 30 min before each behavioral test and electrophysiology. In utero VPA exposure caused male and female rats to present increased repetitive behavior (self-grooming) in early adolescence and deficits in social interaction in adulthood. Male, but not female VPA rats, also presented deficits in recognition memory as adults. SH-053-2'F-R-CH3 attenuated the impairments in sociability and cognitive function in male VPA-exposed rats without attenuating the decreased social interaction in females. Adult male and female VPA-exposed rats also showed an increased VTA DA neuron population activity, which was not changed by SH-053-2'F-R-CH3. Despite sex differences, our findings indicate that α5-GABAARs positive allosteric modulators may effectively attenuate some core ASD symptoms.

CBD specific action on GABAA receptor alpha subunits.

Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central nervous system (CNS) of the mammalian brain and is primarily responsible for mediating fast neuronal inhibition via its action at GABAA receptors.

Unconditioned and learned morphine tolerance influence hippocampal-dependent short-term memory and the subjacent expression of GABA-A receptor alpha subunits.

ɣ-aminobutyric acid (GABA) facilitator valproic acid may be able to curb memory disruption induced by morphine exposure. The effects of the GABA facilitator valproic acid on the behavioral tolerance induced by morphine were investigated. Then hippocampal-dependent tasks named spatial-working and short-term memory procedures using the Y-maze apparatus were examined in morphine tolerant rats. Finally, the changes in the expression of hippocampal GABA-A receptors underlying morphine tolerance were also examined. Rats were treated with daily morphine injections, with or without distinct contextual pairing. To examine the effect of valproic acid on morphine tolerance expression, valproic acid was pretreated an hour before morphine. Spatial-working and short-term memory procedures using the Y-maze apparatus were examined in morphine tolerant rats. Afterwards the changes in the expression of hippocampal GABAα receptors using the quantitative real-time PCR and western blot techniques to detect GABArα subunits mRNAs and protein level were studied. Our results showed that both learned and non-associative morphine tolerance influence short-term memory and the subjacent expression of GABArα mRNAs and protein level. Despite its attenuating effects on the development and expression of both learned and non-associative morphine tolerance, only associative morphine tolerance-induced memory dysfunction was ameliorated by valproic acid pretreatment. We also found that the expression of GABArα1, α2, α5 subunits mRNAs and GABAα protein level were affected heavier in associative morphine tolerant rats. Our data supports the hypothesis that unconditioned and learned morphine tolerance influences short-term memory and the expression of GABArα 1, α2, α5 mRNAs and GABArα protein level differently, and adds to our understanding of the behavioral and molecular aspects of the learned tolerance to morphine effects.

Reductions in midbrain GABAergic and dopamine neuron markers are linked in schizophrenia

Reductions in the GABAergic neurotransmitter system exist across multiple brain regions in schizophrenia and encompass both pre- and postsynaptic components. While reduced midbrain GABAergic inhibitory neurotransmission may contribute to the hyperdopaminergia thought to underpin psychosis in schizophrenia, molecular changes consistent with this have not been reported. We hypothesised that reduced GABA-related molecular markers would be found in the midbrain of people with schizophrenia and that these would correlate with dopaminergic molecular changes. We hypothesised that downregulation of inhibitory neuron markers would be exacerbated in schizophrenia cases with high levels of neuroinflammation. Eight GABAergic-related transcripts were measured with quantitative PCR, and glutamate decarboxylase (GAD) 65/67 and GABAA alpha 3 (α3) (GABRA3) protein were measured with immunoblotting, in post-mortem midbrain (28/28 and 28/26 control/schizophrenia cases for mRNA and protein, respectively), and analysed by both diagnosis and inflammatory subgroups (as previously defined by higher levels of four pro-inflammatory cytokine transcripts). We found reductions (21 – 44%) in mRNA encoding both presynaptic and postsynaptic proteins, vesicular GABA transporter (VGAT), GAD1, and parvalbumin (PV) mRNAs and four alpha subunits (α1, α2, α3, α5) of the GABAA receptor in people with schizophrenia compared to controls (p < 0.05). Gene expression of somatostatin (SST) was unchanged (p = 0.485). We confirmed the reduction in GAD at the protein level (34%, p < 0.05). When stratifying by inflammation, only GABRA3 mRNA exhibited more pronounced changes in high compared to low inflammatory subgroups in schizophrenia. GABRA3 protein was expressed by 98% of tyrosine hydroxylase-positive neurons and was 23% lower in schizophrenia, though this did not reach statistical significance (p > 0.05). Expression of transcripts for GABAA receptor alpha subunits 2 and 3 (GABRA2, GABRA3) were positively correlated with tyrosine hydroxylase (TH) and dopamine transporter (DAT) transcripts in schizophrenia cases (GABRA2; r > 0.630, GABRA3; r > 0.762, all p < 0.001) but not controls (GABRA2; r < − 0.200, GABRA3; r < 0.310, all p > 0.05). Taken together, our results support a profound disruption to inhibitory neurotransmission in the substantia nigra regardless of inflammatory status, which provides a potential mechanism for disinhibition of nigrostriatal dopamine neurotransmission.

Reduced Expression of GABA A Receptor Alpha2 Subunit Is Associated With Disinhibition of DYT-THAP1 Dystonia Patient-Derived Striatal Medium Spiny Neurons.

DYT-THAP1 dystonia (formerly DYT6) is an adolescent-onset dystonia characterized by involuntary muscle contractions usually involving the upper body. It is caused by mutations in the gene THAP1 encoding for the transcription factor Thanatos-associated protein (THAP) domain containing apoptosis-associated protein 1 and inherited in an autosomal-dominant manner with reduced penetrance. Alterations in the development of striatal neuronal projections and synaptic function are known from transgenic mice models. To investigate pathogenetic mechanisms, human induced pluripotent stem cell (iPSC)-derived medium spiny neurons (MSNs) from two patients and one family member with reduced penetrance carrying a mutation in the gene THAP1 (c.474delA and c.38G > A) were functionally characterized in comparison to healthy controls. Calcium imaging and quantitative PCR analysis revealed significantly lower Ca2+ amplitudes upon GABA applications and a marked downregulation of the gene encoding the GABAA receptor alpha2 subunit in THAP1 MSNs indicating a decreased GABAergic transmission. Whole-cell patch-clamp recordings showed a significantly lower frequency of miniature postsynaptic currents (mPSCs), whereas the frequency of spontaneous action potentials (APs) was elevated in THAP1 MSNs suggesting that decreased synaptic activity might have resulted in enhanced generation of APs. Our molecular and functional data indicate that a reduced expression of GABAA receptor alpha2 subunit could eventually lead to limited GABAergic synaptic transmission, neuronal disinhibition, and hyperexcitability of THAP1 MSNs. These data give pathophysiological insight and may contribute to the development of novel treatment strategies for DYT-THAP1 dystonia.

P.074 The effects of positive and negative modulators of alpha5 GABAA receptors on social behavior in 5xFAD model of Alzheimer's disease

In the context of industry 4.0 where the use of new technologies is required to meet productivity and profitability demands, this paper addresses 3D scanning, thermal imaging and computer vision to identify pipe clogging caused by waste accumulation in the fertilizer industry. This paper presents a study using thermal images and the use artificial neural network to model the waste distribution in industrial pipes.

The role of the GABAA receptor Alpha 1 subunit in the ventral hippocampus in stress resilience

Pre-pubertal stress increases post-traumatic stress disorder (PTSD) susceptibility. We have previously demonstrated that enriched environment (EE) intervention immediately after pre-pubertal stress protects from the effects of trauma in adulthood. Here, we examined whether exposure to EE would also be beneficial if applied after exposure to trauma in adulthood. We have recently shown that exposure to juvenile stress and under-water trauma (UWT) is associated with increased expression of GABAA receptor subunit α1 in the ventral hippocampus. However, differentiating between affected and unaffected individuals, this increased expression was confined to stress-exposed, behaviorally unaffected individuals, suggesting upregulation of α1 expression as a potential mechanism of resilience. We now examined whether EE-induced resilience renders increased expression of α1 in the ventral hippocampus redundant when facing a trauma later in life. Adult rats were exposed to UWT, with pre-exposure to juvenile stress, and tested in the open field and elevated plus maze paradigms four weeks later. EE exposure during juvenility prevented pre-pubertal stress-induced vulnerability, but not if performed following UWT in adulthood. Furthermore, juvenile EE exposure prevented the trauma-associated increase in α1 expression levels. Our findings emphasize the importance of early interventions in order to reduce the likelihood of developing psychopathologies in adulthood.

Drinking patterns and alterations in several brain protein levels after binge drinking during adolescence followed by intermittent stress and ethanol drinking during adulthood in male and female C57BL/6J mice

Alcohol abuse is a serious problem in our society with stress likely increasing the risk for escalation to harmful drinking. We are continuing to explore the effect of prior binge drinking on subsequent drinking behaviors and the response to intermittent predator odor stress (PS) exposure (a model of traumatic stress). We assessed responses in mice that were adolescent at the time of the binge drinking sessions, as we are aware that the adolescent brain is particularly vulnerable to ethanol. Male and female C57BL/6J adolescent mice had either 7 binge ethanol sessions (binge) or drank water (control). Following an abstinence period, all mice (now adults) were provided free access to 10% ethanol (10E) and water via lickometers for 4 weeks, with 30 min exposure to PS during the middle 2 weeks (2X/week). For mice exposed to the binge paradigm during adolescence, drinking levels changed across time after repeated PS. In males, ethanol intake increased over baseline by 34% in the binge group vs unchanged in the control group. In females, ethanol intake was increased by 57% (binge) and 38% (control) over baseline. At 24 hr after the final drinking session, brains were harvested and frozen for Western Blot analyses versus separate naïve age‐matched mice. Prefrontal cortex (PFC) and hippocampus (HIPP) were assayed for levels of the GABAA receptor (GABAAR) alpha2 and alpha 4 subunits, P450scc (a steroidogenesis enzyme), and CRF R1 (corticotropin releasing factor receptor) with values compared to naïve mice. We found divergent responses across proteins by sex and brain area. In male PFC, there reduced levels for GABAAR alpha 4 subunit levels (to 0.86 ± 0.04% for control and 0.85 ± 0.04% for binge vs naïve) and a decrease in P450scc levels of 084 ± 0.04% (control) and 0.89 ± 0.04% (binge) whereas the male HIPP also showed a trend towards reduced levels of the GABAAR alpha 4 subunit (0.90 ± 0.04% and 0.85 ± 0.03% for control and binge, respectively) but an increase in CRF‐R1 levels to 1.26 ± 0.05% for control and 1.28 ± 0.04% for binge. In contrast, the female PFC had decreased levels of the GABAAR alpha 2 subunit (0.77 ± 0.12% for control and 0.74 ± 0.07% for binge) with a similar decrease in alpha 4 subunit levels as in male PFC (0.84 ± 0.11% for control and 0.78 ± 0.09% for binge). Also similar to male, female HIPP had increased levels for CRF‐R1 levels of 1.14 ± 0.05% for control and 1.15 ± 0.05% for binge. And while P450scc levels were decreased (0.84 ± 0.04% for both groups) in female HIPP, a similar change was only observed in male PFC. The similar changes in the binge and control groups vs naïve animals suggest that the repeated PS and ethanol drinking history during adulthood influenced neuroadaptations in brain proteins more than the adolescent binge drinking experience. Taken together, these data continue to support the suggestion that a history of ethanol drinking and stress may interact to increase the risk for harm from subsequent drinking with important sex differences in drinking behaviors and brain protein changes.Support or Funding InformationSupported by BX001070 and BX002966 (DF) from the Department of Veteran AffairsThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

3.1 ENHANCED PARVALBUMIN NETWORK ACTIVITY PROLONGS CRITICAL PERIOD PLASTICITY

BackgroundOscillations in neuronal activity tie the pathophysiology of schizophrenia to alterations in local processing and large-scale coordination, and these alterations in turn can lead to the cognitive and perceptual disturbances observed in schizophrenia. Here, we focus on the dual role of fast-spiking, parvalbumin (PV+) networks in the generation of gamma oscillations and critical periods of brain plasticity.MethodsWe generated a mouse model of reduced recurrent inhibition only within local PV+ cell networks by selective removal of GABAA receptor alpha1 subunits (PV-α1 KO mice). Electroencephalography (EEG), PV+ immunohistochemistry, perineuronal net (PNN) labeling and redox balance were compared to cortical measures of brain plasticity (loss of visual acuity, formation of preference behaviors) that are typically limited to a critical period early in life.ResultsPV-α1 KO mice exhibit chronically enhanced gamma-oscillations and extended juvenile forms of cortical plasticity into adulthood. Acute pharmacological suppression of excitatory input restored E-I balance onto these disinhibited PV+ cells and returned baseline EEG power to normal levels, preventing the extended plasticity. Enhanced gamma oscillations were further found to compromise the integrity of perineuronal nets (PNNs) surrounding PV+ cells, elevating oxidative stress and the turnover of metallopeptidases and structural components of the PNN. All of these aspects were also reversed by pharmacological dampening of excitation onto PV+ cells.DiscussionCortical gamma oscillations are associated with plasticity and cognition. Our results provide a cellular explanation of how elevated gamma oscillations may promote ectopic brain plasticity by regulating the extracellular matrix which normally stabilizes cortical circuitry. These results carry broad implications for subjects at-risk for schizophrenia who exhibit heightened gamma oscillations prior to psychosis onset (see talk by P Uhlhaas).

The female epilepsy protein PCDH19 is a new GABAAR-binding partner that regulates GABAergic transmission as well as migration and morphological maturation of hippocampal neurons.

The PCDH19 gene (Xp22.1) encodes the cell-adhesion protein protocadherin-19 (PCDH19) and is responsible for a neurodevelopmental pathology characterized by female-limited epilepsy, cognitive impairment and autistic features, the pathogenic mechanisms of which remain to be elucidated. Here, we identified a new interaction between PCDH19 and GABAA receptor (GABAAR) alpha subunits in the rat brain. PCDH19 shRNA-mediated downregulation reduces GABAAR surface expression and affects the frequency and kinetics of miniature inhibitory postsynaptic currents (mIPSCs) in cultured hippocampal neurons. In vivo, PCDH19 downregulation impairs migration, orientation and dendritic arborization of CA1 hippocampal neurons and increases rat seizure susceptibility. In sum, these data indicate a role for PCDH19 in GABAergic transmission as well as migration and morphological maturation of neurons.

Loop F of the GABAA receptor alpha subunit governs GABA potency

Gamma-amino butyric acid (GABA) is an abundant neurotransmitter in the CNS. GABAergic interneurons orchestrate pyramidal neurons in the cerebral cortex, and thus control learning and memory. Ionotropic receptors for GABA (GABAAR) are heteropentameric complexes of α, β and γ integral membrane-protein subunits forming Cl− -channels operated by GABA, which are vital for brain function and are important drug targets. However, knowledge on how GABAAR bind GABA is controversial. Structural biology versus functional modelling combined with site-directed mutagenesis suggest markedly different roles for loop F of the extracellular domain of the α-subunit when complexed with GABA. Here, we report that contrary to the results of structural studies, loop F of the α-subunit controls the potency of GABA on GABAAR. We examined the effect of replacing a short, variable segment of loop F of the GABAA α5-subunit with the corresponding segment of the α2-subunit (GABAA5_LF2) and vice versa (GABAA2-LF5). When compared with their respective wild-type counterparts, GABAA5_LF2 receptors displayed enhanced sensitivity towards GABA, whilst in GABAA2-LF5 sensitivity was diminished. Mice homozygous for the genetic knock-in of the GABAA5_LF2 subunit showed a marked deficit in long- but not short-term object recognition memory. Working memory in place learning, spontaneous alternation and the rewarded T-maze were all normal. The deficit in long-term recognition memory was reversed by an α5-GABAA negative allosteric modulator compound. The data show that loop F governs GABA potency in a receptor isoform-specific manner in vitro. Moreover, this mechanism of ligand recognition appears to be operative in vivo and impacts cognitive performance.

AnkG hemizygous mice present cognitive impairment and elevated anxiety/depressive-like traits associated with decreased expression of GABA receptors and postsynaptic density protein.

Recent genome-wide association studies (GWAS) of patient populations and genetic linkage assessments have demonstrated that the ankyrin-G (AnkG) gene is involved in neuropsychiatric disorders, including bipolar disorder, schizophrenia, and Alzheimer's disease, but it remains unclear how the genetic variants of AnkG contribute to neuropsychiatric disorders. Here, we generated AnkG hemizygous mice using the gene trapping approach. Homozygous AnkG was embryonically lethal. Western blotting and real-time polymerase chain reaction (qPCR) assessments of wild type (WT) and AnkG +/- mutant mice demonstrated a 50% reduction of ANKG levels, at the gene and protein levels, in AnkG hemizygous mice. In behavioral tests, AnkG hemizygous mice exhibited elevated anxiety- and depression-like traits, as well as cognitive impairment. Moreover, the expression levels of cognitive-related proteins (including metabotropic glutamate receptor subtype-1, brain-derived neurotrophic factor, postsynaptic density-95, GABA-B receptor, and GABA-A receptor alpha-1) were significantly decreased (P<0.05), suggesting a possible role for AnkG in cognition. It is possible that the loss of AnkG in the brain disrupts the excitation/inhibition balance of neurotransmitters, hindering the synaptic plasticity of neurons, and consequently leading to abnormal behavioral symptoms. Therefore, AnkG possibly contributes to neuroprotection and normal brain function, and may constitute a new target for treating neuropsychiatric diseases, especially cognitive dysfunction.

Protective Effect of Resveratrol on the Brain in a Rat Model of Epilepsy.

Accumulating evidence has suggested resveratrol as a promising drug candidate for the treatment of epilepsy. To validate this, we tested the protective effect of resveratrol on a kainic acid (KA)-induced epilepsy model in rats and investigated the underlying mechanism. We found that acute resveratrol application partially inhibited evoked epileptiform discharges in the hippocampal CA1 region. During acute, silent and chronic phases of epilepsy, the expression of hippocampal kainate glutamate receptor (GluK2) and the GABAA receptor alpha1 subunit (GABAAR-alpha1) was up-regulated and down-regulated, respectively. Resveratrol reversed these effects and induced an antiepileptic effect. Furthermore, in the chronic phase, resveratrol treatment inhibited the KA-induced increased glutamate/GABA ratio in the hippocampus. The antiepileptic effects of resveratrol may be partially attributed to the reduction of glutamate-induced excitotoxicity and the enhancement in GABAergic inhibition.

C-Jun N-terminal Kinase mediates prostaglandin-induced sympathoexcitation in rats with chronic heart failure by reducing GAD1 and GABRA1 expression.

Prostaglandin E2 mediates sympathoexcitation in chronic heart failure (CHF) through EP3 receptors (PTGER3) in the paraventricular nucleus (PVN). The aim of this study was to investigate the role of c-Jun N-terminal kinase (JNK) in expressional regulation of gamma-aminobutyric acid signalling in PVN in CHF rats. Chronic heart failure was induced by left coronary ligation in Wistar rats. Renal sympathetic nerve discharge (RSND) and mean arterial pressure (MAP) responses to the PVN infusion were determined in anaesthetized rats. Osmotic minipumps were used for chronic PVN infusion. PTGER3 expression was examined with immunofluorescence staining, quantitative real-time PCR and Western blot. Chronic heart failure rats had increased JNK activation and decreased glutamate decarboxylase 1 (GAD1) and GABAA receptor alpha 1 subunit (GABRA1) expression in the PVN. PVN infusion of the PTGER3 agonist SC-46275 caused sympathoexcitation in sham-operated control (Sham) rats and increased it further in CHF. The PTGER3 antagonist L798106 reduced sympathoexcitation and cardiac dysfunction in CHF. PVN infusion of EP1 receptor antagonist SC-19220, EP2 receptor antagonist AH6809 or EP4 receptor antagonist L-161982 had no effect on sympathoexcitation. The JNK inhibitor SP600125 normalized sympathoexcitation and GAD1 and GABRA1 expression in PVN in CHF rats. Both the p44/42 and p38 mitogen-activated protein kinase inhibitors PD98059 and SB203580 could not prevent the downregulation of GAD1 and GABRA1 expression in PVN in CHF. PTGER3 agonist activated JNK but downregulated GAD1 and GABRA1 expression in NG108 neuronal cells. Prostaglandin signalling through upregulated PTGER3 activates JNK which reduces GAD1 and GABRA1 expression in the PVN, and contributes to sympathoexcitation in CHF.

Role of gabra2, GABAA receptor alpha-2 subunit, in CNS development

gabra2 gene codes for the alpha-2 subunit of the GABAA receptor, one of the ionotropic receptors which has been related to anxiety, depression and other behavioural disorders, including drug dependence and schizophrenia. GABAergic signalling also plays a role during development, by promoting neural stem cell maintenance and renewal. To investigate the role of gabra2 in CNS development, gabra2 deficient zebrafish were generated. The pattern of proliferation during the embryonic development was disrupted in morphant embryos, which also displayed an increase in the number of apoptotic nuclei mainly at the mid- and hindbrain regions. The expression of several genes (notch1, pax2, fgf8 and wnt1) known to contribute to the development of the central nervous system was also affected in gabra2 morpholino-injected embryos, although no changes were found for pax6a and shh a expression. The transcriptional activity of neuroD (a proneural gene involved in early neuronal determination) was down-regulated in gabra2 deficient embryos, and the expression pattern of gad1b (GABA-synthesising enzyme GAD67) was clearly reduced in injected fish. I propose that gabra2 might be interacting with those signalling pathways that regulate proliferation, differentiation and neurogenesis during the embryonic development; thus, gabra2 might be playing a role in the differentiation of the mesencephalon and cerebellum. Given that changes in GABAergic circuits during development have been related to several psychiatric disorders, such as autism and schizophrenia, this work might be helpful to understand the role of neurotransmitter systems during CNS development and to assess the developmental effects of several GABAergic drugs.

PP01.10 – 3014: GABRA1 neonatal encephalopathy: a clinical, genetic and pathological study

Objectives To describe a novel phenotype of neonatal encephalopathy and infantile refractory epilepsy and their genetic and pathological underpinnings. Methods After unremarkable gestation and delivery, a male newborn presented with profound lethargy immediately after birth. Initial physical exam was otherwise normal with no microcephaly or dysmorphic features. He remained in a state of continuous behavioural sleep – arguably a coma state starting at birth – in the ensuing weeks. EEG was initially normal. Brain MRI, metabolic screen and array CGH were normal. By age 2 months, developmental arrest, hypotonic tetraparesis and head growth deceleration were evident and remained unchanged thereafter. Around that age, seizures were first noticed and included daily focal clonic, myoclonic and tonic seizures that proved resistant to multiple AEDs. EEG revealed multifocal epileptiform discharges and diffuse slowing of background activity. Ictal recordings suggested a migrating pattern of the seizures. Throughout patient's life, eye opening was only noted at the time of tonic seizures. He died at age 16 months from respiratory complications. Results Brain pathology showed diffuse hypomyelination and mild gliotic changes. The mamillary bodies were conspicuously absent. Microscopically, there were no cytoarchitectural abnormalities but the neocortex showed abundance of type II Alzheimer astrocytes. Whole exome sequencing revealed a heterozygous c.1303C> G missense mutation in the GABRA1A gene, producing a p.L267V substitution. This de novo variant was confirmed by PCR and Sanger sequencing and is predicted to alter the assembly and functional properties of the GABA receptor. Conclusions Mutations in GABRA1, encoding the GABA-A receptor alpha-1 subunit, have been associated with generalized epilepsies and more recently childhood epileptic encephalopathies. The present observation expands the spectrum of GABRA1-linked phenotypes to include a severe neonatal-onset encephalopathy featuring a continuous sleep state, infantile refractory epilepsy and distinctive neuropathological abnormalities.

Aberrant location of inhibitory synaptic marker proteins in the hippocampus of dystrophin-deficient mice: implications for cognitive impairment in duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is a neuromuscular disease that arises from mutations in the dystrophin-encoding gene. Apart from muscle pathology, cognitive impairment, primarily of developmental origin, is also a significant component of the disorder. Convergent lines of evidence point to an important role for dystrophin in regulating the molecular machinery of central synapses. The clustering of neurotransmitter receptors at inhibitory synapses, thus impacting on synaptic transmission, is of particular significance. However, less is known about the role of dystrophin in influencing the precise expression patterns of proteins located within the pre- and postsynaptic elements of inhibitory synapses. To this end, we exploited molecular markers of inhibitory synapses, interneurons and dystrophin-deficient mouse models to explore the role of dystrophin in determining the stereotypical patterning of inhibitory connectivity within the cellular networks of the hippocampus CA1 region. In tissue from wild-type (WT) mice, immunoreactivity of neuroligin2 (NL2), an adhesion molecule expressed exclusively in postsynaptic elements of inhibitory synapses, and the vesicular GABA transporter (VGAT), a marker of GABAergic presynaptic elements, were predictably enriched in strata pyramidale and lacunosum moleculare. In acute contrast, NL2 and VGAT immunoreactivity was relatively evenly distributed across all CA1 layers in dystrophin-deficient mice. Similar changes were evident with the cannabinoid receptor 1, vesicular glutamate transporter 3, parvalbumin, somatostatin and the GABAA receptor alpha1 subunit. The data show that in the absence of dystrophin, there is a rearrangement of the molecular machinery, which underlies the precise spatio-temporal pattern of GABAergic synaptic transmission within the CA1 sub-field of the hippocampus.

P.1.j.011 Positive modulation at alpha5GABAA receptors is not beneficial for cognitive deficits induced by MK-801 in water maze in rats

Monosomy 1p36 is a clinically recognizable syndrome that is considered to be the most common terminal deletion syndrome. It has characteristic clinical features that include craniofacial dysmorphism, congenital anomalies, hearing deficits, developmental delay, mental retardation, hypotonia, seizures, and brain anomalies. Brain anomalies in patients with 1p36 deletion are frequent but inconsistent. To date, 2 cases with monosomy 1p36 associated with periventricular nodular heterotopia (PNH) have been reported. We report a 2-month-old boy with multiple congenital anomalies; brain magnetic resonance imaging revealed PNH. The first 2 described cases were pure terminal deletions, whereas our patient carried unbalanced translocation due to an adjacent 1 segregation of a balanced maternal translocation, resulting in monosomy 1p36.3 and trisomy 19p13.3 identified by whole-genome array comparative genomic hybridization analysis. Our patient, with a smaller deletion that the 2 previously reported cases, can help narrow the critical region for PNH in association with the 1p36 deletion. Several potential candidate genes are discussed.

The effect of chronic administration of corticosterone on anxiety- and depression-like behavior and the expression of GABA-A receptor alpha-2 subunits in brain structures of low- and high-anxiety rats

The aim of this study was to examine changes in rat emotional behavior and determine differences in the expression of GABA-A receptor alpha-2 subunits in brain structures of low- (LR) and high-anxiety (HR) rats after the repeated corticosterone administration. The animals were divided into LR and HR groups based on the duration of their conditioned freezing in a contextual fear test. Repeated daily administration of corticosterone (20mg/kg) for 21days decreased activity in a forced swim test, reduced body weight and decreased prefrontal cortex corticosterone concentration in both the LR and HR groups. These effects of corticosterone administration were stronger in the HR group in comparison with the appropriate control group, and compared to LR treated and LR control animals. Moreover, in the HR group, chronic corticosterone administration increased anxiety-like behavior in the open field and elevated plus maze tests. The behavioral effects in HR rats were accompanied by a decrease in alpha-2 subunit density in the medial prefrontal cortex (prelimbic cortex and frontal association cortex) and by an increase in the expression of alpha-2 subunits in the basolateral amygdala. These studies have shown that HR rats are more susceptible to anxiogenic and depressive effects of chronic corticosterone administration, which are associated with modification of GABA-A receptor function in the medial prefrontal cortex and basolateral amygdala. The current data may help to better understand the neurobiological mechanisms responsible for individual differences in changes in mood and emotions induced by repeated administration of high doses of glucocorticoids or by elevated levels of these hormones associated with chronic stress or affective pathology.

Genetic association of GABA-A receptor alpha-2 and mu opioid receptor with cocaine cue-reactivity: evidence for inhibitory synaptic neurotransmission involvement in cocaine dependence.

This pilot feasibility study examined the role of genetics in laboratory-induced cocaine craving. Thirty-four African American, cocaine-depend- ent male subjects underwent a baseline assessment, cue-exposure session, and genetic analysis. Subjects were classified as either cue-reactive or nonreactive. Among single nucleotide polymorphism markers in 13 candidate genes examined for association with cocaine cue-reactivity, two were statistically significant: GABRA2 (coding for GABA-A receptor alpha-2 subunit; rs11503014, nominal p= .001) and OPRM1 (coding for mu opioid receptor; rs2236256, nominal p= .03). These pilot results suggest that cocaine craving shows variability among cocaine-dependent subjects, and that GABRA2 and OPRM1 polymorphisms have differential influences on cocaine cue-reactivity, warranting studies in future research.