GABAA Research Articles

The effects of DBS to α5subunit of extrasynapse GABAA receptor in the kainic acid induced epilepsy rats

Objective To investigate the effects of deep brain stimulation (DBS) to α5 subunit of extrasynaptic GABAA receptor in the kainic acid induced epilepsy rats and to explore the better therapeutic targets and possible mechanism of DBS.Methods 24 male Sprague-Dawley rats were divided randomly into 3 groups:epileptic,the subthalamic nucleus of DBS and the hippocampus of DBS group.The expression of α5 subunit of extrasynaptic GABAA receptor as well as the association with the curative effects of DBS were evaluated by behavioristics,real time fluorogenic quantitative PCR and western blot.Results After the treatment,the seizures numbers of epilepsy in epileptic group 8.5 ± 0.9 were significantly higher than that in the subthalamic nucleus of DBS 2.5 ±0.9 and the hippocampus of DBS group 1.9 ±0.6 (P ＜0.01).the results of Real time PCR demonstrated that the expression of mRNA of α5 subunits in epileptic group 0.26 ± 0.04 were obviously lower than that in the subthalamic nucleus of DBS 0.62 ± 0.07 and the hippocampus of DBS 0.79 ± 0.05 groups (P ＜ 0.01),and the subthalamic nucleus of DBS was lower than that in the hippocampus of DBS groups (P ＜ 0.01).Westen blot demonstrated that the protein expression of α5 subunits in epileptic group 0.11 ± 0.03 were obviously lower than that in the subthalamic nucleus of DBS 0.36 ±0.05 and the hippocampus of DBS 0.44 ±0.04 groups (P ＜0.01),and the subthalamic nucleus of DBS was lower than that in the hippocampus of DBS groups(P ＜ 0.01).Conclusions DBS is effective in controlling epilepsy seizures,which might be related with the expression level of α5 subunits of extrasynaptic GABAAreceptor.The hippocampus as DBS's targetis more effective. Key words: Epilepsy; Deep brain stimulation ; Subthalamic nucleus ; Rats

GABAA Receptors Containing ρ1 Subunits Contribute to In Vivo Effects of Ethanol in Mice

GABAA receptors consisting of ρ1, ρ2, or ρ3 subunits in homo- or hetero-pentamers have been studied mainly in retina but are detected in many brain regions. Receptors formed from ρ1 are inhibited by low ethanol concentrations, and family-based association analyses have linked ρ subunit genes with alcohol dependence. We determined if genetic deletion of ρ1 in mice altered in vivo ethanol effects. Null mutant male mice showed reduced ethanol consumption and preference in a two-bottle choice test with no differences in preference for saccharin or quinine. Null mutant mice of both sexes demonstrated longer duration of ethanol-induced loss of righting reflex (LORR), and males were more sensitive to ethanol-induced motor sedation. In contrast, ρ1 null mice showed faster recovery from acute motor incoordination produced by ethanol. Null mutant females were less sensitive to ethanol-induced development of conditioned taste aversion. Measurement of mRNA levels in cerebellum showed that deletion of ρ1 did not change expression of ρ2, α2, or α6 GABAA receptor subunits. (S)-4-amino-cyclopent-1-enyl butylphosphinic acid (“ρ1” antagonist), when administered to wild type mice, mimicked the changes that ethanol induced in ρ1 null mice (LORR and rotarod tests), but the ρ1 antagonist did not produce these effects in ρ1 null mice. In contrast, (R)-4-amino-cyclopent-1-enyl butylphosphinic acid (“ρ2” antagonist) did not change ethanol actions in wild type but produced effects in mice lacking ρ1 that were opposite of the effects of deleting (or inhibiting) ρ1. These results suggest that ρ1 has a predominant role in two in vivo effects of ethanol, and a role for ρ2 may be revealed when ρ1 is deleted. We also found that ethanol produces similar inhibition of function of recombinant ρ1 and ρ2 receptors. These data indicate that ethanol action on GABAA receptors containing ρ1/ρ2 subunits may be important for specific effects of ethanol in vivo.

Effect of low-dose ketamine combined with propofol anesthesia on expression of GluR1 and GABAA R in hippocampus after electroconvulsive therapy in depressed rats

Objective To evaluate the effects of low-dose ketamine combined with propofol anesthesia on the expression of glutamate receptor 1 (GluR1) and γ-aminobutyric acid type A receptor (GABAA R) in hippocampus after electroconvulsive therapy (ECT) in depressed rats.Methods Fifty healthy adult male SpragueDawley rats,aged 2-3 months,weighing 200-250 g,were used in this study.The depressed model was induced by chronic unpredictable mild stress (CUMS).The mentally depressed rats were randomly divided into 5 groups (n =10 each):depression group (group D),ECT group,ketamine + ECT group (group KE),propofol + ECTgroup (group PE) and ketamine + propofol + ECT group (group KPE).Group ECT received ECT once a day for 7 consecutive days after intraperitoneal injection of normal saline 8 ml/kg.KE,PEK and KPE groups received ECT once a day for 7 consecutive days after intraperitoneal injection of ketamine 10 mg/kg,propofol 100 mg/kg,and ketamine 10 mg/kg + propofol 80 mg/kg,respectively.Sucrose fluid consumption was performed before CUMS,at 1 day after CUMS and at 1 day after ECT.The rats were sacrificed and hippocampi were removed for determination of the expression of GluR1 and GABAA R (by immuno-histochemistry).The GluR1/GABAA R ratio was calculated.Results Compared with group D,the sucrose consumption percentage was significantly increased at 1 day after ECT,the expression of GluR1 in hippocampal CA1 and CA3 regions was up-regulated,and the GluR1/GABAA Rratio was increased in the other four groups,and the expression of GABAA R in hippocampal CA1 and CA3 regions was down-regulated in ECT,PE and KPE groups (P ＜ 0.05).Compared with ECT group,the sucrose consumption percentage was significantly increased at 1 day after ECT,the expression of GABAA R and GluR1 in hippocampal CA1 and CA3 regions was up-regulated,and the GluR1/GABAA R ratio was increased in KPE group,the expression of GluR1 and GABAA R in hippocampal CA1 and CA3 regions was up-regulated in KE group,and the expression of GABAA R in hippocampal CA1 and CA3 regions was down-regulated in PE group (P ＜ 0.05).Compared with group PE,the sucrose consumption percentage was significantly increased at 1 day after ECT,the expression of GluR1 and GABAAR in hippocampal CA1 and CA3 regions was up-regulated,and the GluR1/GABAA R ratio was increased in KPE group (P ＜ 0.05).Conclusion The mechanism by which low-dose ketamine combined with propofol enhances the efficacy of ECT in depressed rats may be related to better regulation of the balance between hippocampal GluR1 and GABAA R. Key words: Depression; Ketamine ; Propofol ; Electroconvulsive therapy ; Receptors, AMPA ; Receptors, GABA-A; Hippocampus

AMPA and GABAA/B receptor subunit expression in the cuneate nucleus of adult squirrel monkeys during peripheral nerve regeneration

The primate somatosensory neuroaxis provides an excellent model system with which to investigate adult neural plasticity. Here, we report immunohistochemical staining data for AMPA and GABAA/B receptor subunits in the cuneate nucleus of adult squirrel monkeys 1 and 5 months after median nerve compression. This method of nerve injury allowed the investigation of the way in which patterns of receptor correlates change during peripheral nerve regeneration. These results are compared to cortical data collected within the same animals. As observed in the cortex, the pattern of subunit staining in the brainstem 1 month after nerve compression suggests that the sensory deprived nucleus enters a state of reorganization. That is, the expression of GluR2/3 AMPA receptor subunits is significantly increased, while GABA α1 and GABABR1b receptor subunits are significantly decreased. Five months after nerve injury, the pattern of subunit expression is again very similar to that observed in the infragranular layers of cortex. At this later time we observe a significant increase in GluR2/3 and GABABR1a, with no change in GABAAα1, and a significant decrease in GABABR1b. Together these results suggest that during reorganization and recovery from injury the brainstem and cortex are governed by homogeneous mechanisms of plasticity.

Age-related hearing loss: GABA, nicotinic acetylcholine and NMDA receptor expression changes in spiral ganglion neurons of the mouse

Age-related hearing loss – presbycusis – is the number one communication disorder and most prevalent neurodegenerative condition of our aged population. Although speech understanding in background noise is quite difficult for those with presbycusis, there are currently no biomedical treatments to prevent, delay or reverse this condition. A better understanding of the cochlear mechanisms underlying presbycusis will help lead to future treatments. Objectives of the present study were to investigate GABAA receptor subunit α1, nicotinic acetylcholine (nACh) receptor subunit β2, and N-methyl-d-aspartate (NMDA) receptor subunit NR1 mRNA and protein expression changes in spiral ganglion neurons (SGN) of the CBA/CaJ mouse cochlea, that occur in age-related hearing loss, utilizing quantitative immunohistochemistry and semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) techniques. We found that auditory brainstem response (ABR) thresholds shifted over 40dB from 3 to 48kHz in old mice compared to young adults. DPOAE thresholds also shifted over 40dB from 6 to 49kHz in old mice, and their amplitudes were significantly decreased or absent in the same frequency range. SGN density decreased with age in basal, middle and apical turns, and SGN density of the basal turn declined the most. A positive correlation was observed between SGN density and ABR wave 1amplitude. mRNA and protein expression of GABAAR α1 and AChR β2 decreased with age in SGNs in the old mouse cochlea. mRNA and protein expression of NMDAR NR1 increased with age in SGNs of the old mice. These findings demonstrate that there are functionally-relevant age-related changes of GABAAR, nAChR, NMDAR expression in CBA mouse SGNs reflecting their degeneration, which may be related to functional changes in cochlear synaptic transmission with age, suggesting biological mechanisms for peripheral age-related hearing loss.

Linking γ-aminobutyric acid A receptor to epidermal growth factor receptor pathways activation in human prostate cancer

Neuroendocrine (NE) differentiation has been attributed to the progression of castration-resistant prostate cancer (CRPC). Growth factor pathways including the epidermal growth factor receptor (EGFR) signaling have been implicated in the development of NE features and progression to a castration-resistant phenotype. However, upstream molecules that regulate the growth factor pathway remain largely unknown. Using androgen-insensitive bone metastasis PC-3 cells and androgen-sensitive lymph node metastasis LNCaP cells derived from human prostate cancer (PCa) patients, we demonstrated that γ-aminobutyric acid A receptor (GABAAR) ligand (GABA) and agonist (isoguvacine) stimulate cell proliferation, enhance EGF family members expression, and activate EGFR and a downstream signaling molecule, Src, in both PC-3 and LNCaP cells. Inclusion of a GABAAR antagonist, picrotoxin, or an EGFR tyrosine kinase inhibitor, Gefitinib (ZD1839 or Iressa), blocked isoguvacine and GABA-stimulated cell growth, trans-phospohorylation of EGFR, and tyrosyl phosphorylation of Src in both PCa cell lines. Spatial distributions of GABAAR α1 and phosphorylated Src (Tyr416) were studied in human prostate tissues by immunohistochemistry. In contrast to extremely low or absence of GABAAR α1-positive immunoreactivity in normal prostate epithelium, elevated GABAAR α1 immunoreactivity was detected in prostate carcinomatous glands. Similarly, immunoreactivity of phospho-Src (Tyr416) was specifically localized and limited to the nucleoli of all invasive prostate carcinoma cells, but negative in normal tissues. Strong GABAAR α1 immunoreactivity was spatially adjacent to the neoplastic glands where strong phospho-Src (Tyr416)-positive immunoreactivity was demonstrated, but not in adjacent to normal glands. These results suggest that the GABA signaling is linked to the EGFR pathway and may work through autocrine or paracine mechanism to promote CRPC progression.

Membrane potential differences and GABAA receptor expression in hepatic tumor and non-tumor stem cells

The ability to differentiate tumor initiating stem cells (TISCs) from healthy, normal stem cells (NSCs) could have important diagnostic and therapeutic implications for patients with hepatocellular carcinoma (HCC). The aim of this study was to document and compare cell membrane potentials (PDs) and GABAA receptor subunit expression in hepatic TISCs and NSCs. PD values were determined in CD133(+) Huh-7 TISCs and CD133(+) WBF344 NSCs by single channel microelectrode impalement. GABAA receptor subunit expression was documented using immunohistochemistry (IH) in both cell lines as well as surgically resected HCC and healthy liver tissues. TISCs were significantly depolarized compared with NSCs (-4.0 ± 1.8 versus -11.0 ± 2.4 mV, respectively; p < 0.05). GABAA α6 subunit expression was either absent or markedly attenuated, while γ3 subunit expression was abundant in TISCs and HCC compared with NSCs and healthy liver tissues. Exposure to the GABAA receptor agonist muscimol caused hyperpolarization of TISCs (Δ -4.4 ± 1.1) but depolarization of NSCs (Δ + 5.2 ± 2.3) and attenuation of TISC proliferative activity. We conclude that TISCs and NSCs have significantly different cell membrane potentials and these differences are associated with differences in GABAA receptor subunit expression.

Triple monoamine uptake inhibitors demonstrate a pharmacologic association between excessive drinking and impulsivity in high-alcohol-preferring (HAP) mice.

Approximately 30% of current drinkers in the United States drink excessively, and are referred to as problem/hazardous drinkers. These individuals, who may not meet criteria for alcohol abuse or dependence, comprise binge, heavy drinkers, or both. Given their high prevalence, interventions that reduce the risk of binge and heavy drinking have important public health implications. Impulsivity has been repeatedly associated with excessive drinking in the clinical literature. As impulsivity is correlated with, and may play a critical role in, the initiation and maintenance of excessive drinking, this behavior may be an important target for therapeutic intervention. Hence, a better understanding of pharmacological treatments capable of attenuating excessive drinking and impulsivity may markedly improve clinical outcomes. The high-alcohol-preferring (HAP) mice represent a strong rodent model to study the relationship between impulsivity and excessive alcohol drinking, as recent evidence indicates they consume high levels of alcohol throughout their active cycle and are innately impulsive. Using this model, the present study demonstrates that the triple monoamine uptake inhibitors (TUIs) amitifadine and DOV 102, 677 effectively attenuate binge drinking, heavy drinking assessed via a 24-hour free-choice assay, and impulsivity measured by the delay discounting procedure. In contrast, 3-PBC, a GABA-A α1 preferring ligand with mixed agonist-antagonist properties, attenuates excessive drinking without affecting impulsivity. These findings suggest that in HAP mice, monoamine pathways may predominate as a common mechanism underlying impulsivity and excessive drinking, while the GABAergic system may be more salient in regulating excessive drinking. We further propose that TUIs such as amitifadine and DOV 102, 677 may be used to treat the co-occurrence of impulsivity and excessive drinking.

Stiripentol exhibits higher anticonvulsant properties in the immature than in the mature rat brain

After the first positive experimental data in rodents in the early 1970s demonstrating the anticonvulsant effect of stiripentol (STP), in vitro studies showed that STP acts directly on γ-aminobutyric acid A (GABAA ) receptors. Chloride influx is higher when these receptors contain an α3 subunit, leading to the hypothesis that STP might exhibit higher efficacy in the immature brain. We explored this issue by studying the efficacy of STP in P21 and P75 rats using the pentylenetetrazol model of acute seizures or the lithium-pilocarpine status epilepticus model. P21 and adult rats received vehicle, 150, 250, or 350mg/kg of STP, i.p., 1h before evaluating the anticonvulsant. We also studied the blood and brain levels of STP as well as the expression and the messenger RNA (mRNA) levels of the α3 subunit of the GABAA receptors at both ages. STP exhibited anticonvulsant properties in both models at both ages, but STP was more effective in P21 than in P75 rats. This was shown by the significant suppression of seizure or status epilepticus occurrence in P21 with 350mg/kg STP, whereas the same dose had no significant effect at P75. The blood level, brain level, and blood/brain ratio of STP did not explain these differences between the two age groups. Moreover, the higher anticonvulsant properties in the immature brain were not explained by the mRNA level or protein expression of the GABAA α3 subunit at either age. Stiripentol exhibits higher anticonvulsant properties in the immature than in the mature brain. These findings require further investigation because it might lead to new clinical developments.

Altered GABAA Receptor Expression and Seizure Threshold Following Acute Ethanol Challenge in Mice Lacking the RIIβ Subunit of PKA

Ethanol causes pathological changes in GABAA receptor trafficking and function. These changes are mediated in part by ethanol activation of protein kinase A (PKA). The current study investigated the expression of the GABAA α1 and α4 subunits and the kinase anchoring protein AKAP150, as well as bicuculline-induced seizure threshold, at baseline and following acute injection of ethanol (3.5g/kg IP) in a mouse line lacking the regulatory RIIβ subunit of PKA. Whole cerebral cortices were harvested at baseline, 1h, or 46h following injection of ethanol or saline and subjected to fractionation and western blot analysis. Knockout (RIIβ-/-) mice had similar baseline levels of PKA RIIα and GABAA α1 and α4 subunits compared to wild type (RIIβ+/+) littermates, but had deficits in AKAP150. GABAA α1 subunit levels were decreased in the P2 fraction of RIIβ-/-, but not RIIβ+/+, mice following 1h ethanol, an effect that was driven by decreased α1 expression in the synaptic fraction. GABAA α4 subunits in the P2 fraction were not affected by 1h ethanol; however, synaptic α4 subunit expression was increased in RIIβ+/+, but not RIIβ-/- mice, while extrasynaptic α4and δ subunit expression were decreased in RIIβ-/-, but not RIIβ+/+ mice. Finally, RIIβ knockout was protective against bicuculline-induced seizure susceptibility. Overall, the results suggest that PKA has differential roles in regulating GABAA receptor subunits. PKA may protect against ethanol-induced deficits in synaptic α1 and extrasynaptic α4 receptors, but may facilitate the increase of synaptic α4 receptors.

The parvalbumin-positive interneurons in the mouse dentate gyrus express GABAA receptor subunits alpha1, beta2, and delta along their extrasynaptic cell membrane

Neuronal circuitries in the hippocampus are involved in navigation and memory and are controlled by major networks of GABAergic interneurons. Parvalbumin (PV)-expressing interneurons in the dentate gyrus (DG) are identified as fast-spiking cells, playing a crucial role in network oscillation and synchrony. The inhibitory modulation of these interneurons is thought to be mediated mainly through GABAA receptors, the major inhibitory neurotransmitter receptors in the brain. Here we show that all PV-positive interneurons in the granular/subgranular layer (GL/SGL) of the mouse DG express high levels of the GABAA receptor δ subunit. PV-containing interneurons in the hilus and the molecular layer, however, express the δ subunit to a lower extent. Only 8% of the somatostatin-containing interneurons express the δ subunit, whereas calbindin- or calretinin-containing interneurons in the DG seem not to express the GABAA receptor δ subunit at all. Hence, these cells receive a GABAergic control different from that of PV-containing interneurons in the GL/SGL. Experiments investigating a possible co-expression of GABAA receptor α1, α2, α3, α4, α5, β1, β2, β3, or γ2 subunits with PV and δ subunits indicated that α1 and β2 subunits are co-expressed with δ subunits along the extrasynaptic membranes of PV-interneurons. These results suggest a robust tonic GABAergic control of PV-containing interneurons in the GL/SGL of the DG via δ subunit-containing receptors. Our data are important for better understanding of the neuronal circuitries in the DG and the role of specific cell types under pathological conditions.

Developmental changes in expression of inhibitory neuronal proteins in the Fragile X Syndrome mouse basolateral amygdala

In humans, Fragile X Syndrome (FXS) is characterized by enhanced fear, hyperactivity, social anxiety, and, in a subset of individuals, autism. Many of the emotional and social deficits point to defects in the amygdala. We have previously shown defects in inhibitory neuron drive onto excitatory projection neurons in the basolateral amygdala (BLA) of juvenile Fmr1-/y knockout (KO) mice. Using pharmacological approaches, we have also previously revealed dynamic functional deficits in α1, α2, and α3 subunit-containing GABAA receptors (GABAARs α1, α2, and α3) during early postnatal development. In this study, we sought to determine whether these defects in GABAAR function are accompanied by changes in protein expression of GABAARs α1, α2, and α3 and the post-synaptic GABAAR-clustering protein gephyrin. Interestingly, we found that while the expression of these proteins did not significantly differ between wildtype (WT) and KO mice at each time point, the timing of developmental expression of GABAAR α1, α2, and gephyrin was altered. Collectively, these data reveal novel defects in inhibitory synapse protein expression during critical periods of early postnatal development that could contribute to observed inhibitory neurotransmission deficits in the KO mouse BLA.

Expression of GABAA α2-, β1- and ɛ-receptors are altered significantly in the lateral cerebellum of subjects with schizophrenia, major depression and bipolar disorder

There is abundant evidence that dysfunction of the γ-aminobutyric acid (GABA)ergic signaling system is implicated in the pathology of schizophrenia and mood disorders. Less is known about the alterations in protein expression of GABA receptor subunits in brains of subjects with schizophrenia and mood disorders. We have previously demonstrated reduced expression of GABAB receptor subunits 1 and 2 (GABBR1 and GABBR2) in the lateral cerebella of subjects with schizophrenia, bipolar disorder and major depressive disorder. In the current study, we have expanded these studies to examine the mRNA and protein expression of 12 GABAA subunit proteins (α1, α2, α3, α5, α6, β1, β2, β3, δ, ɛ, γ2 and γ3) in the lateral cerebella from the same set of subjects with schizophrenia (N=9–15), bipolar disorder (N=10–15) and major depression (N=12–15) versus healthy controls (N=10–15). We found significant group effects for protein levels of the α2-, β1- and ɛ-subunits across treatment groups. We also found a significant group effect for mRNA levels of the α1-subunit across treatment groups. New avenues for treatment, such as the use of neurosteroids to promote GABA modulation, could potentially ameliorate GABAergic dysfunction in these disorders.

α2 GABAA receptor sub-units in the ventral hippocampus and α5 GABAA receptor sub-units in the dorsal hippocampus mediate anxiety and fear memory

Temporary neuronal inactivation of the ventral hippocampus with the GABAA agonist muscimol suppresses unconditioned fear behavior (anxiety) but inactivation of the dorsal hippocampus does not. On the other hand, inactivating the dorsal hippocampus disrupts fear memory, while inactivating the ventral hippocampus does not. Here we investigate the roles of hippocampal GABAA receptor sub-units in mediating these anxiolytic and amnesic effects of GABAA receptor agonists. We microinfused TPA023 (α2 agonist) or TB-21007 (inverse α5 agonist) into the dorsal or ventral hippocampus prior to testing rats in two animal models of anxiety: the elevated plus-maze and shock-probe burying test. Twenty-four hours later rats were re-tested in the shock-probe chamber with a non-electrified probe to assess their memory of the initial shock-probe experience (i.e., fear memory). We found that TPA023 was anxiolytic in the plus-maze and shock-probe burying tests when microinfused into the ventral hippocampus. However, TPA023 did not affect anxiety-related behavior when infused into the dorsal hippocampus. Conversely, we found that the α5 sub-unit inverse agonist TB-21007 impaired rats’ memory of the initial shock-probe experience when infused into the dorsal hippocampus, but not when infused into the ventral hippocampus. This double dissociation suggests that α2 GABAA receptor sub-units in the ventral hippocampus mediate unconditioned fear or anxiety, while α5 GABAA receptor sub-units in the dorsal hippocampus mediate conditioned fear memory.

S25 * UNITY IN DIVERSITY APSAAR, LASBRA &amp; ESBRA JOINT SYMPOSIUM

S25 * UNITY IN DIVERSITY APSAAR, LASBRA &amp; ESBRA JOINT SYMPOSIUM

Expression variations of chromogranin A and α1,2,4 GABAARs in discrete limbic and brainstem areas rescue cardiovascular alterations

Recent interferences of hemodynamic functions via modified brain neuronal mechanisms have proven to be major causes of dementia and sleeping disorders. In this work, cerebral expression differences of the neuroactive vesicular chromogranin A (CgA) and distinct α GABAAR subunits were detected in the facultative hibernating hamster. In particular, damaged neuronal fields of hypotensive torpor (TORP) state were correlated to elevated CgA and GABAAR α1, α4 mRNA levels in the paraventricular hypothalamic nucleus (PVN), central amygdalar nucleus (CeA) plus solitary tractus nucleus (NTS). Conversely, few neurodegeneration signals of hypertensive arousal (AROU) state, accounted for mostly lower CgA levels in the same areas. This state also provided increased α2-containing sites in amygdala, hippocampal and NTS neurons together with elevated α4-containing receptors in the periventricular hypothalamic nucleus (Pe). Interestingly in our hibernating model, CgA appeared to preferentially feature inhibitory neurosignals as indicated by preliminary perfusion of amygdalar sites with its highly specific antihypertensive derived peptide (catestatin) promoting GABA-dependent sIPSCs. Overall, evident neuronal damages plus altered expression capacities of CgA and α1-, α2-, α4-GABAARs in CeA, Pe, PVN as well as NTS during both hibernating states corroborate for the first time key molecular switching events guaranteeing useful cardiovascular rescuing abilities of neurodegenerative disorders.

Benzodiazepine Augmented γ-Amino-Butyric Acid Signaling Increases Mortality From Pneumonia in Mice*

Benzodiazepines are used for treating anxiety, epilepsy, muscle spasm, alcohol withdrawal, palliation, insomnia, and sedation as they allosterically modulate γ-amino-butyric acid type A (GABAA) receptors. Despite widespread use, the importance and mechanism of their immune side-effects are poorly understood. Herein we sought to elucidate the impact and mechanism of benzodiazepine-induced susceptibility to infection at anxiolytic doses in mice. Animal randomized controlled trial. Laboratory. Adult female C57BL/6 and BALB/c mice. The effect of a subsedative, anxiolytic dose of diazepam (2 mg kg intraperitoneal) was investigated in a murine Streptococcus pneumoniae pneumonia model. Mortality, bacterial and cytokine load, cell recruitment, and intracellular pH were measured. Diazepam treatment did not affect immune homeostasis in the lung. However, diazepam increased mortality and bacterial load from S. pneumoniae pneumonia. The increases in mortality and bacterial load were reversed by a GABAA antagonist, bicuculline, indicating dependence on GABAA receptor signaling. While cell recruitment was unaltered by diazepam, the cytokine response to infection was affected, suggesting that local responses to the pathogen were perturbed. Macrophage and monocytes expressed benzodiazepine sensitive (α1-γ2) GABAA receptors. Interestingly macrophage GABAA receptor expression was regulated by bacterial toll-like receptor agonists and cytokines indicating an endogenous role in the immune response. Functionally diazepam appeared to counteract the endogenous down-regulation of GABAA signaling during infection. Consistent with augmented GABAA signaling, diazepam provoked intracellular acidosis in macrophage, leading to impaired cytokine production, bacterial phagocytosis and killing. In contrast, selective benzodiazepines that do not target the α1 GABAA subunit did not affect macrophage function ex vivo or increase susceptibility to pneumonia in vivo. Our data highlight the regulation of macrophage function by GABAA receptor signaling and the potential harm of benzodiazepine exposure during pneumonia. Therapeutically, selective drugs may improve the safety profile of benzodiazepines.

Regional mRNA expression of GABAergic receptor subunits in brains of C57BL/6J and 129P3/J mice: Strain and heroin effects

C57BL/6J and 129 substrains of mice are known to differ in their basal levels of anxiety and behavioral response to drugs of abuse. We have previously shown strain differences in heroin-induced conditioned place preference (CPP) between C57BL/6J (C57) and 129P3/J (129) mice, and in the regional expression of several receptor and peptide mRNAs. In this study, we examined the contribution of the GABAergic system in the cortex, nucleus accumbens (NAc), caudate putamen (CPu) and the region containing the substantia nigra and ventral tegmental area (SN/VTA) to heroin reward by measuring mRNA levels of 7 of the most commonly expressed GABA-A receptor subunits, and both GABA-B receptor subunits, in these same mice following saline (control) or heroin administration in a CPP design. Using real-time PCR, we studied the effects of strain and heroin administration on GABA-A α1, α2, α3, β2, and γ2 subunits, which typically constitute synaptic GABA-A receptors, GABA-A α4 and δ subunits, which typically constitute extrasynaptic GABA-A receptors, and GABA-B R1 and R2 subunits. In saline-treated animals, we found an experiment-wise significant strain difference in GABA-Aα2 mRNA expression in the SN/VTA. Point-wise significant strain differences were also observed in GABA-Aα2, GABA-Aα3, and GABA-Aα4 mRNA expression in the NAc, as well as GABA-BR2 mRNA expression in the NAc and CPu, and GABA-BR1 mRNA expression in the cortex. For all differences, 129 mice had higher mRNA expression compared to C57 animals, with the exception of GABA-BR1 mRNA in the cortex where we observed lower levels in 129 mice. Therefore, it may be possible that known behavioral differences between these two strains are, in part, due to differences in their GABAergic systems. While we did not find heroin dose-related changes in mRNA expression levels in C57 mice, we did observe dose-related differences in 129 mice. These results may relate to our earlier behavioral finding that 129 mice are hyporesponsive to the rewarding effects of heroin.

Insights into functional pharmacology of α1 GABAA receptors: how much does partial activation at the benzodiazepine site matter?

Synthesis of ligands inactive or with low activity at α₁ GABA(A) receptors has become the key concept for development of novel, more tolerable benzodiazepine (BZ)-like drugs. WYS8, a remarkably (105 times) α₁-subtype selective partial positive modulator, may serve as a pharmacological tool for refining the role of α₁ GABA(A) receptors in mediation of BZs' effects. Here, the effects of WYS8 on GABA-induced currents and on diazepam-induced potentiation of recombinant BZ-sensitive GABA(A) receptors were studied in more detail. In addition, the behavioral profile of WYS8 (0.2, 1, and 10 mg/kg i.p.), on its own and in combination with diazepam, was tested in the spontaneous locomotor activity, elevated plus maze, grip strength, rotarod, and pentylenetetrazole tests. WYS8, applied at an in vivo attainable concentration of 100 nM, reduced the stimulation of GABA currents by 1 μM diazepam by 57 % at α₁β₃γ₂, but not at α₂β₃γ₂, α₃β₃γ₂, or α₅β₃γ₂ GABA(A) receptors. The administration of WYS8 alone induced negligible behavioral consequences. When combined with diazepam, WYS8 caused a reduction in sedation, muscle relaxation, and anticonvulsant activity, as compared with this BZ alone, whereas ataxia was preserved, and the anxiolytic effect of 2 mg/kg diazepam was unmasked. Hence, a partial instead of full activation at α₁ GABA(A) receptors did not necessarily result in the attenuation of the effects assumed to be mediated by activation of these receptors, or in the full preservation of the effects mediated by activation of other GABA(A) receptors. Thus, the role of α₁ GABA(A) receptors appears more complex than that proposed by genetic studies.

A new target spot for the treatment of postoperative cognitive dysfunction：the GABA_A receptor related-drugs

Background Postoperative cognitive dysfunction （POCD） is one of the most common perioperative complications. The γ-aminobutyricacid type A （GABAA） receptor, which is a type of inhibitory receptor in central nervous system, may play an important role on the development of POCD. Objective To review the effects of GABAA receptor related-drugs on POCD. Content GABAA receptor agonist, GABAA receptor antagonist and GABA_A receptor inverse agonist, may have effects of induction, inversion or improvement on POCD, respectively. Trend The GABAA receptor related -drugs may provide a new attractive therapeutic option for POCD, and it maybe a highlight of future research. Key words: Postoperative cognitive dysfunction; γ-aminobutyricacid type A receptor; γ-aminobutyricacid type Areceptor antagonist; γ-aminobutyricacid type A receptor agonist