Types Of GABA Receptors Research Articles

Molecular cloning, functional characterization and differential expression of two novel GABAAR-like subunits from red swamp crayfish Procambarus clarkii.

In this work, we cloned and functionally expressed two novel GABAA receptor subunits from Procambarus clarkii crayfish. These two new subunits, PcGABAA-α and PcGABAA-β2, revealed significant sequence homology with the PcGABAA-β subunit, previously identified in our laboratory. In addition, PcGABAA-α subunit also shared a significant degree of identity with the Drosophila melanogaster genes DmGRD (GABA and glycine-like receptor subunits of Drosophila) as well as PcGABAA-β2 subunit with DmLCCH3 (ligand-gated chloride channel homolog 3). Electrophysiological recordings showed that the expression in HEK cells of the novel subunits, either alone or in combination, failed to form functional homo- or heteromeric receptors. However, the co-expression of PcGABAA-α with PcGABAA-β evoked sodium- or chloride-dependent currents that accurately reproduced the time course of the GABA-evoked currents in the X-organ neurons from crayfish, suggesting that these GABA subunits combine to form two types of GABA receptors, one with cationic selectivity filter and the other preferentially permeates anions. On the other hand, PcGABAA-β2 and PcGABAA-β co-expression generated a chloride current that does not show desensitization. Muscimol reproduced the time course of GABA-evoked currents in all functional receptors, and picrotoxin blocked these currents; bicuculline did not block any of the recorded currents. Reverse transcription polymerae chain reaction (RT-PCR) amplifications and FISH revealed that PcGABAA-α and PcGABAA-β2 are predominantly expressed in the crayfish nervous system. Altogether, these findings provide the first evidence of a neural GABA-gated cationic channel in the crayfish, increasing our understanding of the role of these new GABAA receptor subunits in native heteromeric receptors.

UNC-30/PITX coordinates neurotransmitter identity with postsynaptic GABA receptor clustering.

Terminal selectors are transcription factors that control neuronal identity by regulating expression of key effector molecules, such as neurotransmitter biosynthesis proteins and ion channels. Whether and how terminal selectors control neuronal connectivity is poorly understood. Here, we report that UNC-30 (PITX2/3), the terminal selector of GABA nerve cord motor neurons in Caenorhabditis elegans, is required for neurotransmitter receptor clustering, a hallmark of postsynaptic differentiation. Animals lacking unc-30 or madd-4B, the short isoform of the motor neuron-secreted synapse organizer madd-4 (punctin/ADAMTSL), display severe GABA receptor type A (GABAAR) clustering defects in postsynaptic muscle cells. Mechanistically, UNC-30 acts directly to induce and maintain transcription of madd-4B and GABA biosynthesis genes (e.g. unc-25/GAD, unc-47/VGAT). Hence, UNC-30 controls GABAA receptor clustering in postsynaptic muscle cells and GABA biosynthesis in presynaptic cells, transcriptionally coordinating two crucial processes for GABA neurotransmission. Further, we uncover multiple target genes and a dual role for UNC-30 as both an activator and a repressor of gene transcription. Our findings on UNC-30 function may contribute to our molecular understanding of human conditions, such as Axenfeld-Rieger syndrome, caused by PITX2 and PITX3 gene variants.

Sleep-Enhancing Effect of Water Extract from Jujube (Zizyphus jujuba Mill.) Seeds Fermented by Lactobacillus brevis L32.

Although Ziziphus jujuba Mill (jujube) is used in folk medicine for hypnotic sedative, anxiolytic, and many other purposes, to date, only a few studies have revealed its sleep-promoting effects and related mechanisms. Currently, drugs used for the treatment of sleep disorders have various side effects, so it is essential to develop safe natural materials. Therefore, we evaluated the sleep-enhancing activity and mechanism of action of an aqueous extract of jujube seeds (ZW) fermented with Lactobacillus brevis L-32 in rodent models. The starch contained in ZW was removed by enzymatic degradation and fermented with L. brevis to obtain a fermented product (ZW-FM) with a high γ-aminobutyric acid (GABA) content. To evaluate the sleep-promoting effect of ZW-FM, pentobarbital-induced sleep tests were performed on ICR mice, and electroencephalography analysis was undertaken in Sprague Dawley rats. Additionally, the awakening relief effects of ZW-FM were confirmed in a caffeine-induced insomnia model. Finally, the mechanism of sleep enhancement by ZW-FM was analyzed using GABA receptor type A (GABAA) antagonists. The ZW-FM-treated groups (100 and 150 mg/kg) showed increased sleep time, especially the δ-wave time during non-rapid eye movement (NREM) sleep. In addition, the 150 mg/kg ZW-FM treatment group showed decreased sleep latency and increased sleep time in the insomnia model. In particular, NREM sleep time was increased and REM sleep time, which was increased by caffeine treatment, was decreased by ZW-FM treatment. ZW-FM-induced sleep increase was inhibited by the GABAA receptor antagonists picrotoxin, bicuculline, and flumazenil, confirming that the increase was the result of a GABAergic mechanism. These results strongly suggest that the increased GABA in water extract from jujube seeds fermented by L. brevis acts as a sleep-promoting compound and that the sleep-promoting activity is related to GABAA receptor binding.

The Effect of the Agonist Cholecystokinin-4 D-GB-115 On the Character of Motor Activity of Paramecium caudatum.

The study investigated the effect of GABA in various concentrations and D-GB-115 at a concentration of 10-7 M on the behavior of Paramecium caudatum. It was shown that GABA increases motor activity and changes the movement strategy of these protozoans, and the dose-effect relationship is domed, which can be explained by the presence of two types of GABA receptors in the outer membrane of paramecia: GABA-A and GABA-B. The active concentrations of GABA range from 10-3 to 10-13 M. The effect of pharmacological agents interacting with the GABA system on the behavior of ciliates (nembutal and D-GB-115) was studied.

THE EFFECT OF THE AGONIST CHOLECYSTOKININ-4 D-GB-115 ON THE CHARACTER OF MOTOR ACTIVITY OF <i>PARAMECIUM CAUDATUM</i>

The study investigated the effect of GABA in various concentrations and D-GB-115 at a concentration of 10–10 mol/ml on the behavior of Paramecium caudatum. It has been shown that GABA increases motor activity and changes the movement strategy of these protozoa, and the dose-effect relationship is domed, which can be explained by the presence of two types of GABA receptors in the outer membrane of paramecia: GABA-A and GABA-B. The range of active concentrations of GABA ranges from 10–6 to 10–16 mol/ml. The effect of pharmacological agents interacting with the GABA system on the behavior of infusoria: nembutal and D-GB-115.

Neurophysiological Approaches for Temporal Sound Analysis in the Mouse Auditory Midbrain Neurons

The dynamics of the response patterns of the mouse auditory midbrain single neurons in the whole neuronal excitatory receptive field was studied by the extracellular recordings of the pulse activity of neurons. The obtained data showed that the V-shaped neurons demonstrated the highest stability of their responses among the whole population of ICC neurons. The discharges of both primary-like and inhibition-dominated neurons were more variable and their variations more likely followed the changes of the sound frequency and intensity. Changes of the discharge pattern of the vast majority of studied neurons occurred 1/3–1/2 octave away the neuronal CF in the direction of both the low-frequency and high-frequency borders of the neural FRA. The results of present study are discussed taking into account the available data about the formation of IC neurons response due the interaction of the excitatory and inhibitory processes mediated by the activation of different types of cellular glutamate and GABA receptors.

Glutamate and GABAA receptor crosstalk mediates homeostatic regulation of neuronal excitation in the mammalian brain

Maintaining a proper balance between the glutamate receptor-mediated neuronal excitation and the A type of GABA receptor (GABAAR) mediated inhibition is essential for brain functioning; and its imbalance contributes to the pathogenesis of many brain disorders including neurodegenerative diseases and mental illnesses. Here we identify a novel glutamate-GABAAR interaction mediated by a direct glutamate binding of the GABAAR. In HEK293 cells overexpressing recombinant GABAARs, glutamate and its analog ligands, while producing no current on their own, potentiate GABA-evoked currents. This potentiation is mediated by a direct binding at a novel glutamate binding pocket located at the α+/β− subunit interface of the GABAAR. Moreover, the potentiation does not require the presence of a γ subunit, and in fact, the presence of γ subunit significantly reduces the potency of the glutamate potentiation. In addition, the glutamate-mediated allosteric potentiation occurs on native GABAARs in rat neurons maintained in culture, as evidenced by the potentiation of GABAAR-mediated inhibitory postsynaptic currents and tonic currents. Most importantly, we found that genetic impairment of this glutamate potentiation in knock-in mice resulted in phenotypes of increased neuronal excitability, including decreased thresholds to noxious stimuli and increased seizure susceptibility. These results demonstrate a novel cross-talk between excitatory transmitter glutamate and inhibitory GABAAR. Such a rapid and short feedback loop between the two principal excitatory and inhibitory neurotransmission systems may play a critical homeostatic role in fine-tuning the excitation-inhibition balance (E/I balance), thereby maintaining neuronal excitability in the mammalian brain under both physiological and pathological conditions.

Positive allosteric modulators of GABAA receptor restore chloride current from blockade by competitive antagonists in a ligand-dependent manner

γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter. GABA receptor type A (GABAAR) possesses binding sites for a large group of pharmacological agents which are supposed to interact allosterically with each other. The aim of this work was to study the interaction between the positive allosteric modulators (PAMs) and the competitive antagonists of GABAARs. The GABA-induced chloride current (IGABA) was measured in isolated Purkinje cells of rat cerebellum using the patch-clamp technique. PAMs, neurosteroid allopregnanolone (Allo) and zolpidem (Zolp), a drug that positively modulates the GABAAR through interaction with the benzodiazepine (BDZ) site, doubled the IGABA amplitude in the control solution. Competitive antagonist of GABAARs, bicuculline (Bic, 5 µM) blocked the IGABA by 90%. The addition of 1 μM Allo or 0.5 µM Zolp to the Bic solution caused an unblocking effect, so that the IGABA amplitude increased 10 and 4 times from control value, correspondingly. This unblocking effect developed slowly, as evidenced by a threefold increase in the current rise time. Competitive antagonist of GABAARs, gabazine (GBZ, 0.5 µM) blocked the IGABA by 87%. The addition of 1 μM Allo to the GBZ solution caused an unblocking effect, so that the IGABA amplitude increased 7-fold. However, the addition of 0.5 µM Zolp to the GBZ solution did not cause an unblocking effect. So, Allo appeared to have a stronger unblocking potential than Zolp, and Bic binding site showed a higher sensitivity to the action of unblocking PAMs than GBZ binding site. The results indicate for the first time the existence of an allosteric relationship between the sites binding PAMs and the competitive antagonists of GABAAR.

An Association Study of Gamma-Aminobutyric Acid Type A Receptor Variants and Susceptibility to Autism Spectrum Disorders.

In this pilot study, we aim to identify the role of few genetic variants of GABA-receptor type A subunits GABRB3 (rs4906902, rs7171660), GABRG3 (rs208129, rs140679), GABRA5 (rs 140681) in the aetiology of autism spectrum disorders in a population of West Bengal. 192 ASD probands, their parents and 184 ethnically-matched healthy controls were recruited for the study. The rs4906902G and the rs140679T conferred significant risk towards ASD. rs7171660 and rs140679 had transmission bias in the family. Neither alleles of rs 208129 and rs 140681 showed significant over-representation in either groups. All these variants were associated with at least one deficit in ASD-associated phenotypes like 'relating to people', 'Imitation', 'emotional response', 'body use', 'taste, smell, touch response' and 'activity levels'.

GABA signaling affects motor function in the honey bee

GABA is the most common inhibitory neurotransmitter in both vertebrate and invertebrate nervous systems. In insects, inhibition plays important roles at the neuromuscular junction, in the regulation of central pattern generators, and in the modulation of information in higher brain processing centers. Additionally, increasing our understanding of the functions of GABA is important since GABAA receptors are the targets of several classes of pesticides. To investigate the role of GABA in motor function, honey bee foragers were injected with GABA or with agonists or antagonists specific for either GABAA or GABAB receptors. Compounds that activated either type of GABA receptor decreased activity levels. Bees injected with the GABAA receptor antagonist picrotoxin lost the ability to right themselves, whereas blockade of GABAB receptors led to increases in grooming. Injection with antagonists of either GABAA or GABAB receptors resulted in an increase in extended wing behavior, during which bees kept their wings out at right angles to their body rather than folded along their back. These data suggest that the GABA receptor types play distinct roles in behavior and that GABA may affect behavior at several different levels.

GABAergic Inhibition Gates Perceptual Awareness During Binocular Rivalry.

Binocular rivalry is a classic experimental tool to probe the neural machinery of perceptual awareness. During rivalry, perception alternates between the two eyes, and the ebb and flow of perception is modeled to rely on the strength of inhibitory interactions between competitive neuronal populations in visual cortex. As a result, rivalry has been suggested as a noninvasive perceptual marker of inhibitory signaling in visual cortex, and its putative disturbance in psychiatric conditions, including autism. Yet, direct evidence causally implicating inhibitory signaling in the dynamics of binocular rivalry is currently lacking. We previously found that people with higher GABA levels in visual cortex, measured using magnetic resonance spectroscopy, have stronger perceptual suppression during rivalry. Here, we present direct causal tests of the impact of GABAergic inhibition on rivalry dynamics, and the contribution of specific GABA receptors to these dynamics. In a crossover pharmacological design with male and female adult participants, we found that drugs that modulate the two dominant GABA receptor types in the brain, GABAA (clobazam) and GABAB (arbaclofen), increase perceptual suppression during rivalry relative to a placebo. Crucially, these results could not be explained by changes in reaction times or response criteria, as determined through rivalry simulation trials, suggesting a direct and specific influence of GABA on perceptual suppression. A full replication study of the GABAB modulator reinforces these findings. These results provide causal evidence for a link between the strength of inhibition in the brain and perceptual suppression during rivalry and have implications for psychiatric conditions including autism.SIGNIFICANCE STATEMENT How does the brain accomplish perceptual gating? Here we use a direct and causal pharmacological manipulation to present insight into the neural machinery of a classic illusion of perceptual awareness: binocular rivalry. We show that drugs that increase GABAergic inhibition in the brain, clobazam (GABAA modulator) and arbaclofen (GABAB modulator), increase perceptual suppression during rivalry relative to a placebo. These results present the first causal link between GABAergic inhibition and binocular rivalry in humans, complementing classic models of binocular rivalry, and have implications for our understanding of psychiatric conditions, such as autism, where binocular rivalry is posited as a behavioral marker of disruptions in inhibitory signaling in the brain.

GABA receptors differentially regulate life span and health span in C. elegans through distinct downstream mechanisms.

GABA, a prominent inhibitory neurotransmitter, is best known to regulate neuronal functions in the nervous system. However, much less is known about the role of GABA signaling in other physiological processes. Interestingly, recent work showed that GABA signaling can regulate life span via a metabotropic GABAB receptor in Caenorhabditis elegans. However, the role of other types of GABA receptors in life span has not been clearly defined. It is also unclear whether GABA signaling regulates health span. Here, using C. elegans as a model, we systematically interrogated the role of various GABA receptors in both life span and health span. We find that mutations in four different GABA receptors extend health span by promoting resistance to stress and pathogen infection and that two such receptor mutants also show extended life span. Different GABA receptors engage distinct transcriptional factors to regulate life span and health span, and even the same receptor regulates life span and health span via different transcription factors. Our results uncover a novel, profound role of GABA signaling in aging in C. elegans, which is mediated by different GABA receptors coupled to distinct downstream effectors.

Efficient synthesis of the GABAA receptor agonist trans-4-aminocrotonic acid (TACA)

Investigations into the pharmacology of different types of cys-loop GABA receptor have relied for years on the chemical modification of GABA-like compounds. The GABA metabolite GABOB is an attractive molecule to modify due to its convenient chemical structure. In the process of developing new GABA-mimic compounds from GABOB as a starting compound three small molecule GABA derivatives were synthesized using a variety of chemical transformations. Amongst these, a new and reliable method to synthesize TACA (trans-4-aminocrotonic acid) is reported.

Formation of GABAergic Neural Networks in the Bötzinger Complex in Rats in the Early Postnatal Period in Normal Conditions and with Prenatal Deficiency of Endogenous Serotonin

The dynamics of the distribution of GABAergic neurons and neurons expressing different types of GABA receptors (GABA-Aα1 and GABA-B1) in the Botzinger complex during the early postnatal period (the period of functional maturation of the receptor system in mammals) were studied in normal conditions and after prenatal reductions in serotonin content in Wistar rats. Brains from rat pups of two groups were studied on days 5, 9, and 20 after birth: controls (n = 9), born to intact females, and experimental (n = 13), born to mothers treated with parachlorophenylalanine during pregnancy to decrease endogenous serotonin content. GABA-synthesizing neurons and neurons expressing GABA-Aα1 and GABA-B1 receptors were detected immunocytochemically. Maturation of the inhibitory GABAergic network in the Botzinger complex occurred during the early postnatal period (by day 9). GABA production occurred simultaneously with GABA-Aα1 and GABA-B1 expression, though their maturation differed. GABA-Aα1 receptors formed earlier (by day 9) and coincided in time with GABA expression. Maturation of GABA-B1 receptors occurred later – only by week 3. Prenatal serotonin deficit led to a delay in the expression of GABA and GABA-Aα1 receptors in neurons of this nucleus and produced impairment to the formation of a network of terminals and synapses containing GABA and GABA-Aα1 and GABA-B1 receptors.

K-Cl Cotransporter 2-mediated Cl- Extrusion Determines Developmental Stage-dependent Impact of Propofol Anesthesia on Dendritic Spines.

General anesthetics potentiating γ-aminobutyric acid (GABA)-mediated signaling are known to induce a persistent decrement in excitatory synapse number in the cerebral cortex when applied during early postnatal development, while an opposite action is produced at later stages. Here, the authors test the hypothesis that the effect of general anesthetics on synaptogenesis depends upon the efficacy of GABA receptor type A (GABAA)-mediated inhibition controlled by the developmental up-regulation of the potassium-chloride (K-Cl) cotransporter 2 (KCC2). In utero electroporation of KCC2 was used to prematurely increase the efficacy of (GABAA)-mediated inhibition in layer 2/3 pyramidal neurons in the immature rat somatosensory cortex. Parallel experiments with expression of the inward-rectifier potassium channel Kir2.1 were done to reduce intrinsic neuronal excitability. The effects of these genetic manipulations (n = 3 to 4 animals per experimental group) were evaluated using iontophoretic injection of Lucifer Yellow (n = 8 to 12 cells per animal). The total number of spines analyzed per group ranged between 907 and 3,371. The authors found a robust effect of the developmental up-regulation of KCC2-mediated Cl transport on the age-dependent action of propofol on dendritic spines. Premature expression of KCC2, unlike expression of a transport-inactive KCC2 variant, prevented a propofol-induced decrease in spine density. In line with a reduction in neuronal excitability, the above result was qualitatively replicated by overexpression of Kir2.1. The KCC2-dependent developmental increase in the efficacy of GABAA-mediated inhibition is a major determinant of the age-dependent actions of propofol on dendritic spinogenesis.

A new approach to understanding structure, functions and classificasion of GABA-benzodiazepine receptor complex, a molecular target for creation of new anticonvulsants on the base of inhibitory amino acids

The GABA molecule was shown to the methods of quantum mechanic characteristics and molecular geometry has three conformational states: linear (GABA-1 conformer), cyclic (GABA-2 comformer) and bucket-like (GABA-3 conformer). The play different functions in the brain neurons: cyclic and bucket-like conformers play role of endogenous transmitters, and linear conformer participates in neuronal metabolism. The theoretical conformational analysis shows there are two types of GABA receptors in the CNS neurons: GABA-2 receptors, agonists of which are cyclic conformer of GABA, glycine and β-alanine and antagonists are bemegride, pentilentetrazol and strychnine; and GABA-3 receptors, agonists of which is bucket-like conformer of GABA and antagonists are picrotoxin and bicuculline. Anticonvulsive and other behavioral effects of derivatives of barbituric acid, benzazepine, benzodiazepine, gidantoine, succinimide and oxasolidindione are realized probably via GABA-2 receptors to switch on them the following functional centers of their structure are nessesary: α, γ and [δ-ε] for barbitirates; β, [δ-ε] and γ for carbamazepine; β and [δ-ε] for benzodiazepine derivatives, gabapentine and vigabatrine; α, β, γ and [δ-ε] for gidantoine and oxasolidindione derivatives; α, β, γ for succinimide derivatives. The power of any behavioral effect of anticonvulsants and inhibitory amino acids depends on power, location and numbers of hydrogen bounds developed between active centers of pharmacophore of anticonvulsant or inhibitory amino acids and active centers of functional skeleton of GABA-2 receptor complex, these properties determine absense of nootropic activity in anticonvulsive drugs and presense of them in inhibitory amino acids. It is concluded there are perspectives of synthesis of conpounds, pharmacophore of which should be like as cyclic conformer of GABA, glycine and β-alanine on their quantum mechanic characteristics and molecular geometry

FORMATION OF GABA-ERGIC NEURAL NETWORK IN BÖTZINGER COMPLEX IN RATS DURING EARLY POSTNATAL PERIOD IN NORM AND IN PRENATAL DEFICIENCY OF ENDOGENOUS SEROTONIN

The dynamics of the distribution of GABAergic neurons and neurons expressing different types of GABA receptors (GABAAα1 and GABAB1) was studied in Bötzingercomplex (BötC) in the early postnatal period (the period of functional maturation of the respiratory system in mammals) in norm and prenatal reduction of serotonin content in Wistar rats. The brain was studied on postnatal Days 5, 9 and 20 in two groups of rat pups: control (n=9), born by intact females, and experimental (n=13), born from mothers that received parachlorophenylalanine, causing the depression of endogenous serotonin level. Imunocytochemical methods were used to detect the neurons producing GABA and expressing GABA and GABA Aα1B1 receptors. It was shown that the maturation of the inhibitory GABAergic network in BötC occurred in the early postnatal period (by Day 9). Simultaneously with GABA, the expression of GABA and GABA Aα1B1 receptors took place, however their maturation has the distinctive features. The formation of GABAAα1 receptors occurred earlier (by Day 9) and coincided in time with the expression of GABA. The maturation of GABAB1 receptors happened later - only by the third week. Prenatal serotonin deficiency caused a delay in the expression of GABA and GABAAα1 receptors by the neurons of BötC, as well as the disruption of the formation of a network of terminals and synapses containing GABA, GABAAα1 and GABAB1 receptors.

Presynaptic GABA Receptors Mediate Temporal Contrast Enhancement in Drosophila Olfactory Sensory Neurons and Modulate Odor-Driven Behavioral Kinetics.

Contrast enhancement mediated by lateral inhibition within the nervous system enhances the detection of salient features of visual and auditory stimuli, such as spatial and temporal edges. However, it remains unclear how mechanisms for temporal contrast enhancement in the olfactory system can enhance the detection of odor plume edges during navigation. To address this question, we delivered to Drosophila melanogaster flies pulses of high odor intensity that induce sustained peripheral responses in olfactory sensory neurons (OSNs). We use optical electrophysiology to directly measure electrical responses in presynaptic terminals and demonstrate that sustained peripheral responses are temporally sharpened by the combined activity of two types of inhibitory GABA receptors to generate contrast-enhanced voltage responses in central OSN axon terminals. Furthermore, we show how these GABA receptors modulate the time course of innate behavioral responses after odor pulse termination, demonstrating an important role for temporal contrast enhancement in odor-guided navigation.

The interactive role of CB(1) and GABA(B) receptors in hippocampal synaptic plasticity in rats.

Long-term potentiation (LTP) of synaptic transmission is a cellular process underlying learning and memory. Cannabinoids are known to be powerful modulators of this kind of synaptic plasticity. Changes in GABAergic inhibition have also been shown to affect synaptic plasticity in the hippocampus. GABA receptor type B (GABAB) and cannabinoid receptor type 1 (CB1) exhibit overlapping anatomical localization in some brain areas including the hippocampus. CB1 and GABAB are also localized to the same cells and share a common signaling pathway in some brain areas. In this study, we examined the hippocampal effects of co-administrating AM251 and CGP55845, which are CB1 and GABAB antagonists, respectively, on LTP induction in the dentate gyrus (DG) of rats. LTP in the hippocampal area was induced by high-frequency stimulation (HFS) of the perforant path. Our results showed that HFS coupled with administration of the CB1 antagonist increased both the population spike (PS) amplitude and field excitatory post-synaptic potential (fEPSP). Conversely, the GABAB antagonist decreased these parameters along with decreased LTP induction. We also demonstrated that the co-administration of CB1 and GABAB antagonists had different effects on the PS amplitude and fEPSP slope. It is likely that GABAB receptor antagonists modulate cannabinoid outputs that cause a decrease in synaptic plastisity, while in the simultaneous consumption of two antagonists, CB1 antagonists can alter the release of GABA which in turn results in enhancement of LTP induction. These findings suggest that there are functional interactions between the CB1 and GABAB receptor in the hippocampus.

Silencing the α2 subunit of γ-aminobutyric acid type A receptors in rat dorsal root ganglia reveals its major role in antinociception posttraumatic nerve injury.

Neuropathic pain (NPP) is likely the result of repetitive high-frequency bursts of peripheral afferent activity leading to long-lasting changes in synaptic plasticity in the spinal dorsal horn. Drugs that promote γ-aminobutyric acid (GABA) activity in the dorsal horn provide partial relief of neuropathic symptoms. The authors examined how in vivo silencing of the GABA receptor type A (GABAA) α2 gene in dorsal root ganglia (DRG) controls NPP. After crush injury to the right sciatic nerve of female rats, the α2 GABAA antisense and mismatch oligodeoxynucleotides or NO-711 (a GABA uptake inhibitor) were applied to the L5 DRG. In vivo behavioral assessment of nociception was conducted before the injury and ensuing 10 days (n = 4 to 10). In vitro quantification of α2 GABAA protein and electrophysiological studies of GABAA currents were performed on acutely dissociated L5 DRG neurons at relevant time points (n = 6 to 14). NPP postcrush injury of a sciatic nerve in adult female rats coincides with significant down-regulation of the α2 subunit expression in the ipsilateral DRG (approximately 30%). Selective down-regulation of α2 expression in DRGs significantly worsens mechanical (2.55 ± 0.75 to 5.16 ± 1.16) and thermal (7.97 ± 0.96 to 5.51 ± 0.75) hypersensitivity in crush-injured animals and causes development of significant mechanical (2.33 ± 0.40 to 5.00 ± 0.33) and thermal (10.80 ± 0.29 to 7.34 ± 0.81) hypersensitivity in sham animals (data shown as mean ± SD). Conversely, up-regulation of endogenous GABA via blockade of its uptake in DRG alleviates NPP. The GABAA receptor in the DRG plays an important role in pathophysiology of NPP caused by sciatic nerve injury and represents promising target for novel pain therapies.