scholarly journals Tonic Extrasynaptic GABAA Receptor Currents Control Gonadotropin-Releasing Hormone Neuron Excitability in the Mouse

Endocrinology ◽  
2011 ◽  
Vol 152 (4) ◽  
pp. 1551-1561 ◽  
Author(s):  
Janardhan P. Bhattarai ◽  
Seon Ah Park ◽  
Jin Bong Park ◽  
So Yeong Lee ◽  
Allan E. Herbison ◽  
...  
Keyword(s):  
Gabaa Receptor ◽  
Gabaa Receptors ◽  
Brain Slice ◽  
Resting Membrane Potential ◽  
Receptor Signaling ◽  
Gaba Transporter ◽  
Gnrh Neurons ◽  
Inward Currents ◽  
Synaptic Receptors ◽  
Tonic Current

Abstract It is well established that the GABAA receptor plays an important role in regulating the electrical excitability of GnRH neurons. Two different modes of GABAA receptor signaling exist: one mediated by synaptic receptors generating fast (phasic) postsynaptic currents and the other mediated by extrasynaptic receptors generating a persistent (tonic) current. Using GABAA receptor antagonists picrotoxin, bicuculline methiodide, and gabazine, which differentiate between phasic and tonic signaling, we found that ∼50% of GnRH neurons exhibit an approximately 15-pA tonic GABAA receptor current in the acute brain slice preparation. The blockade of either neuronal (NO711) or glial (SNAP-5114) GABA transporter activity within the brain slice revealed the presence of tonic GABA signaling in ∼90% of GnRH neurons. The GABAA receptor δ subunit is only found in extrasynaptic GABAA receptors. Using single-cell RT-PCR, GABAA receptor δ subunit mRNA was identified in GnRH neurons and the δ subunit–specific agonist 4,5,6,7-tetrahydroisoxazolo [5,4-c] pyridin-3-ol was found to activate inward currents in GnRH neurons. Perforated-patch clamp studies showed that 4,5,6,7-tetrahydroisoxazolo [5,4-c] pyridin-3-ol exerted the same depolarizing or hyperpolarizing effects as GABA on juvenile and adult GnRH neurons and that tonic GABAA receptor signaling regulates resting membrane potential. Together, these studies reveal the presence of a tonic GABAA receptor current in GnRH neurons that controls their excitability. The level of tonic current is dependent, in part, on neuronal and glial GABA transporter activity and mediated by extrasynaptic δ subunit–containing GABAA receptors.

Allosteric modulation of GABAA receptors in acutely dissociated neurons of the suprachiasmatic nucleus

1996 ◽  
Vol 270 (6) ◽  
pp. C1726-C1734 ◽  
Author(s):  
M. Shimura ◽  
N. Harata ◽  
M. Tamai ◽  
N. Akaike
Keyword(s):  
Gabaa Receptor ◽  
Suprachiasmatic Nucleus ◽  
Gabaa Receptors ◽  
Response Curve ◽  
Equilibrium Potential ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Gabaa Receptor Antagonist ◽  
Inward Currents ◽  
Concentration Response Curve

The gamma-aminobutyric acid (GABA)-induced response was investigated in acutely dissociated suprachiasmatic nucleus (SCN) neurons of 11- to 14-day-old rats, under the voltage-clamp condition of nystatin-perforated patch recording. At a holding potential of -40 mV, application of GABA induced inward currents in a concentration-dependent manner. Pentobarbital and 5 beta-pregnan-3 alpha-ol-20-one (pregnanolone) similarly induced inward currents. GABA-induced inward currents were suppressed in a concentration-dependent manner by pretreating neurons with a GABAA receptor antagonist, bicuculline. Bicuculline (3 x 10(-6) M) shifted the concentration-response curve of GABA to the left in a competitive manner. Reversal potential of the GABA response (EGABA) was -3.4 +/- 0.7 mV, close to the theoretical Cl- equilibrium potential of -4.1 mV. Pretreating SCN neurons with diazepam, pentobarbital, and pregnanolone enhanced the 3 x 10(-6) M GABA response. Diazepam (3 x 10(-8) M), pentobarbital (3 x 10(-5) M), and pregnanolone (10(-7) M) shifted the concentration-response curve of GABA to the left without changing the maximal amplitude of GABA responses. EGABA in the presence of diazepam, pentobarbital, or pregnanolone was the same as that in their absence. These results show that the GABA response in acutely dissociated SCN neurons is mediated by the GABAA receptor. Because the GABAA receptor of SCN neurons is allosterically augmented by diazepam, pentobarbital, and pregnanolone, similarly as in other regions of the central nervous system, the present study opens up ways to functionally modulate the GABAA receptors in SCN.

In vitro and in vivo GABAA Receptor Interaction of the Propanidid Metabolite 4-(2-[Diethylamino]-2-Oxoethoxy)-3-Methoxy-Benzeneacetic Acid

Pharmacology ◽  
2018 ◽  
Vol 103 (1-2) ◽  
pp. 10-16 ◽  
Author(s):  
Alessia Cenani ◽  
Robert J. Brosnan ◽  
Heather K. Knych
Keyword(s):  
Gabaa Receptor ◽  
Gabaa Receptors ◽  
Water Solubility ◽  
Plasma Concentrations ◽  
Receptor Activation ◽  
Receptor Interaction ◽  
Dependent Manner ◽  
Benzeneacetic Acid

Background: Propanidid is a γ-aminobutyric acid type A (GABAA) receptor agonist general anesthetic and its primary metabolite is 4-(2-[diethylamino]-2-oxoethoxy)-3-methoxy-benzeneacetic acid (DOMBA). Despite having a high water solubility at physiologic pH that might predict low-affinity GABAA receptor interactions, DOMBA is reported to have no effect on GABAA receptor currents, possibly because the DOMBA concentrations studied were simply insufficient to modulate GABAA receptors. Our objectives were to measure the propanidid and DOMBA concentration responses on ­GABAA receptors and to measure the behavioral responses of DOMBA in mice at concentrations that affect GABAA receptor currents in vitro. Methods: GABAA receptors were expressed in oocytes using clones for the human GABAA α1, β2 and γ2s subunits. The effects of DOMBA (0.2–10 mmol/L) and propanidid (0.001–1 mmol/L) on oocyte GABAA currents were studied using standard 2-electrode voltage clamp techniques. Based on in vitro results, 6 mice received ­DOMBA 32 mg intraperitoneal and were observed for occurrence of neurologic effects and DOMBA plasma concentration was measured by liquid chromatography tandem mass spectrometry. Results: DOMBA both directly activates GABAA receptors and antagonizes its GABA-mediated opening in a concentration-dependent manner at concentrations between 5–10 and 0.5–10 mmol/L respectively. In vivo, DOMBA produced rapid onset sedation at plasma concentrations that correlate with direct GABAA receptor activation. Conclusion: DOMBA modulation of GABAA receptors is associated with sedation in mice. Metabolites of propanidid analogues currently in development may similarly modulate GABAA, and impaired elimination of these metabolites could produce clinically relevant neurophysiologic effects.

Role of HERG-like K+ currents in opossum esophageal circular smooth muscle

1999 ◽  
Vol 277 (6) ◽  
pp. C1284-C1290 ◽  
Author(s):  
Hamid I. Akbarali ◽  
Hemant Thatte ◽  
Xue Dao He ◽  
Wayne R. Giles ◽  
Raj K. Goyal
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Smooth Muscle Cells ◽  
Single Cells ◽  
Circular Muscle ◽  
Muscle Cells ◽  
Resting Membrane Potential ◽  
Channel Blockers ◽  
Circular Smooth Muscle ◽  
Inward Currents

An inwardly rectifying K+ conductance closely resembling the human ether-a-go-go-related gene (HERG) current was identified in single smooth muscle cells of opossum esophageal circular muscle. When cells were voltage clamped at 0 mV, in isotonic K+ solution (140 mM), step hyperpolarizations to −120 mV in 10-mV increments resulted in large inward currents that activated rapidly and then declined slowly (inactivated) during the test pulse in a time- and voltage- dependent fashion. The HERG K+ channel blockers E-4031 (1 μM), cisapride (1 μM), and La3+ (100 μM) strongly inhibited these currents as did millimolar concentrations of Ba2+. Immunoflourescence staining with anti-HERG antibody in single cells resulted in punctate staining at the sarcolemma. At membrane potentials near the resting membrane potential (−50 to −70 mV), this K+ conductance did not inactivate completely. In conventional microelectrode recordings, both E-4031 and cisapride depolarized tissue strips by 10 mV and also induced phasic contractions. In combination, these results provide direct experimental evidence for expression of HERG-like K+ currents in gastrointestinal smooth muscle cells and suggest that HERG plays an important role in modulating the resting membrane potential.

scholarly journals GABA transporters regulate tonic and synaptic GABAA receptor-mediated currents in the suprachiasmatic nucleus neurons

2017 ◽  
Vol 118 (6) ◽  
pp. 3092-3106 ◽  
Author(s):  
Michael Moldavan ◽  
Olga Cravetchi ◽  
Charles N. Allen
Keyword(s):  
Circadian Clock ◽  
Suprachiasmatic Nucleus ◽  
Dependent Manner ◽  
Circadian Period ◽  
Gaba Concentration ◽  
Gaba Transporter ◽  
Concentration Dependent Manner ◽  
Gaba Transport ◽  
Gaba Transporters ◽  
Tonic Current

GABA is a principal neurotransmitter in the hypothalamic suprachiasmatic nucleus (SCN) that contributes to intercellular communication between individual circadian oscillators within the SCN network and the stability and precision of the circadian rhythms. GABA transporters (GAT) regulate the extracellular GABA concentration and modulate GABAA receptor (GABAAR)-mediated currents. GABA transport inhibitors were applied to study how GABAAR-mediated currents depend on the expression and function of GAT. Nipecotic acid inhibits GABA transport and induced an inward tonic current in concentration-dependent manner during whole cell patch-clamp recordings from SCN neurons. Application of either the selective GABA transporter 1 (GAT1) inhibitors NNC-711 or SKF-89976A, or the GABA transporter 3 (GAT3) inhibitor SNAP-5114, produced only small changes of the baseline current. Coapplication of GAT1 and GAT3 inhibitors induced a significant GABAAR-mediated tonic current that was blocked by gabazine. GAT inhibitors decreased the amplitude and decay time constant and increased the rise time of spontaneous GABAAR-mediated postsynaptic currents. However, inhibition of GAT did not alter the expression of either GAT1 or GAT3 in the hypothalamus. Thus GAT1 and GAT3 functionally complement each other to regulate the extracellular GABA concentration and GABAAR-mediated synaptic and tonic currents in the SCN. Coapplication of SKF-89976A and SNAP-5114 (50 µM each) significantly reduced the circadian period of Per1 expression in the SCN by 1.4 h. Our studies demonstrate that GAT are important regulators of GABAAR-mediated currents and the circadian clock in the SCN. NEW & NOTEWORTHY In the suprachiasmatic nucleus (SCN), the GABA transporters GAT1 and GAT3 are expressed in astrocytes. Inhibition of these GABA transporters increased a tonic GABA current and reduced the circadian period of Per1 expression in SCN neurons. GAT1 and GAT3 showed functional cooperativity: inhibition of one GAT increased the activity but not the expression of the other. Our data demonstrate that GABA transporters are important regulators of GABAA receptor-mediated currents and the circadian clock.

scholarly journals An association study in the Taiwan Biobank elicits the GABAA receptor genes GABRB3, GABRA5, and GABRG3 as candidate loci for sleep duration in the Taiwanese population

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Sheue-Jane Hou ◽  
Shih-Jen Tsai ◽  
Po-Hsiu Kuo ◽  
Wan-Yu Lin ◽  
Yu-Li Liu ◽  
...  
Keyword(s):  
Sleep Quality ◽  
Association Study ◽  
Gabaa Receptor ◽  
Sleep Duration ◽  
Gabaa Receptors ◽  
Aminobutyric Acid ◽  
Gamma Aminobutyric Acid ◽  
Bonferroni Correction ◽  
Taiwanese Population ◽  
Sleep Timing

Abstract Background Gamma-aminobutyric acid type A (GABAA) receptors mainly mediate the effects of gamma-aminobutyric acid, which is the primary inhibitory neurotransmitter in the central nervous system. Abundant evidence suggests that GABAA receptors play a key role in sleep-regulating processes. No genetic association study has explored the relationships between GABAA receptor genes and sleep duration, sleep quality, and sleep timing in humans. Methods We determined the association between single-nucleotide polymorphisms (SNPs) in the GABAA receptor genes GABRA1, GABRA2, GABRB3, GABRA5, and GABRG3 and sleep duration, sleep quality, and sleep timing in the Taiwan Biobank with a sample of 10,127 Taiwanese subjects. There were 10,142 subjects in the original study cohort. We excluded 15 subjects with a medication history of sedative-hypnotics. Results Our data revealed an association of the GABRB3-GABRA5-GABRG3 gene cluster with sleep duration, which has not been previously identified: rs79333046 (beta = − 0.07; P = 1.21 × 10–3) in GABRB3, rs189790076 (beta = 0.92; P = 1.04 × 10–3) in GABRA5, and rs147619342 (beta = − 0.72; P = 3.97 × 10–3) in GABRG3. The association between rs189790076 in GABRA5 and sleep duration remained significant after Bonferroni correction. A variant (rs12438141) in GABRB3 was also found to act as a potential expression quantitative trait locus. Additionally, we discovered interactions between variants in the GABRB3-GABRA5-GABRG3 gene cluster and lifestyle factors, such as tea and coffee consumption, smoking, and physical activity, that influenced sleep duration, although some interactions became nonsignificant after Bonferroni correction. We also found interactions among GABRB3, GABRA5, and GABRG3 that affected sleep duration. Furthermore, we identified an association of rs7165524 (beta = − 0.06; P = 2.20 × 10–3) in GABRA5 with sleep quality and an association of rs79465949 (beta = − 0.12; P = 3.95 × 10–3) in GABRB3 with sleep timing, although these associations became nonsignificant after Bonferroni correction. However, we detected no evidence of an association of individual SNPs in GABRA1 and GABRA2. Conclusions Our results indicate that rs189790076 in GABRA5 and gene–gene interactions among GABRB3, GABRA5, and GABRG3 may contribute to sleep duration in the Taiwanese population.

scholarly journals Lactational Anovulation in Mice Results From a Selective Loss of Kisspeptin Input to GnRH Neurons

Endocrinology ◽  
2014 ◽  
Vol 155 (1) ◽  
pp. 193-203 ◽  
Author(s):  
X. Liu ◽  
R.S.E. Brown ◽  
A.E. Herbison ◽  
D.R. Grattan
Keyword(s):  
Brain Slice ◽  
Third Ventricle ◽  
Late Pregnancy ◽  
Mrna Levels ◽  
Fiber Density ◽  
Selective Loss ◽  
Fold Reduction ◽  
Gnrh Neurons ◽  
Periventricular Area ◽  
Brain Slice Preparation

In mammals, lactation is associated with a period of infertility characterized by the loss of pulsatile secretion of GnRH and cessation of ovulatory cycles. Despite the importance of lactational infertility in determining overall fecundity of a species, the mechanisms by which the suckling stimulus suppresses GnRH secretion remain unclear. Because kisspeptin neurons are critical for fertility, the aim of this study was to test the hypothesis that reduced kisspeptin expression might mediate the lactation-induced suppression of fertility, using mouse models. In the rostral periventricular area of the third ventricle (RP3V), a progressive decrease in RP3V Kiss1 mRNA levels was observed during pregnancy culminating in a 10-fold reduction during lactation compared with diestrous controls. This was associated with approximately 60% reduction in the numbers of kisspeptin-immunoreactive neurons in the RP3V detected during lactation. Similarly, in the arcuate nucleus there was also a significant decrease in Kiss1 mRNA levels during late pregnancy and midlactation, and a notable decrease in kisspeptin fiber density during lactation. The functional characteristics of the RP3V kisspeptin input to GnRH neurons were assessed using electrophysiological approaches in an acute brain slice preparation. Although endogenous RP3V kisspeptin neurons were found to activate GnRH neurons in diestrous mice, this was never observed during lactation. This did not result from an absence of kisspeptin receptors because GnRH neurons responded normally to 100 nM exogenous kisspeptin during lactation. The kisspeptin deficit in lactating mice was selective, because GnRH neurons responded normally to RP3V gamma aminobutryic acid inputs during lactation. These data demonstrate that a selective loss of RP3V kisspeptin inputs to GnRH neurons during lactation is the likely mechanism causing lactational anovulation in the mouse.

Abstract WMP106: Reversal of Tonic Inhibition Contributes to Recovery of Synaptic Function After Transient Focal Cerebral Ischemia

Stroke ◽  
2016 ◽  
Vol 47 (suppl_1) ◽  
Author(s):  
James E Orfila ◽  
Robert M Dietz ◽  
Himmat Grewal ◽  
Takeru Shimizu ◽  
Frank F Strnad ◽  
...  
Keyword(s):  
Western Blot ◽  
Blot Analysis ◽  
Gabaa Receptors ◽  
Western Blot Analysis ◽  
Hippocampal Slices ◽  
Long Term Potentiation ◽  
The United States ◽  
Synaptic Function ◽  
Gaba Transporter ◽  
Adult Mice

Introduction: Ischemic stroke is the fourth leading cause of death in the United States and is increasingly being recognized as a disease that occurs in people of all ages, not just the elderly. Studies suggest that the immature developing brain may have a greater degree of plasticity compared to the adult, thereby enhancing functional recovery to a greater extent during development. Hypothesis: Pediatric mice exhibit greater recovery from hippocampal synaptic function following experimental stroke than adults. Methods: Extracellular field recordings of CA1 neurons were performed in acute hippocampal slices prepared at, 7 or 30 days after recovery from middle cerebral artery occlusion (MCAO). A behavioral fear conditioning paradigm was done to evaluate contextual memory in both pediatric and adult mice 30 days after MCAO. α5 GABAA receptors and GABA transporter expression was evaluated by western blot analysis. Results: In adult mice following MCAO, hippocampal long-term potentiation (LTP), defined as an increase in synaptic strength, remained impaired for at least 30 days in the ipsilateral and contralateral, non-injured hemisphere. However, in pediatric mice following MCAO, LTP was only impaired in the ipsilateral side 7 days after MCAO and showed full recovery of synaptic function at 30 days. Behavioral data confirmed these data, showing that only adult mice displayed memory deficits 30 days after MCAO. L655,708 (100nM), an inverse agonist selective for α5 GABAA receptors, rescued LTP in acute slices in both pediatric and adult mice at all-time points tested. Western blot analysis failed to identify any changes in α5 GABAA receptors or GABA transporter (GAT1 or GAT3) levels after MCAO. Conclusion: The present study demonstrates that transient focal ischemia causes functional impairment in the hippocampus and that recovery of behavioral and synaptic function is more robust in the young brain. In addition, inhibition of tonic GABA activity rescues synaptic function, indicating that targeting of excessive GABA activity may provide a therapeutic approach to improve cognitive recovery after stroke.

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