GABAA Receptor β3 Subunit Deletion Decreases α2/3 Subunits and IPSC Duration

2003 ◽  
Vol 89 (1) ◽  
pp. 128-134 ◽  
Author(s):  
Epolia Ramadan ◽  
Zhanyan Fu ◽  
Gabriele Losi ◽  
Gregg E. Homanics ◽  
Joseph H. Neale ◽  
...  
Keyword(s):  
Gabaa Receptor ◽  
Cortical Neurons ◽  
Behavioral Deficits ◽  
Inhibitory Postsynaptic Currents ◽  
Postsynaptic Currents ◽  
Surface Staining ◽  
Α1 Subunit

Deletion of the β3 subunit of the GABAA receptor produces severe behavioral deficits and epilepsy. GABAA receptor-mediated miniature inhibitory postsynaptic currents (mIPSCs) in cortical neurons in cultures from β3 −/− mice were significantly faster than those in β3 +/+ mice and were more prolonged by zolpidem. Surface staining revealed that the number of β2/3, α2, and α3 (but not of α1) subunit-expressing neurons and the intensity of subunit clusters were significantly reduced in β3 −/− mice. Transfection of β3 −/− neurons with β3 cDNA restored β2/3, α2, and α3 subunits immunostaining and slowed mIPSCs decay. We show that the deletion of the β3 subunit causes the loss of a subset of GABAA receptors with α2 and α3 subunits while leaving a receptor population containing predominantly α1 subunit with fast spontaneous IPSC decay and increased zolpidem sensitivity.

Prolongation of Hippocampal Miniature Inhibitory Postsynaptic Currents in Mice Lacking the GABAA Receptor α1 Subunit

2002 ◽  
Vol 88 (6) ◽  
pp. 3208-3217 ◽  
Author(s):  
Peter A. Goldstein ◽  
Frank P. Elsen ◽  
Shui-Wang Ying ◽  
Carolyn Ferguson ◽  
Gregg E. Homanics ◽  
...  
Keyword(s):  
Pyramidal Cells ◽  
Fluctuation Analysis ◽  
Α Subunit ◽  
Knock Out ◽  
Inhibitory Postsynaptic Currents ◽  
Ca1 Pyramidal Cells ◽  
Postsynaptic Currents ◽  
Decay Times ◽  
Kinetics Of ◽  
Α1 Subunit

GABAA receptors (GABAA-Rs) are pentameric structures consisting of two α, two β, and one γ subunit. The α subunit influences agonist efficacy, benzodiazepine pharmacology, and kinetics of activation/deactivation. To investigate the contribution of the α1 subunit to native GABAA-Rs, we analyzed miniature inhibitory postsynaptic currents (mIPSCs) in CA1 hippocampal pyramidal cells and interneurons from wild-type (WT) and α1 subunit knock-out (α1 KO) mice. mIPSCs recorded from interneurons and pyramidal cells obtained from α1 KO mice were detected less frequently, were smaller in amplitude, and decayed more slowly than mIPSCs recorded in neurons from WT mice. The effect of zolpidem was examined in view of its reported selectivity for receptors containing the α1 subunit. In interneurons and pyramidal cells from WT mice, zolpidem significantly increased mIPSC frequency, prolonged mIPSC decay, and increased mIPSC amplitude; those effects were diminished or absent in neurons from α1 KO mice. Nonstationary fluctuation analysis of mIPSCs indicated that the zolpidem-induced increase in mIPSC amplitude was associated with an increase in the number of open receptors rather than a change in the unitary conductance of individual channels. These data indicate that the α1 subunit is present at synapses on WT interneurons and pyramidal cells, although differences in mIPSC decay times and zolpidem sensitivity suggest that the degree to which the α1 subunit is functionally expressed at synapses on CA1 interneurons may be greater than that at synapses on CA1 pyramidal cells.

scholarly journals Characterization of a Novel Tonic γ-Aminobutyric AcidA Receptor-Mediated Inhibition in Magnocellular Neurosecretory Neurons and Its Modulation by Glia

Endocrinology ◽  
2006 ◽  
Vol 147 (8) ◽  
pp. 3746-3760 ◽  
Author(s):  
Jin Bong Park ◽  
Silvia Skalska ◽  
Javier E. Stern
Keyword(s):  
Gabaa Receptor ◽  
Gabaa Receptors ◽  
Neuronal Excitability ◽  
Tonic Inhibition ◽  
Synaptic Activity ◽  
Inhibitory Postsynaptic Currents ◽  
Postsynaptic Currents ◽  
Gaba Transporters ◽  
Neurosecretory Neurons ◽  
Vasopressin Neurons

In addition to mediating conventional quantal synaptic transmission (also known as phasic inhibition), γ-aminobutyric acidA (GABAA) receptors have been recently shown to underlie a slower, persistent form of inhibition (tonic inhibition). Using patch-clamp electrophysiology and immunohistochemistry, we addressed here whether a GABAA receptor-mediated tonic inhibition is present in supraoptic nucleus (SON) neurosecretory neurons; identified key modulatory mechanisms, including the role of glia; and determined its functional role in controlling SON neuronal excitability. Besides blocking GABAA-mediated inhibitory postsynaptic currents, the GABAA receptor blockers bicuculline and picrotoxin caused an outward shift in the holding current (Itonic), both in oxytocin and vasopressin neurons. Conversely, the high-affinity antagonist gabazine selectively blocked inhibitory postsynaptic currents. Under basal conditions, Itonic was independent on the degree of synaptic activity but was strongly modulated by the activity GABA transporters (GATs), mostly the GAT3 isoform, found here to be localized in SON glial cells/processes. Extracellular activation of GABAergic afferents evoked a small gabazine-insensitive, bicuculline-sensitive current, which was enhanced by GAT blockade. These results suggest that Itonic may be activated by spillover of GABA during conditions of strong and/or synchronous synaptic activity. Blockade of Itonic increased input resistance, induced membrane depolarization and firing activity, and enhanced the input-output function of SON neurons. In summary, our results indicate that GABAA receptors, possibly of different molecular configuration and subcellular distribution, mediate synaptic and tonic inhibition in SON neurons. The latter inhibitory modality plays a major role in modulating SON neuronal excitability, and its efficacy is modulated by the activity of glial GATs.

Effects of volatile anesthetics on the kinetics of inhibitory postsynaptic currents in cultured rat hippocampal neurons

1993 ◽  
Vol 70 (4) ◽  
pp. 1339-1349 ◽  
Author(s):  
M. V. Jones ◽  
N. L. Harrison
Keyword(s):  
Charge Transfer ◽  
Gabaa Receptor ◽  
Hippocampal Neurons ◽  
Slow Component ◽  
Volatile Anesthetics ◽  
Fast Component ◽  
Synaptic Inhibition ◽  
Inhibitory Postsynaptic Currents ◽  
Postsynaptic Currents ◽  
Kinetics Of

1. The effects of the volatile anesthetics enflurane, halothane, and isoflurane on gamma-aminobutyric acid (GABA) receptor-mediated inhibitory postsynaptic currents (IPSCs) were studied in cultured rat hippocampal neurons. The experimental concentrations of anesthetics were measured directly using gas chromatography. All three anesthetics increased the overall duration of IPSCs, measured as the time to half-decay (T1/2). Clinically effective concentrations of anesthetics [between 0.5 and 1.5 times MAC (minimum alveolar concentration)] produced between 100 and 400% increases in T1/2. These effects were fully reversible, and did not involve alterations in the reversal potential for the IPSC (EIPSC). 2. The decay of the IPSC was fitted as a sum of two exponential functions, yielding a fast component (tau fast = 20 ms), and a slow component (tau slow = 77 ms), such that the fast component accounted for 79% of the IPSC amplitude and 52% of the total charge transfer. All three anesthetics produced concentration-related increases in the amplitude and charge transfer of the slow component, while simultaneously decreasing the amplitude and charge transfer of the fast component. Thus T1/2 approximated tau fast under control conditions, but approximated tau slow in the presence of the anesthetics. 3. Varying the calcium chelating agents in the recording pipettes had no effect on the quality or magnitude of alterations in IPSC kinetics produced by halothane, suggesting that variations in intracellular calcium levels are not required for the effect of halothane on the time course of the IPSC. 4. The (+)-stereoisomer of isoflurane produced greater increases in the duration of the IPSC than the (-)-isomer when applied at approximately equal concentrations, suggesting that there is a structurally selective site of interaction for isoflurane that modulates the GABAA receptor. 5. These results suggest that the previously shown abilities of volatile anesthetics to potentiate responses to exogenously applied GABA and to prolong the duration of GABA-mediated synaptic inhibition may be due to an alteration in the gating kinetics of the GABAA receptor/channel complex. Prolongation of synaptic inhibition in the CNS is consistent with the physiological effects that accompany anesthesia and may contribute to the mechanism of anesthetic action.

Hippocampal CA1 lacunosum-moleculare interneurons: comparison of effects of anoxia on excitatory and inhibitory postsynaptic currents

1995 ◽  
Vol 74 (5) ◽  
pp. 2138-2149 ◽  
Author(s):  
R. Khazipov ◽  
P. Congar ◽  
Y. Ben-Ari
Keyword(s):  
Gabaa Receptor ◽  
Reversal Potential ◽  
Pyramidal Cells ◽  
Gabab Receptors ◽  
Stratum Radiatum ◽  
Patch Clamp Technique ◽  
Positive Shift ◽  
Inhibitory Postsynaptic Currents ◽  
Postsynaptic Currents ◽  
Presynaptic Mechanisms

1. The effects of anoxia on excitatory and inhibitory postsynaptic currents (EPSCs and IPSCs, respectively) evoked by electrical stimulation in the stratum radiatum were studied in morphologically and electrophysiologicaly identified lacunosum-moleculare (LM) interneurons of the CA1 region of rat hippocampal slices. The blind whole cell patch-clamp technique was used, and anoxia was induced by superfusion of the slice with an anoxic artificial cerebral spinal fluid saturated with 95% N2-5% CO2 for 4-6 min. 2. In LM interneurons, anoxia generated currents similar to those in pyramidal cells, the most prominent being anoxic and postanoxic outward currents. The adenosine A1 type receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 200 nM) did not significantly affect anoxia-generated currents. 3. EPSCs and polysynaptic IPSCs (pIPSCs) evoked in LM interneurons by "distant" stimulation (> 1 mm) in the stratum radiatum were strongly depressed by anoxia and recovered upon reoxygenation. 4. Responses to pressure application of glutamate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), and N-methyl-D-aspartate (NMDA) were not significantly affected by anoxia, suggesting that the suppression of EPSCs is due to presynaptic mechanisms. 5. DPCPX (200 nM) prevented anoxia-induced suppression of EPSCs, suggesting that this suppression was mediated by presynaptic A1 adenosine receptors. 6. Monosynaptic IPSCs evoked by "close" stimulation (< 0.5 mm) in the stratum radiatum, in the presence of glutamate-receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 20 microM) and D-2-amino-5-phosphopentanoate (APV; 50 microM), were reversibly depressed but not blocked by anoxia. 7. Anoxia depressed monosynaptic GABAA receptor-mediated IPSCs (monosynaptic IPSCAs) by inducing a positive shift in the reversal potential and a decrease in slope conductance. Responses to pressure-applied isoguvacine, a GABAA receptor agonist, were reversibly depressed by anoxia, again because of a positive shift in reversal potential and decrease in conductance. Anoxic effects on slope conductances and reversal potential of isoguvacine responses and monosynaptic IPSCA coincided, suggesting that evoked transmitter release from GABAergic terminals was not affected by anoxia. 8. Anoxic depression of monosynaptic GABAB receptor-mediated IPSCs (monosynaptic IPSCBs) was due to a decrease in the slope conductance of monosynaptic IPSCB. In contrast to EPSCs, DPCPX (200 nM) failed to prevent anoxia-induced depression of mIPSCA and mIPSCB. 9. Paired-pulse depression of monosynaptic IPSCs, partially mediated by presynaptic GABAB receptors, was not affected by anoxia. 10. These data provide direct evidence for the hypothesis that inhibitory interneurons of CA1 stratum LM are functionally disconnected from excitatory inputs by anoxia. This disconnection underlies the preferential block by anoxia of IPSCs recorded in pyramidal cells, and it may occult the postsynaptic modifications in GABAA and GABAB responses. This disconnection involves adenosine-dependent inhibition of glutamate release from excitatory terminals. GABA release and its modulation by presynaptic GABAB receptors, both known to be insensitive to adenosine, seems to be resistant to anoxia.

scholarly journals Perinatal fentanyl exposure leads to long-lasting impairments in somatosensory circuit function and behavior

2020 ◽  
Author(s):  
Jason Alipio ◽  
Catherine Haga ◽  
Megan E Fox ◽  
Keiko Arakawa ◽  
Rakshita Balaji ◽  
...  
Keyword(s):  
Cortical Neurons ◽  
Morphological Changes ◽  
Anterior Cingulate ◽  
Preclinical Model ◽  
Sensory Stimuli ◽  
Synaptic Excitation ◽  
Molecular Abnormalities ◽  
Postsynaptic Currents ◽  
And Behavior

One consequence of the opioid epidemic are lasting neurodevelopmental sequelae afflicting adolescents exposed to opioids in the womb. A translationally relevant and developmentally accurate preclinical model is needed to understand the behavioral, circuit, network, and molecular abnormalities resulting from this exposure. By employing a novel preclinical model of perinatal fentanyl exposure, our data reveal that fentanyl has several dose-dependent, developmental consequences to somatosensory function and behavior. Newborn male and female mice exhibit signs of withdrawal and sensory-related deficits that extend at least to adolescence. As fentanyl exposure does not affect dams' health or maternal behavior, these effects result from the direct actions of perinatal fentanyl on the pups' developing brain. At adolescence, exposed mice exhibit reduced adaptation to sensory stimuli, and a corresponding impairment in primary somatosensory (S1) function. In vitro electrophysiology demonstrates a long-lasting reduction in S1 synaptic excitation, evidenced by decreases in release probability, NMDA receptor-mediated postsynaptic currents, and frequency of miniature excitatory postsynaptic currents, as well as increased frequency of miniature inhibitory postsynaptic currents. In contrast, anterior cingulate cortical neurons exhibit an opposite phenotype, with increased synaptic excitation. Consistent with these changes, electrocorticograms reveal suppressed ketamine-evoked γ oscillations. Morphological analysis of S1 pyramidal neurons indicate reduced dendritic complexity, dendritic length, and soma size. Further, exposed mice exhibited abnormal cortical mRNA expression of key receptors and neuronal growth and development, changes that were consistent with the electrophysiological and morphological changes. These findings demonstrate the lasting sequelae of perinatal fentanyl exposure on sensory processing and function.

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