Wang L, Bradley R M
Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor 48109-1078.
Brain Res. 1993 Jul 9;616(1-2):144-53. doi: 10.1016/0006-8993(93)90203-y.
The role of gamma-aminobutyric acid (GABA) as an inhibitory neurotransmitter in the rostral, gustatory zone of the nucleus of the solitary tract (rNST) was examined using whole cell recordings in brain slices of the adult rat medulla. Superfusion of GABA resulted in a concentration-dependent reduction in input resistance in 68% of the neurons in rNST. The change in input resistance was often accompanied by membrane hyperpolarization. The effect of GABA was a direct action on the postsynaptic membrane since it could be elicited when synaptic transmission was blocked by tetrodotoxin or in a low Ca2+ and high Mg2+ perfusing solution. The mean reversal potential of the GABA effect was about -60 mV, determined by applying GABA at different holding potentials, or from the intersection of current-voltage curves measured in control saline and saline containing GABA. When neurons were separated into groups based on intrinsic membrane properties, some neurons in each group responded to GABA. Superfusion of the slices with either the GABAA agonist, muscimol, or the GABAB agonist, baclofen, caused a decrease in input resistance accompanied by membrane hyperpolarization. The GABAA antagonist bicuculline either totally or partially blocked the neuronal response to GABA and blocked the response to muscimol but did not antagonize responses to baclofen. Superfusion of the GABAB antagonist phaclofen depressed the membrane responses to GABA. The use of the GABAA and GABAB agonists and antagonists demonstrates that some neurons in rNST have both GABAA and GABAB receptors. Since most rNST neurons studied respond to GABA, inhibition probably plays a major role in sensory processing by the rNST.
运用成年大鼠延髓脑片的全细胞记录技术，研究了γ-氨基丁酸（GABA）作为孤束核吻侧味觉区（rNST）抑制性神经递质的作用。在rNST中，68%的神经元经GABA灌流后，其输入电阻呈浓度依赖性降低。输入电阻的变化常伴有膜超极化。GABA的作用是直接作用于突触后膜，因为当河豚毒素阻断突触传递或在低钙高镁灌流液中时，仍可引发该作用。通过在不同钳制电位下施加GABA，或根据在对照盐溶液和含GABA盐溶液中测得的电流-电压曲线的交点，确定GABA作用的平均反转电位约为-60 mV。当根据内在膜特性将神经元分组时，每组中的一些神经元对GABA有反应。用GABAA激动剂蝇蕈醇或GABAB激动剂巴氯芬灌流脑片，会导致输入电阻降低并伴有膜超极化。GABAA拮抗剂荷包牡丹碱完全或部分阻断神经元对GABA的反应，并阻断对蝇蕈醇的反应，但不拮抗对巴氯芬的反应。GABAB拮抗剂巴氯芬灌流可抑制膜对GABA的反应。GABAA和GABAB激动剂及拮抗剂的使用表明，rNST中的一些神经元同时具有GABAA和GABAB受体。由于大多数被研究的rNST神经元对GABA有反应，抑制作用可能在rNST的感觉处理中起主要作用。
