γ-氨基丁酸受体
荷包牡丹碱
化学
海马结构
生物物理学
谷氨酸受体
通道阻滞剂
神经科学
钙
受体
生物
生物化学
有机化学
作者
Xavier Leinekugel,Vadim Tseeb,Yehezkel Ben‐Ari,Pìotr Bregestovski
标识
DOI:10.1113/jphysiol.1995.sp020882
摘要
1. Changes in intracellular Ca2+ concentration ([Ca2+]i) induced by activation of GABAA receptors (synaptic stimulation or application of the GABAA agonist isoguvacine) were studied on pyramidal cells and interneurons from hippocampal slices of rats from two age groups (postnatal days (P) 2-5 and P12-13) using the fluorescent dye fluo-3 and a confocal laser scanning microscope. Cells were loaded with the dye either intracellularly, using patch pipettes containing fluo-3 in the internal solution, or extracellularly, using pressure pulses applied to an extracellular pipette containing the permeant dye fluo-3 AM. 2. Interneurons and pyramidal cells from P2-5 slices loaded with fluo-3 AM responded by an increase in [Ca2+]i to isoguvacine and to glutamate, in contrast to cells from P12-13 slices which responded to glutamate but not to isoguvacine. 3. The isoguvacine-induced rise in [Ca2+]i was reversibly blocked by bath application of the GABAA receptor antagonist bicuculline (20 microM), suggesting the specific involvement of GABAA receptors. The sodium channel blocker tetrodotoxin (TTX, 1 microM in the bath) did not prevent the isoguvacine-induced rise in [Ca2+]i. 4. The isoguvacine-induced rise in [Ca2+]i was reversibly blocked by bath application of the calcium channel blocker D600 (50 microM) suggesting the involvement of voltage-dependent Ca2+ channels. 5. Electrical stimulation of afferent fibres induced a transient increase in [Ca2+]i in neonatal pyramidal cells and interneurons (P5) loaded non-invasively with fluo-3 AM. This elevation of [Ca2+]i was reversibly blocked by bicuculline (20 microM) but not by APV (50 microM) and CNQX (10 microM). 6. During simultaneous electrophysiological recording in the current-clamp mode and [Ca2+]i monitoring from P5 pyramidal cells, electrical stimulation of afferent fibres, in the presence of APV (50 microM) and CNQX (10 microM), caused synaptic depolarization accompanied by a few action potentials and a transient increase in [Ca2+]i. In voltage clamp (-70 mV) however, there was no increase in [Ca2+]i following synaptic stimulation, showing that it is depolarization dependent. 7. Using a non-invasive method of [Ca2+]i monitoring, we demonstrate here that in neonatal (P2-5) hippocampus, GABA is an excitatory neurotransmitter which can cause an elevation of [Ca2+]i in interneurons and pyramidal cells via activation of voltage-dependent Ca2+ channels. This action may underlie the trophic role of GABA in hippocampal development.
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