Neural mechanism of inhibitory syvaptie Trans mission of crayfish local circuil neurones

本研究旨在阐明克氏原虾尾足运动相关局部环路神经元抑制性联系的突触机制。(1)GABA是最有效的抑制性递质候选者，我研究了用荧光黄细胞内染色和GABA免疫细胞化学双重标记来识别GABA能神经元。(1)感觉性非尖峰局部神经元，LDS对节间上行神经元具有横向抑制作用，我发现LDS是GABA能神经元。(Ii)Uropod运动神经元本质上由运动前非尖峰神经元控制，这些非尖峰神经元分为PL和AL两组。所有的PL非尖峰神经元都是GABA能神经元，而约一半的AL非尖峰神经元不是GABA能神经元。(2)上行神经元GABA能受体的电生理特性。根据对GABA_A拮抗剂荷包牡丹碱和印防己毒素的反应，上行中间神经元可分为对印防己毒素敏感和不敏感两种类型。经鉴定，VE-1和RO-4具有与脊椎动物经典的GABA_A受体相似的药理特征。沐浴荷包牡丹碱和印防己毒素均可逆地降低IPSP的波幅。用GABA_A和GABA_B拮抗剂浸泡对CA-1、RO-1和RO-2上行中间神经元无明显影响，但用低氯盐水浸泡可逆转感觉刺激的IPSP。与对印防己毒素不敏感的中间神经元相比，对印防己毒素敏感的中间神经元的IPSP具有更快的时程和更短的持续时间。

This research is aimed to clarify the synaptic mechanisms of inhibitory connections of the local circuit neurones underlying uropod movements of crayfish, Procambarus clarkii Girard.(1)GABA is the most potent candidate as inhibitory transmitter and I have investigated to identify GABAergic interneurones by using double labelling of intracellular staining with Lucifer yellow and immunocytochemical staining against GABA.(i)Sensory nonspiking local interneurone, LDS has a role of lateral transverse inhibition of intersegmental ascending interneurones and I found LDS is a GABAergic interneurone.(ii)Uropod motor neurones are essentially controlled by premotor nonspiking localinterneurones with unilateral stucture and these nonspiking interneurones are classified into PL and AL groups. All the PL nonspiking interneurones are GABAergic neurones while about half of AL nonspiking interneurones are not GABAergic.(2)The properties of GABAergic receptors of ascending interneurones are characterizedelectrophysiologically. According to the response to GABA_A antagonists, bicuculline and picrotoxin, ascending interneurons were classified into two types, picrotoxin-sensitive and picrotoxin-insensitive interneurons. Identified ascending interneurons, VE-1 and RO-4 showed a pharmacological profile similar to classical GABA_A receptor of the vertebrates. Bath application of both bicuculline and picrotoxin reversibly reduced the amplitudes of IPSPs. Another identified ascending interneurons, CA-1, RO-1 and RO-2 were not affected significantly by the bath application of GABA_A and GABA_B antagonists, though bath application of low chloride saline reversed the sensory-stimulated IPSPs. IPSPs of the picrotoxin-sensitive interneurons had rather faster time course and shorter duration in comparison with that of the picrotoxin-insensitive interneurons.