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

本研究旨在阐明克氏原螯虾（Procambarus clarkii吉拉德）尾足运动神经元抑制性连接的突触机制。（1）GABA是最有效的抑制性神经递质，本研究采用荧光黄细胞内染色和GABA免疫细胞化学双标记方法鉴定GABA能神经元。（1）感觉非棘突局部神经元，LDS对节段间上行神经元具有横向抑制作用，发现LDS是GABA能神经元。（ii）尾足运动神经元主要由单侧结构的运动前非发放神经元控制，这些非发放神经元分为PL和AL两组。所有PL非尖峰神经元均为GABA能神经元，而约一半AL非尖峰神经元为非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印防己毒素敏感型和印防己毒素不敏感型。已鉴定的上行中间神经元VE-1和RO-4显示出与脊椎动物经典GABA_A受体相似的药理学特性。浴应用荷包牡丹碱和印防己毒素可逆地降低IPSP的幅度。GABA_A和GABA_B拮抗剂对CA-1、RO-1和RO-2上行中间神经元的影响不显著，但低氯化物盐水可逆转感觉刺激的IPSP。印防己毒素敏感的中间神经元的IPSPs具有更快的时间过程和更短的持续时间相比，印防己毒素不敏感的中间神经元。

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.