|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1997 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1996 : ¥1,400,000 (Direct Cost : ¥1,400,000)
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 local
interneurones 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 characterized
electrophysiologically. 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.