N-甲基-D-天冬氨酸和γ-氨基丁酸对蝙蝠下丘薄片诱发电活动的影响

在47只不同年龄的蝙蝠的86张中脑下丘的冠状薄片上 ,电刺激外侧丘系 ,记录到149例下丘中央核的诱发场电位。分别观察了微电泳N -甲基 -D -天冬氨酸 (NMDA)、2 -氨基 -5 -磷酸戊酸 (2 -APV)、γ -氨基丁酸 (GABA)、荷包牡丹碱 (bicuculline)等对下丘中央核诱发场电位幅度的影响。实验结果表明 ,外侧丘系对蝙蝠中脑下丘中央核的传入影响可能主要由GABA、Glu以及GABAA 、NMDA受体所介导 ;在不同的年龄组 ,对NMDA及GABA等反应的诱发单位比例基本一致、反应幅度无显著差异。鉴于蝙蝠整体实验的结果表明 ,中脑下丘中央核听反应神经元的GA BA能输入在出生后早期存在显著的发育过程。根据对诱发电位幅度的分析结果 ,推测这种GABA能输入在出生后早期的增长可能源于高位中枢的下行投射。

THE EFFECTS OF NMDA AND GABA ON THE EVOKED FIELD POTENTIALS OF BAT INFERIOR COLLICULAR SLICE FROM DIFFERENT POSTNATAL PERIOD

This study examined the effects of GABA and NMDA on evoked potentials in corneal brain slice. The experimental animal was bats(Myotis Chinensis) in different age. Responses were recorded in central inferior colliculus(CIC) by applying electric stimulation at lateral lemniscus(LL). The response parameter reported here is the amplitude of evoked field potential(EFP). Iontophoretic application of the excitant amino acids, N-methyl-D-aspartate(NMDA), resulted in increase of the amplitude of EFP. Iontophoretic application of Gl antagonists that selectively block the NMDA receptor, 2-amino-5-phosphonovalerate(APV), reduced the amplitude of EFP. Iontophoretic application of inhibitory amino acids, GABA, caused decrease of the amplitude of EFP. Application of the GABAA antagonist, bicuculline caused increase of the amplitude of EFP. The presented result supports that the afferent influence of LL on CIC maybe mediated with Glu, GABA and receptors of NMDA and GABAA. Meanwhile, the effects of NMDA and GABA on EFP had no significant difference within different age groups. This suggests that receptors for both NMDA-ergic and GABA-ergic afferent inputs are present and active in the early stage of postnatal as in adult. Previous study suggests that GABA-ergic input at CIC of bat was undergoing an obvious maturation course duration early postnatal period. Therefore, in the author's opinion, this early increasing of GABA-ergic input in CIC maybe due to the maturation of descending project from higher level.