大鼠生后MGBv神经元主动膜特性的变化及GABA受体激动剂的影响  

Alteration of membrane properties of MGBv neurons and the effect of GABA receptor agonist on them during postnatal development in rats

作　　者：姚小红[1] 万子兵[1] 熊鹰[1] 

机构地区：[1]第三军医大学生理学教研室,重庆400038

出　　处：《神经科学通报》2005年第3期182-187,共6页Neuroscience Bulletin

基　　金：This work was supported by the National Natural Science Foundation of china(No 30371532).

摘　　要：目的观察大鼠生后不同发育阶段内侧膝状体腹侧部(ventral of medial geniculate body, MGBv)神经元的主动膜特性的变化及GABA受体激动剂的影响。方法依大鼠MGB的发育特点将实验大鼠按出生后日龄分为出生后(postnatal day,P)3-7,8-11,12-20,21-30,四组,采用脑片膜片钳全细胞记录技术获得MGBv神经元的全细胞记录,电流钳下给予去极化电流刺激,记录神经元动作电位(action potential, AP)发放的变化及GABA受体激动剂的影响。结果出生后不同日龄大鼠MGBv神经元AP的发放模式不同,在出生后不同日龄大鼠MGBv神经元静息电位基础上注入去极化电流脉冲,P3的MGBv神经元只记录到低阈值Ca2 +峰(low threshold Ca2 +spikes,LTS),而P6-30的MGBv神经元可在LTS的基础上记录到AP的发放;P8的MGBv神经元的AP在脉冲起始处出现,其神经元AP的峰后超极化电位(after hyperpolarization potential,AHP)的持续时间较P20神经元的长,而P20神经元经过明显的延搁后,在去极化斜坡上引起了AP发放;GABA受体激动剂,氯苯氨丁酸(GABAB受体激动剂)和毒蕈醇(GABAA受体激动剂)均引起P6的MGBv神经元膜的去极化和AP数目的增加,而氯苯氨丁酸对P15的MGBv神经元AP幅度和时程无影响,毒蕈醇则完全抑制了P15的MGBv神经元AP的发放。结论大鼠MGBv神经元的AP波形成熟较快,可在中枢神经系统的神经元环路中产生协调性的活动;在MGBv神经元发育早期,GABA主要作为兴奋性神经递质而发挥作用,它可使P6的MGBv神经元产生去极化,AP发放频率显著增加,随着出生后日龄的增加,GABA受体的抑制作用才逐渐发育成熟。Objective To observe membrane properties of ventral partition of the medial geniculate body (MGBv) in Wistar rat and the effect of GABA receptor agonist on them during postnatal development. Methods Whole-cell patch clamp recording was used to record waveform of action potential (AP) and the effect of GABA receptor agonist on them from neurons in the MGBv of rats (postnatal days 3-30). Results There was a difference in AP firing pattern in rat MGBv neurons of different postnatal day. We only recorded low threshold Ca2+ spikes (LTS) in P3 MGBv neurons, but recorded AP in P6-30 MGBv neurons after depolarizing currents application; AP was recorded at the start phase of pulse and with a long-last after hyperpolarization potential (AHP) in P8, in P20 AP was recorded after a delay and it appeared on depolarizing ramp with a shorter-last AHP compared with P8.The GABAA receptor agonist, muscimol, and the GABAB receptor agonist, baclofen, had effects on responses evoked by depolarizing current in the MGBv neurons in P6 and P15 rats. Muscimol and baclofen reduced AP firing rather than AP amplitude in P6 MGBv neurons, however,in P15 MGBv neurons baclofen had little effect on AP firing while muscimol greatly reduced the size of voltage shift produced by positive or negative current injection. Conclusion The AP waveform of MGBv neurons matures rapidly during first two postnatal weeks. A similar rapid maturation also has been observed in rat neocortical and hippocampal pyramidal neurons as well as in ferret dorsal lateral geniculate nucleus (LGNd) neurons. These results suggest that in the central nervous system of small mammals, AP waveforms mature rapidly in many types of neurons, thus, coordinated activities in neuronal circuits may occur. In early postnatal development, GABA receptor mainly mediates an excitation effect, depolarizes P6 MGBv neurons and dramatically increases the frequency of AP firing. Inhibition of GABA receptor matures slowly along with increment of postnatal days.

关 键 词：大鼠 MGBv神经元 主动膜特性 GABA受体激动剂 AP 脑片 膜片钳 内侧膝状体 腹侧部 

分 类 号：Q424[生物学—神经生物学]