摘要
应用神经垂体逆向刺激，于下丘脑室旁核内用微电极细胞外记录逆向动作电位的方法，观察青、中、老三组大鼠逆向动作电位的阈值、潜伏期及跟随率的变化。结果发现：在老年大鼠上诱发逆向动作电位的阈值（０．５９ｍＡ±０．２４ｍＡ，ｎ＝１７）高于青年组大鼠（０．５１ｍＡ±０．２８ｍＡ，ｎ＝１７）（Ｐ＜０．０５）；老龄大鼠逆向动作电位阈值小于０．５ｍＡ的神经元比例（３４．６％，ｎ＝９）小于青年鼠（４８．５％，ｎ＝１６）大鼠（Ｐ＜０．０５）；老龄大鼠逆向动作电位潜伏期（１４．４ｍｓ±３．０ｍｓ，ｎ＝９）较青年鼠（１１．８ｍｓ±２．５ｍｓ，ｎ＝１６）明显延长（Ｐ＜０．０１）；老龄大鼠逆向动作电位对高频刺激的跟随能力有下降趋势。这些结果提示：老龄大鼠下丘脑室旁核大细胞兴奋性降低，纤维传导速度减慢，兴奋后不应期延长，说明中枢神经系统的一些部位的神经细胞的功能随增龄出现退行性变化。
By antidromic stimulation of neurohypophysis and extracellular recording of the antidromically induced action potentials(APs) in PVN,the threshold, latency and following frequency of antidromic APs of young,adult and old rats were observed.The results showed that the threshold for eliciting antidromic APs in the old group(0.59 mA±0.24 mA, n =17) was higher than that in the young one (0.51 mA±0.28 mA, n =17) ( P <0 05) The latency of antidromic APs in the old group was longer(14.4 ms±3.0 ms, n =9) than that in the young one (11.8 ms±2.5 ms, n =16)( P <0 01).In addition,the following frequency of antidromic APs in the old group was lower.These findings show that the excitability and conduction velocity of magnocellular paraventricular neurons and fibers decrease and the refractory period after each excitation prolongs,indicating a functional degeneration of some parts of the neurons in the central nervous system.
