副交感神经节细胞5─羟色胺去极化反应的离子基础

使用离体细胞内记录，研究了猫副交感性胰腺神经节细胞的５－羟色胺（５－ＨＴ）去极化反应及其离子基础。５－ＨＴ使大部份细胞（４７／５１）产生去极化反应。反应只有两种类型：快去极化（６／４７）及慢去极化（３５／４７），另有６个细胞出现先快、后慢的双相去极化反应；５－ＨＴ导致的快去极化伴有膜电阻减小，向细胞内通以超极化直流电形成条件性膜超极时其幅度增大，提示Ｎａ＋导增大是其离子基础；５－ＨＴ导致的不同细胞的慢去极化分别伴随膜电阻增大、减小或不变，条件性膜超极时其幅度分别增大或不变，提示不是单一离子、而是多种离子参与其形成。分别用低Ｎａ＋、高Ｋ＋溶液灌注神经节，５－ＨＴ慢去极化均明显减小，而低Ｃｌ－溶液则无明显效应，表明Ｎａ＋导增大和／或Ｋ＋导减少是５－ＨＴ慢去极化的离子基础。

Ionic Basis Of 5-Hydroxytryptamine-Induced Depolarizing Reaction In Parasympathetic Ganglionic Neurons

The studies were designed to investigate the 5-hydroxytrrotamine (5-HT) -induced depolarization and its ionic hosts in cat poracympathetic pancreatic ganglion neurons by means of intfacellular recordings in vitro. 5-HT caused membrane depolarization in the majority of neuronstested (47/51 ). Two types of depolarization were observed: fast depolarization (6/47) and slowdepolarization .(35/47). A biphasic response comprising an initial fast followed by a slow depolarization was observed in the remaining 6 neurons; 5-HT-induced fast depolarization was associated with a decrease of membranne resistance. Conditioning hrperpolarization evoked by intracellular injection of direct hyperpolarizing current increased its amplitude. It is suggested that an increase of Na+ conductance may be the ionic basis of fast depolarization; However, 5-HT-inducedslow depolarization in different neurons accompanied decrease, increase and without detachablechange of membrane resistance respectively, and conditioning hyperpolarization either increasedits amplitude or had no significant effect on it, suggesting that several ions not a single one maybe involved in its generation. Superfusion of the ganglia with low Na+ or high K+ solution reduced the amplitude of 5-HT-induced slow depolarization, but low Cl-solution had no significanteffect on it. It is indicated that an increase of Na+ conductance and/or a decrease of K+ conductance , but not a chang of Cl- conductance, may be the ionic basis of slow depolarization.