Integrative mechanisms for protopathic sensation including pain and g ravitropism

本文研究了线虫伤害性反应和重力反应的神经机制。野生型秀丽隐杆线虫受到有害或高重力刺激的刺激。伤害性刺激有机械刺激(von Frey型仪器)、化学刺激、热刺激、pH刺激和渗透体刺激。重力刺激为1.2~2.0g的高重力刺激。主要研究结果如下：(1)机械刺激对逃避刺激部位的回避反应阈值低于痛觉刺激。(2)缓激肽、组胺、5-羟色胺等致痛物质对线虫的回避反应无明显作用。(3)低pH和低渗透体刺激对诱发卷曲反射非常有效。其次，我们研究了有害刺激和重力刺激之间的相互作用。为此，比较了重力刺激前后的伤害性阈值。使用离心机施加超重力。30分钟。机械阈值，重力刺激后较高。重力模拟的阈值变化程度是剂量-效应关系。例如，2G刺激比1.2G刺激对von Frey诱导的逃避反应更有效。即使在重力刺激后，诱发伤害性反应的化学阈值也没有改变。2G刺激可增强低渗透压诱导的逃避行为。本研究结果提示，中枢神经系统可能整合了原发感觉。伤害性感觉和重力感觉对于动物物种的保护都是至关重要的。

Neuronal mechanisms of nociceptive and gravitational responses were investigated in c. elegans. Wild type c.eleganse was stimulated by noxious or high gravity stimulation. Noxious stimulations were maechanical (von Frey type apparatus), chemical, heat, pH and osmomic ones. Gravity stimulation was high- gravity of 1.2-2.0G. Main results were as follows: (1)Threshold values of mechanical stimulation for avoidance reflex showing escape from the stimulus site were lower than that evoked pain sensation in man. A typical behavior of avoidance reflex is peristalsis or coiling motion (2)Pain producing substances, such as Bradykinin, Histamine, 5-HT were not effective on the avoidance reflex in C. elegans. (3)Low pH and low osmomic stimulation were quite effective for evoking coiling reflex.Next, we investigated interaction between noxious and gravitational stimuli. For this purpose, nociceptive threshold before and after gravitational stimulation were compared. Centrifugal apparatus were used to apply high gravity. For 30 min. For mechanical threshold, it was higher after gravitational stimulation. Degree of threshold changes by gravitational simulation was dose-response fashon For example, 2G was more effective than 1.2 G stimulation on the von Frey-induced escape response. Chemical threshold to evoke nociceptive response were not changed even after gravitational stimulation. 2G stimulation enhanced low osmimic-induced escape behavior. The present results suggest that prtopathic sensation may be integrated in the central nervous system. Both nociceptive and gravitational sensations are critical for the preservation of the species in animals.