Effects And Mechanism Of Cold Water Stimulating Vestibular Organ On Gastric Activity In Rats

Vestibular organ is mainly involved in three reflexes: vestibulo-ocular reflex, vestibulo-spinal reflex and vestibulo-visceral reflex. Vestibulo-visceral reflex can influence blood pressure, breath and heart rate, etc, through vestibular receptor, vestibular nucleus and the center of autonomic nerve. There are some basic researches on the changes blood pressure and breath after stimulating vestibular organ. However, there are fewer researches on the function of gastric regulated by vestibular system, and there are no any reports about directly recording gastric motility after stimulating vestibular organ.Methods:Hyponome was used to record gastric motility, gastrin and motilin were measured by radioimmunoassay(RIA). Male Wistar rats were used for the experiments and divided into 3 groups: cold water stimulating vestibular organ, unilateral labyrinthectomy(UL), vagotomy(Vag). Gastric motility was observed by irrigating 14℃water into middle ear with or without succinylcholine pretreatment in the cold water stimulating group. UL model was prepared by injected arsenate into middle ear and the effects of gastric motility and the concentration of gastrin and motilin were observed. The peripheral nerve mechanism of gastric motility regulated by vestibular stimulating was investigated in Vag group.The results of present experiments are as below: 1. The baseline of Gastric motility frequency(GMF) is 5.20±0.10 time/min before stimulated by cold water. After stimulation, GMF was decreased to 2.60±0.54 time/min(P＜O.01)in the first minute, in the second minute to 3.40±0.62 time/min(P＜0.05), and in the third minute to 3.40±0.70 time/min(P＜0.05) and GMF returned to the baseline in the fourth minute. IGP(control value100%) reduced to 92.19±2.51%(P＜0.05) and 91.97±3.36% (P＜0.05) in the first and second minute respectively, and then returned to normal levels. After succinylcholine pretreatment, GMF and IGP significantly decreased after cold water stimulation(P＜0.05), and there were persistence about 3 minutes and 2 minutes. Without significant differences compared with normal group.2. After Two weeks of UL, IGP was significantly reduced from 4.69±0.41cmH₂O to 3.20±0.42cmH₂O(vs normal saline group, P＜0.05) and GMF was also significantly decreased from 5.94±0.16 time/min to 5.49±0.18 time/min respectively(vs normal saline group, P＜0.05). In UL group, gastrin and motilin were significantly reduced (gastrin, from 255.28±17.03pg/ml to 200.86±30.80pg/ml, P＜0.05 vs normal saline group; motilin, from 200.86±30.80pg/ml to 116.54±18.79pg/ml, P＜0.05 vs normal saline group).3. Stimulated opposite side vestibular organ with cold water in UL group, GMF was decreased from 5.94±0.16 time/min to 4.59±0.34 time/min(P＜0.01) in the first minute and to 4.71±0.36 time/min in the second minute(P＜0.01); IGP was also decreased from control value(100%) to 93.49±1.56% and 93.15±1.31% in the first two minutes. However, there was no significantly differences between UL and normal saline group.4. GMF and IGP were significantly decreased after Vag in all groups(P＜0.05 vs before Vag). In mormal rats, GMF and IGP showed no significantly changes by cold water stimulation vestibular organ after Vag(P＞0.05). In UL group, GMF and IGP showed similarly with normal rats (P＞0.05). However, Vag significantly attenuated the effect of gastric motility decrease by cold water stimulated to vestibular organ (P＜0.05 vs before Vag).These results indicate that:1. The vestibular organ stimulated by cold water may played negative roles for regulating gastric motility frequency and intragastric pressure in rats.2. The gastric motility frequency and intragastric pressure as well as the concentration of gastrin and motilin were significantly inhibited by Unilateral labyrinthectomy.3. Vestibular organ may control for the gastric function via vagus.