促胰液素抑制胃扩张引起膈下迷走神经传入放电的电生理研究

Secretin inhibits vagal afferent nerve discharge in response to gastric distension in rats

目的 :探讨促胰液素对扩胃 -迷走传入放电反应的影响。方法 :实验在Wistar大鼠上进行 ,记录扩张胃引起的膈下迷走传入放电的变化 ,观察静脉注射不同剂量促胰液素、十二指肠灌注HCl和静脉注射兔促胰液素抗血清后再灌注HCl对迷走传入放电的影响。结果 :不同剂量的促胰液素 (2 .5 ,5 .0和 10 pmol/kg/h)静脉注射对扩胃 -迷走传入放电反应的影响不同 ,2 .5 pmol/kg/h(n =6 )没有明显作用 ,5 .0pmol/kg/h(n =7)对扩胃 -迷走传入放电反应有明显抑制 (P <0 .0 1) ,10 pmol/kg/h(n =7)出现抑制作用快而持久。但 10min后 5 .0与 10pmol/kg/h之间无统计学意义。十二指肠灌注HCl可以引起内源性促胰液素释放由此也引起胃扩张 -迷走传入反应的抑制 (n =8,P <0 .0 1)以 2 0min后作用更明显。在观察的 35min期间一直保持抑制效应。用兔促胰液素抗血清 (titer=1:1,0 0 0 ,0 0 0 ) 0 .1mliv .2 0～ 4 0min后上述HCl的抑制效应消失 (n =8,P <0 .0 1)。结论 :迷走神经传入冲动在促胰液素对胃扩张的抑制中发挥了重要作用。

Objective:To study the effect of secretin on subdiaphragmatic vagal afferent response by gastric distension. Methods: Experiments were performed on anesthetized rats. The sensory impulses of subdiaphragmatic vagal nerve were recorded using a window discriminator. Through a midline abdominal incision, a polyethylene cannula (1.0mm ID) for duodenal infusion was inserted into the proximal duodenum 0.5mm distal to the pylorus.Another cannula was placed into jejunum 20 cm distal to the ligament of Treitz.Gastric distension was produced by injecting saline at 37℃ into a small balloon via a polyvinyl tube.Results:Intravenous injection of secretin in a dose of 5.0 pmol/kg/h inhibited significantly the response of afferent discharges induced by gastric distension( n=7, P <0.05), while lower dose secretin (2.5pmol/kg/h iv.) failed to affect this response. The vagal afferent were further suppressed when the dose of secretin was increased to 10pmol/kg/h ( n=7,P <0.01). The inhibitory effect of 10 pmol/kg/h was earlier and larger than 5.0 pmol/kg/h( P <0.05), but no significance was demonstrated after 10 min ( P >0.05). It showed that exogenous secretin in a dose of 5.0pmol/kg/h, in the physiological dose range, played an inhibitory effect. 0.03N HCl was infused intraduodenally at 9 ml/h for 20 min in anesthetized rats with gastric cannulas, ligation of the pylorus, respectively.0.1 ml of a rabbit antisecretin serum (titer=l:l,000,000) was injected intravenously in a bolus 20～40min before HC1 was administered. During the duodenal infusion of 0.03N HCI the gastric distension-vagal afferent responses were suppressed significantly.( n=8, P <0.05). It was reversed by antisecretin serum ( P <0.01). Conclusion:These observations provide a direct electrophysiological evidence that vagal afferent pathway plays an important role in the gastric-distension inhibition by exo- & endogenous secretin.