豚鼠肠系膜下神经节细胞电活动与结肠运动的关系

在豚鼠肠系膜下神经节(IMG)及其支配的结肠段联合标本上,对IMG细胞内电位与肠段纵肌或环肌舒缩活动进行了同步记录。实验结果表明:(1)肠段预置张力为零时,约50％IMG细胞有自发的快兴奋性突触后电位(EPSP)活动,切断结肠神经或以筒箭毒(50μmol/L)灌流IMG后消失;(2)筒箭毒或低钙高镁溶液阻断神经节传递时,环肌节律性收缩幅度增大,节律变慢,但对纵肌节律性收缩无明显影响,(3)串刺激节前神经,在IMG细胞引起一串快EPSP或动作电位并常跟随迟慢的EPSP,同时,纵肌在0.1-0.2s潜伏期后出现迅速的、时程基本与动作电位串一致的舒张波,后者在筒箭毒灌流IMG后消失,而环肌运动可见舒张、舒张波延长或收缩波增大。结果提示:IMG不仅中继经典的胆碱能传出功能,还参与以胆碱能传递为中介的肠-肠反射,该反射活动的传出效应主要在于抑制环肌收缩。

RELATIONSHIP BETWEEN NEURONAL ACTIVITIES OF THE GUINEA-PIG INFERIOR MESENTERIC GANGLION NEURONS AND MUSCULAR CONTRACTION OF THE COLON IN VITRO

A perfused inferior mesenteric ganglion (IMG)-colon preparation was prepared from the guinea-pig for intracellular recording of IMG neurons and for simultaneously recording the muscular contraction. It was found that: (1) At zero preloaded tension of colon, the spontaneous fast excitatory post-synaptic potentials (f-EPSPs) could be recorded in about 50% sampled neurons. These f-EPSPs were abolished by either severing the colonic nerve or superfusing IMG with d-tubocurarine (d-TC, 50 mumol/L). (2) The contraction of circular but not longitudinal muscle was augmented and slowed down by superfusing IMG with d-TC or low Ca/high Mg solution. (3) A train stimulation of the preganglionic nerves initiated a volley of f-EPSPs or orthodromic discharges, in the IMG neurons and a quick relaxation of the longitudinal muscle with a latency of between 0.1 s and 0.2 s. The responses of the neuron and the muscle could be eliminated by superfusing IMG with d-TC. Multiple irregular responses of the circular muscle of the colon to the train stimulation could also be found. The results suggest that the IMG neurons participate in the cholinergic afferents and colo-colonic reflex mediated by cholinoceptors. The output of the reflex mainly inhibited the circular muscle contraction of the colon.