家兔脊髓蛛网膜下腔注射乙酰胆碱对膈神经放电的影响

实验在50例麻醉、麻痹和切断双侧迷走神经的家兔上进行。用双极银丝电极引导膈神经放电,经放大、幅度积分而后记录在 X-Y 记录仪上。脊髓蛛网膜下腔注射乙酰胆碱(ACh)50μg 后,膈神经吸气放电幅度增加,平均增加30.6±11.6%.ACh 的这一效应可被阿托品阻断,但不能被六甲双铵、酚妥拉明和心得安阻断。但单独注射上述任何一种受体阻断剂均不能改变膈神经的放电活动。上述结果提示,脊髓蛛网膜下腔注射 ACh 可兴奋膈运动神经元,而且 ACh 的这一兴奋效应是由 Μ 受体中介的,但在正常生理情况下,胆碱能递质系统对膈神经元似无紧张性兴奋作用。因此,ACh 递质可能在脊髓水平对高级中枢下传的呼吸驱动信息的整合中起兴奋性调制作用。

EFFECT OF INTRATHECAL INJECTION OF ACETYLCHOLINE ON PHRENIC NERVE FIRING ACTIVITY IN RABBITS

Experiments were performed on 50 anesthetized, immobilized and vagotomized rabbits to investigate how acetylcholine (ACh) regulates respiration. The phrenic nerve impulses were led by a bipolar silver electrode and recorded in a X-Y plotter. The results are as follows: 1. The inspiratory firing activity of phrenic nerve following intrathecal injection of ACh was increased by 30.6 +/- 11.6% (P less than 0.01). 2. The excitatory action of ACh on phrenic motoneurons had no correlation with blood pressure but was associated with the direct action of ACh on phrenic motoneurons. 3. The excitatory effect of ACh on phrenic nucleus could be blocked by atropine, but not by hexamethonium, phentolamine or propranolol. 4. The electric activities of phrenic nerve were not altered by intrathecal injection of any of the four receptor-blockers mentioned above. The results suggest that the phrenic nucleus could be excited by intrathecal injection of ACh and this excitatory effect is mediated by M-receptors. It is assumed that the cholinergic system does not show any tonic excitatory action on the phrenic nucleus under normal physiological conditions. Thus it seems that cholinergic transmitter may participate in the integration of signals for respiratory drive at the level of spinal cord.