侧脑室注射阿托品东莨菪碱对兔呼吸心率的影响

EFFECTS OF ATROPINE AND SCOPOLAMINE ON RESPIRATION

给兔侧脑室注射阿托品有兴奋呼吸作用,且可增强毛果芸香碱、氨甲酰甲胆碱、槟榔碱兴奋呼吸效应;东莨菪碱对呼吸影响不明显,但却可拮抗毛果芸香碱、氨甲酰甲胆碱、槟榔碱兴奋呼吸效应。阿托品与东莨菪碱对呼吸影响不同的原因可能与选择性阻滞中枢不同亚型M受体有关。侧脑室注射阿托品似有减慢心率倾向,东莨菪碱对心率影响不明显,但均可拮抗以上拟胆碱药的心率减慢作用。

Since the reported effects of atropine and scopolamine on respiration had been inconsistent, we carried out the experiments on rabbits hoping to clarify this situation. Results showed atropine 0.1 and 0.5 mg/kg icv increased the respiratory rate by 51% and 78% ( p<0.05 ) and the ventilation of the lungs per minute by 83%.However, this excitatory effect was not achieved in the ease of scopolamine, where 0.5, 2.5 and 5.0 mg/kg icv caused neither significant change in respiratory rate nor apparent decrease in ventilation volume. Pilocarpine icv was shown to stimulate respiration and its dose-effect relationship was linear ( r=0.95 ) .Combined use of atropine 0.5 mg/kg icv causeda left shift of the dose-effect curve, indicating a synergism between the 2 drugs; while that of scopolamine 5 mg/kg icv caused a right shift, indicating an antagonism between them.Similarly, the excitatory effect of bethanechol or arecoline on respiration was also shown to be accentuated by atropine and diminished by scopolamine. To conclude, these results indicate that atropine excites the respiratory center while scopolamine does not. The difference between their actions on respiration may be attributed to the possibility that atropine blocks the inhibitory M2 receptor and scopol amine blocks the excitatory M1 receptor in the respiratory center.