Abstract: AIM: To investigate the changes of plasma vascular active substances before and after treatment with neuronal nicotinic receptor antagonist mecamylamine or muscarinic receptor antagonist atropine against the circulation failures induced by the cholinesterase inhibitort sarin in dogs.METHODS: Twenty healthy adult male dogs,weighing 12-15 kg,were divided into four groups randomly:control;treatment with mecamylamine;treatment with atropine and treatment with mecamylamine and atropine at the dose ratio of 1∶10(n=5).Animals were given intramuscularly sarin,and when the mean blood pressure(MBP) was decreased to 40-45 mmHg,the drugs were intramuscularly injected and the changes of vascular active substances such as nitric oxide (NO),PGI₂,atrial natriuretic peptide (ANP),endothelin (ET),angiotensinⅡ(AngⅡ) and TXA₂ before and after treated 15,30 and 60 min were observed.RESULTS: In anesthetized dogs intoxicated with cholinesterase inhibitor sarin,the plasma vascular active substances NO,PGI₂,ANP,ET,AngⅡand TXA₂ were increased significantly.After treated with mecamylamine and atropine 15 min,all the six vascular active substances were decreased markedly.After treated 60 min,they were almost resumed to the normal levels.The therapeutic effects of combination of mecamylamine and atropine were much better than those of mecamylamine or atropine used separately.CONCLUSION: The levels of vascular active substances NO,PGI₂,ANP,ET,AngⅡand TXA₂ in plasma can reflect the severity of circulation failure.There were synergic effects between mecamylamine and atropine against circulation failures induced by sarin.

Key words: cholinesterase inhibitor, sarin, circulatory failure, mecamylamine, vascular active substances