Abstract: AIM: To investigate the changes of hemodynamic parameters and 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 inhibitor DDV in dogs.METHODS: 20 male dogs were randomized into 4 groups:control ;treatment with mecamylamine ;treatment with atropine and treatment with mecamylamine and atropine at the dose ratio of 1 ∶10.Animals were given intramuscularly DDV, and when the mean blood pressure was decreased to 40-45 mmHg, the drugs were intramuscularly injected and the changes of hemodynamic parameters such as mean arterial pressure (MAP), +dp/dt_max, Vpm and-dp/dt_max and vascular active substances such as nitric oxide (NO), endothelin(ET) and 6-Keto-PG1αbefore and after treated 15 and 60 min were observed.RESULTS: In anesthetized dogs intoxicated with cholinesterase inhibitor DDV, the circulation failure was characterized by the significant decreases in hemodynamic parameters MAP, +dp/dt_max, Vpm and-dp dt max.The plasma vascular active substances NO, ET and 6-Keto-PGF1α were increased significantly.After treated with mecamylamine and atropine 15 min, all the hemodynamic parameters were increased markedly and all the three vascular active substances were decreased significantly.After treated 60min, all the parameters were almost resumed to the normal level.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, ET and 6-Keto-PGF1αin plasma can reflect the severity of circulation failure.There were synergic effects between mecamylamine and atropine against circulation failures induced by DDV.

Key words: cholinesterase inhibitor, circulation failure, mecamylamine, NO, endothelin, 6-Keto-PGF1α