Effect of soman on the medullary cardiovascular center of the cat and its relation to cholinergic receptors

Injection of M-cholinergic agonist arecoline 5 microg, N-cholinergic agonist nicotine 7.5 mcirog or cholinesterase inhibitor soman 2 microg into the vertebral artery of the urethan-anesthetized cat elicited a simultaneous decrease of sympathetic efferent discharges of splanchic nerve and blood pressure. Nicotine and soman produced additional bradycardia which disappeared after bilateral cervical vagotomy.After blocking M-cholinergic receptors by pretreatment with M-cholinergic antagonist QNB 20 microg via vertebral artery, the effect of soman on medullary cardiovascular center showed a N-like action characterized by marked hypotension and bradycardia with a marked tendency to spontaneous recovery in a few minutes; while after blocking N-cholinergica receptors by N-cholinergic antagonist mecamylamine 150 microg, the effect of soman showed a M-like action characterized by prolonged hypotension without bradycardia.