Abstract

The chronic oral administration of mecamylamine to cats did not modify the degree of ganglionic blockade obtained at the superior cervical ganglion following acute intravenous doses of the drug and did not modify the responsiveness of the nictitating membrane to postganglionic stimulation. During the chronic administration of the ganglionic blocking agent, a moderate supersensitivity to exogenous norepinephrine was observed. This lasted for about 6 weeks of drug administration and decreased on continued treatment with the blocking agent, being minimal or absent at the end of 12 weeks of drug treatment. Nictitating membranes from mecamylamine hypertensive dogs that had received the ganglionic blocking agent for periods of from 15 to 26 months were not more sensitive to norepinephrine than the nictitating membranes of control dogs. The nictitating membranes of cats chronically treated with mecamylamine showed minimal or no supersensitivity to epinephrine. In rats treated with mecamylamine for a period of 8 months, the blood pressure changes to intravenous injections of epinephrine, angiotensin, or physostigmine were no greater than in control animals. It was concluded that neither development of tolerance to the ganglionic blocking actions of the drug, nor increased sensitivity to postganglionic stimulation nor supersensitivity to catecholamines or angiotensin plays a significant part in the development of hypertension in animals to which mecamylamine is administered over a prolonged period of time.