Tricyclic antidepressant drugs as antagonists of muscarinic receptors in sympathetic ganglia.

Close arterial injection of McN-A-343 into the superior cervical ganglion of the cat resulted in contractions of the nictitating membrane. The ganglionic effects of McN-A-343 but not those of DMPP were antagonized in a dose-related manner by 2-10 mug of desipramine, imipramine, chlorimpramine, iprindole and viloxazine. No correlation was found between the dose of each drug which blocked the effects of McN-A-343 and that required to potentiate the responses of the nictitating membrane to intra-arterial administration of noradrenaline. It is concluded that clinically effective antidepressant agents can block muscarinic receptors in neural tissue, even if they do not do so in smooth muscle and gland cells.