Cholinergic stimulation and blockade on urinary bladder

¹ Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois; and Geigy Research Laboratories, Ardsley, New York

The relative potency and mode of action of some cholinomimetics were investigated on the pelvic nerve-bladder preparation of the dog and cat. Most of the cholinomimetic agents used proved to be considerably more potent than acetylcholine (ACh). The peak activity was shown by muscarine and dl-muscarone, which were 100–300 times more potent than ACh. Atropine did not markedly influence the effect of the electrical stimulation on the pelvic nerve. Atropine also proved to be ineffective against the actions of 1,1-dimethyl,4-phenyl piperazinium iodide, serotonin, histamine, and BaCl₂. It antagonized the effects of ACh only moderately, but completely inhibited the effects of muscarine and methacholine. After atropinization, hexamethonium inhibited the effects of nerve stimulation and ACh. ACh has a significant ganglionic component of its action on the bladder. It is postulated that part of the parasympathetic effector sites of the bladder functionally resemble autonomic ganglions. These ganglionic type of receptors seem to play an important role in the effects of parasympathetic nerve stimulation and in the action of ACh.