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Summary— Imipramine at 1 mg/kg body weight reduced contractions of the urethra and bladder produced in response to pelvic nerve stimulation by 58 and 56% in female anaesthetised dogs. Responses to injection into the internal iliac artery of acetylcholine, histamine and 5 hydroxytryptamine (5HT) were also reduced but those to ATP and noradrenaline were not altered. Atropine (0.1 mg/kg) blocked responses to acetylcholine and pelvic nerve stimulation but was without action on responses to ATP, histamine or 5HT. Mepyramine (1 mg/kg) but not metiamide (0.5 mg/kg) selectively blocked responses to histamine. The responses to pelvic nerve stimulation or acetylcholine were not altered.

It was concluded that imipramine does not have significant anticholinergic action and is unlikely to block uptake of biogenic amines. The powerful inhibitory action on histamine responses could reduce the effects of circulating histamine but cannot explain the reduction of the nerve-induced response.