Influence of oxotremorine on histamine level and histamine synthesis in the rat brain.

The i.p. administration of oxotremorine (2 mg/kg) produced a decrease of both formation of 14C-histamine and the activity of specific histamine-synthetizing enzyme--histidine decarboxylase (HD). Oxotremorine had no effect on histamine level in the brain when given alone, but lowered the amine content in L-histidine-treated rats. All of these effects of oxotremorine were antagonized by atropine sulphate, but not by atropine methyl nitrate--a cholinolytic drug which does not penetrate the blood-brain barrier. Presented findings indicate a possibility of ACh--HI interaction in the rat brain. Possible mechanism of oxotremorine action is discussed.