Effects of histamine on the human penis muscle in vitro.

Histamine produced three types of effects on corpus cavernosa muscle of the human penis: contraction, relaxation or a contraction followed by a relaxation. 2-Methylhistamine, which acts mainly on histamine H1-receptors, stimulated all the penile strips tested. 4-Methylhistamine, which acts predominantly on H2-receptors produced relaxation in two-thirds of the strips and contraction in the rest. Contractions produced by histamine, 2-methyl histamine and 4-methylhistamine were selectively abolished by mepyramine. Burimamide antagonised the relaxant effect of histamine and of 4-methylhistamine. Corpus cavernosa muscle of the human penis has both histamine H1- and H2-receptors.