Inhibitory histamine receptors in the rat vas deferens

The effect of histamine on the field stimulated rat vas deferens preparation was studied and compared to mouse vas deferens. Histamine produced a concentration dependent inhibition of rat vas deferens (ID50 14 microM) similar to that seen with mouse vas deferens (ID50 2.4 microM). Unlike mouse however, where only H2 receptors are observed, the histamine inhibition of rat vas deferens was attenuated by both H1, (diphenhydramine) and H2 (cimetidine) antagonists. It is concluded that rat vas deferens contains both H1 and H2 receptor types.