Histamine receptors in urethrovesical smooth muscle

Through the method of pharmacologic antagonism, the contractile effect of histamine was studied simultaneously on isolated smooth muscle preparations obtained from the body and base of the bladder and from the proximal urethra of the guinea pig. Histamine had a contractile effect mediated specifically through H1 receptors, with no H2 activity. This effect was most marked in the body of the bladder, comparatively moderate in the base, and slight in the proximal urethra. It appears that histamine effect is not mediated through either a cholinergic or an adrenergic mechanism. Clinical implications are discussed.