Impromidine, a potent dilator of cat pial arterioles.

Impromidine (SKF 92676) has been demonstrated to have highly potent and selective activity at histamine H2-receptors in a variety of physiological systems. We compared responses produced by perivascular microapplication of histamine and impromidine in cat pial arterioles in situ. Impromidine caused twice as much maximal dilation as histamine, and was ten times more potent. These observations emphasize the pronounced effects that can result from stimulation of histamine H2-receptors in brain arterioles.