A NONADRENERGIC MUSCULOTROPIC EFFECT OF 2-(CYCLOHEXYLAMINO)-ETHYLGUANIDINE SULFATE (SU-9707) IN RABBIT AORTIC STRIPS

¹ Department of Pharmacology, Burroughs Wellcome & Co. (U.S.A.) Inc., Tuckahoe, New York, and Department of Pharmacology, University of Vermont, Burlington, Vermont

Su-9707, 2-(cyclohexylamino)-ethylguanidine sulfate, was compared with guanethidine in rabbit aortic strips. Guanethidine produces infrequent and small contractions over a wide concentration range, whereas Su-9707 invariably produces large, concentration-dependent contractions. Guanethidine and Su-9707 both release tritiated norepinephrine and inhibit its uptake; Su-9707 appears to be one-tenth as potent as guanethidine in these respects. The contractions elicited by Su-9707 are not blocked by concentrations of phentolamine which readily block norepinephrine and tyramine responses. It is concluded that Su-9707, which has structural and pharmacologic similarities to guanethidine, elicits a nonadrenergic contraction of aorta presumably by direct interaction with smooth muscle. It is inferred that guanethidine may have a similar effect but that this is masked by a relaxant action which it exerts concomitantly.