THE ADRENERGIC BLOCKING ACTIVITY OF N-tert.- BUTYLMETHOXAMINE (BUTOXAMINE)

¹ Department of Pharmacology, University of Texas, Medical Branch, Galveston, Texas

The effects of butoxamine upon a number of adrenergic responses were determined in the anesthetized dog and the isolated rat uterus. Studies in the dog included a determination of the intrinsic effects of butoxamine on mean arterial pressure, heart rate, intestinal motility, cardiac contractile force, retractor penis muscle contractions and femoral vascular flow. These studies in the dog also included the effects of pretreatment with butoxamine on the responses to epinephrine, isoproterenol, ethylnorepinephrine and phenylephrine on these same parameters. Studies with the isolated, spontaneously contracting rat uterus consisted of a determination of both the intrinsic action of butoxamine and its ability to modify the uterine inhibitory responses to epinephrine, isoproterenol, norepinephrine, phenylephrine and papaverine. Butoxamine reduced the vasodilator response to isoproterenol and reversed the vasodilator response to ethylnorepinephrine. Butoxamine also produced isoproterenol and ethylnorepinephrine blood pressure "reversal" (depressor to pressor). None of the other parameters measured were reduced to any significant extent in the dog. In the isolated rat uterus, butoxamine produced a blockade of the uterine inhibitory responses to the catecholamines that was similar to the blockade produced by N-isopropylmethoxamine, dichloroisoproterenol and pronethalol. Butoxamine appears to be capable of producing a selective blockade of some, but not all, beta adrenergic receptors.