CONTRACTILE RESPONSE OF RAT AORTA TO NOREPINEPHRINE AND TYRAMINE

¹ Laboratory for Experimental Medicine, Department of Pathology, University of Texas Southwestern Medical School, Dallas, Texas

Rat aortic strip gave consistent contractile responses to norepinephrine and tyramine but not to amphetamine, methamphetamine, hydroxyamphetamine and electric stimulation. The effects of both tyramine and norepinephrine were blocked to an equal degree by phentolamine, an alpha adrenergic antagonist; this antagonism was essentially unchanged by pretreatment with cocaine or reserpine. These results and the effects of pretreatment with desipramine and 6-hydroxydopamine are interpreted as indicating that the action of tyramine on rat aorta is predominantly a direct one without neuronal mediation and confirms earlier studies indicating that the innervation of this tissue is scant.