Cardiovascular effect of a naphthylmethyl substituted tetrahydroisoquinoline, YS 49, in rat and rabbit.

A novel tetrahydroisoquinoline, 1-alpha-naphthylmethyl-6,7-dihydroxy-1,2,3,4- tetrahydroisoquinoline (YS 49) 1) increased heart rate and force in isolated rat atria; 2) relaxed PE- and KCl-contracted rat aorta, and 3) decreased blood pressure and increased heart rate in anesthetized rabbit. These effects were blocked by propranolol, a nonselective beta-antagonist, but not by phentolamine, an alpha-blocker, and/or depletion of catecholamine by reserpine. These results suggest that the mechanism of action of YS 49 is due, at least in part, to beta-adrenergic receptor stimulation.