Abstract

The present study was undertaken to evaluate the effects of α-blocking agents on the rate of catecholamine synthesis in vivo. It was found that phentolamine and phenoxybenzamine increase the formation of radioactive norepinephrine and epinephrine in rat tissues when L-tyrosine-¹⁴C is used as a precursor but not when L-dopa-³H is the precursor. These findings indicate that α-blocking agents increase catecholamine synthesis by stimulating tyrosine hydroxylase activity.