Biosynthesis of Cerebral Phenolic Amines. II. In Vivo Regional Formation of p-Tyramine and Octopamine from Tyrosine and Dopamine

Abstract

In rats pretreated with pargyline the highest cerebral concentration of ¹⁴C-labeled p-tyramine and octopamine following an intraventricular injection of tyrosine-¹⁴C was found in the hypothalamus. In the case of dopamine-¹⁴C the maximum formation was in the hypothalamus and brainstem. In the absence of pargyline only very small quantities of these amines were found in some regions. Following injection of p-tyramine-³H, β-hydroxylation to octopamine-³H occurred in all regions, the most active being the hypothalamus. Unchanged p-tyramine was most actively concentrated in the caudate nucleus. The formation and localization of p-tyramine and octopamine from their respective precursors tyrosine, dopamine, and p-tyramine itself are discussed with regard to the endogenous distribution of p-tyramine and certain of the enzymes involved in the synthesis and metabolism of these phenolic amines.