rather , since the staining could be inhibited by pretreatment with the catecholaminergic uptake blocker desmethylimipramine , it is postulated that this effect may be due to either ( 1 ) the non-specific uptake of 5-ht or 5-hydroxytryptophan ( 5-htp ) into the dopaminergic cells of a9 and a10 due to elevated levels of these substances in the dense serotonergic axonal plexus passing through this region or ( 2 ) to an increased uptake of circulating l-tryptophan by these a9 and a10 cells followed by conversion of this amino acid to tryptamine by aromatic amine decarboxylase , an enzyme common to both 5-ht and dopaminergic neurons .
C0000578
5-htp
C0041249
tryptophan