Abstract
Peripherally administered 5-hydroxytryptophan (5-HTP) has been shown to increase the amount of 5-hydroxytryptamine (5-HT) in brain (1, 2). The pretreatment with reserpine inhibited this increase (2). After monoamine oxidase inhibitor a large amount of 5-HT could be found to be accumulated by the administration of 5-HTP regardless of whether the animals were treated with reserpine or not (1-3). Histochemical studies have shown that most of 5-HTP-induced 5-HT was ascribable to increased amine content in 5-HT neurons in the central nervous system (4), but part of it was found in an extraneuronal site (2). However, because the majority of these structures are small, being of submicroscopical size, it seems difficult for histochemical procedure to identify the subcellular site of uptake and storage of 5-HTP-induced 5-HT. Therefore, in this paper an attempt was made to fractionate rabbit brain stem homogenate after intravenous administration of 5-HTP and to determine 5-HT concentration in each fraction. In addition the effects of pretreatment with reserpine, pheniprazine and desipramine in the increased amount of 5-HT were also investigated.
