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Behavioral effects of L-5-hydroxytryptophan after destruction of ascending serotonergic pathways in the rat: the role of catecholaminergic neurons.
- Source :
-
The Journal of pharmacology and experimental therapeutics [J Pharmacol Exp Ther] 1976 Feb; Vol. 196 (2), pp. 307-15. - Publication Year :
- 1976
-
Abstract
- Lesions in the medial forebrain bundle of the rat produced a 68 to 74% decrease in telencephalic serotonin (5-HT) and a 30 to 43% decrease in jump threshold. L-5-Hydroxytryptophan (L-5-HTP; 37.5 mg/kg) returned the 5-HT content and jump threshold of lesioned rats to normal levels. These effects of L-5-HTP were also observed after the inhibition of extracerebral decarboxylase activity with Ro 4-4602 (50 mg/kg). Pretreatment with 6-hydroxydopamine (6-OHDA), which selectively destroys catecholamine neurons, had no effect on the jump threshold of nonlesioned rats nor did it further change the 5-HT content or jump threshold of lesioned rats. Lesioned rats pretreated with 6-OHDA demonstrated an increase in 5-HT content after L-5-HTP; however, their jump threshold remained significantly lower than that of controls. This ability of 6-OHDA to block the behavioral effects of L-5-HTP in lesioned rats was also observed after Ro 4-4602. In rats given Ro 4-4602, the accumulation of 5-HT at 90 minutes after injection of L-5-HTP was significantly correlated (r = 0.98) with total monoamine content. Thus, 6-OHDA pretreatment significantly decreased the net accumulation of 5-HT from L-5-HTP in nonlesioned rats. These rats also demonstrated further decreases in norepinephrine and dopamine content after L-5-HTP. It was concluded that L-5-HTP can be decarboxylated to 5-HT in serotonergic and catecholaminergic neurons and that the behavioral effects of L-5-HTP in lesioned rats may be due to the formation of 5-HT in catecholaminergic neurons where it may act as a "false-transmitter."
Details
- Language :
- English
- ISSN :
- 0022-3565
- Volume :
- 196
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- The Journal of pharmacology and experimental therapeutics
- Publication Type :
- Academic Journal
- Accession number :
- 1255478