Effect of L-dopa loading on 5-HTP decarboxylation in rat brain areas |
| |
Authors: | JH Trouvin MC Maubrey H Raynal and C Jacquot |
| |
Institution: | UA CNRS 594, Faculté de Pharmacie, Chatenay-Malabry, France. |
| |
Abstract: | The time course of 5-hydroxytryptophan (5-HTP), serotonin (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) concentrations in four rat brain areas (hypothalamus, hippocampus, striatum and olfactory bulbs) were investigated after treatment with L-dopa (125 mg/kg, ip) + benserazide (50 mg/kg, ip). 5-HTP levels increased as early as 0.5 h, showed maximum accumulation at 1.5 h and returned to control levels within 4 h, while 5-HT was markedly decreased in all four structures, with a maximum effect at 1.5 h (approximately -70%) in the four areas. The decrease in 5-HT was not accompanied by changes in 5-HIAA levels. In agreement with previous studies, these data demonstrate that L-dopa loading interferes with serotonin metabolism in the rat brain. However, in addition to the releasing action of newly-synthesized dopamine, the accumulation of 5-HTP and the parallel decrease in 5-HT indicate a reduction in 5-HT synthesis. This inhibition could be explained by a competitive effect of L-dopa for aromatic aminoacid decarboxylase activity. |
| |
Keywords: | serotonin l-dopa 5-HTP decarboxylase |
|
|