Serotonergic and catecholaminergic (dopaminergic) oscillations in the reproductive regulation of Japanese quail

Abstract

Specific temporal phase relation of serotonergic and dopaminergic oscillations alters reproductive responses in many species. Aim of the study was to confirm whether effect of serotonergic drug (5-HTP) and dopaminergic drug (L-DOPA) is due to their conversion into serotonin and dopamine respectively or other products. For this study, PCPA (p-chlorophenylalanine, a long lasting inhibitor of serotonin synthesis), DDC (Diethyldithiocarbamate, which inhibits biosynthesis of nor-adrenaline), α-MT (Methyl-p-tyrosine, an inhibitor for the conversion of tyrosine to DOPA) and DOPS (Dihydroxyphenylserine, a specific precursor for noradrenaline) were used in different groups in addition to 5-HTP and L-DOPA given at specific time interval. Reproductive responses monitored at 10 weeks post treatment indicate that gonadal activity was significantly low in HTP:DOPA (8-hr quail), HTP+PCPA:DOPA and HTP:DOPA+DDC quail compare to control (S:S). However, gonadal activity of HTP:S(HTP control), S:DOPA(DOPA control) and HTP: α-MT+DOPS was not different from S:S control and remained in active condition. These findings indicate that it is not the dose of neurotransmitter precursor drugs (5-HTP and L-DOPA) and the neurotransmitters (serotonin and dopamine itself) that cause the effect, instead it is the function of interval between the drug administration which induces or entrains specific phase relation between serotonergic and dopaminergic oscillations. Further, gonadal suppression observed in HTP:DOPA, HTP+PCPA:DOPA and HTP:DOPA+DDC group three groups is not due to injection of 5-HTP or L-DOPA (alone) but due to conversion of administered 5-HTP into serotonin and conversion of L-DOPA (administered) into dopamine; not due to their further conversion into catecholamines other than dopamine i.e. noradrenaline or adrenaline.