Synergistic Effect of Melatonin, 5-HTP and L-DOPA on Reproductive Conditions in Spotted Munia Lonchura Punctulata

Seasonal changes in reproduction and other metabolic conditions may result from interaction of circadian neural oscillations and hormonal secretion that change seasonally. To test this hypothesis, the present study was designed to study the effect of melatonin and circadian neurotransmitter activity on reproductive and hormonal conditions in a subtropical finch, spotted munia (Lonchura punctulata). During progressive phase of reproductive cycle adult male birds were divided into four groups. Group I administered with normal saline twice a day, group II administered with 5-HTP (serotonin precursor) at 8 AM and L-DOPA (dopamine precursor) at 8 PM, group III received single injection of melatonin in late afternoon. Group IV received melatonin + 5-HTP and L-DOPA. Melatonin and circadian neurotransmitter (Serotonergic and Dopaminergic) activity affected the body weight, testicular growth and plasma LH and testosterone. Birds treated with 5-HTP and L-DOPA showed significantly higher gonadal growth and activity, body weight gain and plasma LH and testosterone level in comparison to control while administration of melatonin alone and together with 5-HTP and L-DOPA induced inhibition but the degree of inhibition in later was less, it seems that melatonin inhibits the full expression of Pituitary-Testicular axis induced by 12-hr circadian phase relation of serotonergic and dopaminergic activity. These findings suggest that seasonal reproductive and hormonal conditions of this avian species might be related to daily rhythm in serotonergic and dopaminergic activities and melatonin secretion; however the exact mechanism by which they drive hypophysial gonadal axis needs to be ascertained.