EFFECTS OF EXOGENOUS MELATONIN ON SOME ENDOCRINE, BEHAVIORAL AND METABOLIC PARAMETERS IN JAPANESE-QUAIL COTURNIX-COTURNIX-JAPONICA

1. Melatonin administration in drinking water (5 mug/ml) to Japanese quail resulted in a 20-fold increase of plasma melatonin levels in comparison with the control, day time concentration (0.34 +/- 0.05 vs 6.88 +/- 1. 10 nmol/1). 2. Plasma triiodothyronine levels increased (5.8 +/- 0.93 vs 7.97 +/- 0.64 nmol/1), corticosterone decreased (28.04 +/- 3.42 vs 15.96 +/- 2.56 nmol/1) and no significant changes were recorded in thyroxine concentration after the treatment. 3. A higher occurrence of sleeping and lower occurrence of pecking were found in melatonin treated quail. 4. Abdominal fat deposition as well as the content of total lipids in the breast muscle and triacylglycerols in plasma were decreased in treated birds indicating an inhibitory effect of melatonin on lipogenesis. 5. Melatonin increased RNA content in the breast muscle but did not affect plasma glucose concentration and body weight.