Effect of acute acetyl-l-carnitine treatment on daytime melatonin synthesis in the rat.

The effects of acute treatment of young male rats with 350 mg/kg of acetyl-l-carnitine (ALCAR) at 15.00 hr on the synthesis and secretion of melatonin by the pineal gland and the retinas were studied 1 hr after injection. The pineal N-acetyltransferase (NAT) activity was unchanged when compared with the control. However, there was a non-significant but slight increase in the melantonin content of the pineal glands in the ALCAR-treated rats. The serum level of melantonim in the ALCAR-treated group was significantly higher (P < 0.05) when compared with the control. The melatonin content of the retinas in the ALCAR treated rats was significantly higher than the control (P < 0.03). This result suggests that the high melatonin content in blood 1 hr after treatment with ALCAR was not as a result of the increased synthesis and secretion rate of melatonin by the pineal gland but rather from extra-pineal source, retina.