Sexual dimorphism in N-acetyltransferase and melatonin levels in the giant freshwater prawn Macrobrachium rosenbergii de Man.

N-acetyltransferase (NAT) and melatonin were determined in the optic lobe of the giant freshwater prawn Macrobrachium rosenbergii de Man. The prawns were divided into three groups: fast-growing "jumper" males; slow-growing "laggard" males; and females. Both NAT and melatonin levels in the jumper and laggard males were comparable, whereas those of the female were significantly lower. The results suggested a sexual dimorphism in the NAT and melatonin in the optic lobe of this species. It was also found that when one optic lobe was isolated, the level of NAT and melatonin in the contralateral optic lobe did not show a compensatory increase in either males or females. On the contrary, melatonin was suppressed in the remaining optic lobes in both sexes.

Melatonin increases nerve growth factor in mouse submandibular gland.

The effect of melatonin administration on nerve growth factor (NGF) was studied in the submandibular glands of adult Swiss male mice. Melatonin injection, at 1 microg daily for 30 days, resulted in an increase in the NGF content as detected by immunohistochemistry. The submandibular gland weight and the area of the granular convoluted tubules, which contained NGF, were also increased significantly. These effects were not observed when the dose of melatonin was increased to 10 and 50 microg daily. None of the melatonin treatments used influenced the weights or histology of the testes or seminal vesicles of the mice. The results suggest that melatonin, at physiological concentrations, directly regulates NGF synthesis in the mouse submandibular gland.