The effect of melatonin administration on nerve growth factor (NGF) wa
s studied in the submandibular glands of adult Swiss male mice. Melato
nin injection, at 1 mu g daily for 30 days, resulted in an increase in
the NGF content as detected by immunohistochemistry. The submandibula
r gland weight and the area of the granular convoluted tubules, which
contained NGF, were also increased significantly. These effects were n
ot observed when the dose of melatonin was increased to 10 and 50 mu g
daily. None of the melatonin treatments used influenced the weights o
r histology of the testes or seminal vesicles of the mice. The results
suggest that melatonin, at physiological concentrations, directly reg
ulates NGF synthesis in the mouse submandibular gland.