Melatonin enhances lymphocyte proliferation and decreases the release of pituitary pro-opiomelanocortin-derived peptides in surgically traumatized rats

The present study was undertaken to evaluate the effects of melatonin (MT) on spleen lymphocyte proliferation and release of pituitary pro-opiomelanocortin (POMC)-derived peptides in surgically traumatized rats. MT prevented the depression of lymphocyte proliferation induced by trauma in vivo and in vitro, and prevented the decrease of beta-endorphin and adrenocorticotropin in the pituitary in vivo, but dose-dependently inhibited the release of POMC-derived peptides from the pituitary in vitro. The culture media of the pituitaries derived from the traumatized rats inhibited lymphocyte proliferation of normal rats. These results suggest that MT can improve the trauma-induced depression of lymphocyte proliferation and inhibit the release of POMC-derived peptides. The neuroimmunomodulatory role of MT and POMC-derived peptides deserves further study. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.