[Immunoregulatory actions of melatonin microinjected into hippocampus in rats and their mechanisms of action].

This paper reports that melatonin(MT) microinjected into hippocampus (ih) produces immunoregulatory actions. In ih MT rats, the contents of norepinephrine (NE) were increased in the hippocampus, and the immunologic effects of the ih MT could be related to alpha 2 adrenergic receptors of sympathatic systems. It was also found that MT could be produced by the splenocytes where the two key enzymes (NAT, HIMOT) exist. The immunoregulatory actions of ih MT could be related to the increased production of MT in the splenocytes, which induced the release of beta-Endorphin. The increased NE in the hippocampus in ih MT rats, could inhibit the release of MT in pineal gland and the actions may also be mediated through alpha 2 adrenergic receptors. The result suggested that a feed back circuit may exist between the hippocampus and the pineal, which balances the immunologic function in the body.