ADRENERGIC AND PEPTIDERGIC REGULATIONS OF HYDROXYINDOLE-O-METHYLTRANSFERASE ACTIVITY IN RAT PINEAL-GLAND

Mechanisms involved in the regulation of hydroxyindole-O-methyltransfe rase (HIOMT) activity were investigated in the rat pineal. Isoproteren ol, db-cAMP, PACAP or VIP had no acute (6 h) effect whereas NPY, thaps igargin and a PKC activator stimulated HIOMT activity by 30-40%. Chron ic stimulation (6 days) with isoproterenol, db-cAMP, or each peptide p revented the long-term decrease of HIOMT activity. Phenylephrine had n either short- nor long-term effect on enzyme activity. These results i ndicate that HIOMT activity is long- and short-term regulated by vario us neurotransmitters. (C) 1997 Elsevier Science B.V.