Adrenergic and peptidergic regulations of hydroxyindole- O-methyltransferase activity in rat pineal gland

Abstract

Mechanisms involved in the regulation of hydroxyindole- O-methyltransferase (HIOMT) activity were investigated in the rat pineal. Isoproterenol, db-cAMP, PACAP or VIP had no acute (6 h) effect whereas NPY, thapsigargin and a PKC activator stimulated HIOMT activity by 30–40%. Chronic stimulation (6 days) with isoproterenol, db-cAMP, or each peptide prevented the long-term decrease of HIOMT activity. Phenylephrine had neither short- nor long-term effect on enzyme activity. These results indicate that HIOMT activity is long- and short-term regulated by various neurotransmitters.