GONADOTROPHIN- AND PROLACTIN-INDUCED INCREASE OF RAT PINEAL HYDROXYINDOLE-O-METHYL TRANSFERASE: INVOLVEMENT OF THE SYMPATHETIC NERVOUS SYSTEM

Abstract

Instituto Latinoamericano de Fisiología de la Reproducción (I.L.A.F.I.R.), C.C. 10- San Miguel, P.B.A., Argentina (Received 6 May 1975) Previous investigations have indicated that the rat pineal gland, besides constituting a neuroendocrine transducer able to convert neural inputs originating in retinal photoreceptors and reaching the pinealocytes through their sympathetic nerves (Wurtman & Antón-Tay, 1969), has the capacity to respond to a variety of hormone signals in the circulation which include gonadal steroids (see below) and catecholamines (Lynch, Eng & Wurtman, 1973). Protein receptors for sex hormones are present within pineal cells and are controlled via a β-adrenergic receptor by the noradrenaline released from pineal nerve-endings (Cardinali, Nagle & Rosner, 1975). Treatment with oestradiol (Cardinali, Nagle & Rosner, 1974) or testosterone (Nagle, Cardinali & Rosner, 1974, 1975) enhances pineal melatonin and protein synthesis, a finding which suggests that a negative feedback operates between the gonads and the pineal gland of the rat.