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Purinergic and noradrenergic cotransmission in the rat pineal gland
E J Mortani Barbosa1, Z S Ferreira, R P Markus
1Department of Physiology, Institute of Bioscience, University of São Paulo, Rua do Matão, travessa 14, 05508-900, São Paulo, Brazil.
Abstract:
ATP is coreleased with noradrenaline in several noradrenergic synapses, and P2-like receptors were shown to be present in rat pineal glands. A new method of functional investigation was developed to assess the importance of both transmitters (noradrenaline and ATP) in eliciting the synthesis of melatonin and its precursor N'-acetyl-5-hydroxytryptamine (N'-acetyl-5-HT) through transmural electrical field stimulation of cultured pineal glands. Incubation with the beta-adrenoceptor antagonist propranolol (>10(-7) M) blocked almost completely the production of N'-acetyl-5-HT, whilst the P2 receptor antagonists pyridoxalphosphate-6 azophenyl-2',4'-disulfonic acid (PPADS, >3x10(-6) M) and suramin (>10(-6) M) blocked it partially. These findings indicate a physiologically relevant role for the purinergic cotransmission in this system.