Los receptores de nucleótidos P2Y reducen la entrada de calcio inducida por despolarización en terminales sinápticos de cerebro medio de rata

Abstract

Studies were carried out to determine the presence and function of P2Y receptors in synaptic terminals from rat midbrain. Immunochemical essays have shown the expression of the nucleotide P2Y2 and P2Y4 receptors. Activation of these receptors induces a reduction of the calcium entrance into the terminals, when stimulated with depolarising agents. A similar effect is produced by agonists of metabotropic receptors, such as the adenosine A1 or GABAB receptors, which are well known for its role in the presynaptic control or transmitter release. Activation of the P2Y receptors also triggers a reduction in the intrasynaptosomal cAMP concentration. Thus, these receptors seem to be negatively coupled to adenylate cyclase activity. However, we postulate that P2Y receptors are able to reduce calcium entrance into the terminals by the activation of the corresponding G protein, dissociation of the trimer and action of the âã subunits on voltage activated calcium channels.