Coupling to protein kinases A and C of adenosine A 2B receptors involved in the facilitation of noradrenaline release in the prostatic portion of rat vas deferens

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In the prostatic portion of rat vas deferens, the non-selective adenosine receptor agonist NECA (0.1–30 μM), but not the A 2A agonist CGS 21680 (0.001–10 μM), caused a facilitation of electrically evoked noradrenaline release (up to 43±4%), when inhibitory adenosine A 1 receptors were blocked. NECA-elicited facilitation of noradrenaline release was prevented by the A 2B receptor-antagonist MRS 1754, enhanced by preventing cyclic-AMP degradation with rolipram, abolished by the protein kinase A inhibitors H-89, KT 5720 and cyclic-AMPS-Rp and attenuated by the protein kinase C inhibitors Ro 32-0432 and calphostin C. The adenosine uptake inhibitor NBTI also elicited a facilitation of noradrenaline release; an effect that was abolished by adenosine deaminase and attenuated by MRS 1754, by inhibitors of the extracellular nucleotide metabolism and by blockade of α 1-adrenoceptors and P2X receptors with prazosin and NF023, respectively. It was concluded that adenosine A 2B receptors are involved in a facilitation of noradrenaline release in the prostatic portion of rat vas deferens that can be activated by adenosine formed by extracellular catabolism of nucleotides. The receptors seem to be coupled to the adenylyl cyclase–protein kinase A pathway but activation of the protein kinase C by protein kinase A, may also contribute to the adenosine A 2B receptor-mediated facilitation of noradrenaline release.