Post-junctional excitatory adenosine A1 receptors in the rat vas deferens.

1. At concentrations between 1 nM and 1 microM, the A1-selective agonists N6-cyclopentyladenosine (CPA) and (R)-N6-phenylisopropyladenosine (R-PIA) each enhanced contractions of the rat vas deferens induced by ATP (10 microM), and this enhancement was blocked by an A1-selective concentration (1 nM) of the antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX). 2. No such enhancement was observed with the non-selective agonists adenosine and 5'-N-ethylcarboxamidoadenosine (NECA) at concentrations between 1 nM and 100 microM, which instead inhibited the contractions. 3. These results show that in addition to the previously demonstrated inhibitory A1 and A2 adenosine receptors, the rat vas deferens also possesses post-junctional excitatory A1 adenosine receptors.