POSTJUNCTIONAL EXCITATORY ADENOSINE A(1) RECEPTORS IN THE RAT VAS-DEFERENS

1. At concentrations between 1 nM and 1 mu M, the A(1)-selective agonists N-6-cyclopentyladenosine (CPA) and (R)-N-6-phenylisopropyladenosine (R-PIA) each enhanced contractions of the rat vas deferens induced by ATP (10 mu M), and this enhancement was blocked by an A(1)-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-ethyrcarboxamidoadenosine (NECA) at concentrations between 1 nM and 100 mu M, which instead inhibited the contractions. 3. These results show that in addition to the previously demonstrated inhibitory A(1) and A(2) adenosine receptors, the rat vas deferens also possesses post-junctional excitatory A(1) adenosine receptors.