The inhibitory effects of adenosine as well as its related analogues on the contractile
response of the rat vas deferens to field stimulation were compared in the absence and in
the presence of nitrobenzylthioguanosine (NBTGR), a potent adenosine uptake inhibitor. In
the presence of NBTGR, the order of potency was N 6-cyclohexyladenosine (CHA)≧ lN 6-
phenylisopropyladenosine (l-PIA)> 2-chloroadenosine> dN 6-phenylisopropyladenosine (d-
PIA)≧ adenosine> 2′-deoxyadenosine. The inhibitory effect of adenosine but not that of …

The inhibitory effect of adenosine on the electrically evoked contractions in the rat prostatic
vas deferens was markedly dependent on the calcium concentration in the medium, with
adenosine being 20 times more potent at lower calcium levels (1.26 mM vs 3.6 mM). Similar
calcium dependence of adenosine inhibition was observed in the presence of a potent
nucleoside uptake inhibitor, nitrobenzylthioguanosine (NBTGR), suggesting that this calcium
dependence of adenosine inhibition was not secondary to an alteration in adenosine …