Prostaglandin E2 selectively affects purinergic transmission in guinea pig vas deferens

The effect of prostaglandin E2 (PGE2) on the contractile response of the guinea pig vas deferens was examined. Postganglionic hypogastric nerve stimulation for 7 sec at 20 Hz induced a biphasic contractile response, consisting of fast phasic and delayed tonic components. Prostaglandin E2 delayed the onset and increased the maximum contractile responses. Stimulation in the presence of prazosin induced only a fast phasic contraction. Treatment with PGE2, in the presence of prazosin, delayed the onset of this response and increased its maximum. The delayed contraction, observed on stimulation in the presence of alpha,beta-methylene adenosine triphosphate (ATP), was enhanced moderately and concentration-dependently by PGE2. Short-term stimulation with 5 pulses induced a small fast phasic contraction. This contraction, which could be desensitized by alpha,beta-methylene ATP, was inhibited by PGE2 but not by prazosin. Prostaglandin E2 significantly enhanced the transient phasic contraction, induced by addition of exogenous ATP to the organ bath and had a similar but somewhat smaller effect on the tonic contraction induced by the addition of exogenous norepinephrine (NE). These findings suggest that PGE2 selectively delayed neurotransmission, mediated by ATP and enhanced contractions of the smooth muscle of guinea pig vas deferens, elicited by ATP or NE.