INHIBITION OF NEURAL ATP RELEASE BY ATRIAL-NATRIURETIC-PEPTIDE IN GUINEA-PIG VAS-DEFERENS

Effects of atrial natriuretic peptide (ANP) and 8-bromoguanosine 3':5' -cyclic monophosphate (8-BrcGMP) on contraction, overflow of tritium ( after [H-3]noradrenaline labelling) and overflow of ATP elicited by el ectrical field stimulation (210 pulses/7 Hz) were studied in guinea-pi g vas deferens. ANP (1-100 nM) slightly increased contractions, did no t alter the overflow of tritium but decreased the overflow of ATP by u p to 50%. 8-BrcGMP (3-300 mu M) markedly reduced contractions and ATP overflow with no effect on tritium overflow. Contractions were suppres sed in the presence of prazosin plus suramin, and evoked overflow of A TP declined to 11%. ANP now gradually increased tritium overflow but a gain decreased the overflow of ATP. 8-BrcGMP did not change tritium ov erflow, as before, but increased ATP overflow. The results indicate th at ANP inhibits neural release of ATP by a mechanism independent of gu anylyl cyclase activation with no major effect on noradrenaline releas e.