MODULATORY EFFECTS OF ENDOTHELIN-1 ON PURINERGIC AND ADRENERGIC COMPONENTS OF SYMPATHETICALLY-MEDIATED CONTRACTILE ACTIVITY OF RABBIT SAPHENOUS ARTERY

1 The present study has been performed to evaluate the modulatory effe cts of endothelin-1 (ET-1) on the purinergic and adrenergic components of sympathetically-mediated contractile responses of endothelium-free rabbit saphenous artery preparations. 2 ET-1 increased the smooth mus cle tone, the pot value being 7.77 +/- 0.05. 3 Postjunctionally, ET-1 enhanced the responses to exogenous adenosine 5'-triphosphate (ATP) an d did not influence those to exogenous noradrenaline (NA). 4 ET-1 incr eased the contractile responses to short-lasting and to long-lasting e lectrical held stimulation at a frequency of 5 or 10 Hz, showing a ten dency towards decreasing the prazosin-sensitive component and increasi ng the mATP-sensitive component of the contractile responses. 5 In pra zosin-treated preparations ET-1 increased the residual mATP-sensitive responses and this effect was more pronounced after yohimbine. 6 In mA TP-treated preparations ET-1 increased the residual electrically-induc ed contractions and this increase was abolished after yohimbine. 7 It is suggested that ET-1 modulates co-transmission in the rabbit sapheno us artery by potentiating postjunctionally the purinergic component of the contractile responses to both exogenous ATP or electrical stimula tion.