CHANGES IN PURINERGIC RESPONSES OF THE RABBIT ISOLATED CENTRAL EAR ARTERY AFTER CHRONIC ELECTRICAL-STIMULATION INVIVO

1 The effect of chronic (4-16 days) electrical stimulation (5 Hz, 0.3 ms, 4- 10 V) of the great auricular nerve in vivo on sympathetic cotransmission in the rabbit isolated central ear artery was examined. 2 Chronic stimulation had no significant effect on frequency-dependent (4-60 Hz) neurogenic contractions or contractile responses induced by exogenous noradrenaline (0.1-300 muM). 3 In contrast, contractions induced by exogenous alpha,beta-methylene ATP (10.0 muM) were significantly decreased in preparations from 16-day stimulated animals in comparison with sham-operated, 4-day and 8-day chronically stimulated animal groups. 4 It is concluded that chronic electrical stimulation of nerves supplying the ear artery may lead to the selective alteration of postjunctional P2x-purinoceptor mechanisms, while the effects mediated by postjunctional alpha1-adrenoceptors remain unchanged.