EFFECTS OF UPTAKE INHIBITORS ON RESPONSES OF SHEEP CORONARY ARTERIES TO CATECHOLAMINES AND SYMPATHETIC NERVE STIMULATION

Abstract

1 Transmural stimulation of intrinsic sympathetic nerves and exogenous catecholamines produce β₁-adrenoceptor mediated relaxant responses in strips of contracted sheep coronary artery. 2 The neuronal uptake inhibitors, metaraminol, cocaine and desipramine and the extraneuronal uptake inhibitor, cortisol, failed to potentiate responses to noradrenaline or sympathetic stimulation; responses to isoprenaline were enhanced by cortisol. 3 Oxytetracycline, which inhibits binding to connective tissue fibres, did not affect responses to noradrenaline or nerve stimulation. 4 17β-Oestradiol, caffeine and U0521 proved to be unsuitable compounds for studying catecholamine inactivation since they non-selectively potentiated responses to noradrenaline and isoprenaline. 5 It is concluded that catecholamine inactivation processes do not modify transmitter function in sheep coronary arteries.