Experiments were designed to determine the influence of endothelin A (ET_A) receptors on the pressor response to acute environmental stress in Dahl salt-resistant (DR) and Dahl-sensitive (DS) rats. Mean arterial pressure (MAP) was chronically monitored by telemetry before and after treatment with the selective ET_A receptor antagonist, ABT-627. Rats were restrained and subjected to pulsatile air jet stress (3 minutes). In untreated animals, the total pressor response (area under the curve) to acute stress was not different between DR vs. DS rats (8.1±1.7 vs. 15.6±2.6 mmHg x 3 min, p=0.10). Conversely, treatment with ABT-627 potentiated the total pressor response only in DR rats (36.3±6.2 vs. 22.6±5.9 mmHg x 3 min, p<0.05). Treatment with ABT-627 allowed greater responses in anesthetized DR rats to exogenous phenylephrine (1-4 µg/kg) during ganglionic blockade(p<0.05), and produced a significant increase in plasma norepinephrine at baseline and during stress in conscious DR rats compared to untreated animals (p<0.05). ET_A receptor blockade had no effect on these responses in DS rats. Our results suggest that ET-1 can inhibit -adrenergic-mediated effects in DR, but not DS rats, consistent with the hypothesis that ET_A receptor activation functions to reduce sympathetic nerve activity and responses in vascular smooth muscle to sympathetic stimulation.