Beta 2-adrenoceptors mediate adrenaline's facilitation of neurogenic vasoconstriction.

Acute bilateral adrenal demedullation significantly reduced pressor responses in pithed spontaneously hypertensive rats. The subsequent infusion of adrenaline (50 ng/min i.v.) significantly enhanced neurogenic pressor responses without affecting those induced by noradrenaline. The adrenaline-induced enhancement of neurogenic pressor responses was unaffected by pretreatment with the beta 1-selective adrenoceptor antagonist atenolol (0.3 mg/kg i.v.), but was completely abolished by pretreatment with the beta 2-selective antagonist ICI 118551 (0.01 mg/kg i.v.). Pressor responses to noradrenaline remained unaltered.