Interrelationship between angiotensin and vascular alpha adrenergic receptors

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Abstract
Blood pressure responses elicited by angiotensin in pithed rats were significantly facilitated by infusions of phenylephrine, metaraminol, and the ganglion stimulant AHR-602 [N-benzyl-3-pyrrolidyl acetate methobromide]. Angiotensin vasopressor responses were not affected by infusions of vasopressin but were attenuated by infusions of angiotensin. Norepinephrine infusions only inconstantly facilitated angiotensin vasopressor responses. Dibenzyline pretreatment abolished the facilitation of angiotensin vasopressor responses caused by infusions of phenylephrine, metaraminol, and AHR-602. Reserpine pretreatment abolished the facilitation of angiotensin vasopressor responses by AHR-602, attenuated the facilitation of responses by metaraminol, and did not appear to affect the facilitation caused by phenylephrine. Phenylephrine vasopressor responses were not affected by infusions of AHR-602 or phenylephrine. Vasopressin pressor responses were facilitated by infusions of metaraminol. It was hypothesized that stimulation of vascular alpha adrenergic receptors sensitizes vascular alpha adrenergic receptors sensitizes vascular smooth muscle to myo-tropic agents acting at other vascular receptor sites.