Role of Vascular α2-Adrenoceptors as Targets for Circulating Catecholamines in the Maintenance of Blood Pressure in Anaesthetised Spontaneously Hypertensive Rats

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Abstract
We examined the blood pressure-lowering effects of the α2-adrenoceptor antagonist rauwolscine in anaesthetised spontaneously hypertensive rats (SHR). In the absence of prior drug, rauwolscine (1–10 mg kg−1) produced dose-dependent falls in diastolic blood pressure (DBP). In the presence of prazosin (1 mg kg−1) to eliminate α1-adrenoceptor-mediated responses, rauwolscine (0.1–1 mg kg−1) lowered DBP in unoperated and sham-operated animals but not in adrenal demedullated animals. Hence, we were able to demonstrate that α2-adrenoceptors are involved in the control of blood pressure in intact anaesthetised SHR but not following adrenal de-medullation, suggesting that circulating catecholamines are responsible for these α2-adrenoceptor-mediated pressor effects.