EFFECT OF PERTUSSIS TOXIN TREATMENT ON THE PUTATIVE ADENOSINE A3 RECEPTOR-MEDIATED HYPOTENSIVE RESPONSE IN THE RAT

The effect of pertussis toxin pretreatment on the putative A3 receptor -mediated hypotensive response to N6-2-(4-aminophenyl)ethyladenosine ( APNEA) has been investigated in the anaesthetised rat. Pertussis toxin pretreatment essentially abolished the bradycardia induced by the pro totype A1 receptor agonist. N6-cyclopentyladenosine, whereas the fall in blood pressure induced by the selective A2A receptor agonist, CGS 2 1680 was enhanced. Pertussis toxin substantially reduced the hypotensi ve response to APNEA. In this respect, the mechanism of action resembl es that of the cloned A3 receptor which when expressed in CHO cells co uples negatively to adenylate cyclase by a pertussis toxin-sensitive m echanism. The data provide further evidence that adenosine A3 receptor s mediate the hypotensive response to APNEA in the rat.