Effects of Adenosine and its Analogues on Porcine Basilar Arteries: Are Only A2 Receptors Involved?

The aim of this study was to test the effect of adenosine and four of its analogues, 5'-(N-ethyl)carboxamidoadenosine (NECA), 2-chloroadenosine (2-CADO), L-phenylisopropyladenosine (L-PIA), and N6-cyclohexyladenosine (CHA), on prostaglandin (PG) F2α-constricted pig basilar arteries, and from their rank order of potency determine the receptor type involved, The order of potency for the relaxation of the PGF2α constriction was NECA > adenosine, 2-CADO > L-PIA > CHA, which is in keeping with the A2 receptor subtype, The study also investigated the effects of a known adenosine antagonist, namely, the xanthine derivative 8-phenyltheophylline, which at concentrations having no intrinsic effect (10−8 and 10−7M) produced a significant shift to the right only for the NECA dose-response curve.