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-cyclohexyl-adenosine (CHA), on prostaglandin (PG) F2 alpha-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 PGF2 alpha constriction was NECA greater than adenosine, 2-CADO greater than L-PIA greater than 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(-7) M) produced a significant shift to the right only for the NECA dose-response curve.