the role of adenosine a2 receptors in regulation of pial vessels blood flow in anesthetized morphine dependent rats.

introduction:adenosine as a potent vasodilator has physiological role in regulation of regional cerebral blood flow (rcbf). metod: laser-dِoppler flowmetry technique was used to study pial vessels blood flow responses to adenosine receptors agonists and antagonist. male sprague dawley rats (250-350g) that were housed in standard conditions, were anesthetized with urethane (1.5g/kg). adenosine (general agonist), neca (a2aand a2b receptor agonist) and cgs-21380(a2aselective agonist), were used in absence and presence of a2a receptors- selective antagonist, zm-243185, in naive and morphine-dependent rats. results: adenosine, neca and cgs-21680 increased pial vessels blood flow in naive and dependent rats dose dependently. these responses were blocked significantly by zm-243185. responses of pial vessels to adenosine (10-4, 10-5, 10-6 m) and neca (10-4, 10-5, 10-6 m) were increased significantly in morphine- dependent rats in comparison to naive rats. pial vessels responses to cgs-21680 had not shown any significant deferences between morphine- dependent and naive rats. conclusion:based on these results it could be concluded that the role of a2b receptors in regulation of rcbf in morphine-dependent rats is more effective than a2a receptors.