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.

Keywords: Adenosine receptors, morphine-dependence, pial vessels blood flow.

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