en Cardiovascular Physiology/Pharmacology Cardiovascular Physiology/Pharmacology Experimental research article Experimental research article 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. Adenosine receptors, morphine-dependence, pial vessels blood flow. 22 30 http://ppj.phypha.ir/browse.php?a_code=A-10-175-2&slc_lang=en&sid=1 Marzeieh Hoseini 320031947532846003759 320031947532846003759 No Tarbiat Modares university Sohrab Hajizadeh hajizads@modares.ac.ir 320031947532846003760 320031947532846003760 Yes Tarbiat Modares university yaghoub Fathollahi 320031947532846003761 320031947532846003761 No Tarbiat Modares university Mojtaba Golmohammadi 320031947532846003762 320031947532846003762 No Batoul Erfani 320031947532846003763 320031947532846003763 No Ali Heidarian Pour 320031947532846003764 320031947532846003764 No