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As important as perceiving pain is the ability to modulate this perception in some contextual salient situations. The periaqueductal gray (PAG) is perhaps the most important site of endogenous pain modulation; however, little is known about dopaminergic mechanisms underlying PAG-mediated antinociception. In this study, we used a pharmacological approach to evaluate this subject. We found that µ-opioid receptor-induced antinociception (DAMGO, 0.3 μg) from PAG was blocked by the coadministration of either D1-like or D2-like dopaminergic antagonists (SCH23390, 2, 4, and 6 μg or raclopride, 2 and 4 μg, respectively) both in the tail-flick and in the mechanical paw-withdrawal test. A selective D2-like receptor agonist (piribedil, 6 and 12 μg into the PAG) induced antinociception in the mechanical paw-withdrawal test, but not in the tail-flick test. This effect was blocked by the coadministration of its selective …