• Giovane Galdino, Thiago Romero, Pinho da SilvaJosé FelippeJF, Daniele Aguiar, Ana Maria de Paula, Jader Cruz, Cosimo Parrella, Fabiana Piscitelli, Igor Duarte, Vincenzo Di Marzo, and Andrea Perez.
• From the Department of Pharmacology, Department of Physiology, Institute of Biological Sciences, Department of Physics, and Department of Biochemistry, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil; and Endocannabinoid Research Group, Institute of Biomolecular Chemistry, Pozzuoli, Napoli, Italy.
• Anesth. Analg. 2014 Sep 1; 119 (3): 702-715.

BackgroundResistance exercise (RE) is also known as strength training, and it is performed to increase the strength and mass of muscles, bone strength, and metabolism. RE has been increasingly prescribed for pain relief. However, the endogenous mechanisms underlying this antinociceptive effect are still largely unexplored. Thus, we investigated the involvement of the endocannabinoid system in RE-induced antinociception.MethodsMale Wistar rats were submitted to acute RE in a weight-lifting model. The nociceptive threshold was measured by a mechanical nociceptive test (paw pressure) before and after exercise. To investigate the involvement of cannabinoid receptors and endocannabinoids in RE-induced antinociception, cannabinoid receptor inverse agonists, endocannabinoid metabolizing enzyme inhibitors, and an anandamide reuptake inhibitor were injected before RE. After RE, CB1 cannabinoid receptors were quantified in rat brain tissue by Western blot and immunofluorescence. In addition, endocannabinoid plasma levels were measured by isotope dilution-liquid chromatography mass spectrometry.ResultsRE-induced antinociception was prevented by preinjection with CB1 and CB2 cannabinoid receptor inverse agonists. By contrast, preadministration of metabolizing enzyme inhibitors and the anandamide reuptake inhibitor prolonged and enhanced this effect. RE also produced an increase in the expression and activation of CB1 cannabinoid receptors in rat brain tissue and in the dorsolateral and ventrolateral periaqueductal regions and an increase in endocannabinoid plasma levels.ConclusionsThe present study suggests that a single session of RE activates the endocannabinoid system to induce antinociception.

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