title: Acute resistance exercise induces antinociception by activation of the endocannabinoid system in rats.
abstract: BACKGROUND
  Resistance 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.
  
  
  METHODS
  Male 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.
  
  
  RESULTS
  RE-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.
  
  
  CONCLUSIONS
  The present study suggests that a single session of RE activates the endocannabinoid system to induce antinociception.
authors: 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.
authors: Giovane
authors: G
authors: Galdino
authors: Thiago
authors: T
authors: Romero
authors: José Felippe
authors: JF
authors: Pinho da Silva
authors: Daniele
authors: D
authors: Aguiar
authors: Ana Maria
authors: AM
authors: de Paula
authors: Jader
authors: J
authors: Cruz
authors: Cosimo
authors: C
authors: Parrella
authors: Fabiana
authors: F
authors: Piscitelli
authors: Igor
authors: I
authors: Duarte
authors: Vincenzo
authors: V
authors: Di Marzo
authors: Andrea
authors: A
authors: Perez
mesh_terms: D000818:Animals; D015153:Blotting, Western; D063386:Cannabinoid Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology; D063387:Cannabinoid Receptor Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D063388:Endocannabinoids / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D007276:Injections, Intraventricular; D007278:Injections, Spinal; D007279:Injections, Subcutaneous; D008297:Male; D013058:Mass Spectrometry; D008845:Microinjections; D059225:Nociception / Q000187:drug effects / Q000502:physiology*; D010147:Pain Measurement / Q000187:drug effects; D010487:Periaqueductal Gray; D010805:Physical Conditioning, Animal / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D043884:Receptor, Cannabinoid, CB1 / Q000096:biosynthesis / Q000187:drug effects; D055070:Resistance Training
chemical_list: D063386:Cannabinoid Receptor Agonists; D063387:Cannabinoid Receptor Antagonists; D063388:Endocannabinoids; D016760:Proto-Oncogene Proteins c-fos; D043884:Receptor, Cannabinoid, CB1