Differential effects of exercise on brain opioid receptor binding and activation in rats

Physical exercise stimulates the release of endogenous opioid peptides supposed to be responsible for changes in mood, anxiety, and performance. Exercise alters sensitivity to these effects that modify the efficacy at the opioid receptor. Although there is evidence that relates exercise to neuropeptide expression in the brain, the effects of exercise on opioid receptor binding and signal transduction mechanisms downstream of these receptors have not been explored. Here, we characterized the binding and G protein activation of mu opioid receptor, kappa opioid receptor or delta opioid receptor in several brain regions following acute (7 days) and chronic (30 days) exercise. As regards short-(acute) or longterm effects (chronic) of exercise, overall, higher opioid receptor binding was observed in acute-exercise animals and the opposite was found in the chronic-exercise animals. the binding of [S-35]GTP gamma S under basal conditions (absence of agonists) was elevated in sensorimotor cortex and hippocampus, an effect more evident after chronic exercise. Divergence of findings was observed for mu opioid receptor, kappa opioid receptor, and delta opioid receptor receptor activation in our study. Our results support existing evidence of opioid receptor binding and G protein activation occurring differentially in brain regions in response to diverse exercise stimuli.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Instituto Nacional de Neurociencia Translacional (INNT)National Council for Sciences and Technology of MexicoUniversidade Federal de São Paulo, Escola Paulista Med UNIFESP EPM, Dept Fisiol, São Paulo, BrazilHosp Israelita Albert Einstein, Inst Cerebro, São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med UNIFESP EPM, Disciplina Neurol Expt, São Paulo, BrazilCtr Res & Adv Studies, Dept Pharmacobiol, Mexico City, DF, MexicoUniv Basel, Hosp Psychiat, Ctr Affect Stress & Sleep Disorders, Basel, SwitzerlandUniv Basel, Inst Exercise & Hlth Sci, Basel, SwitzerlandUniversidade Federal de São Paulo, Escola Paulista Med UNIFESP EPM, Dept Fisiol, São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med UNIFESP EPM, Disciplina Neurol Expt, São Paulo, BrazilNational Council for Sciences and Technology of Mexico: 98386Web of Scienc