Neurobiological mechanism in the mesolimbic dopaminergic system involved in the physical exercise modulation of persistent hyperalgesia

Abstract

Epidemiological studies indicate a close association between depressive disorder and chronic pain. Several clinical and biological characteristics are shared between pain and depression, and several neuroanatomical structures, neural circuitry, and neurotransmitter systems show similar changes in these conditions. Evidence has emerged of the involvement of the Mesolimbic Dopaminergic System (MDS) in the modulation of pain mechanisms. Our group recently demonstrated that the Nucleus Accumbens, a structure of the MDS, has a facilitatory role in the maintenance of the persistent hyperalgesia of imflamatory origin. The MDS also plays a role in mediating the behavioral abnormalities observed in depression, and has been proposed that alterations in the Brain-Derived Neurotrophic Factor (BDNF) expression and signaling in MDS are involved in depression. Thus, the MDS constitutes one of the neural structures where occur neuroplastic changes that can be shared between chronic pain and depression. While exercise plays a well-documented antidepressant effect, it has been indicated as non pharmacologic intervention for relief chronic pain conditions, such as back ache, rheumatic diseases, and especially fibromyalgia. The aim of the present study is to investigate the effect of voluntary physical activity performed by mice on the induction of persistent hyperalgesia and to verify whether the expression of BDNF in the MDS participates of this modulation. The aim of this study is also to verify whether persistent hyperalgesia in rats induces depression that depends on the expression of BDNF in the MDS. (AU)