PS136. Time-dependent alteration of reward-induced dopamine release in the nucleus accumbens of the neuropathic pain model rats.

Abstract

Abstract Chronic pain is frequently comorbid with psychiatric disorders such as depression, suggesting the common neuroplastic changes in the central nervous system. It has been considered that chronic pain lowers the function of mesolimbic reward circuits and leads to depression-like states. Nucleus accumbens (NAc) is one of the key structures of the mesolimbic dopaminergic system, which is well known to play an important role in the reward circuits. Extracellular dopamine (DA) levels in the NAc elevate after the acquisition or prediction of rewards. In this study, we examined the reward-induced DA release in the NAc of neuropathic pain model rats. To prepare the neuropathic pain model, the spinal nerve was ligated (SNL model), and reward-induced DA release in the NAc was examined 2 and 4 weeks after SNL surgery. The animals were given with two types of rewards, 30% sucrose solution or pain relief by intrathecally injection of pregabalin (100 μg/10 μl PBS), and DA release was monitored using an in vivo microdialysis technique. Both rewards increased extracellular DA levels in the NAc 2 weeks after SNL surgery. In contrast, neither sucrose solution nor pain relief increased the DA release 4 weeks after SNL surgery. These results suggest that dysfunction of the mesolimbic reward circuits occurred 4 weeks, but not 2 weeks, after SNL surgery.