Chronic cocaine exposure induces long lasting modifications in reward processing brain areas such as Pre-Frontal Cortex (PFC), Nucleus Accumbens (NAc) and Ventral Tegmental Area (VTA) that lead to cocaine sensitization.There are evidences showing that BDNF and Opioid Peptides (OP) play a critical role in the expression of cocaine sensitization and that their signaling pathways are highly modified by drug exposure. In order to elucidate if both signaling cascades interact, we evaluated BDNF, TrkB and pTrkB levels in NAc,VTA and PFC of cocaine treated mice with and without using an unspecific inhibitor of OP receptors, Naloxone. We found that chronic cocaine administration increases pTrkB levels in NAc and BDNF levels in VTA compared to control animals. These effects were reverted in naloxone pre-treated animals, remaining both BDNF and pTrkB levels similar to that observed in the control group. We conclude that both signali

ng pathways are closely connected and their alteration, by cocaine consumption, is one of the numerous modifications that lead to the expression of cocain e sensitization.