Sirtuin 1 inhibitor EX527 suppresses morphine-induced behavioral sensitization.

Morphine addiction is categorized as a chronic recurrent brain disease which always results in mental disturbance, concomitant diseases and early death. Recent evidence suggested that Sirtuin 1 (SIRT1) played a crucial role in learning, memory and reward, nevertheless, its role in morphine addiction is still unclear. We explored whether SIRT1 in the ventrolateral orbital cortex (VLO) is associated with morphine addiction and its potential mechanism. We applied the morphine-induced behavioral sensitization paradigm to investigate whether microinjection of EX527, a SIRT1 inhibitor, into the VLO could affect the rat behaviors. Furthermore, we focused on the expression of extracellular signal-regulated protein kinases (ERK) and brain-derived neurotrophic factor (BDNF), potential downstream targets of SIRT1. Microinjecting EX527 into the VLO significantly suppressed morphine-induced behavioral sensitization. We found that the expression of SIRT1, phosphorylated ERK (p-ERK) and BDNF in the VLO were markedly up-regulated by morphine administrations in expression phase. These positive changes were significantly inhibited by microinjecting EX527 into the VLO. These results suggest that SIRT1 in the VLO may mediate morphine-induced behavioral sensitization and the overexpression of SIRT1, p-ERK and BDNF could be the potential mechanism. Taken together, the results of our research provide evidence to support that SIRT1 play an important role in morphine vulnerability and microinjecting EX527 into the VLO could significantly suppress morphine addiction in rats.