Decreased morphine analgesia in rat overexpressing beta-arrestin 2 at periaqueductal gray.

Beta-arrestin 2 plays important physiological roles in regulating the function of the mu opioid receptor (muOR) in vivo. Periaqueductal gray (PAG) is a potential structure where morphine produces its antinociception, but it is unclear whether beta-arrestin 2 plays its regulatory effect on morphine at PAG. In the present study beta-arrestin 2 overexpression was induced by adenovirus at PAG of rats. Morphine was administrated in these rats through PAG microinjection and systemic administration. The antinociceptive effects of morphine were abolished in rats received microinjection of morphine at PAG and partially attenuated in rats received systemic administration of morphine. These findings support the notion that PAG is an important site where beta-arrestin 2 plays its regulatory effects on morphine analgesia.