Behavioral effects of oxycodone following traumatic brain injury in rats

Abstract

Epidemiological data indicate that drug abuse rates increase following traumatic brain injury (TBI), but the underlying reasons remain unclear. There is overlap in reward pathways and regions commonly damaged in TBI suggesting that TBI could alter risk for drug abuse. Adult male Sprague Dawley rats underwent sham (control) or lateral fluid percussion injury of moderate severity followed by assesment of tolerance development and intravenous self ‐administration behavior. The antinociceptive effects of oxycodone were evaluated using hot plate‐induced paw withdrawal and warm water tail withdrawal models both acutely and following chronic administration of oxycodone. The reinforcing effects of oxycodone were examined using acquisition of oxycodone self‐administration behavior. No consistent differences have been detected in the antinociceptive effects of oxycodone between TBI subjects and sham injured subjects. However the data suggest that the high (0.03 mg/kg/infusion) and intermediate (0.01 mg/kg/infusion) doses of oxycodone resulted in a faster rate and a higher total percentage of TBI subjects acquiring self‐administration. Additionally, the TBI subjects appeared to be less sensitive to oxycodone's effects, self‐administering the highest number of infusions at the 0.03 mg/kg/infusion dose as compared to sham injured subjects. Research supported by DoD grant W81XWH‐11–1‐0374.