Effects of traumatic brain injury on oxycodone self-administration in rats

Epidemiological data indicate that patients who experience a traumatic brain injury (TBI) have an elevated risk of developing substance abuse disorders, but the underlying neurobiological connections remain unclear. To further understand the relationship between TBI and substance abuse, we investigated the effects of TBI on the rewarding effects of oxycodone in clinically-relevant models. Our evaluation utilized lateral fluid percussion injury of moderate severity followed by assessment of oxycodone self-administration behavior in adult male Sprague-Dawley rats. The reinforcing effects of oxycodone were examined under fixed ratio (FR) and progressive ratio (PR) schedules as well as in a reinstatement model of relapse. Relative to control, TBI subjects self-administered greater levels of the intermediate doses of oxycodone under FR conditions and exhibited up to 8-fold higher responding during time out periods when no drug or cues were available. Under PR conditions, multiple doses of oxycodone also mainta...