Cocaine self-administration and naltrindole, a delta-selective opioid antagonist

Recent reports from several laboratories have suggested a role for delta opioid receptors in expressing some of the biochemical and behavioral effects of cocaine. Here, this possibility has been further explored by evaluating the propensity of rats to self-administer i.v. cocaine in the absence or presence of naltrindole, a selective delta opioid antagonist. Following a number of days of stable cocaine intake, and before a day’s session, naltrindole (3 or 10 mg kg^-1) reduced pressing for cocaine, regardless of the schedule of reinforcement. These data further support the role of processes associated with delta opioid receptors in the ability of cocaine to reinforce its own use.