Rats were pretreated with systemic infusions of vehicle or GEP44 prior to fentanyl self-administration test sessions. Food intake, water consumption, and body weight were measured up to 24 hours post infusion. In self-administration tests, total active lever responses (A) and total fentanyl infusions (B) were significantly decreased in rats pretreated with 0.3 and 2.4 nmol/kg GEP44 versus vehicle (n=24/treatment; *p<0.01, Bonferroni). (C) GEP44 did not affect 24-hour kaolin intake in fentanyl-experienced rats (n=10/treatment). (D) GEP44 significantly decreased cumulative chow intake in fentanyl-experienced rats compared to vehicle-treated controls (n=13/treatment; *p<0.05, Bonferroni). (E) No effects of systemic exendin-4 were found on 24-hour water intake in fentanyl-experienced rats. (F) GEP44 significantly decreased body weight in fentanyl-experienced rats compared to vehicle-treated controls (n=13/treatment; *p<0.05, Bonferroni).