Leptin status alters buprenorphine-induced antinociception in obese mice with dysfunctional leptin receptors.

Buprenorphine is an opiate used for pain management and to treat opiate addiction. The cytokine leptin can modulate nociception, but the extent to which buprenorphine-induced antinociception varies as a function of leptin signaling has not been characterized. Four congenic mouse lines with phenotypes that include differences in body weight and leptin status were used to test the hypothesis that the antinociceptive effects of buprenorphine vary as function of sex and leptin signaling. Each mouse line was comprised of males (n=12) and females (n=12) for a total of 96 animals. Groups included C57BL/6J (B6) mice (wild type), B6 mice with diet-induced obesity (DIO), obese B6.Cg-Lep/J (ob/ob) mice lacking leptin, and obese B6.BKS(D)-Lepr/J (db/db) mice with dysfunctional leptin receptors. The dependent measure was tail flick latency (TFL) in seconds for mouse-initiated tail removal from a warm water bath. Independent variables were intraperitoneal administration of saline (control) or buprenorphine (0.3mg/kg). Within every mouse line, buprenorphine significantly increased TFL relative to saline. Compared to the other mouse lines, db/db mice with dysfunctional leptin receptors had a significantly longer TFL after saline and after buprenorphine. TFL did not vary significantly by body weight or sex. The results provide novel support for the interpretation that acute thermal nociception is associated with altered leptin signaling.