Sex differences in the effectiveness of buprenorphine to decrease rates of responding in rhesus monkeysSchwienteck, Kathryn L.; Negus, S. Stevens; Banks, Matthew L.Behavioural Pharmacology: June 2019 - Volume 30 - Issue 4 - p 358–362 doi: 10.1097/FBP.0000000000000437 SHORT REPORTS Buy Abstract Author InformationAuthors Article MetricsMetrics Sex differences in μ-opioid receptor (MOR) agonist-induced antinociception have been reported in nonhuman primates. The degree to which μ-opioid receptor agonist sex differences in nonhuman primates extend to other behavioral endpoints remains unknown. The present study compared the behavioral effects of three MOR ligands (fentanyl, buprenorphine, and naltrexone) that varied in efficacy to stimulate [35S]-GTPγS binding (from highest to lowest: fentanyl, buprenorphine, and naltrexone) in male and female rhesus monkeys. Male (n=3) and female (n=3) monkeys were trained to respond under a fixed-ratio 10 schedule of food presentation during daily sessions consisting of multiple components. Once rates of responding were stable, cumulative dose–effect functions were determined for intramuscular fentanyl (0.00032–0.032 mg/kg), buprenorphine (0.001–1 mg/kg), and naltrexone (0.01–0.1 mg/kg). Fentanyl dose-dependently decreased rates of responding in both sexes and the corresponding ED50 values were not significantly different. Buprenorphine dose-dependently decreased rates of responding in females, but not males. Naltrexone did not significantly alter behavior in either females or males. Overall, these results suggest that the expression of sex differences in MOR pharmacology depends upon both the efficacy of the MOR ligand and the behavioral endpoint. Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia, USA Correspondence to Matthew L. Banks, PharmD, PhD, Department of Pharmacology and Toxicology, 410 North 12th Street, Box 980613, Richmond, VA 23298, USA E-mail: firstname.lastname@example.org Received June 15, 2018 Accepted August 11, 2018 Copyright © 2019 YEAR Wolters Kluwer Health, Inc. All rights reserved.