UWEC CERCA 2026

Opioids have serious repercussions including overdose and death. Drugs that counteract the opioid overdose have become imperative. Naltrexone is an opioid antagonist that limits endorphin functions in the brain; its specific mechanism is unknown. Chronic, intermittent sucrose solution access increases endorphin function. Previously, our laboratory demonstrated male rats with chronic, intermittent sucrose learned to discriminate naltrexone (0.1 to 3.2 mg/kg) from saline. In this study, we sought to establish discrimination in female and male rats. Rats were trained to lever press in operant chambers. Rats then received 12-hour access to 25% sucrose solutions for two weeks. After which, discrimination training began. Rats were trained to discriminate between naltrexone (1.0 mg/kg) and saline. After naltrexone administration, left lever responses resulted in 45 mg sugar pellet delivery; right lever presses produced eight seconds of darkness. Contingencies were reversed following saline administration. After training, rats received sucrose for 12 hours. Training continued until > 80% condition-appropriate responses occurred for 8 of 10 sessions. During tests, responses toward either lever were reinforced. Naltrexone dose-effect curves (0.1-1 mg/kg) were created. Naltrexone was more potent in females than males. Knowledge about the naltrexone and its uses can be used to combat opioid use and dependency.