Researchers studying sugar addiction gave rats chronic, intermittent sucrose access (10-25% sucrose solutions for 12 hours). Increased endorphin and dopamine levels were observed and naloxone (Narcan) administration induced opioid withdrawal signs. We trained male rats to discriminate between injections the opioid antagonist naltrexone and saline. We found sucrose consumption an hour before the training session (and 11 hours after) produced long-term changes in opioid function. Sucrose’s effects on endorphins lasted about 2 weeks. In this study, we assessed potential sex differences (trained the discrimination in female and male rats) and are interested in determining which opioid receptor type(s) are influenced by chronic, intermittent sucrose administration. We also changed the procedure. Rats received all sucrose post-session. We found fewer rats learned the discrimination indicating pre-session sucrose is important. Females and males acquired the discrimination similarly. Smaller naltrexone doses induced effects in females. Although access to chronic, intermittent sucrose solutions produces long-lasting changes in opioid function, the timing of sucrose access is important in training a naltrexone-saline discrimination in this paradigm.
