Clinically utilized kappa-opioid receptor agonist nalfurafine combined with low-dose naltrexone prevents alcohol relapse-like drinking in male and female mice.

Alcohol relapse is a treatment goal for alcohol dependence and the target for medications' development. Clinically utilized nalfurafine (NFF) is a potent and selective kappa- opioid receptor (KOP-r) agonist, with fewer side effects (e.g., sedation or anhedonia) than classic KOP-r full agonists. We have recently found that NFF reduces excessive alcohol drinking in mice via a KOP-r-mediated mechanism. Here, we further investigated whether NFF alone (1-10 μg/kg) or in combination with naltrexone (NTX, mu-opioid receptor [MOP-r] antagonist) altered alcohol relapse-like drinking using a mouse alcohol deprivation effect (ADE) paradigm to mimic the relapse episodes in human alcoholics. Nalmefene (NMF, clinically utilized KOP-r partial agonist with MOP-r antagonism) was used as a reference compound for the effects on mouse ADE of new NFF + NTX combination. After exposed to 3-week intermittent- access alcohol drinking (two-bottle choice, 24-h access every other day), both male and female mice displayed excessive alcohol intake and then pronounced ADE after 1-week abstinence. NFF prevented the ADE in a dose-dependent manner in both male and female mice. A combination of NFF with NTX reduced the ADE without sex differences at doses lower than those individual effective ones, suggesting synergistic effects between the two compounds. NMF prevented the ADE in both sexes, while selective KOP-r antagonist nor-BNI had no effect. Our new study suggests that a combination of clinically-utilized, potent KOP-r agonist NFF with low-dose NTX has therapeutic potential in alcohol "relapse" treatment.