Alcohol Use Disorder (AUD) necessitates effective treatment options, as current pharmacotherapies show limited clinical success despite preclinical efficacy. Oxytocin (OXT), crucial for social behaviors, is a potential AUD pharmacotherapy due to its role in mediating processes associated with alcohol use and its potential to bolster abstinence through social support. To improve translational validity, this study used intranasal (IN) OXT administration—a clinically relevant route—in socially housed prairie voles, a rodent model exhibiting translational validity for social behavior mechanisms and alcohol consumption patterns similar to humans. A mixed-cage design, including treated and untreated voles, mirrored real-world medication-assisted scenarios. While previous studies demonstrated OXT's efficacy in reducing AUD measures, the molecular mechanisms, including its brain transport, remain unclear. OXT's transport across the blood-brain barrier (BBB) is known, and evidence suggests central action to inhibit alcohol intake. However, the precise mechanisms remain elusive. Recent research suggests the Receptor for Advanced Glycation End-products (RAGE) as a potential mediator of OXT transport. Given OXT's poor pharmacokinetic properties, the study also investigated the efficacy of LIT-001, a small-molecule OXTR agonist with a superior pharmacokinetic profile and high OXTR selectivity, in modulating alcohol intake. Experiments assessed the effects of IN OXT on alcohol intake in socially housed prairie voles, RAGE's contribution to OXT brain penetrance, and LIT-001's ability to modulate alcohol intake, considering known sex differences in OXT functioning.

The existing literature highlights the limitations of current AUD pharmacotherapies, underscoring the need for novel treatment approaches. Oxytocin's role in social behavior and its potential to influence alcohol use have garnered significant attention. Previous research indicated OXT's involvement in mediating processes associated with alcohol consumption, suggesting that its social effects could be leveraged to enhance abstinence through social support. However, inconsistencies in preclinical findings and limited understanding of OXT's molecular mechanisms of action, particularly its brain penetration, emphasize the need for further research using translationally relevant models and approaches. The use of prairie voles as an animal model, intranasal administration of OXT, and the mixed-cage design aimed to bridge the gap between preclinical and clinical research in AUD treatment.

Adult male and female prairie voles from the laboratory colony at Oregon Health & Science University were used. All procedures adhered to ethical guidelines and were approved by the Institutional Animal Care and Use Committee. For experiments examining OXT's effects on alcohol consumption, a continuous-access two-bottle choice (CA-2BC) paradigm was employed, with animals given ad libitum access to alcohol and water for six days. Fluid consumption was meticulously measured using the Herdsman-2 (HM2) cage system, which allowed for precise, individualized fluid intake measurements in socially housed animals. A mixed-cage design ensured that treated and control animals were housed together. Intranasal OXT (5.0 mg/kg and 10.0 mg/kg) or intraperitoneal LIT-001 (10 mg/kg) were administered, along with respective vehicle controls. To assess OXT brain penetration and RAGE's involvement, animals received either IN or IP administration of deuterium-labeled OXT (d5 OXT) following pretreatment with either a RAGE antagonist (FPS ZM1) or saline. Brain levels of d5 OXT were then quantified using liquid chromatography-tandem triple quadrupole mass spectrometry (LC-MS/MS). RAGE expression in the prairie vole brain was confirmed using RT-PCR and immunohistochemistry. Alcohol and water intake, drink size, and number of visits were analyzed using non-parametric statistics due to non-normal data distribution. Experiments were conducted on both male and female animals.

Intranasal OXT significantly decreased alcohol intake in male, but not female, prairie voles. This effect was primarily attributed to a reduction in drink size rather than the number of drinking episodes. LC-MS/MS analysis confirmed that exogenously administered OXT penetrated the prairie vole brain, and this penetration was significantly reduced by RAGE antagonist pre-treatment when administered intranasally, indicating RAGE's involvement in IN OXT transport into the brain, but not via IP. Intraperitoneal administration of LIT-001, a small-molecule OXTR agonist, also selectively decreased alcohol intake in males. RAGE was detected in the prairie vole brain, particularly in the choroid plexus, hypothalamus, and hippocampus, confirming its expression in areas relevant to central OXT penetration. The study confirmed that the intranasal route is more effective in decreasing alcohol consumption than the intraperitoneal route.

The findings highlight a sex-dependent effect of OXTR agonism on alcohol consumption, with males showing a significant reduction in alcohol intake following both IN OXT and IP LIT-001 administration. The lack of significant effect in females may be related to the importance of OXT for female reproductive and maternal behaviors, making their drug- and socially-targeted behaviors less susceptible to alterations in OXT activity. The involvement of RAGE in OXT brain penetration via the IN route suggests that this transport mechanism should be considered in clinical trials using this administration route. The sex differences observed might also be explained by differences in OXTR expression and distribution in the brain between males and females or by differential effects on the salience of social stimuli. The use of LIT-001, a small molecule agonist, opens avenues to develop more convenient and effective therapies.

This study demonstrates a male-selective reduction in alcohol intake following OXTR agonism in socially housed prairie voles. RAGE plays a role in OXT transport into the brain, primarily via the intranasal route. Small-molecule OXTR agonists provide a promising alternative to OXT for the treatment of AUD. Future research should explore the underlying mechanisms of the sex differences and the potential of other administration methods.

The study primarily focused on acute effects of OXT and LIT-001 on alcohol consumption. Long-term effects and potential tolerance development were not investigated. The specific brain regions and neural pathways involved in the observed sex-dependent effects require further elucidation. The study only used one dose of the RAGE antagonist, and additional research would be beneficial to investigate a dose response. Further investigation into the mechanisms underlying the sex-specific responses could inform the development of more targeted and effective therapies.