A review of operant ethanol self-administration using the sipper model: Methodological advances and a novel standardized analysis tool
AbstractDespite decades of research, no new FDA-approved medications for alcohol use disorder (AUD) have emerged in over 25 years. Enhancing the translational relevance of preclinical models by more precisely capturing the behavioral and neurobiological features of AUD offers a promising path toward identifying novel therapeutic targets. Operant self-administration paradigms are essential for modeling voluntary ethanol intake in rodents, yet traditional approaches often confound appetitive (seeking) and consummatory (intake) behaviors. The sipper model addresses this limitation by allowing extended, uninterrupted access to ethanol following operant responding, enabling a clearer dissociation between seeking and consumption. In this review, we synthesize key findings from studies employing the sipper model to investigate the behavioral and neurobiological mechanisms underlying alcohol use. We emphasize how over two decades of research employing the sipper model have demonstrated that ethanol- directed behaviors are dynamic processes, shaped by internal states, environmental cues, and prior experience. Finally, we introduce medparser, a new open-source R package designed to standardize the analysis of high-resolution licking data generated by sipper paradigms. By promoting reproducibility and cross-study comparability, this tool supports rigorous behavioral phenotyping. Together, these methodological and analytical advances enhance the translational potential of preclinical models and may ultimately aid in the discovery of novel therapeutic targets for AUD.