Project Summary Alcohol use disorder is characterized by escalating alcohol intake over time, accompanied by development of tolerance to alcohol’s reinforcing effects that may promote further increases in drinking. Binge and high- intensity drinking (BHID) is a pattern of excessive drinking marked by both rapid alcohol intake and sustained high alcohol consumption over time, but the role of reward tolerance in and the neurobiological causes of BHID are unknown. C57BL/6J mice and the selectively bred crossed High Alcohol Preferring (cHAP) mice provide ideal models to investigate the neural bases of BHID: C57BL/6J mice develop rapid, binge-like drinking in the Drinking in the Dark paradigm, whereas cHAP steadily consume alcohol throughout the day under 2-bottle choice (10% alcohol vs. water) access to achieve blood ethanol concentrations three times the legal driving limit. Using these two mouse genotypes and their respective models of BHID, this project examines how BHID alters alcohol motivation, measured as changes in alcohol seeking and taking in operant self-administration and conditioned place preference. Additionally, neurocircuits that may underlie these shifts in behavior will be investigated, centering on the dorsomedial striatum (DMS) as a terminal region that shows tolerance to alcohol at the single neuron level after excessive alcohol intake in cHAP mice, particularly in females. This proposal investigates whether increased DMS excitatory activity after drinking and the associated alcohol tolerance is due to strengthening of inputs from the basolateral amygdala (BLA), assessed using slice electrophysiology. Centrality of potentiated BLA input to DMS for neuroadaptations to BHID, as well as involvement of this BLA- DMS circuit in alcohol-motivated behaviors altered after BHID, will be investigated using chemogenetics to manipulate circuit activity. Finally, cortical inputs to the BLA from the anterior insula and medial prefrontal cortex will be tested for their ability to regulate the activity of BLA neurons that project to DMS and plasticity following BHID. Together, these studies examine if BHID is associated with reward tolerance and examine one putative neuroadaptive mechanism that may underlie this tolerance. By elucidating how BHID alters activity in a disynaptic circuit terminating in the DMS, and how the BLA-DMS node of the circuit regulates alcohol reinforcement and consumption, this project will provide knowledge about one putative source of BHID effects on the brain and behavior. Given the sex differences in DMS adaptation to alcohol history, these studies may also elucidate sex-specific mechanisms for neuroadaptations underlying excessive alcohol intake.