Silencing the insular-striatal circuit decreases alcohol self-administration and increases sensitivity to alcohol

Internal drug states/cues can impact drug taking, as pretreatment with a moderate to high alcohol dose (i.e., loading dose) can decrease subsequent alcohol self-administration, alcohol-seeking, and relapse-like drinking. The insular cortex (IC) is implicated in processing information about internal states and findings show that silencing the IC and its projections to the nucleus accumbens core (AcbC) enhance sensitivity to the interoceptive effects of alcohol. Therefore, the goal of the present work was to determine the functional role of IC-AcbC projections in modulating the effects of alcohol pretreatment on operant alcohol self-administration. Long-Evans rats were trained to self-administer a sweetened alcohol solution (15% alcohol (v/v) + 2% sucrose (w/v)) and on test sessions received pretreatment with an alcohol loading dose. A chemogenetic strategy (i.e., hM4D Designer Receptors Exclusively Activated by Designer Drugs [DREADDs]) was implemented to silence the IC-AcbC projections and test the functional role of the insular-striatal circuitry in regulating self-administration following the alcohol loading doses. Alcohol self-administration decreased following pre-session treatment with alcohol, confirming titration of alcohol drinking following a loading dose of alcohol. Chemogenetic silencing of IC-AcbC projections decreased alcohol self-administration under baseline conditions (i.e., water loading dose) and the reduction in self-administration of an alcohol loading dose, implicating a role for this circuit in the maintenance of alcohol self-administration and suggesting increased sensitivity to the alcohol loading dose. These findings provide evidence for the critical nature of insular-striatal circuitry in ongoing alcohol self-administration, and specifically in relation to interoceptive/internal cues that can impact alcohol drinking.