Anterior Insular Cortex is Critical for the Propensity to Relapse Following Punishment-Imposed Abstinence of Alcohol Seeking

Anterior insula stimulation suppresses appetitive behavior while inducing forebrain activation in alcohol-preferring rats

The anterior insular cortex plays a key role in the representation of interoceptive effects of drug and natural rewards and their integration with attention, executive function, and emotions, making it a potential target region for intervention to control appetitive behaviors. Here, we investigated the effects of chemogenetic stimulation or inhibition of the anterior insula on alcohol and sucrose consumption. Excitatory or inhibitory designer receptors (DREADDs) were expressed in the anterior insula of alcohol-preferring rats by means of adenovirus-mediated gene transfer. Rats had access to either alcohol or sucrose solution during intermittent sessions. To characterize the brain network recruited by chemogenetic insula stimulation we measured brain-wide activation patterns using pharmacological magnetic resonance imaging (phMRI) and c-Fos immunohistochemistry. Anterior insula stimulation by the excitatory Gq-DREADDs significantly attenuated both alcohol and sucrose consumption, whereas the inhibitory Gi-DREADDs had no effects. In contrast, anterior insula stimulation failed to alter locomotor activity or deprivation-induced water drinking. phMRI and c-Fos immunohistochemistry revealed downstream activation of the posterior insula and medial prefrontal cortex, as well as of the mediodorsal thalamus and amygdala. Our results show the critical role of the anterior insula in regulating reward-directed behavior and delineate an insula-centered functional network associated with the effects of insula stimulation. From a translational perspective, our data demonstrate the therapeutic potential of circuit-based interventions and suggest that potentiation of insula excitability with neuromodulatory methods, such as repetitive transcranial magnetic stimulation (rTMS), could be useful in the treatment of alcohol use disorders.

A glutamatergic insular-striatal projection regulates the reinstatement of cue-associated morphine-seeking behavior in mice

Recently, the insular cortex (IC) was identified as part of the neuronal circuit responsible for the reward expectations in cue-triggered behaviours. Moreover, there are evidences that connections between the IC and the ventral striatum, particularly with the nucleus accumbens (NAc), may mediate the retrieval and performance of actions based on incentive memory. However, the precise role of the IC-NAc connections in cue-related drug-seeking behaviour remains unclear. We used the morphine-induced conditioned place preference (CPP) paradigm to assess the formation and relapse of cue-related drug-seeking. cFos immunostaining was used to determine the activation of the brain regions. Chemogenetic and optogenetic methods were used to manipulate the activity of IC-to-NAc projection neurons. The result showed that neurons in IC and NAc core but not NAc shell were activated following cue-induced morphine-seeking behaviour. Negligible effect of inhibition of IC-to-NAc core projection (IC^{→NAc core}) on morphine CPP expression, whereas chemogenetic inactivation of this projection potently blocked the reinstatement of expressed morphine CPP. Furthermore, optogenetic inhibition of glutamatergic IC^{→NAc core} inputs significant suppressed the CPP reinstatement without significant effect on CPP expression. We demonstrated here, for the first time, that IC^{→NAc core} glutamatergic projection is required for the reinstatement of cue-associated drug seeking behaviour in mice. The present study provide insights into modulations of relapse of cue-associated drug-seeking behaviour following repeated overexposure to opioids in humans.