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

Abstract

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.

Chemogenetic Stimulation and Silencing of the Insula, Amygdala, Nucleus Accumbens, and Their Connections Differentially Modulate Alcohol Drinking in Rats

“…When we challenged these animals by giving them CNO 60 min before the onset of the alcohol drinking sessions, we saw significant changes in alcohol consumption in animals expressing the DREADDs in all three brains areas. First, as a replication of our previously published data (Haaranen et al, 2020 ), CNO significantly altered alcohol intake in rats expressing Gq-DREADDs in the insula, as shown by a significant effect for session ( F (1,27) = 7.31, p = 0.012) and a significant session × vector interaction ( F (2,27) = 7.60, p = 0.002). A comparison of the CNO challenge sessions with the baseline sessions indicated that the 54% decrease in drinking produced by the Gq-DREADDs was significant ( t (9) = 4.00, p = 0.003), with no changes in the other CNO-challenged groups.…”

“…In a replication of our previous study, we found that anterior insula stimulation by the Gq-DREADDs reduced alcohol consumption (Haaranen et al, 2020 ). The simple limited access alcohol drinking model does not allow us to analyze which aspects of drinking behavior were affected by insula stimulation apart from the consumed alcohol volume.…”

“…This could suggest that insula stimulation causes aversive states or general malaise. We have recently demonstrated with c-Fos mapping and pharmacological magnetic resonance imaging that anterior insula stimulation activates also the more posterior insula areas (Haaranen et al, 2020 ). Optogenetic or chemogenetic stimulation of the posterior insula induced freezing and escape movements, and stimulation of posterior insula projections to the central amygdala caused aversive states and avoidance behavior (Schiff et al, 2018 ; Gehrlach et al, 2019 ).…”

“…Ethanol and water intake during the sessions were measured. We chose the 10 mg/kg CNO dose to maximally activate both Gq- and Gi-DREADDs without disturbing motivated behaviors or locomotion, as reported previously (Farrell and Roth, 2013 ; Mahler and Aston-Jones, 2018 ; Haaranen et al, 2020 ). We also controlled the possible nonspecific off-target effects by including an EGFP-expressing non-DREADD group in all experiments.…”

Chemogenetic Inactivation of Orbitofrontal Cortex Decreases Cue‐induced Reinstatement of Ethanol and Sucrose Seeking in Male and Female Wistar Rats

“…As with OFC, contributions of AI to alcohol seeking are complex and depend on a number of factors such as whether alcohol is presented in conjunction with a paired aversive outcome (Seif et al, 2013) or punishment-imposed abstinence (Campbell et al, 2019). Intriguingly, recent work has shown that chemogenetic inhibition of AI increases alcohol operant self-administration (Jaramillo et al, 2018a) and that chemogenetic activation of AI decreases alcohol (and sucrose) intake (Haaranen et al, 2020). Together these results show that, like OFC, AI is strongly involved in the use of alcohol and other reinforcers.…”