Somatostatin (SST) neurons have been implicated in a variety of neuropsychiatric disorders such as depression and anxiety, but their role in substance use disorders, including alcohol use disorder (AUD), is not fully characterized. Here, we found that repeated cycles of alcohol binge drinking via the Drinking-in-the-Dark (DID) model led to hypoactivity of SST neurons in the prelimbic (PL) cortex by diminishing their action potential firing capacity and excitatory/inhibitory transmission dynamic. We examined their role in regulating alcohol consumption via bidirectional chemogenetic manipulation. Both hM3Dq-induced excitation and KORD-induced silencing of PL SST neurons reduced alcohol binge drinking in males and females, with no effect on sucrose consumption. Alcohol binge drinking disinhibited pyramidal neurons by augmenting SST neurons-mediated GABA release and synaptic strength onto other GABAergic populations and reducing spontaneous inhibitory transmission onto pyramidal neurons. Pyramidal neurons additionally displayed increased intrinsic excitability. Direct inhibition of PL pyramidal neurons via hM4Di was sufficient to reduce alcohol binge drinking. Together these data revealed an SST-mediated microcircuit in the PL that modulates the inhibitory dynamics of pyramidal neurons, a major source of output to subcortical targets to drive reward-seeking behaviors and emotional response.

Human adolescence is a period of development characterized by wide ranging emotions and behavioral risk taking, including binge drinking (Konrad et al., 2013). These behavioral manifestations of adolescence are complemented by growth in the neuroarchitecture of the brain, including synaptic pruning (Spear, 2013) and increases in overall white matter volume (Perrin et al., 2008). During this period of profound physiological maturation, the adolescent brain has a unique vulnerability to negative perturbations. Alcohol consumption and stress exposure, both of which are heightened during adolescence, can individually and synergistically alter these neurodevelopmental trajectories in positive and negative ways (conferring both resiliency and susceptibility) and influence already changing neurotransmitter systems and circuits. Importantly, the literature is rapidly changing and evolving in our understanding of basal sex differences in the brain, as well as the interaction between biological sex and life experiences. The animal literature provides the distinctive opportunity to explore sex-specific stress- and alcohol- induced changes in neurocircuits on a relatively rapid time scale. In addition, animal models allow for the investigation of individual neurons and signaling molecules otherwise inaccessible in the human brain. Here, we review the human and rodent literature with a focus on cortical development, neurotransmitters, peptides, and steroids, to characterize the field’s current understanding of the interaction between adolescence, biological sex, and exposure to stress and alcohol.

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Adolescent drug consumption has increased risks to the individual compared to consumption in adulthood, due to the likelihood of long-term and permanent behavioral and neurological adaptations. However, little is known about how adolescent alcohol consumption influences the maturation and trajectory of cortical circuit development. Here, we explore the consequences of adolescent binge drinking on somatostatin (SST) neuronal function in the prelimbic (PL) cortex. We find that adolescent drinking-in-the-dark (DID) produces sex-dependent increases in intrinsic excitability of SST neurons, persisting well into adulthood. We found a complementary reduction in pyramidal neuron excitability immediately after binge drinking; however, this hypoexcitability rebounded towards increased pyramidal neuron activity in adulthood in females, suggesting long-term homeostatic adaptations in this circuit. Together, this suggests that binge drinking during key developmental timepoints leads to permanent changes in PL microcircuitry function, which may have broad behavioral implications.