Corey Fee, former PhD student in the Sibille Lab, just published part of his thesis in the International Journal of Neuropsychopharmacology

Deficits in somatostatin-positive gamma-aminobutyric acid interneurons (“SST+ GABA cells”) are commonly reported in human studies of mood and anxiety disorder subjects. A causal link between SST+ cell dysfunction and symptom-related behaviors has been proposed based on rodent studies showing that chronic stress, a major risk factor for mood and anxiety disorders, induces a low SST+ GABA cellular phenotype across corticolimbic brain regions, that lowering Sst, SST+ cell, or GABA functions induces depressive-/anxiety-like behaviors (a rodent behavioral construct collectively defined as ‘behavioral emotionality’), and that disinhibiting SST+ cells has antidepressant-like effects. Recent studies found that compounds preferentially potentiating receptors mediating SST+ cell functions, α5-GABAA receptor positive allosteric modulators (α5-PAMs), achieved antidepressant-like effects. Together, evidence suggests that SST+ cells regulate mood and cognitive functions that are disrupted in mood disorders and that rescuing SST+ cell function via α5-PAM may represent a targeted therapeutic strategy.

We developed a mouse model allowing chemogenetic manipulation of brain-wide SST+ cells and employed behavioral characterization 30 min after repeated acute silencing to identify contributions to symptom-related behaviors. We then assessed whether an α5-PAM, GL-II-73, could rescue behavioral deficits.

Brain-wide SST+ cell silencing induced features of stress-related illnesses, including elevated neuronal activity and plasma corticosterone levels, increased anxiety- and anhedonia-like behaviors, and impaired short-term memory. GL-II-73 led to antidepressant- and anxiolytic-like improvements among behavioral deficits induced by brain-wide SST+ cell silencing.

Our data validate SST+ cells as regulators of mood and cognitive functions and demonstrate that bypassing low SST+ cell function via α5-PAM represents a targeted therapeutic strategy.