GABAA receptor agonists(Universitätsmedizin der Johannes Gutenberg-Universität Mainz)

Clinical and preclinical studies have identified somatostatin (SST)-positive interneurons as critical elements that regulate the vulnerability to stress-related psychiatric disorders. Conversely, disinhibition of SST neurons in mice results in resilience to the behavioral effects of chronic stress. Here, we established a low-dose chronic chemogenetic protocol to map these changes in positively and negatively motivated behaviors to specific brain regions. AAV-hM3Dq-mediated chronic activation of SST neurons in the prelimbic cortex (PLC) had antidepressant drug-like effects on anxiety- and anhedonia-like motivated behaviors in male but not female mice. Analogous manipulation of the ventral hippocampus (vHPC) had such effects in female but not male mice. Moreover, the activation of SST neurons in the PLC of male mice and the vHPC of female mice resulted in stress resilience. Activation of SST neurons in the PLC reversed prior chronic stress-induced defects in motivated behavior in males but was ineffective in females. Conversely, activation of SST neurons in the vHPC reversed chronic stress-induced behavioral alterations in females but not males. Quantitation of c-Fos⁺ and FosB⁺ neurons in chronic stress-exposed mice revealed that chronic activation of SST neurons leads to a paradoxical increase in pyramidal cell activity. Collectively, these data demonstrate that GABAergic microcircuits driven by dendrite targeting interneurons enable sex- and brain-region-specific neural plasticity that promotes stress resilience and reverses stress-induced anxiety- and anhedonia-like motivated behavior. The data provide a rationale for the lack of antidepressant efficacy of benzodiazepines and superior efficacy of dendrite-targeting, low-potency GABA_A receptor agonists, independent of sex and despite striking sex differences in the relevant brain substrates.

Dimdazenil (Junoenil^®) is a small-molecule, oral, partial positive allosteric modulator of the gamma-aminobutyric acid (GABA)_A receptor that is being developed by Zhejiang Jingxin Pharmaceutical in collaboration with Evotec for the treatment of insomnia. Dimdazenil is designed to overcome issues associated with full GABA_A receptor agonists, such as tolerance, withdrawal symptoms and associated adverse effects. On 29 November 2023, dimdazenil oral capsules received approval in China for the short-term treatment of insomnia. This article summarizes the milestones in the development of dimdazenil leading to this first approval for insomnia.