Fukushima, C. T. | bioRxiv Science

bioRxiv2026

Negative allosteric modulation of α5-GABAA receptors engages dynamic cortical glutamatergic and GABAergic mechanisms underlying adaptive behavior in mice

Chronic stress disrupts glutamatergic and GABAergic plasticity in the medial prefrontal cortex (mPFC), impairing circuit integration and contributing to the pathophysiology of stress-related disorders, such as Major Depressive Disorder (MDD). Rapid-acting antidepressants like ketamine can rapidly reverse these deficits, but its clinical use is limited by psychotomimetic side effects. Notably, the 5-GABAAR negative allosteric modulator (5-NAM) Basmisanil (BSM), reproduces ketamine-like behavioral outcomes in preclinical models, although the cellular mechanisms underlying its actions remain unclear. Here, we investigated whether BSM promotes ketamine-like enhancement of cortical plasticity and engages cell type-specific mechanisms to support adaptive behaviors over time. We show that BSM produced rapid and sustained facilitation of motivational, hedonic, and active coping behaviors via mPFC circuits. BSM induced c-Fos expression in mPFC D1R- and somatostatin-expressing cells, suggesting activation of specific subsets of pyramidal and GABA interneurons. In both mPFC and hippocampus, BSM rapidly activated Erk- or Akt-mTOR signaling pathways as well as increased synaptic proteins critical for glutamatergic and GABAergic function. BSM also reversed maladaptive behaviors induced by chronic unpredictable stress, including impairment in object recognition memory and social interaction. Finally, chemogenetic silencing of mPFC CaMKII-expressing neurons blocked both rapid and sustained actions of BSM, whereas inhibition of mPFC GABA interneurons reversed only long-term behavioral outcomes. These results indicate that 5-GABAAR modulation requires early activation of pyramidal neurons to drive rapid plasticity, while GABAergic adaptations support sustained improvements. This dynamic mechanism restores excitation-inhibition (E/I) balance and highlights GABAergic pathways as therapeutic targets for prefrontal dysfunction in stress disorders.

pharmacology and toxicology↗

bioRxiv2023

Reactive Oxygen Species Generation by Reverse Electron Transfer at Mitochondrial Complex I Under Simulated Early Reperfusion Conditions.

Ischemic tissues accumulate succinate, which is rapidly oxidized upon reperfusion, driving a burst of mitochondrial reactive oxygen species (ROS) generation that triggers cell death. In isolated mitochondria with succinate as the sole metabolic substrate under non-phosphorylating conditions, 90% of ROS generation is from reverse electron transfer (RET) at the Q site of respiratory complex I (Cx-I). Together, these observations suggest Cx-I RET is the source of pathologic ROS in reperfusion injury. However, numerous factors present in early reperfusion may impact Cx-I RET, including: (i) High [NADH]; (ii) High [lactate]; (iii) Mildly acidic pH; (iv) Defined ATP/ADP ratios; (v) Presence of the nucleosides adenosine and inosine; and (vi) Defined free [Ca2+]. Herein, experiments with mouse cardiac mitochondria revealed that under simulated early reperfusion conditions including these factors, overall mitochondrial ROS generation was only 56% of that seen with succinate alone, and only 52% of this ROS was assignable to Cx-I RET. The residual non-RET ROS could be partially assigned to complex III (Cx-III) with the remainder likely originating from other ROS sources upstream of the Cx-I Q site. Together, these data suggest the relative contribution of Cx-I RET ROS to reperfusion injury may be overestimated, and other ROS sources may contribute a significant fraction of ROS in early reperfusion.

biochemistry↗