Optogenetic Inhibition of Striatal GABAergic Neuronal Activity Improves Outcomes After Ischemic Brain Injury.

BACKGROUND AND PURPOSE: Striatal GABAergic neuron is known as a key regulator in adult neurogenesis. However, the specific role of striatal GABAergic neuronal activity in the promotion of neurological recovery after ischemic stroke remains unknown. Here, we used optogenetic approach to investigate these effects and mechanism.

METHODS: Laser stimulation was delivered via an implanted optical fiber to inhibit or activate the striatal GABAergic neurons in Gad2-Arch-GFP or Gad2-ChR2-tdTomato mice (n=80) 1 week after 60-minute transient middle cerebral artery occlusion. Neurological severity score, brain atrophy volume, microvessel density, and cell morphological changes were examined using immunohistochemistry. Gene expression and protein levels of related growth factors were further examined using real-time polymerase chain reaction and Western blotting.

RESULTS: Inhibiting striatal GABAergic neuronal activity improved functional recovery, reduced brain atrophy volume, and prohibited cell death compared with the control ( P <0.05). Microvessel density and bFGF (basic fibroblast growth factor) expression in the inhibition group were also increased ( P <0.05). In contrast, activation of striatal GABAergic neurons resulted in adverse effects compared with the control ( P <0.05). Using cocultures of GABAergic neurons, astrocytes, and endothelial cells, we further demonstrated that the photoinhibition of GABAergic neuronal activity could upregulate bFGF expression in endothelial cells, depending on the presence of astrocytes. The conditioned medium from the aforementioned photoinhibited 3-cell coculture system protected cells from oxygen glucose deprivation injury.

CONCLUSIONS: After ischemic stroke, optogenetic inhibition of GABAergic neurons upregulated bFGF expression by endothelial cells and promoted neurobehavioral recovery, possibly orchestrated by astrocytes. Optogenetically inhibiting neuronal activity provides a novel approach to promote neurological recovery.