Alterations in Purkinje cell GABAA receptor pharmacology following oxygen and glucose deprivation and cerebral ischemia reveal novel contribution of β1-subunit-containing receptors

Cerebellar Purkinje cells (PCs) are particularly sensitive to cerebral ischemia, and decreased GABAA receptor function following injury is thought to contribute to PC sensitivity to ischemia‐induced excitotoxicity. Here we examined the functional properties of the GABAA receptors that are spared following ischemia in cultured Purkinje cells from rat and in vivo ischemia in mouse. Using subunit‐specific positive modulators of GABAA receptors, we observed that oxygen and glucose deprivation (OGD) and cardiac arrest‐induced cerebral ischemia cause a decrease in sensitivity to the β2/3‐subunit‐preferring compound, etomidate. However, sensitivity to propofol, a β‐subunit‐acting compound that modulates β1–3‐subunits, was not affected by OGD. The α/γ‐subunit‐acting compounds, diazepam and zolpidem, were also unaffected by OGD. We performed single‐cell reverse transcription–polymerase chain reaction on isolated PCs from acutely dissociated cerebellar tissue and observed that PCs expressed the β1‐subunit, contrary to previous reports examining GABAA receptor subunit expression in PCs. GABAA receptor β1‐subunit protein was also detected in cultured PCs by western blot and by immunohistochemistry in the adult mouse cerebellum and levels remained unaffected by ischemia. High concentrations of loreclezole (30 μm) inhibited PC GABA‐mediated currents, as previously demonstrated with β1‐subunit‐containing GABAA receptors expressed in heterologous systems. From our data we conclude that PCs express the β1‐subunit and that there is a greater contribution of β1‐subunit‐containing GABAA receptors following OGD. Cerebellar Purkinje cells (PCs) are particularly sensitive to cerebral ischemia and decreased GABAA receptor function following injury is thought to contribute to PC sensitivity to ischemia‐induced excitotoxicity. Here we examined the functional properties of the GABAA receptors that are spared following ischemia.