Ischemic insult to cerebellar Purkinje cells causes diminished GABAA receptor function and Allopregnanolone neuroprotection is associated with GABAA receptor stabilization

Cerebellar Purkinje cells (PC) are particularly vulnerable to ischemic injury and excitotoxicity, although the molecular basis of this sensitivity remains unclear. We tested the hypothesis that ischemia causes rapid down-regulation of GABAA receptors in cerebellar PC, thereby increasing susceptibility to excitotoxicity. Oxygen-glucose deprivation (OGD) caused a decline in functional GABAA receptors, within the first hour of re-oxygenation. Decreased amplitude of miniature inhibitory post-synaptic potentials confirmed that OGD caused a significant decrease in functional synaptic GABAA receptors and quantitative Western blot analysis demonstrated the loss of GABAA receptor current was associated with a decline in total receptor protein. Interestingly, the potent neuroprotectant allopregnanolone (ALLO) prevented the decline in GABAA receptor current and protein. Consistent with our in vitro data, global ischemia in mice caused a significant decline in total cerebellar GABAA receptor protein and PC specific immunoreactivity. Moreover, ALLO provided strong protection of PC and prevented ischemia-induced decline in GABAA receptor protein. Our findings indicate that ischemia causes a rapid and sustained loss of GABAA receptors in PC, whereas ALLO prevents the decline in GABAA receptors and protects against ischemia-induced damage. Thus, interventions which prevent ischemia-induced decline in GABAA receptors may represent a novel neuroprotective strategy.