Dysregulation of oxygen hemodynamic responses to synaptic train stimulation in a rat hippocampal model of subarachnoid hemorrhage

We investigated microvascular reactivity to synaptic train stimulation after induction of subarachnoid hemorrhage in adult rats, analyzing tissue oxygen levels [pO2] in intact hippocampus. In control rats, hippocampal pO2averaged 11.4 mm Hg whereas hemodynamic responses averaged 13.1 mm Hg (to a 25 s train). After subarachnoid hemorrhage (at 2 days), we recorded a dramatic elevation in baseline pO2in the hippocampus (to 68.4 mm Hg) accompanied by inverted pO2responses to synaptic train stimulation (-9.46 mm Hg). These significant changes in baseline hippocampal pO2and inverted pO2responses after subarachnoid hemorrhage indicate severe alterations of neurovascular coupling and neuronal viability.