Malignant infarction in cats after prolonged middle cerebral artery occlusion: glutamate elevation related to...

Area of Science:

• Neuroscience
• Cerebrovascular Research
• Biochemistry

Background:

• Investigating glutamate's role in ischemic stroke is crucial for understanding secondary deterioration.
• Space-occupying ischemic stroke models are vital for studying outcomes after reperfusion.

Purpose of the Study:

• To determine the predictive significance of glutamate elevation in space-occupying ischemic stroke.
• To correlate perfusional disturbances with glutamate alterations in a feline transient ischemia model.

Main Methods:

• Transient middle cerebral artery occlusion (3 hours) followed by reperfusion (6 hours) in anesthetized cats.
• Simultaneous measurement of regional cerebral blood flow (CBF), extracellular amino acids, arterial blood pressure, and intracranial pressure.
• Assessment of CBF using Laser-Doppler flowmetry and positron emission tomography; glutamate levels via microdialysis and HPLC.

Main Results:

• Middle cerebral artery occlusion reduced CBF to <25% of control.
• A 30-fold increase in glutamate was observed during ischemia in 50% of cats, with subsequent recovery.
• A secondary glutamate rise during reperfusion correlated with decreased cerebral perfusion pressure (CPP <60 mm Hg) and herniation.

Conclusions:

• Glutamate levels during ischemia and CPP during reperfusion are predictive of fatal outcomes in malignant focal ischemia.
• Secondary glutamate elevation in reperfusion is associated with critically low CPP (<50 mm Hg) and signs of transtentorial herniation.
• Further glutamate increase may be irrelevant to fatal outcome when CPP drops drastically in late-stage ischemia.