THE OLIGEMIC PHASE OF CORTICAL SPREADING DEPRESSION IS NOT BLOCKED BY TIRILAZAD MESYLATE (U-74006F)

Cortical spreading depression is characterised by a wave of depolarization that moves across the cortex leaving in its wake a state of hyperpolarization. Characteristic changes in cerebral blood flow are also seen and these consist of a wave of hyperemia followed by an oligemia, the latter lasting some hours in some experimental animals including the cat. In this study cerebral blood flow was measured using laser Doppler flowmetry in the anesthetised ventilated cat. Spreading depression was initiated with a pin-prick injury prior to or following administration of U74006F (tirilizad mesylate; 3 mg/kg, ivi) or an identical volume of vehicle. Laser Doppler probes were placed bilaterally and in each case studied both the hyperemic and oligemic phases of spreading depression were preserved after administration of either U74006F or its vehicle. These data suggest that free radical mechanisms have no significant role in mediating the blood flow changes of spreading depression and are consistent with data in the literature of a quantitative using single-point measurements that again U74006F does not affect spreading depression.