A rat model of endothelin-3-induced middle cerebral artery occlusion with controlled reperfusion

Surge hyperemia and mechanical damage to the cerebrovascular endothelium may serve to exacerbate the neuropathological outcome in animal models of focal cerebral ischemia. We have modified an existing model of endothelin-1-induced middle cerebral artery (MCA) occlusion to enable controlled reperfusion without damage to the cerebral vasculature. Endothelin-1 (ET-1) and endothelin-3 (ET-3) were injected via a double-injection cannula into brain parenchyma adjacent to the MCA of anesthetized rats to produce focal cerebral ischemia. ET-1 and ET-3 produced large ischemic lesions that were restricted to those cortical and subcortical structures supplied by the MCA. The volume of ischemic damage produced by 100 pmol of ET-1 and ET-3 was similar. The endothelin-A (ET_A) receptor antagonist FR139317 (3 or 30 nmol) injected 10 min after ET-1 did not significantly alter the volume of damage. By contrast, the lesion produced by ET-3 was completely inhibited by FR139317 at the 10 min time-point. FR139317 partially attenuated the ET-3-induced lesion when administered 30 min post-occlusion, but injection 90 min following ET-3 produced a lesion not different to that produced by ET-3 alone. These findings were supported by laser Doppler flowmetry which determined FR139317 induces reperfusion when injected 10 or 90 min following ET-3. ET-3-induced MCA occlusion is therefore amenable to reversal by the ET_A receptor antagonist FR139317, and this model may offer a means to investigate the neuropathology of reperfusion without the procedure-related artifacts associated with some reperfusion models.