Ischemic postconditioning (IPost) has been shown to attenuate
cerebral ischemia-
reperfusion injury. However, the mechanism remains elusive. Because opening of the
mitochondrial permeability transition pore (MPTP) is a crucial determinant of cell death after
ischemia-reperfusion, we hypothesized that the
neuroprotective effect of IPost may be associated with inhibition of
MPTP opening. In part 1 of this study,
pentobarbital-anesthetized rats subjected to
middle cerebral artery occlusion for 90 min, followed by reperfusion for 72 h, were assigned to receive one of the following treatments: three cycles of IPost (15s each), intracerebroventricular injection of saline (control), administration of the
MPTP inhibitor
cyclosporin A (CsA) (2 μmol/L, 15 μL) or its vehicle alcohol, administration of the
MPTP opener
atractyloside (Atr) (2 mmol/L, 15 μL), or IPost plus CsA/Atr treatment. Neurological deficit scores (
NDS) and
infarct volumes were assessed. Mitochondrial ultrastructure and swelling were also examined after reperfusion. In part 2, control and IPost groups underwent
ischemia (90 min) and reperfusion (15 min). CsA and Atr groups were treated as described in part 1. Brain mitochondria were isolated after reperfusion and
MPTP activity was evaluated. IPost or CsA treatment significantly improved
NDS and reduced
infarction volume, while Atr reversed the
neuroprotective effects of IPost, and attenuated the decrease in mitochondrial swelling induced by IPost or CsA. Thus, inhibiting
MPTP opening may play a crucial role in the
neuroprotective effects of IPost, which may have potential clinical value against
cerebral ischemia-
reperfusion injury.