Mild hypothermia reduces activated caspase-3 up to 1 week after a focal cerebral ischemia induced by endothelin-1 in rats

Hypothermia is a promising neuroprotective therapy that has been shown to reduce apoptosis after an ischemic insult. This study evaluated the effect of mild hypothermia on activated caspase-3 up to 1 week after the induction of a stroke.Endothelin-1 (Et-1) was used to elicit transient focal cerebral ischemia in rats. Twenty minutes after the ischemic insult, a state of mild hypothermia (33 °C) was imposed for a duration of 2 h. The functional outcome, infarct volume and activated caspase-3 immunoreactivity (IR) were assessed at 8, 24 and 72 h, and one week after the insult. During the experiment the cerebral blood flow (CBF) was measured via Laser Doppler Flowmetry.Hypothermia improved the neurological outcome at all of the time points studied compared to the normothermic group, and was associated with a reduction in infarct volume. In both groups, activated caspase-3 IR peaked 24 h after the Et-1 induced insult and hypothermia significantly reduced the number of apoptotic cells at 8 h, 24 h and 1 week after ischemia. Furthermore, the hypothermic treatment did not affect the CBF in the Et-1 model.These findings indicate that in the Et-1 model, hypothermia exerts a long lasting effect on stroke-induced apoptosis.

► Cortical apoptotic activity peaks 24 h after an endothelin-1 induced stroke.
► Hypothermia has a long lasting effect on stroke induced apoptosis.
► Cerebral blood flow is not influenced by hypothermia in the endothelin-1 model.