Neuroprotective Effects of Local Surface Hypothermia during Endothelin-1-Induced Focal Ischemia in Rat Cerebral Cortex. II. Morphometric Analysis of Ischemic Lesions

In the present study, we investigated the neuroprotective effects of local therapeutic hypothermia (LTH) in a model of focal ischemia induced by epipial application of Endothelin-1 to the somatosensory cortex of the rat brain by morphometric analysis of ischemic foci formed 3 hours after Endothelin-1 application. The size of ischemic foci was measured in serial coronal brain slices after staining with 2,3,5-triphenyltetrazolium chloride (TTC). It was found that cooling the cortical surface to 28°C using a subdural Peltier element at 0, 10 and 60 minutes delay after Endothelin-1 application, caused a significant reduction in the size of ischemic focus compared to normothermic conditions. The neuroprotective effects of LTH were inversely correlated with the delay of LTH onset from the time of Endothelin-1 application and were most pronounced with LTH initiated with the shortest (0 and 10 minutes) delay after Endothelin-1 application. The size of the ischemic focus was also found to correlate significantly with the degree of electrical activity suppression analyzed in parallel paper. Taken together, the results of morphological and electrophysiological analysis indicate pronounced neuroprotective effects of surface LTH, particularly significant at minimal LTH latency after ischemic onset, in a model of Endothelin-1-induced focal ischemia in the rat cerebral cortex.