Strain-dependent response to cerebral ischemic preconditioning: differences between spontaneously hypertensive and stroke prone spontaneously hypertensive rats.
Ischemic preconditioning (PC) is a phenomenon whereby a brief exposure to ischemia renders a tissue more tolerant to a subsequent sustained ischemic insult. Animals of the Spontaneously Hypertensive (SHR) and the Spontaneously Hypertensive Stroke-Prone (SHR-SP) rat strains produce cerebral infarcts that are larger and more reproducible in size than infarcts of normotensive rats. This study compared the effects of PC in SHR and SHR-SP rats, under the hypothesis that PC may not be as effective in the SHR-SP, a strain genetically predisposed to stroke. There were two groups per strain, with between eight and ten animals each. The Precondition group (PC) had a 10 min occlusion of the middle cerebral artery on day -1. On the same day the Sham group (Sham) received sham surgery. On day 0, both groups underwent permanent occlusion of the middle cerebral artery. The ischemic lesion was measured on day 1 using T(2)-weighted magnetic resonance imaging. Percent hemispheric infarct was significantly reduced in SHR PC vs. SHR Sham, SHR-SP PC vs. SHR-SP Sham, and SHR PC vs. SHR-SP PC. Thus, rats of the SHR-SP strain respond to PC less markedly than SHR animals. Both models may now be used to elucidate the mechanisms underlying PC.