Neuroprotective Effect of KR-31378, a Novel Potassium Channel Activator, on Spinal Cord Ischemic Injury in Rabbits

Cyclosporin A Has a Protective Effect with Induced Upregulation of Hsp70 and nNOS on Severe Spinal Cord Ischemic Injury in Rabbits

The purpose of this study is to ascertain the neuroprotective effect of cyclosporin A on the 25-min surgical ischemia model in the spinal cords of rabbits with neuropathological correlation and histoimmunochemical analyses measuring HSP70 and neuronal NOS (nNOS). New Zealand white rabbits were randomly divided into four groups (each n = 8): the C2, C7, Cs2, and Cs7 groups. The C2 and C7 groups underwent a 25-min surgical aortic cross-clamp without intervention and were sacrificed respectively on day 2 and on day 7 postoperatively. The Cs2 and Cs7 groups received cyclosporin A (25 mg/kg) intravenously 15 min after the 25-min cross-clamp and were sacrificed respectively on day 2 and day 7 postoperatively. Neurologic functions were evaluated on postoperative days 2 and 7 using the Tarlov scoring system. Then the rabbits were sacrificed for histopathologic observation. HSP 70 and nNOS stains with TUNEL assay were done for the C2 and Cs2 groups. All rabbits survived the experimental procedure. Tarlov's score for the Cs7 group (2.75 +/- 0.89) was significantly higher than that of the C7 group (1.25 +/- 1.39) (p < .05). Tarlov's score of the Cs7 group was also statistically higher on day 7 than on day 2 (p < .05). Strong correlation between the neurological and histological scorings was found. The TUNEL assay showed that the mean number of positive cells in the C2 group was 17.5 +/- 22.6 and in the Cs2 group was 12.5 +/- 11.1, but there was no statistically significant difference between the groups. There was more expression of HSP70 and nNOS in the cyclosporin groups than in the ischemia groups. In conclusion, this study demonstrates that cyclosporin A reduces neurological injury in the rabbit model of 25-min spinal cord ischemia. The neuroprotective effect of cyclosporin A against ischemia seems to be related to overexpressions of nNOS and HSP70.

KR-31761, a novel K+(ATP)-channel opener, exerts cardioprotective effects by opening both mitochondrial K+(ATP) and Sarcolemmal K+(ATP) channels in rat models of ischemia/reperfusion-induced heart injury

The cardioprotective effects of KR-31761, a newly synthesized K+(ATP) opener, were evaluated in rat models of ischemia/reperfusion (I/R) heart injury. In isolated rat hearts subjected to 30-min global ischemia/30-min reperfusion, KR-31761 perfused prior to ischemia significantly increased both the left ventricular developed pressure (% of predrug LVDP: 17.8, 45.1, 54.2, and 62.6 for the control, 1 microM, 3 microM, and 10 microM, respectively) and double product (DP: heart rate x LVDP; % of predrug DP: 17.5, 44.9, 56.2, and 64.5 for the control, 1 microM, 3 microM, and 10 microM, respectively) at 30-min reperfusion while decreasing the left ventricular end-diastolic pressure (LVEDP). KR-31761 (10 microM) significantly increased the time to contracture during the ischemic period, whereas it concentration-dependently decreased the lactate dehydrogenase release during reperfusion. All these parameters were significantly reversed by 5-hydroxydecanoate (5-HD, 100 microM) and glyburide (1 microM), selective and nonselective blockers of the mitochondrial K+(ATP) (mitoK+(ATP)) channel and K+(ATP) channel, respectively. In anesthetized rats subjected to 30-min occlusion of left anterior descending coronary artery/2.5-h reperfusion, KR-31761 administered 15 min before the onset of ischemia significantly decreased the infarct size (72.2%, 55.1%, and 47.1% for the control, 0.3 mg/kg, i.v., and 1.0 mg/kg, i.v., respectively); and these effects were completely and almost completely abolished by 5-HD (10 mg/kg, i.v.) and HMR-1098, a selective blocker of sarcolemmal K+(ATP) (sarcK+(ATP)) channel (6 mg/kg, i.v.) administered 5 min prior to KR-31761 (72.3% and 67.9%, respectively). KR-31761 only slightly relaxed methoxamine-precontracted rat aorta (IC50: > 30.0 microM). These results suggest that KR-31761 exerts potent cardioprotective effects through the opening of both mitoK+(ATP) and sarcK+(ATP) channels in rat hearts with a minimal vasorelaxant effect.