[Effects of combined ischemic postconditioning, remote ischemic postconditioning and naloxone postconditioning on focal cerebral ischemia-reperfusion injury in rats].

OBJECTIVE: To assess the effects of ischemic postconditioning, remote ischemic postconditioning and naloxone postconditioning on focal cerebral ischemia-reperfusion injury in rats.

METHODS: A total of 110 adult SD rats were randomly divided into 5 groups (n = 22 each). The focal cerebral ischemia-reperfusion injury was induced by a 90-minute occlusion of right middle cerebral artery (MCA) and a 24-hour reperfusion sequentially. Group 1 was of ischemia-reperfusion control; Group 2 ischemic postconditioning induced by three 30-second cycles of MCA occlusion followed by a 30-second reperfusion; Group 3 remote ischemic postconditioning performed via a transient occlusion of right femoral artery at 5 min before the initiation of reperfusion; Group 4 naloxone postconditioning with naloxone 10 mg/kg intraperitoneally injected at the initiation of reperfusion; Group 5 combined ischemic, remote ischemic & naloxone postconditioning performed simultaneously in accordance with the methods used in Groups 2, 3 & 4. The neurologic deficit scores (NDS) were obtained at 2 h & 24 h post-reperfusion. At 24 h post-reperfusion, the anesthetized rat was sacrificed by decapitation and the brain rapidly extracted to assess the size of cerebral infarct (n = 10), detect the cerebral expression of microtubule-associated protein-2 (MAP2) (n = 6), measure the plasma volume of cerebral tissues and quantify the diameter and segment length of cerebral microvessel (n = 6).

RESULTS: There were no significant differences in the heart rate (HR) and mean arterial pressure (MAP) among the above five groups at all observed time points (P > 0.05). At 24 h post-reperfusion, the percentage of ischemic cerebral infarct size was 43% ± 6%, 31% ± 4%, 32% ± 5%, 28% ± 6% & 21% ± 7% in ipsilateral hemisphere area (i.e., cerebral infarct severity) in Groups 1-5 respectively. Compared with Group 1, the levels of NDS and cerebral infarct severity significantly decreased at ischemic side in Groups 2-5 (P < 0.05). And the cerebral expression of MAP2, plasma volume of cerebral tissues, diameter and segment length of cerebral microvessel significantly increased at the ischemic side (all P < 0.05). However, there were no significant differences in the above-mentioned parameters at ischemic side among Groups 2, 3 and 4 (all P > 0.05). The parameters of NDS, cerebral infarct severity, cerebral expression of MAP2 and plasma volume of cerebral tissues in the ischemic side significantly increased in Group 5 compared with Groups 1, 2, 3 and 4 (all P < 0.05). The diameter and segment length of cerebral microvessel at ischemic side were not different among Groups 2, 3, 4 and 5 (all P > 0.05).

CONCLUSION: In focal cerebral ischemia-reperfusion rats, ischemic, remote ischemic and naloxone postconditioning may produce significant neuroprotective effects of reduced cerebral infarct severity and improved neurologic dysfunctions. A combination of three postconditioning approaches enhances the above neuroprotective effects.