Effects of fastigial nucleus electrical stimulation on lateral ventricle nestin expression after focal cerebral ischemia/reperfusion in adult rats

摘要

BACKGROUND: Previous studies have confirmed that fastigial nucleus electrical stimulation can induce endogenous neuroprotective mechanisms and produce wide and long-lasting neuroprotective effects. Nevertheless, the precise mechanisms remain poorly understood. OBJECTIVE: This study was designed to observe the effects of fastigial nucleus electrical stimulation on nestin-positive cell expression in adult rat lateral ventricle after focal cerebral ischemia/reperfusion, as well as neurological functional changes as a function of time. DESIGN: A randomized controlled animal experiment. SETTING: Department of Neurology, First Affiliated Hospital of Chongqing Medical University; Chongqing Key Laboratory of Neurology. MATERIALS: This study was performed in the Department of Neurology, First Affiliated Hospital of Chongqing Medical University and Chongqing Key Laboratory of Neurology from September 2004 to February 2006. A total of 180 healthy, adult, male Wistar rats, aged 8 weeks old, were provided by the Laboratory Animal Center of Chongqing Medical University. The main reagents and equipments were as follows: rabbit anti-rat nestin monoclonal antibody (Wuhan Boster Company, China). METHODS: The included male Wistar rats were randomly divided into 5 groups: normal control, sham-operated, model, fastigial nucleus sham-stimulation (sham-stimulation for short), and fastigial nucleus electrical stimulation (stimulation for short) groups. Six time points (1 hour of ischemia and 1, 3, 7, 14, 21, and 28 days of reperfusion, 6 rats per time point) were allotted to each group. Cerebral ischemia/reperfusion was performed by occlusion to the right middle cerebral artery with suture, followed by suture removal. In the stimulation group, subsequent to reperfusion, the rat left cerebellar fastigial nucleus was immediately subjected to 1 hour of stimulation. After anesthesia, the rat left cerebellar fastigial nucleus was stimulated for 1 hour using a square-wave electronic stimulator with a current intensity of 50 μA, frequency of 50-100 Hz, and duration of 0.5 ms. In the sham-stimulation group, the procedure was identical to the stimulation group, except the needle was retained for 1 hour and current stimulation was withdrawn. In the model group, rats were subjected to cerebral ischemia/reperfusion, but electrical stimulation was omitted. In the sham-operated group, the internal carotid artery, rather than the middle cerebral artery, was inserted with suture, and simultaneously, electrical stimulation was omitted. In the normal control group, the rats received no treatments. MAIN OUTCOME MEASURES: Nestin-positive cells were detected by immunohistochemical staining in the rat ischemic lateral cerebral ventricle at 1, 3, 7, 14, 21, and 28 days post-reperfusion. RESULTS: Morphological changes of nestin-positive cells in the ischemic lateral ventricle: in the normal control group, very few nestin-positive cells were detected in the choroid plexus, ependyma, and subependymal region of the lateral ventricle. In the model group, the number of nestin-positive cells exhibited a tendency towards a single peak, i.e., cells increased at day 1, reached peak levels by day 7, and then decreased sharply. Fastigial nucleus electrical stimulation was administered following focal cerebral ischemia/reperfusion, and results revealed that nestin-positive cell morphology was similar to horizontal cell morphology on day 7. The number of nestin-positive cells decreased after 14 days; however, the proportion of horizontal cell-like cells increased. In the sham-stimulation group, there was no change in nestin-positive cells. nestin-positive cell expression in the ischemic lateral ventricle: nestin-positive cell expression increased in the ischemic lateral cerebral ventricle, exhibiting a tendency towards unimodality; the number of cells peaked on day 7 (P < 0.01) and gradually decreased after 14 days (P < 0.01). Following fastigial nucleus electrical stimulation, the number of nestin-positive cells increased significantly (P < 0.05-0.01), reached peak levels by day 7 (P < 0.01), and remained at very high levels after 14 days (P < 0.01). Neurofunctional changes: neurofunctional deficits were gradually alleviated with prolonged focal cerebral ischemia/reperfusion time. At 1 hour of ischemia, and 6 hours to 7 days of reperfusion, rat neurological scores were significantly lower in the stimulation group than in the model and sham-operation groups (P < 0.05-0.01). CONCLUSION: Fastigial nucleus electrical stimulation increased nestin-positive cells in the rat lateral ventricle after focal cerebral ischemia/reperfusion in a time-dependent manner and simultaneously improved neurological deficits, as well as promoted differentiation of nestin-positive cells towards a cell type with neuronal and neuroglial cellular morphology.