| Neonatal hypoxic-ischemic brain damage (HIBD) is one of themost common disease which leads to newbom death and severely -neurologic deficit of survivors. There is no effective treatthent -method now Recent study showed that mild to moderatehypothermia (28oC -35 oC ) can inhibit cell metabolism, the activatonof enZyme and delay cell death. Bllt, there is not so much eXPeriencein the treatment of mBD with hyPothermia. In this study, weevaluated the effect of hypothermia with different temperature,different sted time and different duration on mBD by the parametersof brain water content, hematoxylin and eosin(HE) staining, infarctarea, leaming and memory ability.Objective: seven-day-old newborn Wstar rats wererandomized to groups:(1)To study effect of differenttemperature,including 29 oC hypothermia group \ 3l C hypothermiagroup\ 34 Chypothermia grollP' normothermic group (37C ).control group(Sham-ligated grouP).(2)To study effect of different6mf6X$2002 tyMR$$&itx ffilXk$$*&ttatjfiffiME{teffi$6duration of hypothermia,including 24h hypothermia group\ 48 hhyPothermia group\ 72h hypothermia group\ normothermic group(37oC ) and control grouP(Sham-ligated grouP); (3 ) To study effectof hypothermia at differeni stat time, including started at 0 min,30min,60 min, 90 min,l20 min,6 h group after m and normothermicgrouP (37oC )' control group(Sham-ligated group) o There were 22 ratpuPs in each above grouP, 2 animals were randomizly selected asprobe animal in each grouP for monitoring temPerature. (4)TO studylong term protective effects of hypothermia, including: hyPothermiagrouP (started immediately after HI with 29 oC for 72h,normothermic group (37oC ) and control grouP. Each group containedl 0 rat puPs.Methods:(l)The preparaion ofmBD model: At postnatal d&y(p) 7, the pups were anesthetized and the left common carotid wterywas cut between double ligatllres. After the surgical procedure,thepuPs were allowed to recover for 1h. The litters were placed in achamber perfused with humidified air for preheating for l5-30 minand then exposed to a gas mixture (8% oxygen in 92% nitrogen )for55min in a chamber which was kept at 37C. The control grouP7m}11x# 2002%FRR&$nitx #tXK$k$thttfoffifoghM{6klth6subected to neither ligation nor hyPoxia. (2)ProtocoI ofhypothermia:animals were placed in a stable water bath and the temperature wasadjusted according to the hypothermia protocol. (3 )Measurements forbrain water content: Pups were sacrificed at 78h after hypoxia and thebrain was dissected out, the olfactorial tubercles, cerebellum and thebrainstem were discarded. The hemispheres were separated in themidline and weighted with an accuracy of l0-'g electronic balanceand then desiccated at l00C for 5h. Brain water content wasdetermined according to the formula:[(wet weight- dry weight)/wetweight ]x 100%. (4)Histology examination: PuPs were sacrificed 78hafter hypoxia,the brains were peffosion fixed with 5%paraformaldehyde in 0.lM PBS. The brains were dissected out and..immersion-fixed in 5% paraformaldehyde at 4C fOr 24h, then cutinto two coronal planes(one was the median eminence plane and theother was anterior commissure plane).After paraffin embedding,serial coronal sections were stained with HE and MAP-2immunohistochemistry. Infarct area was calculated with an.image-analyzing system. (5) Measurement of study and memoryability: Pups were trained and tested at P42 using Y-radiaI maZe8$NX# 2002 tyWR$$ntet mtkKte$tenttatffitsMnf$afa6stimulator. All rats were tested in the same day the leaming abilitywas tested in the first day and the memory ability was tested inthe second day. (6 ) statiStical analysis: one way-ANOVA, t test wereused in statistical analysis,all the data were dealed with SPSSsoftware. The significant different level was P<0.05.Results:: (l ) HE staining: the neuronal degeneration and.necrosis were found in ipsilateral...
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