A rat model of focal cerebral ischemia has been established by the technique of electrocatutery for the size of infarction and the regional cerebral blood flow (rCBF). Another purpose o this study was to determine the effective dose (high-or low
dose)
in focal cerebral ischemia. The rats were give 1mg/kg i.v. (low-dose), 4mg/kg i.v(high-dose) of naloxone 30 min before MCAO and infused continuously with 0.5mg/kg/hr (low-dose) or 2mg/kg/hr(high-dose) over next 1 hour by an infusion pump.The
control
group was given normal salin of the same amount by the same method.During the period of saline and naloxone infusion, mean arterial blood pressure was monitored. Arterial biood gas analysis and blood glucose measurement were performed just after
MCAO.
The rectal temperature of rat was maintained within 37±0.5℃ by a heating lamp. Twenty-four hours after MCAO, eight 2mm-thich coronal sections of one rat brain were stained by TTC solution and the size of infarction was descried as the
percentage
of
ipsilateral hemisphere. The rCBFs were measured by an autoradiography using 14C-iodoantipyrine and the changes of rCBFs were analyzed by three methods of ⓛ rCBF ratio, ② l m-serial rCBF measurement of cerebral cortex, and ③ areas of rCBF below
critical values (<25,25-50, >50ml/100g/min).
The results were as follows;
1. there was no significant change of blood pressure during the infusion of saline, low-dose and high-dose naloxones.
2. Arterial blood gas analysis and blood glucose measurement showed that there were no significant differences of pH, PCO2 PO2 and blood glucose between saline and low-dose and high-dose naloxone groups.
3. High-dose naloxone pretreatment reduced significantly the size of infarction (p<0.05 vs saline-treated group by Mann whitney U test).
4. High-dose naloxone pretreatment improved significantly the rCBF ratios of caudate head and CA 3 area(p<0.05 vs. saline-treated group by Mann-Whitney U test). There was no significant improvement of rCBF ratios in the low-dose naloxone treated
group
5. One-mm serial rCBF measurement of cerebral cortex indicated that while low-dose naloxone group showed no improvement of rCBF or cerebral cortex, high-dose nalxoone pretreatment produced an improvement of rCBF in penumbra and its neighboring
area.
6. the area below 25ml/100g/min or rCBF was reduced signifioantly by high-dose naloxone pretreatment (high-dose naloxone group : 15.0±4.1mm², saline group :23.3±5.3mm², p<0.05).
In summary, these results indicate that high-dose naloxone pretreatment reduced the size of infarction and improved the rCVBFs in the focal cerebral lschemia of rats.
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