ラマン分光法による幼若ラット脳含水量の解析

Analysis of Water Content in Young Rats Brain Edema by Raman Spectroscopy

要旨　小児の脳浮腫は，成人とは異なった動態を示すとされている。この複雑な動態を解明するために様々な研究がなされているが，これまで灰白質と白質を区別して脳含有水分量を測定した報告は少ない。今回，我々は可能な限り生理的状態に近く，解剖学的な違いを考慮し脳浮腫の解析を行うためにラマン分光法を用いた。幼若ラットを用い，凍結損傷と有機錫損傷による脳浮腫モデルを作成し測定した。各損傷とも脳浮腫の主体となる白質では，成熟ラットに比べ幼若ラットの方が急激に含水量が増加した。しかし，その回復は速やかであった。また，灰白質および白質の最大水分増加率は低値を示し，幼若ラットではcytotoxic edemaがvasogenic edemaに比べ起こりやすいことが分光学的に示された。今回の解析により，小児の脳浮腫時の動態が成人と時間的空間的にも異なることが示唆された。

　Cerebral edema, classified into vasogenic edema and cytotoxic edema, has long been studied and recognized to be complicated.

　The authors studied the cerebral edema models of young rats suffered from cryo-injury and triethyl tin chrolide (TET) jnjury by Raman spectroscopy which can physiologically evaluate the cerebral water content (%) of very restricted area.

　The cryo-injury model was conducted in the following manner. A cryo-probe (-196℃) was contacted to the exposed cranium for 20 seconds in an anesthetized 4~5-week-old Sprague-Dawley young rat. A coronal section of the injured brain covered with a slide glass and wrapped by Parafilm^® was obtained 2, 4, 6, 8, 12, 24, 48, 72 hours after the cryo-injury in order to measure the water content by Raman spectroscopy employed by Tashibu and Huizinga.

　TET injury model was obtained by intraperitoneal administration of TET (4.5 mg/Kg). The water content was observed by the same manner as for the cryo-injury model.

　Subsequent to the cryo-injury, the water content of the white matter which seemed to be higher than in adult rats increased rapidly and persisted in the same condition within 72 hours.

　Subsequent to TET injury, the water content of the white matter increased more rapidly than that of the gray matter, however, in adult rats the water content of the gray matter showed more rapid increase than that of the white matter. Increased water content followed by TET injury was higher in adult rats than in young rats.

　These results suggest that the different pattern of the cerebral edema should exist between young and adult rats.