Basic study of heavy-ion irradiated to the normal brain tissue -Effects of carbon particles exposure to rat's hypothalamus on the spontaneous motor activity-

放射治疗适用于几种脑肿瘤。据估计，对大脑的照射，特别是在年轻时，会产生一些不良影响。重离子束治疗脑瘤比普通X射线更有效。然而，重离子照射脑对自发运动活动的影响尚未见报道。本研究用290 MeV/核子、单峰60 Gy、中脑照射野5 mm^2的碳粒子照射大鼠下丘脑，观察其对雄性大鼠自发运动的影响。用跑轮试验测定自发运动活动。使用甲基苯丙胺（MAP）的活性增加效应测量活性。在照射后2、6、14、22、26和30周进行90 min的跑轮活动观察，结果表明：对照组和照射组在第1次跑轮试验（<st>照射后2周注射MAP 1次）时跑轮活动最高，而对照组在第2次跑轮<nd>试验（照射后6周）至第5次跑轮<th>试验（照射后22周）时跑轮活动下降。另一方面，60戈伊照射组大鼠的跑轮活动无明显减少，其减少程度与运动试验次数（MAP注射时间）有关。这些结果可能说明下丘脑受碳照射后，照射野水肿。此外，据推测，周围血流量增加，以弥补水肿造成的血流动力学紊乱。

Radiation therapy is applied to several brain tumors. It is expected that irradiation to the brain, especially in younger age, gives some adverse effects. Heavy-ion beams are more effective to treat brain tumors than ordinary X-rays. However, the effect of heavy-ion irradiation to brain on spontaneous motor activity is not reported. This study was designed to determine whether irradiation (carbon particles 290 MeV/nucleon, mono peak 60Gy, irradiation field 5 mm^2 in midbrain) to rat's hypothalamus modifies the spontaneous motor activity of male rats.The irradiation field in rat's brain after carbon particles irradiation was identified by imaging plate method. The spontaneous motor activity was determined with the wheel-running test. The activity was measured using an active increase effect of methamphetamine (MAP). The observation of wheel-running activity was conducted for 90 min after 2, 6, 14, 22, 26 or 30 weeks following irradiation.Results are as follows.The control group and irradiated group were highest motor activity in wheel-running test at first test ( 1^<st> injection of MAP, 2 weeks after irradiation) ; however, motor activity of the control group decreased after from 2^<nd> test (6 weeks) to 5^<th> test (22 weeks). On the other hand, 60 Gy exposed rats were not decrement of wheel-running activity which depended on number of times in motor activity test (injection time of MAP). These results may be possible to describe that carbon irradiation to hypothalamus is caused edema at the irradiated field. Furthermore, it was supposed that an ambient blood flow increased to make up for disordered hemodynamics by the edema.