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-

放射疗法应用于几种脑肿瘤。预计对大脑的辐射，特别是对年轻人，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性运动活动的影响尚未见报道。本研究旨在确定（碳粒子290 MeV/核子，单峰60Gy，中脑辐照场5 mm^2）辐照大鼠下丘脑是否改变雄性大鼠自发运动活动。采用成像板法对碳颗粒辐照后大鼠脑区的辐照场进行了识别。用轮跑试验测定自发性运动活动。使用甲基苯丙胺（MAP）的活性增加效应来测量活性。分别在照射后2、6、14、22、26、30周观察小鼠轮跑活动90 min。结果如下：对照组和辐照组在第一次试验时轮跑试验时运动活性最高（1^<st>注射MAP，辐照后2周）；然而，对照组的运动活动在2^<和>试验（6周）至5^< >试验（22周）后下降。另一方面，60 Gy暴露大鼠的轮跑活动不受运动活动试验次数（MAP注射时间）的影响。这些结果可能描述了碳照射下丘脑在照射场引起的水肿。此外，假设环境血流量增加以弥补水肿引起的血流动力学紊乱。

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.