Expression and changes of HSP70 in the rat forebrain subjected to gamma knife (100Gy) irradiation targeted on the caudate putamen and survived for different times

Forebrain heat shock protein 70 (HSP70) immunohistochemical reactivity was investigated in rats subjected to gamma knife irradiation focusing on the r ight caudate putamen nucleus. The forebrain sections of all experimental an imals were processed with anti-HSP70 antiserum and then by avidin-biotin pe roxidase complex immunohistochemistry after gamma ray irradiation with a do se of 100Gy and they each survived for different times (from 30 min to 30 d ays). Some neurons, glial cells, and endothelial cells were HSP70-like immu noreactivity (HSP70-LI) positive. HSP70-LI was mainly distributed in the ta rget area of irradiation, as well as in non-target regions e.g, the cortex, hippocampus, and hypothalamus, etc. The expression and change of HSP70-LI from 3 h to 30 days after irradiation followed the following rules: (1)With in 3 to 24 h, the dilated vessels with HSP70-LI endothelial cells were foun d at first, and a few lightly stained HSP70-LI neurons and glias were obser ved in the target and non-target regions; (2) In 3-7 days, darkly stained H SP70-LI neurons and glias were apparently increased and formed an expressio n peak. From 14 to 30 days, HSP70-LI cells were distinctly decreased and be came weakly stained or negative. These results suggested that although the irradiation target of the gamma knife was localized, the response to irradi ation occurred extensively. (C) 2000 Elsevier Science Ireland Ltd and the J apan Neuroscience Society. All rights reserved.