Xq. Duan et al., Expression and changes of fos protein in the rat forebrain after gamma knife irradiation targeted to the caudate putamen, NEUROSURGER, 45(1), 1999, pp. 139-145
OBJECTIVE: Forebrain expression and changes of Fos protein immunoreactivity
were investigated in rats subjected to gamma knife irradiation (dose, 100
Gy), focusing on the right caudate nucleus.
METHODS: Serial cryostat forebrain sections were processed with Fos protein
antiserum and then by avidin-biotin-peroxidase complex immunohistochemistr
y after gamma knife irradiation.
RESULTS: Some neurons, glial cells, and endothelial cells were positive for
Fos-like immunoreactivity (LI). Fos-LI was mainly distributed in the targe
t area of irradiation, as well as in white matter surrounding lateral ventr
icles, cortex, hippocampus, and certain nuclei reportedly implicated in the
regulation of stress responses. From 0.5 hour to 30 days after irradiation
, expression of Fos-LI displayed two peaks. The first peak arose from 3 hou
rs to 24 hours, with cell nuclei being positive for Fos-LI. The second peak
was noticeable at the 14th day postirradiation. Subsequently, three types
of Fos-LI-positive cells were identified during the period between -14 and
30 days: in the first type, only the nucleus was positive; in the second ty
pe, the cytoplasm was stained; and in the third type, the cells were positi
ve in both the nucleus and the cytoplasm.
CONCLUSION: During the early stages after gamma knife irradiation, a specif
ic stress response (significant Fos expression with two peaks) is observed
not only in the target region but also in the surrounding forebrain regions
. The characteristics and significance of two types of Fos-LI-positive cell
s are discussed in the context of this investigation.