Cell proliferation in the adult rat rostral migratory stream following exposure to gamma irradiation

One of the few areas of the adult CNS, that are known to be competent for neuronal proliferation, is the subventricular zone (SVZ) lining the brain lateral ventricles. Cells proliferating in the SVZ migrate along a defined pathway, the rostral migratory stream (RMS), where their proliferation continues until reaching the olfactory bulb. 1. In relation to the fact that brain is, in general, regarded as a radioresistant organ composed from non dividing cells, the aim of the present study was to investigate effect of ionizing radiation on proliferating cell numbers in the RMS of adult rats. 2. Male Wistar rats were investigated 25 and 80 days after whole body gamma irradiation with the dose of 3 Gy. Dividing cells were labeled by bromodeoxyuridine (BrdU). BrdU-positive cells were counted by Disector program. The mean number of BrdU(+) cells in the whole RMS and in its individual parts (vertical arm, elbow, and horizontal arm) was evaluated. 3. Temporary increase in proliferating cell number (by 30%) was seen in the whole RMS at the 25th day after irradiation. 4. The most expressive increase occurred in the vertical arm (by 60%) and elbow (about 37%). The values reduced till the 80th day after exposure. Our results show that ionizing irradiation significantly influences the extent of cell proliferation and migration in the adult rat RMS.