No abstract

Accumulating evidence confirms that the exposure of neonatal rats to maternal separation can significantly alter individual processes of postnatal neurogenesis in the olfactory neurogenic region - the subventricular zone (SVZ) and the rostral migratory stream (RMS). To establish the stressful influence of MS on postnatal neurogenesis we have investigated whether altered olfactory environment caused by short-term MS induces expression of Fos protein in the SVZ/RMS and in the olfactory cortical area - anterior olfactory nucleus (AON) of neonatal rats. Pups were separated from mothers for 2 hours at the postnatal days 7, 14 and 21. Immunohistochemically labeled Fos protein was assessed. Our results revealed that single exposure to MS is a stressful event that selectively and in age-dependent manner stimulates cellular activity in the SVZ and AON. A few Fos+ cells were found in the SVZ of P21 control animals and MS significantly increased their number. This suggests that some SVZ cells are included in the circuitry, which is activated by MS and that these cells have complete equipment for the Fos signal transduction. MS significantly increased the number of Fos+ cells in the AON in all age stages examined suggesting that its effect is mediated by olfaction.

Processes of adult neurogenesis can be influenced by environmental factors. Here, we investigated the effect of microwave radiation (MWR) on proliferation and cell dying in the rat rostral migratory stream (RMS) -a migration route for the neuroblasts of the subventricular zone. Adult and juvenile (two weeks old) rats were exposed to a pulsed-wave MWR at the frequency of 2.45 GHz for 1 or 3 h daily during 3 weeks. Adult rats were divided into two groups: without survival and with two weeks survival after irradiation. Juvenile rats survived till adulthood, when were tested in the light/dark test. Proliferating cells in the RMS were labeled by Ki-67; dying cells were visualized by Fluoro-Jade C histochemistry. In both groups of rats irradiated as adults we have observed significant decrease of the number of dividing cells within the RMS. Exposure of juvenile rats to MWR induced only slight decrease in proliferation, however, it strikingly affected cell death even two months following irradiation. In addition, these rats displayed locomotor hyperactivity and decreased risk assessment in adulthood. Our results suggest that the long-lasting influence of radiation is manifested by affected cell survival and changes in animals´ behavior.