At least two regions (the subventricular zone and hippocampal dentate gyrus) of the adult brain are responsible for proliferation and migration of neural precursor cells. The subventricular zone functions as the largest region of neurogenesis in the adult brain. Cells born in the subventricular zone migrate via a restricted pathway, called the rostral migratory stream, to the olfactory bulb where they differentiate into local interneurons.
Newborn postnatal day 7 (P7) and young adult rats (P28) were exposed to pulsed electromagnetic fields (each group n=10).
For further information on the setup see also: Orendác M, Feník A, Mojzis M, Orendácová J. Biological effects of electromagnetic radiation on living systems with respect to the brain. Psychiatrie 2005 (Suppl.2):83-5.
The data showed that short-term exposure induced increased c-Fos immunoreactivity in the cells of the subventricular zone of P7 and P28 rats. There were no c-Fos positive cells visible within the rostral migratory stream of exposed rats. This finding indicates that probably only the subventricular zone progenitor cells have the complete prerequisites necessary for the c-Fos signal transduction cascade.
Short-term exposure also caused earlier maturation of nitrergic cells (NADPH-diaphorase positive cells) within the rostral migratory stream of P7 rats. The NADPH-diaphorase positive cells appeared several days earlier than in the appropriate controls, and their number and morphology showed characteristics of adult rats. On the other hand, in the young adult P28 rats, electromagnetic field exposure induced morphological signs typical of early postnatal age (i.e. signs of dedifferentiation). These data indicate that electromagnetic field irradiation causes age-related changes in the production of nitric oxide, which may lead to different courses of the proliferation cascade in newborn and young adult neurogenesis.
In conclusion, the data indicate that a single dose of electromagnetic field irradiation represents a stressful event for proliferating cells, and they show that although proliferation runs during the whole of postnatal life, some age-and site-related specificities exist in the subventricular zone and rostral migratory stream neurogenic regions.