Low-dose X-irradiation reduces neuronal and glial cell populations in the juxtaglomerular region of rat olfactory bulb.

Rats were subjected to fragmented, low-dose, whole body X-ray irradiation from last prenatal to third postnatal week of life. Consequences of the irradiation were examined at the cellular and synaptic level and evaluated by light- and electron microscopy. The fate of several cell types of the glomerular layer was assessed by semi-quantitative morphometry. All known neuronal and glial cell subtypes and varieties of synaptic connections of this layer were spared. X-irradiation, however, had a marked influence on the composition of the juxtaglomerular cell population even at the youngest examined, two week old rat pups and this impact still persisted, without recovery, at six weeks of age. Density (and so, absolute number) of the small periglomerular neurones and astrocytes was depressed to 52-55% and 32-48% of control, respectively, while the density of the superficial tufted cells and the rest of glial cells remained at the control level. These results suggest that the small periglomerular neurones may primarily be responsible for the shrinkage of this layer. This means, in the same time that, selective depression of the development of a superficial interneuron (in addition to the deeply situated granule cells) could be achieved.