Ontogenesis of the functional activity of guinea-pig olfactory bulb: autoradiographic study with the 2-deoxyglucose...

An ontogenetic study of [14C]2-deoxyglucose (2-DG) uptake within the olfactory bulbs was performed in 1-, 4-, 7- and 21 day-old guinea-pigs exposed to a pure chemical odor, ethyl acetoacetate (EAA). Whatever the age studied, the patterns of glomerular activity are characterized by restricted spots which extend along the bulb, and by sheets of increased density overlapping 10-30 contiguous glomeruli, found only on the lateral aspect of the bulb. Even if the main features of the 2-DG patterns related to EAA are already present at birth, a perceptible evolution of these patterns is observed during the first 3 postnatal weeks. The changes include on the one hand, an increase of the spot-like glomerular labeling which appears particularly prominently on the medial and dorsal aspects. On the other hand, whereas the restricted spots overlaying 1-3 glomeruli become more numerous with age, a decrease in size and in extension of the sheet-like glomerular activity is noted. The results confirm the high maturation level of the olfactory bulbs in newborn guinea-pigs. Some implications related to the mainly prenatal maturation of the olfactory system are discussed.