Expression of c-Fos in the main olfactory bulb of neonatal rabbits in response to garlic as a novel and conditioned odour

Expression of c-Fos was examined in the olfactory bulbs of 3-day-old rabbits after they had been presented with the odour of garlic as a novel stimulus, as a learned odour, or during conditioning, and this expression compared with baseline levels in non-stimulated controls. Exposure to garlic odour resulted in substantial and widespread increases in c-Fos expression in the olfactory bulbs of all animals. However, although conditioned pups showed a specific behavioural response to the learned garlic odour, neither the amount nor pattern of c-Fos expression differed compared to pups exposed to garlic as a novel odour. The odour-induced expression of c-Fos was not well localised, although there was a significant increase in the number of granule cells expressing c-Fos in the ventrolateral region of the bulb. These results support previous reports that the response to odours in the olfactory bulb of new-born animals is not as spatially distinct as that in adults. Nevertheless, the immature olfactory system of these young animals is clearly capable of very specific odour learning. (C) 1999 Elsevier Science B.V. All rights reserved.