Elaboration of glial cell processes in the rat olfactory bulb associated with early learning.

Odor preference training early in life induces anatomical changes in focal areas of the glomerular layer of the rat main olfactory bulb. We examined the associated focal changes in glial cell morphology using immunohistochemistry for glial fibrillary acidic protein (GFAP) and found that the density of immunoreactive processes was higher in glomeruli responsive to an odor for which pups had developed a preference. The increase in process density in trained pups was specific to focal responsive regions of the bulb, revealed with [14C]2-deoxyglucose autoradiography. There was no change in the number of GFAP-immunoreactive cells between trained and control pups.