EXPRESSION OF EGFR-LIKE, P75NGFR-LIKE, AND PSTAIR (CDC2)-LIKE IMMUNOREACTIVITY BY PROLIFERATING CELLS IN THE ADULT-RAT HIPPOCAMPAL-FORMATION AND FOREBRAIN

Immunocytochemical and autoradiographic techniques were used to examin e proliferating cells in the adult rat brain along with the expression of specific growth factor receptors and cell cycle proteins. Two hour s following an injection of [H-3]thymidine ([H-3]Thy), dividing cells were detected in the subgranular region of the dentate gyrus and in th e subependymal region (SER) extending into the olfactory bulb. Many ce lls continued to divide over the next 24 h as demonstrated by the abil ity for thymidine-labeled cells to incorporate bromodeoxyuridine (BrdU ); however, the results of BrdU, PSTAIR, and vimentin staining suggest that the majority of the progeny cells detectable by [H-3]Thy autorad iography at 3 days and 1 week after injection are postmitotic and at l ease partially differentiated. Significant numbers of thymidine-labele d cells detected 2 h following thymidine injection in the subgranular region of the dentate gyrus and in the SER of the lateral ventricle st ained positively for epidermal growth factor receptor-, vimentin-, and PSTAIR-like immunoreactivity, Significant numbers of thymidine-labele d cells in the SER also stained positively for the low-affinity neurot rophin receptor p75NGFR. No [H-3]Thy/p75NGFR-labeled cells were detect ed in the dentate gyrus. In addition, very few [H-3]Thy/PSTAIR- or [H- 3]Thy/vimentin-labeled cells were detected in region CA4. These data s uggest that proliferating cells located in different regions of the ad ult brain may not be homogeneous and may be subject to different growt h factor regulation.