EXPRESSION OF THE LOW-AFFINITY P75 NERVE GROWTH-FACTOR RECEPTOR IN THE DEVELOPING RAT PITUITARY-GLAND

We investigated, by means of in situ hybridization with a digoxigenin- labelled RNA probe, the expression of the low-affinity p75 nerve growt h factor receptor (NGFR) in the developing pituitary primordium of the rat. In 13-day pc embryos, intense staining of p75 NGFR mRNA was pres ent in the cytoplasm of all cells of Rathke's pouch. In day-17 pc embr yos p75 NGFR expression was present primarily in the cells of the inte rmediate lobe. In the newborn rat pituitary only very weak staining wa s observed, predominantly in the intermediate lobe. In neural structur es the staining at day 13 pc was comparable to that of day 17 pc. Sinc e p75 expression is seen very early during pituitary development and d eclines during the time the expression of pituitary hormonal phenotype s are steadily increasing, we suggest that the p75 NGFR expression in Rathke's pouch may play a temporally defined role in the commitment ra ther than in the differentiation of the various pituitary cell types.