Differential regulation of the low-affinity nerve growth factor receptor during postnatal development of the rat brain.

We studied the temporal and spatial localization of the low-affinity nerve growth factor receptor (LNGF-R) during the early postnatal period in rat brain in order to understand better the relationship between nerve growth factor (NGF)-like responsiveness and the development of specific central neuronal populations. Four different developmental patterns of LNGF-R mRNA hybridization were found in this study. First, some neurons contain high levels of LNGF-R mRNA from postnatal time points into adulthood, as exemplified by neurons of the cholinergic basal forebrain and mesencephalic trigeminal nucleus. Second, several cell groups exhibit robust hybridization during the early postnatal period but contain much reduced levels of LNGF-R mRNA in the adult brain. These include striatal neurons, Purkinje cells of the cerebellum, and several medullary nuclei. A third group of cells produces the LNGF-R transiently during development, including cranial nerve nuclei of the brainstem, the periolivary nuclei complex, the reticular formation, and the deep cerebellar nuclei. Finally, cell populations which may exist only transiently during central nervous system (CNS) development, such as subplate neurons of the cerebral cortex, appear to express the LNGF-R during only a brief period. These results show that the LNGF-R gene is differentially regulated in a cell type-specific manner during development, and suggests that diverse neuronal populations require only transient growth factor sensitivity, while others exhibit NGF-like responsitivity into maturity.