Localization and regulation of low affinity nerve growth factor receptor expression in the rat olfactory system during development and regeneration

Abstract

Nerve growth factor (NGF), a classic neurotrophic factor, promotes neuronal survival, maintenance, regeneration and differentiation in the peripheral nervous system and parts of the central nervous system. NGF activity is mediated by cell surface bound receptors including the low affinity NGF receptor (LNGFr) which is expressed by some peripheral and central neurons and is present on peripheral nerve Schwann cells during development and regeneration. The olfactory system is a useful model for the study of the role of LNGFr in neuronal development and regeneration. The growth of olfactory axons into the brain begins in the embryo and continues through the first few postnatal weeks. In mature animals there is persistent turnover and generation of olfactory receptor neurons (ORNs) and continuous growth of new axons into the olfactory bulb. These new axons grow along the preexisting olfactory pathway. In the mature olfactory system, LNGFr has been observed in the glomerular layer of the olfactory bulb, the target of ORNs. However, neither the cellular localization nor the developmental expression of LNGFr has been characterized. Here, we tested the hypothesis that LNGFr expression is developmentally regulated in the olfactory nerve and is reinduced following injury to the mature olfactory nerve. LNGFr-immunoreactivity (IR) was first observed in the olfactory mucosa at embryonic day (E)13 and in the olfactory nerve at E14. LNGFr-IR increased in the nerve during embryonic development, began to decrease at around postnatal day (P)5 and was scarcely detectable in normal adults. The staining pattern suggests that LNGFr is located on the olfactory nerve Schwann cells. Streaks of LNGFr-IR were present in the adult olfactory nerve. We reasoned that these streaks might represent transient reexpression of LNGFr associated with normal olfactory neuron turnover and replacement. Consistent with this hypothesis, LNGFr was robustly reexpressed in the adult olfactory nerve following lesion of the olfactory epithelium. Starting late in development (E21) and in the adult, LNGFr-IR was also observed on fibers in deep layers of the olfactory bulb. LNGFr-IR was also observed in neurons of the nucleus of the diagonal band (NDB) in the basal forebrain. NDB is the sole source of cholinergic afferents of the olfactory bulb. Thus, we tested the hypothesis that LNGFr in the deep layers of the olfactory bulb is located on NDB axons by making lesions of NDB. Following the lesion, LNGFr-IR disappeared in the deep layers of the olfactory bulb but remained in the glomerular layer.(ABSTRACT TRUNCATED AT 400 WORDS)

Cultured olfactory ensheathing cells express nerve growth factor, brain-derived neurotrophic factor, glia cell line-derived neurotrophic factor and their receptors

“…NT R [20,23,61] and S-100 protein [3,44]. In this study double staining with anti-S-100 and Nuclear Yellow (Sigma, St. Louis, MO) was randomly performed in different batches to ascertain the high purity of EC cultures which has been consistently obtained in earlier studies (Fig.…”

Development of olfactory glomeruli: Temporal and spatial interactions between olfactory receptor axons and mitral cells in opossums and rats

“…Perhaps very fine processes of olfactory nerve Schwann cells might not have been labeled for S-100 protein or detected in our study. Alternatively, species differences might exist: Gong et al (1994) in studies of the rat also indicated that somata and processes of olfactory nerve Schwann cells remain within the nerve layer. Olfactory nerve Schwann cells might constrain mitral cell dendrites by forming a mechanical border or by emitting chemorepulsive cues.…”

Erratum for Ann. N.Y. Acad. Sci. 1088: A1–A10

“…S100 is useful as a marker for the olfactory ensheathing cells (OECs) of the ONL-o, 9,10,12 and p75 is positive in the OECs of the ONL-o, the glomeruli, and glial cells of the GL from late embryonic stages to adult stages. 10,13 Although GFAP is expressed in the astrocytes of the ONL-i and the GL during postnatal stages, 11,14 it has been reported that GFAP is also contained in OECs of the ONL. 15,16 TROY was highly observed in the ONL-i and was colocalized with GFAP in the GL and the ONL-i and with p75 in some glial cells of the GL of adult mice.…”