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Published June 1987 | Published
Journal Article Open

Changes of Nerve Growth Factor Synthesis in Nonneuronal Cells in Response to Sciatic Nerve Transection

Abstract

The intact sciatic nerve contains levels of nerve growth factor (NGF) that are comparable to those of densely innervated peripheral target tissues of NGF-responsive (sympathetic and sensory) neurons. There, the high NGF levels are reflected by correspondingly high mRNA^(NGF) levels. In the intact sciatic nerve, mRNA^(NGF) levels were very low, thus indicating that the contribution of locally synthesized NGF by nonneuronal cells is small. However, after transection an increase of up to 15-fold in mRNA^(NGF) was measured in 4-mm segments collected both proximally and distally to the transection site. Distally to the transection site, augmented mRNA^(NGF) levels occurred in all three 4-mm segments from 6 h to 2 wk after transection, the longest time period investigated. The augmented local NGF synthesis after transection was accompanied by a reexpression of NGF receptors by Schwann cells (NGF receptors normally disappear shortly after birth). Proximal to the transection site, the augmented NGF synthesis was restricted to the very end of the nerve stump that acts as a "substitute target organ" for the regenerating NGF-responsive nerve fibers. While the mRNA^(NGF) levels in the nerve stump correspond to those of a densely innervated peripheral organ, the volume is too small to fully replace the lacking supply from the periphery. This is reflected by the fact that in the more proximal part of the transected sciatic nerve, where mRNA^(NGF) remained unchanged, the NGF levels reached only 40% of control values. In situ hybridization experiments demonstrated that after transection all nonneuronal cells express mRNA^(NGF) and not only those ensheathing the nerve fibers of NGF-responsive neurons.

Additional Information

© 1987 Rockefeller University Press. After the Initial Publication Period, RUP will grant to the public the non-exclusive right to copy, distribute, or display the Article under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 International license, as described at https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode, or updates thereof. Received for publication 17 December 1986; in revised form 6 February 1987; Published 1 June 1987. We wish to thank A. Tolle for excellent technical assistance and Dr. H. Rohrer for help with ^(125)I-NGF autoradiography in cultured cells.

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August 19, 2023
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