Biochemical and morphological differentiation of acetylcholinesterase-positive efferent fibers in the mouse cochlea
Article first published online: 4 FEB 2005
Copyright © 1990 Wiley-Liss, Inc.
Journal of Electron Microscopy Technique
Volume 15, Issue 2, pages 123–143, June 1990
How to Cite
Emmerling, M. R., Sobkowicz, H. M., Levenick, C. V., Scott, G. L., Slapnick, S. M. and Rose, J. E. (1990), Biochemical and morphological differentiation of acetylcholinesterase-positive efferent fibers in the mouse cochlea. J. Elec. Microsc. Tech., 15: 123–143. doi: 10.1002/jemt.1060150205
- Issue published online: 4 FEB 2005
- Article first published online: 4 FEB 2005
- Manuscript Revised: 13 MAR 1989
- Manuscript Accepted: 13 MAR 1989
- Manuscript Received: 10 JAN 1989
- Electron microscopy;
We have compared the biochemical expression of cholinergic enzymes with the morphological differentiation of efferent nerve fibers and endings in the cochlea of the postnatally developing mouse. Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) are present in the newborn cochlea at specific activities 63% and 25%, respectively, of their mature levels. The relative increases in ChAT, in AChE, and in its molecular forms over the newborn values start about day 4 and reach maturity by about day 10. The biochemical results correlate well with the massive presence of nerve fibers stained immunocytochemically for ChAT and AChE or enzymatically for AChE in the inner and outer hair cell regions. Ultrastructural studies, however, indicate the presence of only few vesiculated fibers and endings in the inner and outer hair cell regions. The appearance of large, cytologically mature endings occurs only toward the end of the third postnatal week. The discrepancy may be resolved in the electron microscope using the enzymatic staining for AChE. Labeling is seen on many nonvesiculated fibers and endings in the hair cell regions, suggesting that the majority of the efferent fibers in the perinatal organ may be biochemically differentiated but morphologically immature. The results may imply that the efferents to inner and outer hair cells develop earlier than indicated by previous ultrastructural studies. Moreover, the pattern of development suggests that in the cochlea, as in other tissues, the biochemical differentiation of the efferent innervation may precede the morphological maturation.