Age- and Condition-Related Changes in Levels of Neuron Specific Enolase in Spiral Ganglion Neurons of C57BL/6 Mice

Abstract

The mouse strain C57BL/6 suffers from the early onset of deafness. The deafness is attributable to sweeping degeneration of hair cells and the auditory nerve. Degeneration advances with age from the base to the apex of the cochlea. In the present study, neuronal condition was determined by linking relative levels of neuron specific enolase (NSE) in spiral ganglion neurons to their cytological appearances. NSE is an enolase isoform that is expressed only in nervous tissue and neuroendocrine glands.Mice ranged in age from 3 days to 10 months. Inner ears were fixed with 2.5% paraformaldehyde in 0.1 M cacodylate buffer, decalcified for 24 hrs with EDTA, and then embedded in either paraffin or polyester wax. The latter, which melts at a lower temperature, caused much less neuronal shrinkage during routine processing. Deparaffinized sections were exposed first to rabbit anti-bovine NSE antibodies, then to biotinylated swine anti-rabbit antibodies, and finally to peroxidase-labelled avidin.