Scanning Microscopy


The effects of hypoxia on the sensory epithelium of the cochlea were investigated in the chinchilla. Systemic hypoxia was produced by increasing the dead space of the respiratory tidal volume.

A disarrangement of hair-cell stereocilia, and cytoplasmic protrusions from sensory cells are the main findings in cochleas from hypoxic animals; these changes take place firstly at the inner hair-cells then, with the increase in degree of hypoxia, at the outer hair-cells.

These degenerative changes of sensory cells correlate well with both respiratory suppression and with the elevation of auditory threshold to click stimulation as monitored using the compound action potential recording from the cochlear nerve. The latter measure appears to be a useful indicator of cochlear hypoxia.

Our morphological findings are similar to other studies including those which have reported on post-mortem cochlear hair-cell degeneration.

Our studies indicate the deleterious effects of long term hypoxia on cochlear mechanisms and point to the need for careful monitoring of cardiovascular and respiratory functions in animals under anaesthesia for physiological studies of the auditory system.

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