On the function of the spiral prominence

Changes in cochlear blood flow during acoustic stimulation as determined by 14C-iodoantipyrine autoradiography

Local blood flow was measured in the tissues of the cochlea using the [14C]iodoantipyrine autoradiographic technique. Flow observed without acoustic stimulation was compared with that seen during exposure to wide-band noise at 85 or 105 dB SPL. Compared with the unexposed cochlea, substantial increases in blood flow were observed during exposure to 85 dB SPL noise in the spiral ganglion, VIII nerve and spiral lamina. Little or no change was noted in external wall structures. These results are consistent with changes in cochlear metabolism which have been reported previously using similar techniques, suggesting that increases in blood flow may be linked to increases in local metabolism. No changes in blood flow were measured during exposure to 105 dB SPL noise. This result is similar to those of other investigators using potentially damaging intensities of acoustic stimulation.

Auditory stimulation alters the pattern of 2-deoxyglucose uptake in the inner ear

The 2-deoxy-D-glucose (2-DG) autoradiographic technique was adapted for application to the inner ear. The uptake of [14C]-DG during silence was compared with that observed during exposure to wide band noise (WBN) or pure tones at an intensity level of 85 db SPL. In silence, the highest levels of 2-DG uptake were observed in the spiral ligament, spiral prominence and stria vascularis, with approximately equal levels of uptake in each structure. The high levels of 2-DG uptake observed in the ligament and prominence are surprising, and suggest a more active role for these structures in cochlear function than has previously been suspected. Levels of uptake in the organ of Corti, spiral ganglion and VIIIth nerve were much lower, although well above background. During exposure to WBN, 2-DG uptake increased markedly in the VIIIth nerve, and spiral ganglion throughout the cochlea, and in the organ of Corti in the lower basal turn. 2-DG uptake did not change significantly in the spiral ligament or stria vascularis. During pure tone exposure, increased 2-DG uptake was noted in localized regions of the VIIIth nerve and spiral ganglion.