Calcium Metabolism Profile in Rat Inner Ear Indicated by MRI After Tympanic Medial Wall Administration of Manganese Chloride.

OBJECTIVES

To evaluate the efficacy of the novel method for the targeted delivery of Mn(++) to the inner ear and monitor calcium metabolism activity in the inner ear.

MATERIALS AND

METHODS

Dynamic signal changes of Mn(++) in the rat inner ear were followed using T1-weighted magnetic resonance imaging (MRI) after administration of 2.5 µl MnCl₂(500 mM) to the medial wall of the middle ear cavity.

RESULTS

Mn(++) passed through both the oval and round windows and distributed in the perilymphatic compartments, where it formed bright sharp lines along the fluid-cellular borders 12 minutes post administration and entered the endolymph sufficiently after 45 minutes. After 6 hours, the distribution of Mn(++) shifted from a fluid-dominant pattern to a cell-dominant pattern. Mn(++) concentrated in the area of the basilar membrane, periphery process, and soma of the spiral ganglion on day 2; became more distinguishable on day 4; declined on day 8; and remained detectable for 16 days post administration.

CONCLUSIONS

The novel targeted delivery method efficiently introduced Mn(++) into the inner ear. The dynamic distribution pattern of Mn(++) in the inner ear shown by MRI indicates that this method can be used to monitor calcium metabolism activity in the inner ear.