Quantitation of nerve fibers in habenula perforata in chinchilla

OBJECTIVE: To examine the number of nerve fibers in the habenula perforata of the cochlea in normal and carboplatin-treated chinchillas. METHODS: Three months following administration of carboplatin (100 mg/kg x 2), six carboplatin-treated animals, together with 6 controls, were sacrificed, prepared for semi-thin sectioning of the cochlea. The sections were stained with toluidine blue and basic fuchsin, examined under a light microscope and photographed. RESULTS: In normal chinchillas, the numbers of the nerve fibers in each habenula opening varied across the cochlea, with 93.7 +/- 12.2(mean +/- s) fibers at the hook, 181.5 +/- 30.4 at the upper of basal turn, 129.7 +/- 27.8 at the second turn and 75.8 +/- 13.2 at the apical turn. In cochlear devoid of type I ganglion cells and inner hair cells as a result of carboplatin treatment, only one-seventh of the fiber population remained. CONCLUSION: Approximately six-seventh of the nerve fibers in the habenula are type I afferent axons that innervate the inner hair cells. The remaining fibers are type II afferents and surviving efferents.