EXOGENOUS GM1 GANGLIOSIDE EFFECTS ON CONDUCTIVE AND SENSORINEURAL HEARING LOSSES

Both CBA/J mice with neonatal cochlea removals and CBA/J mice with neonatal atresias of the external auditory meatus have significantly smaller ventral cochlear nucleus volumes and significantly smaller neuronal somata of their ventral cochlear nucleus. The volume reduction of the ventral cochlear nuclei is greater in the mice with cochlea removals, but the soma area reduction is greater in the mice with external auditory meatus atresias. GM1 gangliosides were subcutaneously injected daily into a group of CBA/J mice with conductive hearing loss caused by neonatal removals of their left external auditory meatus, and into a group of CBA/J mice unilaterally deafened by left cochlea removals. In the mice with conductive hearing loss, the ganglioside treatment significantly ameliorated the atrophy of spiral ganglion neurons, ventral cochlear nucleus neurons, and ventral cochlear nucleus volume. In unilaterally deafened mice, the ganglioside treatment had no measurable effect on the atrophy of ventral cochlear nucleus neurons or of ventral cochlear nucleus volume. It is suggested that GM1 ganglioside treatment potentiates growth factors which sustain spiral ganglion integrity and that this sustained activity of the spiral ganglion in turn maintains the integrity of the cochlear nuclei.