[Vestibular compensation studies]

The following topics are reported: neurophysiological studies on MVN neurons during vestibular compensation; effects of spinal cord lesions on VNC neurons during compensation; a closed-loop vestibular compensation model for horizontally canal-related MVN neurons; spatiotemporal convergence in VNC neurons; contributions of irregularly firing vestibular afferents to linear and angular VOR's; application to flight studies; metabolic measures in vestibular neurons; immediate early gene expression following vestibular stimulation; morphological studies on primary afferents, central vestibular pathways, vestibular efferent projection to the vestibular end organs, and three-dimensional morphometry and imaging

Inner ear dysfunction in caspase-3 deficient mice

<p>Abstract</p> <p>Background</p> <p>Caspase-3 is one of the most downstream enzymes activated in the apoptotic pathway. In caspase-3 deficient mice, loss of cochlear hair cells and spiral ganglion cells coincide closely with hearing loss. In contrast with the auditory system, details of the vestibular phenotype have not been characterized. Here we report the vestibular phenotype and inner ear anatomy in the caspase-3 deficient (<it>Casp3</it>^<it>-/-</it>) mouse strain.</p> <p>Results</p> <p>Average ABR thresholds of <it>Casp3</it>^{<it>-/- </it>}mice were significantly elevated (<it>P </it>< 0.05) compared to <it>Casp3</it>^{<it>+/- </it>}mice and <it>Casp3</it>^{<it>+/+ </it>}mice at 3 months of age. In DPOAE testing, distortion product 2F1-F2 was significantly decreased (<it>P </it>< 0.05) in <it>Casp3</it>^{<it>-/- </it>}mice, whereas <it>Casp3</it>^{<it>+/- </it>}and <it>Casp3</it>^{<it>+/+ </it>}mice showed normal and comparable values to each other. <it>Casp3</it>^{<it>-/- </it>}mice were hyperactive and exhibited circling behavior when excited. In lateral canal VOR testing, <it>Casp3</it>^{<it>-/- </it>}mice had minimal response to any of the stimuli tested, whereas <it>Casp3</it>^{<it>+/- </it>}mice had an intermediate response compared to <it>Casp3</it>^{<it>+/+ </it>}mice. Inner ear anatomical and histological analysis revealed gross hypomorphism of the vestibular organs, in which the main site was the anterior semicircular canal. Hair cell numbers in the anterior- and lateral crista, and utricle were significantly smaller in <it>Casp3</it>^{<it>-/- </it>}mice whereas the <it>Casp3</it>^{<it>+/- </it>}and <it>Casp3</it>^{<it>+/+ </it>}mice had normal hair cell numbers.</p> <p>Conclusions</p> <p>These results indicate that caspase-3 is essential for correct functioning of the cochlea as well as normal development and function of the vestibule.</p