Article
C-Fos functional mapping after electrical stimulation of the cochlear nerve in the rat: animal model for experimental auditory neuroprosthesis
Funktionelles Mapping mit c-Fos nach elektrischer Stimulation des Nervus cochlearis der Ratte: ein Tiermodell für experimentelle auditorische Neuroprothesen
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Published: | May 4, 2005 |
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Outline
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Objective
The functional response of auditory brainstem nuclei using C-Fos immunoreactivity mapping after direct electrical stimulation of the cochlear nerve was investigated in the rat. Aim of this study is to simulate and analyze effects of central electrical stimulation by auditory prosthesis in an animal model.
Methods
The cochlear nerve was electrically stimulated with biphasic pulses (120-250 mA, 5 Hz) for 30 minutes in the cerebellopontine angle of Lewis rats. In a control group, bilateral cochlectomy was performed in order to investigate basal expression of c-Fos in the auditory brainstem nuclei. The completeness of cochlear ablations and the response of auditory brainstem nuclei to electrical stimulation were electrophysiologically verified. C-Fos immunohistochemistry was performed using the free floating method. The results were morphologically analyzed and statistically compared among groups.
Results
In anaesthetized animals with unilateral electrical stimulation of the cochlear nerve, increased expression of c-Fos was detected in the ipsilateral ventral cochlear nucleus (VCN), bilateral dorsal cochlear nucleus (DCN), ipsilateral lateral superior olive (LSO) and contralateral inferior colliculus (IC). A bilateral slight increase of c-Fos expression in all subdivisions of the lateral lemniscus was statistically not significant. Contralateral inhibition of the nuclei of the trapezoid body was observed.
Conclusions
Our data show that electrical stimulation of the cochlear nerve leads to increased expression of c-Fos in most auditory brainstem nuclei, similar to the results after monaural auditory stimulation. C-Fos immunoreactivity mapping is an efficient tool to detect functional changes after direct electrical stimulation of the cochlear nerve on cellular level. This could be particularly helpful in studies of the differential activation of the central auditory system by experimental auditory brainstem implants.