DISTRIBUTION OF FOS-LIKE IMMUNOREACTIVITY IN THE AUDITORY PATHWAY OF THE SPRAGUE-DAWLEY RAT ELICITED BY COCHLEAR ELECTRICAL-STIMULATION

Fos-like immunoreactivity (FLI) was mapped in the auditory pathway of Sprague-Dawley rats in response to unilateral electrical stimulation o f the cochlea implanted with two stimulating electrodes. Densely packe d FLI neurons were widely distributed in the dorsal cochlear nucleus ( more ipsilaterally than contralaterally), while FLI neurons were rare in the posteroventral cochlear nucleus and virtually absent in the ant eroventral cochlear nucleus. Sparse FLI was detected in the superior o livary complex, the pontine nuclei and the ipsilateral dorsal nucleus of the lateral lemniscus, whereas the contralateral dorsal nucleus of the lateral lemniscus was moderately labeled. In the inferior collicul us, the pattern of FLI was similar on both sides, restricted mainly to its dorsal and external cortices. At the thalamic level, FLI neurons were seen in the dorsal and medial divisions of the medial geniculate body as well as in the peripeduncular nucleus. A significant increase of FLI was observed in the temporal cortex. This study demonstrates th e presence of selective functional changes along the auditory pathway elicited by electrical stimulation of the cochlea, as revealed by FLI.