Electrically induced Fos-like immunoreactivity in the auditory pathway of the rat: Effects of survival time, duration, and intensity of stimulation (original) (raw)

The goal of the present study was to establish how Fos-like immunoreactivity (FLI) elicited in the rat auditory pathway by unilateral electric stimulation of the cochlea is affected by the following experimental parameters: duration and intensity of stimulation, duration of survival time after offset of stimulation. The dense FLI found in the ipsilateral dorsal cochlear nucleus, as well as the moderate FM found in the contralateral dorsal cochlear nucleus and in the posteroventral cochlear nucleus on both sides, were consistent after survival times ranging from 0 to 2-3 h, but they significantly decreased after longer survival times (5 and 6 h). In the same nuclei, FLI was increased even by short durations of stimulation (5 and 10 min) as compared to control rats, although FM progressively increased for longer stimulation (20 and 45 min). In the auditory thalamus, FLI was found mainly in the peripeduncular nucleus, the dorsal and medial divisions of the medial geniculate body, whereas its ventral division was virtually devoid of immunoreactive neurons. This pattern of FLI distribution in the auditory thalamus persisted even after relatively long survival times (5 and 6 h). In both the cochlear nucleus and auditory thalamus, the density of FLI slightly increased in parallel with the intensity of stimulation. In other auditory nuclei, such as the inferior colliculus and the nucleus of the lateral lemniscus, there was no simple relation between the density of FLI and the three tested experimental parameters. Thus, the distribution and density of FLI did not vary in parallel in the various nuclei of the auditory pathway as a function of the tested experimental parameters; different pattems of FLI changes were instead observed in different auditory nuclei.