ACOUSTICALLY ACTIVATED C-FOS EXPRESSION IN AUDITORY NUCLEI OF THE ANESTHETIZED GUINEA-PIG

The spatial expression of the immediate-early gene c-fos in central au ditory nuclei of the anaesthetised guinea pig was investigated followi ng exposure of the animal to acoustic stimulation. Accurate control of both the spectra and the level of the stimulus was designed so that t he presumed excitation of central auditory nuclei was similar across a nimals. For unstimulated anaesthetised control animals, levels of labe lling were significantly higher when compared with unanaesthetised con trols. This appeared to be a result of the combination of the experime ntal manipulations and also the use of the anaesthetic. A surprising f inding was that unstimulated control animals placed in an anechoic cha mber demonstrated the highest levels of fos-like immunoreactivity (Fos -LIR). When anaesthetised animals were exposed to acoustic stimuli the total number of cells showing Fos-LIR was elevated when compared to a naesthetised, but unstimulated animals. There was no evidence at any l evel of the auditory pathway that these animals demonstrated spatially restricted Fos-LIR which may have suggested place-frequency mapping. In contrast, spatially restricted labelling was found in awake animals exposed to an identical stimulus.