Induction of Fos-like immunoreactivity in the ventral thalamus after electrical or chemical stimulation of various subcortical centres of rats

We have examined the patterns of Fos-like immunoreactivity in the ventral thalamus (thalamic reticular nucleus (Rt), zona incerta (ZI) and ventral lateral geniculate nucleus (LGv)) after electrical or chemical stimulation of nuclei in either the brainstem (midbrain reticular nucleus), basal forebrain (substantia innominata) or dorsal thalamus (parafascicular nucleus). Sprague–Dawley rats were anaesthetised with Halothane or Ketamil/Rompun and the above mentioned centres were stimulated either electrically or chemically (using kainic acid). Brains were then processed for Fos-like immunocytochemistry using standard methods. We detected no major differences in the labelling patterns after either electrical or chemical stimulation or after using Halothane or Ketamil/Rompun anaesthesia. After brainstem or dorsal thalamic stimulations, many Fos-like immunoreactive cells were seen within the rostral pole of the Rt, the dorsal sector of the ZI and the parvocellular lamina of the LGv. After basal forebrain stimulations, many Fos-like immunoreactive cells were seen in the rostral pole of the Rt and rostral sector of the ZI, but very few were apparent in the LGv. Overall, our results show that distinct groups of cells in the ventral thalamus show increased levels of Fos-like immunoreactivity after stimulation of different subcortical centres. These activated cells of the ventral thalamus, are in turn, in a position to influence particular thalamocortical pathways through their dorsal thalamic projections.