Author:

Abstract:

Using a cat specific Fos antibody, we examined the expression profile of the immediate early gene c-fos in thalamic structures receiving direct or indirect trans-synaptic retinal input within the cat lateral geniculate nucleus (LGN). Visual stimulation succeeding a period of darkness induced considerable Fos expression in the dorsal and ventral part of the LGN (dLGN and vLGN), the perigeniculate nucleus (PGN) and the nucleus reticularis thalami (RT). In particular, Fos immunoreactivity was present in the nuclei of geniculate cells in both A laminae and all C laminae of the dLGN. Interestingly, a characteristic Fos expression profile was apparent for the vLGN. Fos is therefore considered to be an efficient anatomical marker allowing the parcellation of the cat vLGN in a medial and lateral subdivision. Double immunocytochemical stainings between Fos and seven cellular markers, i.e. GAD, Calbindin, Parvalbumin, Calretinin, Enkephalin, Neuropeptide Y and Neurofilament protein (SMI-32), revealed the neurochemical character of distinct subpopulations of visually responsive neurons expressing Fos in different subcortical compartments of the LGN. This immunocytochemical study also revealed distinguished neurochemical reactivity for each of the cellular markers within the medial and lateral zone of the vLGN. These findings extend and confirm that the medial zone of the cat vLGN might be homologues to the rodent intergeniculate leaflet (IGL).