REDUCED RETINAL ACTIVITY INCREASES GFAP IMMUNOREACTIVITY IN RAT LATERAL GENICULATE-NUCLEUS

Dynamic regulation of astrocytic processes by the electrical activity of local neurons has been previously described in chick cochlear nucle us. The present study extends this observation by showing that astrocy tes in the rat lateral geniculate nucleus (LGN) also increase their im munoreactivity for glial fibrillary acidic protein (GFAP) soon after d eprivation of afferent visual neuronal activity. Within 6 h of enuclea tion, which eliminates a major source of afferent input to the contral ateral LGN, GFAP immunoreactivity increases relative to the ipsilatera l LGN. A similar increase in GFAP immunoreactivity can be induced by i ntraocular injections of tetrodotoxin, demonstrating that a reversible manipulation of optic nerve electrical activity is sufficient to regu late LGN astrocytes. This rapid response to activity deprivation is le ss dramatic than the gliotic reaction observed 3 weeks following deaff erentation, by which time afferent terminals have degenerated. These r esults support the notion that regulation of astrocytic processes by n eural activity may play an important role in activity-dependent synapt ic regulations in the various sensory systems of vertebrates.