NT-4-MEDIATED RESCUE OF LATERAL GENICULATE NEURONS FROM EFFECTS OF MONOCULAR DEPRIVATION

ALTERING the balance of activity between the two eyes during the criti cal period for visual-system development profoundly affects competitiv e interactions among neurons in the lateral geniculate nucleus and pri mary visual cortex(1-6). Neurons in the lateral geniculate nucleus tha t are deprived of activity by closing or silencing one eye atrophy as a result of competition with non-deprived neurons for some critical fa ctor(s) presumed to be present in the cortex. Based on their actions i n the developing visual system(7-12) neurotrophins are attractive cand idates for such factors. We tested whether neurotrophins mediate intra cortical competition of afferents from the lateral geniculate nucleus by using monocular deprivation and a new method for highly localized, in vivo delivery of neurotrophins. This method allowed unambiguous ide ntification of neurons that were exposed to neurotrophin. Here we repo rt that only one neurotrophin, the TrkB ligand NT-4, rescued neurons i n the lateral geniculate nucleus from the dystrophic effects of monocu lar deprivation.