The action of neurotrophins in the development and plasticity of the visual cortex

Nerve growth factor (NGF) and the other members of the the NGF gene family have been extensively characterized as neurotrophic factors. Recently a modulatory action of these neurotrophic factors on synapse efficacy has emerged. The developing visual system has provided a convenient model to test the role of neurotrophins on neural plasticity in vivo. Copyright (C) 1996 Elsevier Science Ltd NGF does not interfere with the development of the visual cortex but has an effect only when the visual system is confronted with abnormal vision. All the effects of manipulations of the visual experience such as monocular deprivation, strabismus and dark rearing are prevented if NGF is provided exogenously. NGF can antagonize the destabilization of cortical connections induced by manipulations of the visual input during early postnatal development. Anti-NGF has complementary effects, delaying the stabilization of visual cortical synapses. The mechanism of NGF action remains unclear. The cells expressing NGF receptors in the visual system are yet to be identified, but some lines of evidence suggest that NGF exerts a direct action on cortical neurons. The distribution of BDNF and its receptor trkB in the visual system is known in much greater detail, BDNF production is regulated by visual input and BDNF responsive cells are present along the entire visual pathway. Yet, the effects of BDNF on the visual cortex are difficult to interpret. BDNF interferes with the development of the visual cortex and induces a paradoxical plasticity in monocularly deprived kittens. The effects of exogenous administration of BDNF on the visual cortex are dramatic, but the action of BDNF under physiological conditions is still unclear. Copyright (C) 1996 Elsevier Science Ltd