Effects of nerve growth factor on visual cortical plasticity require afferent electrical activity

It is known that administration of nerve growth factor (NGF) prevents the ocular dominance shift induced by monocular deprivation in the rat. To determine whether electrical activity in the visual afferent pathway is required for NGF effects on ocular dominance, we infused NGF into the cortex of animals subjected to complete monocular blockade of retinal discharges. Rats at the peak of the critical period received intravitreal tetrodotoxin (TTX) injections to silence activity in one eye for a period of 6-7 days; NGF was concurrently delivered into the visual cortex by means of osmotic minipumps. At the end of the treatment period, the ocular dominance distribution of cortical neurons was assessed by single-cell recordings. The results demonstrate that while infusion of NGF is effective in preventing the ocular dominance shift in lid-sutured rats, virtually no rescue can be observed in TTX-injected animals. Identical results were obtained when a specific agonist of the NGF receptor TrkA...