Effects of neurotrophins on cortical plasticity: Same or different?

Neurotrophins are important regulators of visual cortical plasticity. It is still unclear, however, whether they play similar or different roles and w hich are their effects on the electrical activity of cortical neurons in vi vo. We therefore compared the effects of all neurotrophins, nerve growth fa ctor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-4 (NT-4) , and neurotrophin-3 (NT-3) on visual cortical plasticity and on cell spont aneous and visually evoked activity. Rats were monocularly deprived for 1 w eek at the peak of the critical period, and neurotrophins were infused intr acortically. The main finding is that, with the exception of NT-3, all neur otrophins affect the outcome of monocular deprivation, but there are clear differences in their mechanisms of action. In particular, NT-4 and NGF coun teract monocular deprivation effects without causing detectable alterations either in spontaneous or visually evoked neuronal activity. BDNF is less e ffective on ocular dominance plasticity and, in addition, strongly affects spontaneous and visually evoked activity in cortical neurons.