RAPID AND OPPOSITE EFFECTS OF BDNF AND NGF ON THE FUNCTIONAL-ORGANIZATION OF THE ADULT CORTEX IN-VIVO

THE adult cortex is thought to undergo plastic changes that are closel y dependent on neuronal activity (reviewed in ref. 1), although it is not yet known what molecules are involved. Neurotrophins and their rec eptors have been implicated in several aspects of developmental plasti city(2-4), and their expression in the adult cortex suggests additiona l roles in adult plasticity(5-9). To examine these potential roles in viva, we used intrinsic-signal optical imaging to quantify the effects of nerve growth factor (NGF) and brain-derived neurotrophic factor (B DNF) on the functional representation of a stimulated whisker in the ' barrel' subdivision of the rat somatosensory cortex. Topical applicati on of BDNF resulted in a rapid and long-lasting decrease in the size o f a whisker representation, and a decrease in the amplitude of the act ivity-dependent intrinsic signal, In contrast, NGF application resulte d in a rapid but transient increase in the size of a representation, a nd an increase in the amplitude of the activity-dependent intrinsic si gnal. These results demonstrate that neurotrophins can rapidly modulat e stimulus-dependent activity in adult cortex, and suggest a role for neurotrophins in regulating adult cortical plasticity.