The cholinergic pathway ascending from the nucleus basalis magnocellularis (NBM) to the cortex has been implicated in several important higher brain functions such as learning and memory. Following infarction of the frontoparietal cortical area in the rat, a retrograde atrophy of cholinergic cell bodies and fiber networks occurs in the basalocortical cholinergic system. We have observed that neuronal atrophy in the NBM induced by this lesion can be prevented by intracerebroventricular administration of exogenous nerve growth factor (NGF) or the monosialoganglioside GM1. In addition, these agents can upregulate levels of cortical choline acetyltransferase (ChAT) activity in the remaining cortex adjacent to the lesion site. Furthermore, an enhancement in cortical high-affinity 3H-choline uptake and a sustained in vivo release of cortical acetylcholine (ACh) after K+ stimulation are also observed after the application of neurotrophic agents. Moreover, these biochemical changes in the cortex are accompanied by an anatomical remodeling of cortical ChAT-immunoreactive fibers and their synaptic boutons.