NGF-dependent sprouting and regeneration in the hippocampus

Abstract

While a variety of sprouting and regenerative responses have been investigated in the hippocampus, the cellular and molecular events responsible for these plastic responses have not been determined. One transmitter system, the cholinergic system, shows several distinct responses to damage in the septohippocampal circuit. Present evidence strongly supports a role for nerve growth factor (NGF) in these responses. NGF is not only important for the survival of the adult cholinergic neurons, but can also induce regrowth of the damaged fibers given an appropriate substratum for growth. These reparative effects of NGF can manifest themselves in functional recovery in the aged rat and the young rat with fimbria-fornix lesions. Finally, a role for glia cells is proposed to clarify how NGF availability may be regulated during the degenerative and regenerative events. While all plasticity events certainly cannot be explained by the coincidence of NGF and the cholinergic system, their interaction may provide a template for other transmitter/trophic factor interactions.