NGF expression in the developing rat brain: effects of maternal separation

A number of studies have shown that mothering style in rodents can produce neuroendocrine, neurochemical and behavioural changes in the adult, althoug h the basic mechanisms initiating this cascade of events still need to be i nvestigated. Long term changes in neuronal function might be due to alterat ions in the expression of neurotrophins which have been shown to promote ne uronal survival, differentiation and function during development, such as N erve Growth Factor (NGF). NGF is essential for proper development of sympat hetic and neural crest-derived sensory neurons of the peripheral nervous sy stem as well as of central cholinergic neurons. In previous studies, using a maternal separation paradigm, we have shown that NGF expression is increa sed in the dentate gyms and the hilus of the hippocampus as a result of bri ef (45 min) maternal separations. In the present study neonatal rats were s eparated for longer periods of time (up to 3 h) and at different ages durin g development (9 and 16 days postnatally). Results indicate that the effect s of maternal separation on NGF expression are stronger with longer separat ions and are not restricted to the hippocampal region but can be seen also in other brain areas. Overall these results indicate that external factors, such as the presence/absence of the mother, can modify neurotrophic factor 's availability in the brain, thus indicating NGF as a potential player in environmentally-mediated brain plasticity during development. (C) 2000 Else vier Science B.V. All rights reserved.