Long-term environmental enrichment leads to regional increases in neurotrophin levels in rat brain

A number of studies have demonstrated that both morphological and biochemic al indices in the brain undergo alterations in response to environmental in fluences. In previous work we have shown that rats raised in an enriched en vironmental condition (EC) perform better on a spatial memory task than rat s raised in isolated conditions (IC), We have also found that EC rats have a higher density of immunoreactivity than IC rats for both low and high aff inity nerve growth factor (NGF) receptors in the basal forebrain. In order to determine if these alterations were coupled with altered levels of neuro trophins in other brain regions as well, we measured neurotrophin levels in rats that were raised in EC or IC conditions. Rats were placed in the diff erent environments at 2 months of age and 12 months later brain regions wer e dissected and analyzed for NGF, brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) levels using Promega ELISA kits. We found that N GF and BDNF levels were increased in the cerebral cortex, hippocampal forma tion, basal forebrain, and hindbrain in EC animals compared to age-matched IC animals. NT-3 was found to be increased in the basal forebrain and cereb ral cortex of EC animals as well. These findings demonstrate significant al terations in NGF, BDNF, and NT-3 protein levels in several brain regions as a result of an enriched versus an isolated environment and thus provide a possible biochemical basis for behavioral and morphological alterations tha t have been found to occur with a shifting environmental stimulus. (C) 2000 Academic Press.