Changes in neurotransmitter amino acids and protein in CNS areas of mice subjected to differential housing conditions.

The amino acid and protein content of mice exposed to enriched, restricted and impoverished environments have been studied in six discrete CNS areas. Differences between enriched and either restricted or impoverished groups were found whereas no difference was observed between restricted and impoverished ones. In the first case, a significant increase for aspartate was found in spinal cord, whereas glutamate significantly decreased in colliculi and cerebral cortex. Similarly, glycine increased in cerebral cortex and decreased in colliculi and pons-medulla, and gamma-aminobutyrate (GABA) increased in spinal cord, pons-medulla and cerebellum and decreased in thalamus-hypothalamus. No changes in concentrations of five non-transmitter amino acids (serine, threonine, alanine, isoleucine, leucine) were observed. Significant increases of the protein concentration in cerebellum and spinal cord were found. The changes were due to enrichment, not to aggregation conditions. The results corroborate the proposed plasticity of the aminoacidergic system.