Impaired growth of the cerebral cortex of rats treated neonatally with 6-hydroxydopamine under different environmental conditions.

Male Wistar rat pups received subcutaneous injections of either 100 mg/kg 6-hydroxydopamine (6-OHDA) or saline on days 1, 3, 5 and 7. The noradrenaline (NA) content of the cerebral cortex was reduced by 70% while sleep registration during the first two weeks of life did not show any significant differences between drug- and saline-treated animals. After weaning (day 25), both 6-OHDA- and saline-injected animals were reared under standard and enriched environmental conditions. Whereas a clear increase in cerebral cortical weight after experience with an enriched environment was found in saline-treated rats, 6-OHDA-treated animals had lower cortical weights and showed less increase due to the environment. These results demonstrate that catecholamine neurotransmission during early development influences the development and plasticity of the cerebral cortex.