Forebrain norepinephrine and neurobehavioral plasticity: neonatal 6-hydroxydopamine eliminates enriched-impoverished experience effects on maze performance.

Newborn male rats were depleted of forebrain norepinephrine (NE) by systemic 6-hydroxydopamine injection and then reared from 25 to 60 days under either isolated or enriched conditions. They were subsequently tested for acquisition of either the Lashley III maze or the Hebb-Williams maze problems. Isolated rearing impaired Lashley maze performance of the controls but not the 6-OHDA injected rats. Similarly, for the Hebb-Williams maze, the isolation-reared controls made more errors than their enriched-reared counterparts while no differences were observed between the isolated and enriched reared, 6-OHDA injected rats. These results are consistent with the hypothesis that forebrain NE is permissive to the deleterious behavioral consequences of restricted experience during maturation.