Apparent sprouting of striatal serotonergic terminals after dopamine-depleting brain lesions in neonatal rats.

Near-total dopamine-depleting brain lesions produced in 3-day-old rats by intracerebroventricular injection of the neurotoxin 6-hydroxydopamine led to pronounced increases in striatal serotonin (5-HT) and 5-hydroxyindoleacetic acid contents 1-8 months later. This effect was associated with an increase in in vitro high affinity 5-HT uptake, suggesting that proliferation of new serotonergic terminals had occurred within the striatum. No such effect was obtained when comparable brain lesions were produced in adult rats.