Muscarinic hyposensitivity in the developing rat pretreated with 6-hydroxydopa.

Atropine-induced locomotor stimulation was investigated in the developing rat pretreated with 6-hydroxydopa at birth. The locomotor stimulation by atropine was first observed on day 20 and gradually increased with age. The treatment with 6-hydroxydopa potentiated atropine-induced locomotor stimulation on days later than day 20 and inhibited a pilocarpine-induced catalepsy on day 30. This suggests that central cholinergic neurons, probably in the neostriatum, reach functional maturity between 15 and 20 days, and that the pretreatment with 6-hydroxydopa induced muscarinic hyposensitivity in the developing rat.