Abstract
The influence of 6-OHDA on the nigro-neostriatal dopaminergic system of the rat from birth to 45 days after birth was investigated with respect to the completion of the BBB to DA. The caudate nucleus and substantia nigra of infant rats were examined by Falck-Hillarp's fluorescence histochemistry and electron microscopy. The most pronounced decrease of DA fluorescence was detected in rats in whom 6-OHDA was repeatedly administered between the end of the first week to the middle of the second week after birth. DA fluorescence also began to decrease gradually in rats after administration of 6-OHDA in the middle of the second week. No further change, however, occurred in DA neurons of rats treated with 6-OHDA at the end of the second post natal week. It was determined that the BBB to DA began to be constituted from the middle of the second week after birth. We also conjectured that 6-OHDA had no potentiality to produce irreversible degeneration of DA neurons in infant animals, since DA fluorescence recovered to the same level as the controls in rats surviving for 4 to 6 weeks after administration of 6-OHDA during the first and second weeks after birth.
