Correlation of functional recovery after a 6-hydroxydopamine lesion with survival of grafted fetal neurons and release of dopamine in the striatum of the rat.

Female rats were lesioned with 6-hydroxydopamine in the left substantia nigra. At least two weeks later they were tested with amphetamine (5 mg/kg, s.c.) and apomorphine (0.25 mg/kg, s.c.). A cell suspension from the ventral mesencephalon of rat embryos was distributed in three sites in a triangular fashion in the center of the denervated striatum. The amphetamine test was then repeated every month for six months. The pattern of circling to amphetamine before the graft was strictly ipsiversive in all animals. From the first month we observed a progressive change and three patterns of rotation could be observed. In 21% of animals, the total number of ipsiversive turns in 90 min actually increased but during the first 20 min the animals turned contralaterally to the lesion (and to the graft). In 38% of animals, the total number of turns switched from ipsiversive to contraversive with the animals turning initially toward the intact side and during the second half of the test toward the lesion. Finally 41% of rats progressively switched to turning only toward the intact side. In all cases, maximal contraversive turning occurred during the initial 20 min. In these rats, tyrosine hydroxylase-positive cells were detected mainly in the dorsal striatum with a few in the central portion. Moreover there was a strong correlation between the number of surviving grafted neurons and the growth of their fiber into the host striatum and the extent of recovery.(ABSTRACT TRUNCATED AT 250 WORDS)