Changes of the striatal 3H-spiperone binding 3-6 weeks after nigrostriatal denervation and after two years.

A complete unilateral lesion of the nigrostriatal pathway by 6-hydroxydopamine injection in the substantia nigra induced a drastic increase in striatal dopaminergic binding sites labelled by 3H-spiperone, 30 days after the lesion. This increase (75% over controls) was time restricted: it was only 39% and 34% over control values at respectively 25 and 35 days after the lesion. Furthermore, 45 days after the destruction of the substantia nigra, the density of labelled sites returned close to the homolateral control values, but remained higher than the contralateral ones, according to the right-left difference found in control animals. Quite later (2 years after the lesion), there was a decrease in the density of labelled sites as compared to the respective homolateral control levels. However, such binding sites tend to remain higher in the striatum of the lesioned side than in the striatum of the intact one, although such a difference was not statistically significant, being very close to the right-left asymmetry observed in control animals. Contrary to our previous results with 3H-Haloperidol, the apparent dissociation constant did not vary significantly, whatever the considered delay after the lesion. These results are discussed in the light of previous results obtained by others and by us.