types of MSNs is essentially unaltered. In contrast to the D1 and the D2 MSNs, the D1/D2 neurons do not show any significant reduction in the length of their dendritic arborization after intoxication with 6-OHDA. However, a reduction in dendritic spine density was noted in all three types of MSNs following DA depletion, but this pruning phenomenon was more prominent in the D1 than in the D2 or D1/D2 MSNs. The significance of these results will now be discussed in the light of relevant literature.
