striatum, as it is also the case for D1 and D2 MSNs. Reduction of the dendritic length of D1 and D2 MSNs following DA lesion is supported by observations gathered in mice3435, monkeys36 and PD patients373839. However, some studies in rats60 and mice33 failed to demonstrate such a phenomenon. The time between DA lesion and animal sacrifice might explain such a discrepancy. The interval between 6-OHDA injection and animal perfusion in the latter two studies ranged from 4 to 5 weeks, whereas the delay was much longer (8 weeks) in the present study. In face of such differences, it is tempting to speculate that the reduction in dendritic length occurs after the spine loss has occurred, that is in the late stages of the disease.
