Lesions with 6-OHDA in rats were shown to increase the expression of D2 and decrease that of D1 by MSNs59. Here we report that the density and regional distribution of D1/D2 MSNs in mice striatum are unaltered by 6-OHDA lesions, suggesting that DA denervation does not alter the D1 expression by D2 MSNs or the D2 expression by D1 MSNs. However, it should be noted that the BAC transgenic reporter system used here does not fully allow to rule out the possibility that DA lesion may induce more subtle variations of DA receptor gene expression or receptor trafficking and degradation that could have remained undetected. The D1/D2 MSNs do not display any reduction of their dendritic tree following 6-OHDA lesions, in contrast to D1 and D2 MSNs, but the D1/D2 MSNs show a lower dendritic spine density in the DA-denervated 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
