Because less numerous, the number of striatal cells containing both tdTomato (D1) and GFP (D2), here called the D1/D2 MSNs, was estimated with stereological parameters different from those employed to estimate the number of D1 and D2 MSNs. Selected transverse sections of the striatum were entirely examined with an optical disector of the same size of the one described above. An average of 599 ± 106 D1/D2 cells were counted in the striatum compared to 993 ± 191 D1/D2 neurons in the Acb of each mouse, yielding coefficient of error (Gundersen, m = 1) ranging between 0.08 and 0.27. The density of D1, D2 and D1/D2 MSNs was obtained by dividing the number of striatal cells estimated with the optical disector by the volume of striatal sectors sampled, as estimated with the Cavalieri’s method71.
