Figure 2.

Degeneration of dopaminergic neurons in the rostral SN of Smad3 null mice. (A) Quantification of TH-ir neurons was determined using unbiased stereological methods in the midbrain A9, A10 and A8 dopaminergic areas (which include the SN, ventral tegmental area and retrorubral field, respectively). No clear differences were observed between mice when the entire pool of TH-ir cells was counted in these areas. The stereological counting method had a CE < 0.07 for each mouse. (B-C) Representation of the SN (A9) along the rostro-caudal axis showed that Smad3^-/- mutant mice had fewer TH-ir neurons than Smad3^+/+ in the initial rostral 500 μm of the SN (*P < 0.05, **P < 0.01, Mann-Whitney Rank Sum test). Similar values were detected between mice in the middle and caudal regions. Unpaired t-test, n = 5 for Smad3^+/+ and n = 6 for Smad3^-/- mice. (D) Unbiased stereological quantification of Nissl(+) neurons in the ST of Smad3^+/+ and Smad3^-/- mice (Unpaired t-test, n = 4 mice per genotype). CE ≤ 0.05. (E) Quantification of TH-ir neurons in the rostral portion of the midbrain at perinatal stage (P0). Similar values were found between Smad3^+/+ and Smad3^-/- mice, indicating no developmental defect, but a postnatal degenerative process in Smad3 deficiency (Student's t-test, n = 3-4 per genotype). (F) Confocal microscopic images of Smad3/TH double-labelled neurons in the SN of Smad3^+/+ and Smad3^-/- mice. In control tissues, some neurons show Smad3 translocated to the nucleus (arrow). Smad3 null mutant mice have no expression of the protein.