Effect of intracerebral infusion of a Fzd receptor antagonist in Fzd-1 and β-catenin expression within the SNpc. Spatio-temporal analyses of Fzd-1 (A-B) receptors and β-catenin (C-D) protein levels by western blot (A-B) and immunohistochemical (C-F) analyses within the SN ipsilateral and contralateral to saline or Dkk1 infusion. A-B: Representative images showing dual staining with Fzd-1 (red) and TH (green) in the SNpc of saline (C) and Dkk1- (D) infused SN, 3 days post-infusion. Colocalization (C, orange to yellow and Mag) of the two markers reveals Fzd-1 receptor expression in TH+ neurons. Note Fzd-1 receptor punctate distribution in TH+ processes and bright signal also in DA cell bodies, occasionally Fzd-1-IF signal was observed in TH- neurons, but not in GFAP+ astrocytes (not shown). Dkk1 infusion induces loss Fzd-1 receptor in ipsilateral SNpc (B). C-D: Dual staining with DAT (E, green) and β-catenin (red) revealed colocalization, of both markers, with β-catenin staining mainly in plasma membrane and TH+ cell bodies, abundantly beneath the cell nucleus (C and Mag), whereas in SN ipsilateral to Dkk1 infusion, β-catenin signal was down-regulated (D). E-G: Fzd-1 and β-catenin protein within the ipsi- and contra SN of saline and Dkk1-infused mice (n = 4/time-point) by western blot, showing downregulation of Fzd-1 and β-catenin in Dkk1-ipsi but not contralateral SN. Data from the experimental bands were normalized to β-actin, and values expressed as per cent (%) of saline-injected controls. *p < 0.05 ipsilateral vs contralateral, within each respective group; ° p < 0.01 compared to ipsi-lesioned side.