Fig. 3.

Images of M₁-mEGFP expression. Fluorescence imaging of brain slices from homozygous M₁-mEGFP and WT mice shows the profile of expression of M₁-mEGFP. (A) The hippocampal CA1 region and the dentate gyrus are noted. Endogenous fluorescence of the mEGFP tag in the hippocampus is preserved following fixation. (B) Images of cultures of (B, i) M₁-mEGFP–expressing or (B, ii) M₁-knockout (KO) neurons (Left) with corresponding bright-field image (Right). (C) Immunostaining of such neurons from M₁-mEGFP–expressing (C, i) or M₁-KO (C, ii) neurons with an anti-M₁ receptor antiserum shows strong colocalization with mEGFP fluorescence in C, i but not C, ii. DAPI (blue) provides nuclear staining. (D) Addition to such neurons of a fluorescent form of the M₁ selective antagonist pirenzepine (100 nM; red) also shows strong colocalization with mEGFP fluorescence. Scale bars, 500 µm.