Cre-mediated recombination in forebrain-projecting serotonergic neurons, inferior olive neurons and hypothalamic neurons in the adult brain. A-D: Individual optical sections obtained using confocal imaging of saggital sections from adult pdx1-creCre/0; ZegGFP/0 mice. A: Wide-field image of the serotonergic dorsal raphe nucleus (dr) demonstrating extensive and anatomically restricted expression of TPH and GFP in this structure. B: Higher-magnification image of the dorsal raphe nucleus: a large majority of TPH+ neurons express GFP and that all GFP+ cells in this region are serotonergic neurons. C: In the median raphe nucleus (mr), there was partial overlap between GFP and TPH expression. D: In the caudal hindbrain, GFP expression was observed in the inferior olive nucleus (io), adjacent to but not overlapping with serotonergic raphe nuclei. E-F: Brightfield images of saggital sections obtained from adult pdx1-creCre/0; rosa26LacZ/+ mice, processed for LacZ activity. E: The inferior olive nucleus was labeled with LacZ. F: Multiple nuclei of the hypothalamus, notably the dorsomedial, lateral and arcuate nuclei, were labeled with LacZ. Scale bars: 80 μm (A); 60 μm (B, C, D); 200 μm (E); 150 μm (F).