Expression of Cre recombinase in injected areas results in deletion of Y2 mRNA and a profound reduction in Y2 receptor binding. A, In situ hybridization showing expression of Cre mRNA in the BLA and CEA. Middle and bottom, Dark-field (middle) and bright-field (bottom) photomicrographs of photoemulsion-dipped sections showing Cre-positive cells (arrows) in the CEA. B, In situ hybridization showing Cre and Y2 mRNA expression and Y2 receptor binding in adjacent sections of the CEA in rAAV-Cre- and rAAV-GFP-injected Y2^lox/lox mice (arrows mark injections sites). Note the significant reduction in Y2 mRNA levels as compared to the more modest loss of Y2 binding, as quantified in C. In contrast to changes in Y2 receptor mRNA, there was no change in concentrations of GABA_A α2 subunit mRNA in the CEA 4 weeks after injection of rAAV-Cre into the CEA versus mice injected with rAAV-GFP (arrow heads), excluding an unspecific effect of Cre (B). Scale bars: A, 1 mm (film autoradiography), 50 μm (dark field), 10 μm (bright field); B, 500 μm. C, **p < 0.01, ***p < 0.001 as compared to all the respective controls (Student's t test).