Figure 1.

Pharmacogenetic activation of PPG neurons robustly reduces food intake. A: Expression of hM₃Dq:mCherry (magenta) in PPG neurons (detected with an anti-GFP antibody; green) 3 weeks after stereotaxic injection of AAV2-hM₃Dq:mCherry into the NTS of Glu-Cre/GCaMP3 mice. Scale bar, 100 µm. B: Increase in [Ca²⁺]_i in GCaMP3-expressing PPG neurons in response to superfusion of ex vivo brainstem slices with 1 μmol/L CNO. Data are displayed as traces (top left panel) and a heat map (bottom left panel) representing the fractional change in fluorescence from baseline. Right panel: Representative pseudocolored cell responding to 1 μmol/L CNO with an increase in [Ca²⁺]_i. Scale bar, 10 μm; n = 11 cells. C: Expression of the immediate early gene cFOS (green) in PPG neurons expressing hM₃Dq:mCherry (magenta) after i.p. injection of 2 mg/kg CNO (top panels) or saline (bottom panels). White arrows, representative cFOS-positive hM₃Dq-expressing cells; white stars, representative cFOS-negative hM₃Dq-positive cells. Scale bars: middle panel, 100 μm; right panel, 20 μm. Noncumulative (D) and cumulative (E) food intake in the first 4 h of dark phase after injection of CNO (2 mg/kg i.p.) or saline. CNO was delivered 30 min prior to dark onset. Data are given as the mean ± SEM; n = 9 mice. D: No significant time × drug interaction (F(2,16) = 2.897, P = 0.0844), but a significant main effect of drug treatment (F(1,8) = 17.31, P = 0.0032). E: Significant time × drug interaction (F(2,16) = 5.626, P = 0.0141). One-hour P = 0.0005; 2-h P < 0.0001; 4-h P < 0.0001 (Sidak multiple-comparisons test). Inset: P = 0.20 (paired t test). F: Daily chow intake in hM₃Dq-expressing (n = 7) and control (n = 6) Glu-Cre mice in response to twice-daily i.p. injection of 2 mg/kg CNO (indicated with black arrows). Significant time × virus interaction (F(11,121) = 2.06, P = 0.0283); day 6 P = 0.0119 (Sidak multiple-comparisons test). Data are given as the mean ± SEM. *P < 0.05, ***P < 0.001, ****P < 0.0001.