Growth and body composition of control and Mch1r^−/− mice maintained on regular chow. (A) Growth curves of group-housed male and female wild-type (Mch1r^+/+; filled squares), Mch1r^+/− (filled triangles), and Mch1r^−/− littermate mice (open circles; n = 14–16 per group). (B) DEXA analysis of 5–7-month-old group-housed male and female Mch1r^+/+ (white bars), Mch1r^+/− (hatched bars), and Mch1r^−/− (shaded bars; n = 12–14 per group) littermates from A. (C) Adipose tissue mass in Mch1r^+/+ (white bars) and Mch1r^−/− littermates (shaded bars; n = 14 per group) from B. Epi, epididymal; Retro, retroperitoneal; Scap, scapular white, BAT, interscapular brown. All P values are from comparisons between Mch1r^+/+ and Mch1r^−/− littermates. **, P < 0.01; *, P < 0.05.

Energy expenditure of control and Mch1r^−/− mice. (A) Ambulatory activity of ≈12-week-old individually housed male wild-type (Mch1r^+/+, n = 11; filled squares), Mch1r^+/− (n = 6; filled triangles), and Mch1r^−/− (n = 11; open circles), and female Mch1r^+/+ (n = 10), Mch1r^+/− (n = 4), and Mch1r^−/− (n = 8) littermates. Mch1r^−/− curves were significantly different (P < 0.005) from Mch1r^+/+ and Mch1r^+/− curves for the entire dark phase. (B) Metabolic rate of ≈8-week-old individually housed male Mch1r^+/+ (n = 10) and Mch1r^−/− (n = 13) littermates. From 10 p.m. to 5 a.m., the Mch1r^−/− curve was significantly different (P < 0.05) from the Mch1r^+/+ curve. (C) Respiratory quotient (RQ) of mice from B. The Mch1r^−/− curve was significantly different (P < 0.01) from the Mch1r^+/+ curve for the entire light phase. Solid horizontal bars represent the dark phases of the studies.

Response of control and Mch1r^−/− mice to intracerebroventricular administration of NPY, AgRP, or MCH. (A) Effect of NPY on daytime feeding. NPY (≈0.25 nmol; shaded bars) or vehicle (white bars) were injected into either the left lateral ventricle (LV; n = 10–11 per genotype) or the dorsal third ventricle (D3V; n = 6–8 per genotype) of 12–14-week-old male wild-type (Mch1r^+/+) and Mch1r^−/− littermates. Food intake was measured 2 h later. P values are from comparisons between treatment groups of the same genotype. *, P < 0.001. (B) Effect of AgRP on daily feeding. AgRP (≈0.9 nmol; filled symbols) or vehicle (open symbols) were injected into either the LV (n = 8–10 per genotype) or the D3V (n = 6–10 per genotype) of 18–20-week-old male Mch1r^+/+ (squares) and Mch1r^−/− (circles) littermates on day 0. Food intake was measured daily for 6 days. All AgRP curves were significantly different (LV, P < 0.005; D3V, P < 0.01) from corresponding vehicle curves. (C) Effect of MCH on daytime feeding. MCH (≈2 nmol; shaded bars) or vehicle (white bars) were injected into either the LV (n = 9 per genotype) or the D3V (n = 5–10 per genotype) of 14–16-week-old male Mch1r^+/+ and Mch1r^−/− littermates. Food intake was measured 2 h later. (D) Effect of chronic MCH infusion on daily food intake. Male 11–13-week-old Mch1r^+/+ (squares) and Mch1r^−/− (circles) littermates received chronic D3V infusions of either MCH (≈12 nmol per mouse per day; filled symbols) or vehicle (open symbols) for 6 days (n = 9–11 per group). Mice were cannulated and implanted with osmotic pumps containing only vehicle on day −5. On day 0, original pumps were replaced with new pumps containing either vehicle or MCH. Beginning on day 1, all mice were maintained on a moderate fat diet. From days 1 to 6, the Mch1r^+/+/MCH treatment curve was significantly different (P < 0.005) from the three other curves. (E) Effect of chronic MCH infusion on cumulative body weight gain. Body weights of mice from D were measured daily, and values from day −4 were used to calculate cumulative body weight gains. From days 1 to 6, the Mch1r^+/+/MCH treatment curve was significantly different (P < 0.0001) from the three other curves. (F) Effect of chronic MHC infusion on body composition. DEXA analysis of body composition was performed on mice from D at the end of the 6-day chronic infusion period (Mch1r^+/+: vehicle, white bars; MCH, hatched bars; Mch1r^−/−: vehicle, shaded bars; MCH, striped bars). P values are from comparisons between treatment groups of the same genotype (*) or between genotypes of the same treatment (**). *, P < 0.005; **, P < 0.01.

Targeted disruption of Mch1r. (A) Illustrations and partial restriction map of the mouse Mch1r wild-type allele, targeting vector, and mutant allele. Filled, open, and hatched boxes represent exons, the neomycin-resistance cassette (Neo), and the probe used for Southern blot analysis in B or the thymidine kinase gene (TK), respectively. R, EcoRI; K, KpnI; Rv, EcoRV; S, SalI; H, HpaI. (B) Southern blot analysis of tail DNA from wild-type (Mch1r^+/+), Mch1r^+/−, and Mch1r^−/− mice using the Mch1r coding region probe depicted in A. Genomic DNA was digested with EcoRV and HpaI. (C) In situ hybridization performed on coronal brain sections from Mch1r^+/+ and Mch1r^−/− mice. NAc, nucleus accumbens; Hip, hippocampus; PCtx, piriform cortex; Str, striatum.

Appetitive behavior of control and Mch1r^−/− mice maintained on regular chow. (A) Daily food intake of ≈10-week-old individually housed male wild-type (Mch1r^+/+), Mch1r^+/−, and Mch1r^−/− (n = 10–11 per genotype), and female Mch1r^+/+ (n = 10), Mch1r^+/− (n = 4), and Mch1r^−/− (n = 8) littermates. (B) Daily feeding duration of 8–10-week-old individually housed male Mch1r^+/+ and Mch1r^−/− littermates (n = 12 per genotype) maintained in a 12-h/12-h light/dark cycle (LD) or constant darkness (DD). White portions of bars represent 12-h light phase (LD) or 12-h subjective day (DD), and shaded portion represents 12-h dark phase (LD) or 12-h subjective night (DD). All P values are from comparisons between Mch1r^+/+ and Mch1r^−/− littermates. **, P < 0.001; *, P < 0.05.

Response of control and Mch1r^−/− mice to DIO. (A) Cumulative body weight gains of female wild-type (Mch1r^+/+) and Mch1r^−/− littermates maintained simultaneously on either a regular chow (RC) or a high-fat (HF) diet for 7 weeks (n = 9–12 per group). All groups were weight-matched and all mice were 6–8-weeks-old at the initiation of the study. (B) Cumulative food intake by mice in A during the 7-week period (n = 9–11 per group). P values are from comparisons between chow and high-fat groups of the same genotype (*) or between Mch1r^+/+ and Mch1r^−/− littermates maintained on the same diet (**). *, P < 0.05; **, P < 0.001.