FIGURE 1.

HPT-axis is active in summer and winter euthermia, but not in torpor. All AGS in the study were maintained under the constant environmental conditions (4L:20D and T_a = 2°C) after capture as shown in (A), AGS maintain seasonal rhythm under the set constant environmental conditions. Results from samples collected at times shown in (B), illustrate that TRH activation in the PVN is lower in Torpor (D). Photomicrographs of double stained brain sections in (C), TRH neurons (brown) and cFos (black) in the PVN are shown in Sum.VEH, as representative of the higher activation group, and in torpor; the insert in PVN images show higher magnification area, scale bar 200 μm (lower magnification), scale bar 50 μm (higher magnification). Thyroid activity is significantly higher during the Fall (E) and concentration of TT3 and TT4 is higher in Torpor (F,G). No changes have been detected in FT3 or FT4 (H,I). Symbols in (E–G) represent outliers. Horizontal bars represent differences between groups, p < 0.05, t-test in (D,G) and Wilcoxon’s rank-sum test in (E,F), n = 4–7.