Neuropeptide expression. mRNA levels of NPY (A,E), AgRP (B,F), POMC-A1 (C,G), and CART (D,H) in hypothalamus (A–D) and telencephalon (E–H) of rainbow trout 6 h after intraperitoneal administration of 0.5 mL⋅100 g-1 body mass of saline solution alone (control) or containing 40 μmol⋅mL-1 of L-leucine, 40 μmol⋅mL-1 of L-valine, or 40 μmol⋅mL-1 of L-proline. Each value is the mean + SEM of n = 6 fish per treatment. Gene expression results are referred to control group and are normalized by EF1α and β-actin expression. Different letters indicate significant differences (P < 0.05) between different groups. P-values are: for (A), C vs L = 0.328, C vs V = 0.019, C vs P = 0.310, L vs V = 0.005, L vs P = 0.561, V vs P = 0.029; for (B), C vs L = 0.436, C vs V = 0.610, C vs P = 0.868, L vs V = 0.036, L vs P = 0.420, V vs P = 0.410; for (C), C vs L = 0.041, C vs V = 0.014, C vs P = 0.322, L vs V = 0.215, L vs P = 0.292, V vs P = 0.047; for (D), = 0.718; for (E), C vs L = 0.858, C vs V = 0.031, C vs P = 0.812, L vs V = 0.039, L vs P = 0.739, V vs P = 0.130; for (F), = 0.734; for (G), C vs L = 0.387, C vs V = 0.165, C vs P = 0.351, L vs V = 0.919, L vs P = 0.189, V vs P = 0.045; and for (H), = 0.505.