miR-133b distribution in zebrafish embryos at 48 hpf by whole-mount <i>in situ</i> hybridization (ISH).

<p>Control Group (A, C and E) and cocaine group (B, D and F). The expression of miR-133b is mostly found in the skeletal muscles (A, C and E) and to a lesser extent in the CNS (A, C and E). miR-133b is weakly expressed in the diencephalon, midbrain, and hindbrain. Embryos exposed to cocaine (B, D, and F) show a decrease mainly in the CNS (D), midbrain (red arrow head) and hindbrain (red arrow), while in the diencephalon (black arrow) the decrease less patent. The effect of cocaine on the expression of miR-133b in muscle is difficult to determine (D and F). Scale bars: 300 µm. A, B = 5X, and C, D, E, F = 10X. A: anterior; D: dorsal; L: lateral; d: diencephalon; m: midbrain; h: hindbrain; MHB: Midbrain Hindbrain Boundary; sm: skeletal muscle.