(A–C) Water-immersed WT, (D–F) Dox-immersed WT, (G–I) water-immersed Tg(Zα:TetON-Rtn4al), and (J–L) Dox-immersed Tg(Zα:TetON-Rtn4al). Adult fish of all groups were treated for one week before histopathological examination. (A–L) Transverse section. (A, D, G, J) Green fluorescent signal detection of synaptic vesicle glycoprotein 2A (SV2) labeled in the peripheral motor neuron. (B, E, H, K) Red fluorescence signal using α-Bungarotoxin (α-BTX)-labeled acetylcholine receptor on motor endplate. (C, F, I, L) comprised the merge picture. Arrowhead indicates the location of NMJ denervation. Scale bar, 20 μm. (M) Four experimental groups of SV2 and α-BTX signal colocalization percentage quantitative data. Data from three adult fish from each experimental group; three images each magnified at 600X, using Metamorph software to quantify SV2 and α-BTX signal colocalization area (400 × 400 pixels), followed by conversion to percentage after Student’s t-test and used for statistical analysis (**, significant difference at p<0.01).