Toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent, bioaccumulative and toxic contaminant widely distributed in the environment. Fishes are the most sensitive vertebrates to TCDD, especially during their early developmental stages. TCDD induces various toxic effects including yolk sac edema, craniofacial malformation and neural damage in developing fish embryos. However, the effects of TCDD on peripheral nervous system (PNS) remain unclear. To clarify how TCDD affects the morphology of PNS in developing red seabream (Pagrus major) embryos, the present study investigated the TCDD-induced effects on nervous system using an anti-acetylated tubulin antibody and a HNK-1 antibody. The embryos at 10 h post-fertilization (hpf) were exposed to various concentrations (0–100 μg/L) of TCDD in seawater for 80 min. The PNS of craniofacial region was completely disrupted at 120 hpf in 12.5 μg/L TCDD-treated embryos, whereas no significant effect in trunk PNS was observed. As for neural crest cells (NCC) and their differentiated tissues, the hindbrain segments could not be clearly seen at 48 hpf in TCDD-exposed embryos. These results suggest that TCDD may have a specific effect on developing craniofacial PNS that might be initiated by disrupting NCC differentiation and/or its migration.