2,3,7,8-Tetrachlorodibenzo-p-dioxin treatment induces c-Fos expression in the forebrain of the Long-Evans rat.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is one of the most toxic environmental pollutants. In the present study, we examined c-Fos expression in the central nervous system (CNS) after administration of a lethal dose of TCDD to the adult Long-Evans rat to clarify if the CNS participates in TCDD-induced intoxication. A single dose of TCDD (dissolved in olive oil, 50 microg/kg) or olive oil alone was administered to the rats by gavage. Animals were allowed to survive for 1 day to 5 weeks. Three days after the administration, a significantly large number of Fos-immunopositive cells were found in the hypothalamus (i.e. dorsomedial hypothalamic nucleus, paraventricular hypothalamic nucleus, medial preoptic nucleus), central amygdaloid nucleus and bed nucleus of the stria terminalis. These results suggest that some TCDD toxicity may be induced by its direct action on the CNS.