Effects of gestational and lactational exposure to TCDD or coplanar PCBs on spatial learning

Neurotoxicol Teratol. May-Jun 1996;18(3):305-13. doi: 10.1016/s0892-0362(96)90033-1.

Abstract

Recently we reported that in utero and lactational exposure to specific ortho-substituted polychlorinated biphenyl (PCB) congeners resulted in a learning deficit on a delayed spatial alternation (DSA) task in female rats. In this study, spatial learning and memory was assessed following in utero and lactational exposure to coplanar PCBs or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Time-mated Sprague-Dawley rats were dosed with PCB 77 (3,3',4,4'-tetrachlorobiphenyl), 2 or 8 mg/kg/day; PCB 126 (3,3',4,4',5-pentachlorobiphenyl), 0.25 or 1.0 micrograms/kg/day; TCDD, 0.025 or 0.1 micrograms/kg/day; or corn oil vehicle via gavage on gestation days 10-16. Litters were culled to eight on day 2 and weaned on day 21. Beginning on day 80, one male and one female from each litter were tested on an eight-arm radial maze working memory task. The TCDD-exposed rats displayed pronounced decreases in errors relative to controls. PCB 77- and PCB 126-exposed rats showed similar, but less pronounced, decreases in errors. The same animals were later tested on a T-maze DSA task, but no differences among groups were observed. In conclusion, perinatal exposure to low doses of TCDD or structurally related coplanar PCBs appeared to facilitate acquisition of a working memory task on the radial arm maze. This effect was very different from that previously observed in rats exposed to ortho-substituted PCB congeners. The rats exposed to ortho-substituted PCBs did not differ from controls on the radial arm maze and were impaired on the T-maze DSA task. Together these findings suggest that coplanar and ortho-substituted PCBs may have different mechanisms of action on the CNS.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Female
  • Male
  • Maze Learning / drug effects*
  • Polychlorinated Biphenyls / toxicity*
  • Polychlorinated Dibenzodioxins / toxicity*
  • Pregnancy
  • Prenatal Exposure Delayed Effects*
  • Rats
  • Rats, Sprague-Dawley

Substances

  • Polychlorinated Dibenzodioxins
  • Polychlorinated Biphenyls
  • 3,4,5,3',4',5'-hexachlorobiphenyl
  • 3,4,3',4'-tetrachlorobiphenyl