title: Effects of gestational and lactational exposure to TCDD or coplanar PCBs on spatial learning.
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.
authors.affiliation: Institute for Environmental Studies and Neuroscience Program, University of Illinois at Urbana-Champaign, 61801, USA. schantz@uiuc.edu
authors.forename: S L
authors.initials: SL
authors.lastname: Schantz
authors.forename: B W
authors.initials: BW
authors.lastname: Seo
authors.forename: J
authors.initials: J
authors.lastname: Moshtaghian
authors.forename: R E
authors.initials: RE
authors.lastname: Peterson
authors.forename: R W
authors.initials: RW
authors.lastname: Moore
mesh_terms: D000818:Animals; D005260:Female; D008297:Male; D018782:Maze Learning / Q000187:drug effects*; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000072317:Polychlorinated Dibenzodioxins; D011078:Polychlorinated Biphenyls; C027309:3,4,5,3',4',5'-hexachlorobiphenyl; C028451:3,4,3',4'-tetrachlorobiphenyl