SPATIAL-LEARNING DEFICITS IN ADULT-RATS EXPOSED TO ORTHO-SUBSTITUTED PCB CONGENERS DURING GESTATION AND LACTATION

Spatial learning and memory was assessed in rats following gestational and lactational exposure to specific ortho-substituted PCBs. Time-mat ed Sprague-Dawley rats were exposed to PCB 28 (2,4,4'-trichlorobipheny l), 8 or 32 mg/kg/day, PCB 118 (2,3',4,4',5-pentachlorobiphenyl), 4 or 16 mg/kg/day, PCB 153 (2,2',4,4',5,5'-hexachlorobiphenyl), 16 or 64 m g/kg/day, or corn oil vehicle via gavage on Gestation Days 10-16. Litt ers were culled to eight on Day 2 and weaned on Day 21. Beginning on D ay 90, one male and one female from each litter were tested on a worki ng/reference memory task on an eight-arm maze. For each rat, the same four arms were baited throughout training. Animals were tested Monday- Friday, for seven consecutive weeks. No differences in working or refe rence memory errors were observed. The same animals were later tested on a T-maze delayed spatial alternation task. On each trial, the reinf orcer was placed in the arm opposite that chosen by the rat on the pre vious trial. Intertrial delays of 15, 25, or 40 sec appeared in counte rbalanced order. Rats were tested Monday-Friday for three consecutive weeks. The higher doses of all three congeners resulted in slower acqu isition by female rats. Males were not affected. PCB-exposed females w ere impaired at all delays and were not differentially more impaired a t longer delays, suggesting a learning or attentional deficit, rather than a mnemonic deficit. These findings demonstrate that perinatal exp osure to ortho-substituted PCBs can result in long-lasting deficits in learning and suggest that the effects of PCBs on learning may be sex specific. (C) 1995 Society of Toxicology.