BEHAVIORAL HYPERACTIVITY IN RATS FOLLOWING POSTNATAL EXPOSURE TO SUBTOXIC DOSES OF POLYCHLORINATED BIPHENYL CONGENER-153 AND CONGENER-126

Rats were exposed through mother's milk either to the di-ortho-substit uted polychlorinated biphenyl (PCB) congener 2,2',4,4',5,5'-CB (IUPAC no. 153) or to the non-ortho-substituted PCB congener 3,3',4,4',5-CB ( IUPAC no. 126). The different groups of mothers were dosed via gavage with corn oil vehicle, 5 mg/kg b.w. of PCB 153 or 2 mu g/kg b.w. of PC B 126 every second day from day 3 to 13 after delivery. The exposure d id not affect the body weight (b.w.) of the dams or the physical devel opment of the pups. A two-component schedule of reinforcement was used to study behavioural effects of the PCB exposures in male offspring. One component was operating when the house light was turned on. Then a reinforcer, a drop of water, was delivered every 2-min. This componen t is called a 2-min fixed interval (FI) schedule of reinforcement. The other component was in effect when the house light was turned off. Th en no reinforcer was ever delivered. This is called an extinction (EXT ) component. It was shown that the PCB-exposed offspring were hyperact ive as they had an increased frequency of lever presses. In addition, the PCB 153-exposed male pups showed a behavioural pattern similar to that observed in spontaneously hypertensive rats (SHR), an animal mode l of attention-deficit hyperactivity disorder (ADHD). This behaviour i s characterized by 'burst' of lever presses with short interresponse t imes (IRT) just before the next reinforcer is given. These results sho w that both PCBs 153 and 126 may produce significant neurotoxic effect s following postnatal exposure through mother's milk. (C) 1998 Elsevie r Science B.V. All rights reserved.