Developmental neurotoxicity of four ortho-substituted polychlorinated biphenyls in the neonatal mouse.

The objective of the present study was to investigate whether neonatal exposure to single PCB (polychlorinated biphenyl) congeners 2,4,4'-trichlorobiphenyl (IUPAC 28), 2,2',5,5'-tetrachlorobiphenyl (IUPAC 52), 2,3',4,4',5-pentachlorobiphenyl (IUPAC 118) and 2,3,3',4,4',5-hexachlorobiphenyl (IUPAC 156) when given as one single dose (0.7-14 μmol/kg body weight per os) to 10-day-old male NMRI mice could induce persistent neurotoxic effects in the adult animal. Furthermore, to ascertain whether behavioural aberrations, both in spontaneous behaviour and in learning and memory function, were followed by changes in the cholinergic and/or the dopaminergic system. It was found that neonatal exposure to lightly chlorinated ortho-substituted PCBs, 2,4,4'-tri- and 2,2',5,5'-tetrachlorobiphenyls, can induce persistent aberrations in spontaneous behaviour. Neonatal exposure to 2,2',5,5'-tetrachlorobiphenyl also affected learning and memory functions in the adult animal. In the animals showing a deficit in memory and learning function, the cholinergic nicotinic receptors in the cerebral cortex were affected. Exposure to 2,3',4,4',5-penta- and 2,3,3',4,4',5-hexachlorobiphenyl, mono-ortho congeners ('co-planar-like'), in the same dose range did not cause any significant change in the investigated behavioural variables, spontaneous and swim-maze behaviour.