Effects of Great Lakes fish consumption on brain PCB pattern, concentration, and progressive-ratio performance

This study investigated the effects of consumption of Great Lakes fish on p rogressive ratio performance, and on the pattern and concentrations of brai n polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethene (DDE), a nd mirex in the rat. Adult, male Sprague-Dawley rats were fed a 30% diet of either Lake Ontario salmon (LAKE), Pacific Ocean salmon, or lab chow contr ol for 20 or 65 days. Following the treatment regimen, half the rats from e ach group were sacrificed immediately for gas chromatographic analysis of o rganochlorine contaminants, and the other half were tested on a multiple fi xed-ratio-progressive-ratio reinforcement schedule and then sacrificed for analysis. Consumption of Lake Ontario fish resulted in significantly higher levels of brain PCBs, DDE, and mirex relative to controls, but still web w ithin human exposure ranges (<1 mu g/g fat). Consumption of Lake Ontario fi sh for 20 or 65 days produced an average brain PCB concentration of 457 and 934 ng/g fat, respectively. Consumption of laboratory rat chow or Pacific Ocean salmon for 20 or 65 days produced an average brain PCB concentration of 240, 464, and 441 ng/g fat, respectively. Moreover, both LAKE-fed groups showed a much more heavily chlorinated pattern of brain PCBs than all cont rol groups, as evidenced by both significant increases in the most heavily chlorinated PCB congeners and significant increases in the average chlorine biphenyl. All LAKE brains contained significant concentrations of DDE and mirex, whereas no control brains contained any detectable quantities. Analy sis of progressive-ratio performance indicated that LAKE rats responded nor mally during fixed-ratio schedules but quit significantly sooner than contr ol rats on a progressive-ratio 5 (PR5) schedule, indicating reduced persist ence on progressively leaner reinforcement schedules. Analysis of brain PCB s indicated that total PCBs were most strongly related to PR5 performance. These data indicate that consumption by rats of contaminated Lake Ontario f ish produces (1) increased concentrations of PCBs, DDE, and mires in the br ain, (2) a more heavily chlorinated distribution of PCBs in the brain, and (3) reduced persistence of progressive-ratio reinforcement schedules. While these behavioral changes are related to brain PCB level, more work is nece ssary before the effects can be directly attributed to PCBs. (C) 2000 Acade mic Press.