Toxic, neurochemical and behavioral effects of dieldrin exposure in mallard ducks.

Toxic, neurochemical and behavioral alterations were evaluated in ducks fed various dietary levels of dieldrin. Increasing amounts of dieldrin in the diet caused an appreciable decrease in the levels of three biogenic amines in whole brain, i.e. serotonin, norepinephrine and dopamine. No effect was noted in whole brain gamma aminobutyric acid contents. Hepatic microsomal enzymes were assayed in these birds using p-nitroanisol and O-ethyl-O-p-nitrophenyl benzenethionophosphate as substrates. Sublethal amounts of dieldrin caused an increase in hepatic drug metabolizing enzymes. Similar alterations were noted in liver protein, deoxyribonucleic acid and ribonucleic acid contents. Studies involving encounters between mallard drakes indicated a decline in the tendency for dieldrin exposed drakes to take the initiative and establish rights of access in approach confrontations. Although many of these changes are compatible with life processes, their significance is not well understood, especially in terms of lifelong exposure to persistent pesticides. The possible relationship between neurochemical alterations and the mechanisms of insecticide neurotoxicity is discussed.