symptoms of Parkinson's disease, Alzheimer's disease, and others erupt, the underlying processes have been active for many years, perhaps decades. Perhaps they even began, as Waddington postulated for schizophrenia, with abnormal fetal development ( Calne, Eisen, McGeer, & Spencer, 1986).
Sexual function is surely an aspect of brain development with enormous implications for psychiatry. It, too, it turns out, is a pawn of toxic exposure. Dioxin, known more precisely as 2,3,7,8-tetrachlorodibenzoparadioxin (TCDD) and to the public as a notorious contaminant of Agent Orange, is the most potent known poison apart from biotoxins such as venoms. Until fairly recently, its primary health threats had been viewed through the lens of cancer. Now, however, behavior has mounted to the summit of concerns. Cancer appears in rodents exposed to doses in the microgram range. In contrast, male offspring of rats treated during gestation and lactation with nanogram quantities of TCDD display aberrations in mating behavior ( Mably, Moore, Goy, & Peterson, 1992) and other aspects of sexual development. These responses provide the most sensitive endpoints so far documented for TCDD exposure. They have stirred a lively debate about chemicals with similar properties, such as some of the polychlorinated biphenyls, that have been labeled environmental estrogens or endocrine disrupters. One question lurking at the borders of the debate is the extent to which these agents may modify other, much more subtle, sexually dimorphic behaviors and brain development in general. A recent book ( Colborn, Myers, & Dumanoski, 1996) offers an extensive review of these issues.
Behavioral toxicology is still a relatively young discipline. Few of its practitioners are psychiatrists. But no other medical specialty is so closely allied with its aims, techniques, and content. Psychiatric training and textbooks would profit by acknowledging its contributions and perspectives.
Chapter preparation was supported in part by grants ES01247 and ES05433 from the National Institute for Environmental Health Sciences, grant DA07737 from the National Institute on Drug Abuse, and by a grant from the International Life Sciences Institute.
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