Neurotoxins/neurotoxicity behavioral effects

The clearest refutation of the idea advanced by hereditarian behavior geneticists that the prenatal environment is of only small consequence for childhood and adult IQ is the research on known IQ effects of prenatal exposure to certain neurotoxins. Any argument that this neurotoxic impact is extreme, rare, and therefore irrelevant is unsound. In addition, every known neurotoxic effect confirms the possible prenatal impact of other environmental agents not yet studied, and we do know there are literally hundreds of such neurotoxins already dispersed in the environment.15... 

With respect to neurotoxins, there are a number of industrial chemicals (acrylamide, n-hexane, methyl n-butyl ketone, cresyl phosphate), pharmaceuticals (nitrofuradantoin, isoniazid), and pesticides (leptophos, Kepone ) which have been associated with neuropathic effects in humans (for reviews, see References 107,123, 124). Subchronic exposure studies in rodents and other animals such as cats have been used to identify and study the mechanism of action of neurotoxic chemicals which produce paralysis and behavioral changes in exposed animals. Studies are currently underway to evaluate the relative sensitivities of behavioral tests and morphological assays of peripheral and central nervous system axon morphology for detecting the earliest signs of chemically induced neuropathies. " ... 

Neurotoxicity can include effects on behavior and physiology, including motor function, sensory function, and cognitive function. These aspects are mainly studied in safety pharmacology, where the emphases are on functional and behavioral tests (e.g., functional observational battery FOB) (OECD 2004), and neurotoxicity may or may not be associated with changes in neuropathology. Neurotoxins may target different parts of the neuron, and neuronopathies may involve injury to the neurones, followed by necrosis and loss the effects may be broad or selective for a subpopulation of neurons. 

Neurotoxic chemicals can induce an adverse effect on the structure or function of the central and/or peripheral nervous system, which can be permanent or reversible. In some cases the detection of neurotoxic effects may require specialized laboratory techniques, but often they can be inferred from behavior such as slurred speech and staggered gait. Many neurotoxins... 

In comparative studies of the neurotoxic effects of NMDA and kainic acid in the hippocampal formation, we have found that NMDA is approximately 100-fold less potent as a neurotoxin than kainic acid on a molar basis (Zaczek et aL, 1981). The lesion associated with local injection of NMDA is limited to the injection site in the hippocampal formation and appears to uniformly affect all neuronal perikarya within its circumference. However, doses of NMDA effective in causing significant lesions in the dentate gyrus precipitated a severe electroencephalographic and behavioral seizure disturbance punctuated by frequent tonic-clonic convulsions occasionally resulting in death. Thus, the superiority of NMDA over kainic acid and ibotenic acid for intracerebral injection remains to be established. 

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