Neurotoxicity and Behavioral Effects of Environmental Chemicals - Organic Pollutants: An Ecotoxicological Perspective - page 297

taBLe 16.1
neurotoxic action of Some environmental chemicals
Sites of action Human-made chemicals notes natural toxins notes

Na + Channels DDT

Pyrethroids

Both can prolong the passage of
Na + current

Pyrethrins
Veratridine

Veratridine appears to act at a
different part of pore channel
from DDT or pyrethroids

Nicotinic acetylcholine
receptors

Neonicotinoids Similar action to Nicotine Nicotine Act as agonists causing

desensitization of receptor

Gamma aminobutyric acid
(GABA) receptors

Dieldrin, endrin, gamma HCH
(BHC), toxaphene

Inhibitors of receptor, reducing
chloride inlux

Picrotoxinin Inhibitor of GABA receptors

Acetylcholinesterase OP and carbamate insecticides Inhibitors of enzyme causing

buildup of acetylcholine in
synapses

Physostigmine Inhibitor of acetylcholinesterase

Neuropathy target esterase Certain OP compounds including

DFP, mipafox, and leptophos

Aging of inhibited enzyme leads to
degeneration of peripheral nerves

Cause damage to CNS of
vertebrates

Organomercury and organolead
compounds

Toxicity may be connected with
ability to combine with SH groups

Methyl mercury Occurs naturally as well as being

human made

Sources: Eldefrawi and Eldefrawi (1990), Johnson (1992), Ballantyne and Marrs (1992), and Salgado (1999).