Mammalian neuropathology: a paradigm for the study of teleost neurotoxicity?

In vertebrates, neurotoxicants are chemicals whose primary toxic effect is on the nervous system, either the central nervous system (CNS {brain and spinal cord}) or the peripheral nervous system (PNS {spinal roots, sensory ganglia, peripheral nerves}). Pathological aspects of neurotoxicity are well documented in experimental mammals. We illustrate the neurotoxicity of two chemicals, which both produce lesions in selective regions of the rat brain, a thiocarbamate herbicide (cycloate) and an industrial chemical, chloropropionic acid (L-CPA). Cycloate exposure results in neuronal cell death by apoptosis in specific areas of the forebrain, whereas L-CPA produces granule cell necrosis in the cerebellum. Our studies in rodents demonstrate the discriminative power of neuropathological tools for neurotoxicity. Many agrochemicals/industrial chemical products enter the aquatic environment, some with the potential for neurotoxicity. The teleost CNS is the most primitive among the vertebrates but has features in common with the CNS of more advanced forms. Even allowing for differences in phylogenetic organisation, neuropathological tools should have the potential to identify neurotoxicants that affect teleosts.