Question

Why does susceptibility to neurotoxic effects vary depending upon the age (developmental stage) of the individual ?

Answer 1

The developing nervous system is more sensitive to toxicants than the adult nervous system. Neurotoxicity can also occur as a result of indirect effects, such as damage to hepatic or cardiovascular structures, or because of interference with the endocrine systems. Some chemicals may have multiple modes of action and may affect the nervous system both directly and indirectly. In the developing nervous system, neurotransmitters may have function other than neurotransmission, such as modulation of cell proliferation, survival, and differentiation. Thus, any toxicant that interferes with neurotransmission during development may cause permanent defects in the CNS.The development of the nervous system is intimately associated with the presence of circulating hormones such as thyroid hormone.The nature of nervous system deficit, which could include cognitive dysfunction, altered neurological development,or visual deficits, depends on the severity of the thyroid disturbance and specific developmental period when exposure to the chemical occured .