Organophosphate pesticides, cholinergic function and cognitive performancein advanced age

Overstreet DH. Organophosphate pesticides, cholinergic function, and cognit ive performance in advanced age. The present communication will address the question of whether older individuals/animals are at greater risk to the c ognitive impairment induced by exposure to organophosphates (OPs). There is considerable evidence for a decline in cholinergic indices (choline acetyl transferase, acetylcholinesterase, and muscarinic acetylcholine receptors) with aging. Whether these decreases lead to a greater or smaller response t o OPs will depend on the relative rate of change in the specific indices. S ome studies have shown that aged animals are more sensitive to cholinergic (muscarinic) agonists, even though the receptors are reduced. These finding s suggest that aged individuals may be more sensitive to OPs. There is also much evidence documenting the decline in cognitive function in aged animal s, a process which is accentuated in Alzheimer's disease and which has been attributed, in part, to the decline in cholinergic indices. Several studie s have reported an improvement in cognitive functioning in aged animals/hum ans following treatment with acetylcholinesterase inhibitors. Thus, it is p ossible that the cognitive impairment, which occurs during aging, may be pa rtially counteracted during treatment with certain cholinesterase inhibitor s (both OPs and nonOPs). Whether the cognitive impairment reported by young er individuals some time after exposure to OPs would be greater in the elde rly cannot be predicted on the basis of the available evidence. However, th e findings in an animal model of dietary-induced cholinergic hypofunction d eveloped by Roger Russell and colleagues may shed light on this question. ( C) 2000 Inter Press, Inc.