Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.8 (cholinesterase)
 12,691 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Chronic, low-level exposure to cholinesterase inhibitor organophosphate (OP) insecticides or chemical warfare agents produces abnormalities in CNS acetylcholine (ACh) function, and in humans, may be associated with impaired cognitive function as well after withdrawal from such exposure. The purpose of the present study was to identify the severity of impairment in spatial learning of rats following protracted withdrawal from chronic, low-level exposure to the OP agent diisopropylfluorophosphate (DFP). Assessment of spatial learning began either 3 or 17 days after completion of a 14-day DFP treatment regimen (50, 250, or 500 micrograms/kg). During the 14-day treatment regimen, spontaneous activity and olfactory behaviors were suppressed, effects which subsided with repeated exposure to the 250 micrograms/kg dose regimen. In contrast, both behaviors were stimulated by exposure to the 50 micrograms/kg dose regimen, as was body weight gain. Performance of the spatial test of working memory was impaired for up to 21 days after withdrawal from treatment with a 250 micrograms/kg dose of DFP. AChE activity in the frontal cortex and hippocampus was suppressed to 42.58% and 50.35% of control levels, respectively, 3 days after completion of the DFP (250 micrograms/kg) treatment regimen. By 7 days after withdrawal from treatment, AChE activity in the cortex and hippocampus had recovered to 81.87% and 64.61% of control levels, respectively. These levels represent increases in activity of 39.29% and 14.26% in these regions, as compared to AChE activity in 3 days after DFP withdrawal. By 21 days after withdrawal from treatment, AChE in both brain regions had recovered to levels similar to those of controls. Chronic, low-level OP exposure, therefore, produces protracted impairment of working memory after drug withdrawal that is not associated with continued suppression of AChE activity. This impairment may, however, be associated with a decreased rate of AChE recovery in the hippocampus, relative to the cortex. This decreased rate of enzyme recovery may contribute to hippocampal toxicity underlying protracted impairment of working memory.
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PMID:Chronic, low-level exposure to diisopropylfluorophosphate causes protracted impairment of spatial navigation learning. 904 Jan 25

Recent data suggest that Alzheimer's patients who discontinue treatment with cholinesterase inhibitors have a significantly delayed cognitive decline as compared to patients receiving placebo. Such observations suggest cholinesterase inhibitors to provide a disease-modifying effect as well as symptomatic relief and, moreover, that this benefit remains after drug withdrawal. Consistent with this suggestion, we now demonstrate that chronic administration of tacrine, nefiracetam, and deprenyl, drugs that augment cholinergic function, increases the basal frequency of dentate polysialylated neurons in a manner similar to the enhanced neuroplasticity achieved through complex environment rearing. While both drug-treated and complex environment reared animals continue to exhibit memory-associated activation of hippocampal polysialylated neurons, the magnitude is significantly reduced suggesting that such interventions induce a more robust memory pathway that can acquire and consolidate new information more efficiently. This hypothesis is supported by our findings of improved learning behavior and enhanced resistance to cholinergic deficits seen following either intervention. Furthermore, the level of enhancement of basal neuroplastic status achieved by either drug or environmental intervention correlates directly with improved spatial learning ability. As a combination of both interventions failed to further increase basal polysialylated cell frequency, complex environment rearing and chronic drug regimens most likely enhanced cognitive performance by the same mechanism(s). These findings suggest that improved memory-associated synaptic plasticity may be the fundamental mechanism underlying the disease modifying action of drugs such as cholinesterase inhibitors. Moreover, the molecular and cellular events underpinning neuroplastic responses are identified as novel targets in the search for interventive drug strategies for the treatment of neurodegenerative and neuropsychiatric disorders.
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PMID:Chronic exposure of rats to cognition enhancing drugs produces a neuroplastic response identical to that obtained by complex environment rearing. 1598 69