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Relationship: 11


A descriptive phrase which clearly defines the two KEs being considered and the sequential relationship between them (i.e., which is upstream, and which is downstream). More help

AchE Inhibition leads to ACh Synaptic Accumulation

Upstream event
The causing Key Event (KE) in a Key Event Relationship (KER). More help
Downstream event
The responding Key Event (KE) in a Key Event Relationship (KER). More help

Key Event Relationship Overview

The utility of AOPs for regulatory application is defined, to a large extent, by the confidence and precision with which they facilitate extrapolation of data measured at low levels of biological organisation to predicted outcomes at higher levels of organisation and the extent to which they can link biological effect measurements to their specific causes.Within the AOP framework, the predictive relationships that facilitate extrapolation are represented by the KERs. Consequently, the overall WoE for an AOP is a reflection in part, of the level of confidence in the underlying series of KERs it encompasses. Therefore, describing the KERs in an AOP involves assembling and organising the types of information and evidence that defines the scientific basis for inferring the probable change in, or state of, a downstream KE from the known or measured state of an upstream KE. More help

AOPs Referencing Relationship

AOP Name Adjacency Weight of Evidence Quantitative Understanding Point of Contact Author Status OECD Status
Acetylcholinesterase inhibition leading to acute mortality adjacent High Moderate Dan Villeneuve (send email) Under Development: Contributions and Comments Welcome Under Development
Acetylcholinesterase Inhibition Leading to Neurodegeneration adjacent High Moderate Karen Watanabe (send email) Under development: Not open for comment. Do not cite
Acetylcholinesterase Inhibition leading to Acute Mortality via Impaired Coordination & Movement​ adjacent Kristie Sullivan (send email) Under development: Not open for comment. Do not cite
Organo-Phosphate Chemicals induced inhibition of AChE leading to impaired cognitive function adjacent High Moderate SAROJ AMAR (send email) Under development: Not open for comment. Do not cite

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KER.In general, this will be dictated by the more restrictive of the two KEs being linked together by the KER.  More help
Term Scientific Term Evidence Link
Metapenaeus monoceros Metapenaeus monoceros High NCBI
Philosamia ricini Samia ricini High NCBI
Rana cyanophlyetis Euphlyctis cyanophlyctis Moderate NCBI
Tilapia mossambica Oreochromis mossambicus High NCBI
rat Rattus norvegicus High NCBI
mouse Mus musculus High NCBI
zebrafish Danio rerio Moderate NCBI
Japanese quail Coturnix japonica Moderate NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help
Sex Evidence
Unspecific High

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER.  More help
Term Evidence
All life stages

Key Event Relationship Description

Provides a concise overview of the information given below as well as addressing details that aren’t inherent in the description of the KEs themselves. More help
  • AChE is an enzyme responsible for controlling the level of acetylcholine available at cholinergic synapses by degrading this neurotransmitter via hydrolysis to acetic acid and choline (Wilson 2010). Inhibition of AChE prevents degradation of acetylcholine which leads to accumulation of acetylcholine in synapses associated with muscarinic and nicotinic receptors (Soreq and Seidman, 2001; Lushington 2006).

  • See KEGG Reaction R01026

Evidence Collection Strategy

Include a description of the approach for identification and assembly of the evidence base for the KER. For evidence identification, include, for example, a description of the sources and dates of information consulted including expert knowledge, databases searched and associated search terms/strings.  Include also a description of study screening criteria and methodology, study quality assessment considerations, the data extraction strategy and links to any repositories/databases of relevant references.Tabular summaries and links to relevant supporting documentation are encouraged, wherever possible. More help

As it pertains to AOP 281, evidence was collected in multiple ways: literature searches of external databases, review of related KEs and KERS in the AOPWiki, and consultation with experts.   Extensive literature searches were conducted in Scopus, Pubmed, and Google Scholar using keywords applicable to each KE, with an initial focus on zebrafish data to then focusing on rat data. Related KEs and KERs in the AOPWiki were also reviewed for relevant evidence and their sources.  The “snowball method” was used to find additional articles, i.e., relevant citations within an article were obtained if they provided additional evidence. EndNote reference managing software was used to store results from the literature searches and when possible, a pdf of the manuscript was attached to each record. Papers were reviewed and categorized by whether they contained data to support one or more parts of the AOP. An Excel spreadsheet was used to record reviewed papers and any information worth noting.

Evidence Supporting this KER

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help
Biological Plausibility
Addresses the biological rationale for a connection between KEupstream and KEdownstream.  This field can also incorporate additional mechanistic details that help inform the relationship between KEs, this is useful when it is not practical/pragmatic to represent these details as separate KEs due to the difficulty or relative infrequency with which it is likely to be measured.   More help
  • Acetylcholine is a critical neurotransmitter localized to neuronal synapses. Biological plausibility to support the relationship between AChE inhibition and accumulation of acetylcholine is rooted in evidence demonstrating that AChE catalyzes degradation of acetylcholine into choline and acetate. Therefore, inhibition of the AChE leads to acetylcholine accumulation.
Uncertainties and Inconsistencies
Addresses inconsistencies or uncertainties in the relationship including the identification of experimental details that may explain apparent deviations from the expected patterns of concordance. More help
  • No known qualitative inconsistencies or uncertainties associated with this relationship.

Known modulating factors

This table captures specific information on the MF, its properties, how it affects the KER and respective references.1.) What is the modulating factor? Name the factor for which solid evidence exists that it influences this KER. Examples: age, sex, genotype, diet 2.) Details of this modulating factor. Specify which features of this MF are relevant for this KER. Examples: a specific age range or a specific biological age (defined by...); a specific gene mutation or variant, a specific nutrient (deficit or surplus); a sex-specific homone; a certain threshold value (e.g. serum levels of a chemical above...) 3.) Description of how this modulating factor affects this KER. Describe the provable modification of the KER (also quantitatively, if known). Examples: increase or decrease of the magnitude of effect (by a factor of...); change of the time-course of the effect (onset delay by...); alteration of the probability of the effect; increase or decrease of the sensitivity of the downstream effect (by a factor of...) 4.) Provision of supporting scientific evidence for an effect of this MF on this KER. Give a list of references.  More help
Modulating Factor (MF) MF Specification Effect(s) on the KER Reference(s)
enzyme butylcholinesterase Butylcholinesterase can affect the substrate interaction and should be accounted for Wilson (2001)
Response-response Relationship
Provides sources of data that define the response-response relationships between the KEs.  More help

Striatal AChE activity and extracellular ACh levels were measured in rats intracerebrally perfused with paraoxon (0, 0.03, 0.1, 1, 10 or 100 μM, 1.5 μl/min for 45 min). Acetylcholine was below the limit of detection at the low dose of paraoxon (0.1 uM), but was  transiently elevated (0.5–1.5 hr) with 10 μM paraoxon. Concentration-dependent AchE inhibition was noted but reached a plateau of about 70% at 1 μM and higher concentrations (Ray, 2009).

Information regarding the approximate time-scale of the changes in KEdownstream relative to changes in KEupstream (i.e., do effects on KEdownstream lag those on KEupstream by seconds, minutes, hours, or days?). More help

The relationship between AChE inhibition and ACh accumulation at the synapse can be observed within 30 minutes after application of an AChE inhibitor (Ray, 2009).  Other experiments have shown significant differences in ACh after AChE inhibition as soon as an hour after application of a chemical stressor (Kim et al., 2003, Faria et al., 2015).

Known Feedforward/Feedback loops influencing this KER
Define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits. More help

Domain of Applicability

A free-text section of the KER description that the developers can use to explain their rationale for the taxonomic, life stage, or sex applicability structured terms. More help

Cholinergic transmissions mediated by acetylcholinesterase occur in a wide variety of species, both vertebrates and invertebrates, and cholinergic transmissions occur at all stages in life.

Taxonomic Applicability

  • The literature includes many studies linking increases in acetylcholine in brain tissues after exposure to an OP or carbamate pesticide with increased AChE inhibition in various taxa. Examples include studies with crustacea (Reddy et al., 1990); tadpoles (Nayeemunnisa and Yasmeen, 1986); fish (Rao and Rao 1984; Verma et al., 1981); birds (Kobayashi et al., 1983); and rodents (Kobayashi et al., 1988).


List of the literature that was cited for this KER description. More help
  • Chen, L., Huang, C., Hu, C., Yu, K., Yang, L. & Zhou, B. 2012. Acute exposure to DE-71: Effects on locomotor behavior and developmental neurotoxicity in zebrafish larvae. Environmental Toxicology and Chemistry, 31, 2338-2344. DOI: 10.1002/etc.1958.
  • Del Pino, J., Moyano, P., Díaz, G. G., Anadon, M. J., Diaz, M. J., García, J. M., Lobo, M., Pelayo, A., Sola, E. & Frejo, M. T. 2017. Primary hippocampal neuronal cell death induction after acute and repeated paraquat exposures mediated by AChE variants alteration and cholinergic and glutamatergic transmission disruption. Toxicology, 390, 88-99. DOI: 10.1016/j.tox.2017.09.008.
  • Faria, M., Garcia-Reyero, N., Padrós, F., Babin, P. J., Sebastián, D., Cachot, J., Prats, E., Arick Ii, M., Rial, E., Knoll-Gellida, A., Mathieu, G., Le Bihanic, F., Escalon, B. L., Zorzano, A., Soares, A. M. & Raldúa, D. 2015. Zebrafish Models for Human Acute Organophosphorus Poisoning. Sci Rep, 5, 15591. DOI: 10.1038/srep15591.
  • Karanth, S., Liu, J., Mirajkar, N. & Pope, C. 2006. Effects of acute chlorpyrifos exposure on in vivo acetylcholine accumulation in rat striatum. Toxicology and Applied Pharmacology, 216, 150-156. DOI:
  • Karanth, S., Liu, J., Ray, A. & Pope, C. 2007. Comparative in vivo effects of parathion on striatal acetylcholine accumulation in adult and aged rats. Toxicology, 239, 167-179. DOI:
  • Kim, Y. K., Koo, B. S., Gong, D. J., Lee, Y. C., Ko, J. H. & Kim, C. H. 2003. Comparative effect of Prunus persica L. BATSCH-water extract and tacrine (9-amino-1,2,3,4-tetrahydroacridine hydrochloride) on concentration of extracellular acetylcholine in the rat hippocampus. J Ethnopharmacol, 87, 149-54. DOI: 10.1016/s0378-8741(03)00106-5.
  • Kobayashi, H., Sato, I., Akatsu, Y., Fujii, S., Suzuki, T., Matsusaka, N. & Yuyama, A. 1994. Effects of single or repeated administration of a carbamate, propoxur, and an organophosphate, DDVP, on jejunal cholinergic activities and contractile responses in rats. J Appl Toxicol, 14, 185-90. DOI: 10.1002/jat.2550140307.
  • Kobayashi, H., Yuyama, A., Kajita, T., Shimura, K., Ohkawa, T. & Satoh, K. 1985. Effects of insecticidal carbamates on brain acetylcholine content, acetylcholinesterase activity and behavior in mice. Toxicology Letters, 29, 153-159. DOI:
  • Kobayashi, H., Yuyama, A., Kudo, M. & Matsusaka, N. 1983. Effects of organophosphorus compounds, O,O-dimethyl O-(2,2-dichlorovinyl)phosphate (DDVP) and O,O-dimethyl O-(3-methyl 4-nitrophenyl)phosphorothioate (fenitrothion), on brain acetylcholine content and acetylcholinesterase activity in Japanese quail. Toxicology, 28, 219-227. DOI:
  • Kobayashi, H., Yuyama, A., Ohkawa, T. & Kajita, T. 1988. Effect of Single or Chronic Injection with a Carbamate, Propoxur, on the Brain Cholinergic System and Behavior of Mice. The Japanese Journal of Pharmacology, 47, 21-27. DOI: 10.1254/jjp.47.21.
  • Kosasa, T., Kuriya, Y., Matsui, K. & Yamanishi, Y. 1999. Effect of donepezil hydrochloride (E2020) on basal concentration of extracellular acetylcholine in the hippocampus of rats. European Journal of Pharmacology, 380, 101-107. DOI: 10.1016/S0014-2999(99)00545-2.
  • Lushington, G. H., Guo, J. X. & Hurley, M. M. 2006. Acetylcholinesterase: molecular modeling with the whole toolkit. Curr Top Med Chem, 6, 57-73. DOI: 10.2174/156802606775193293.
  • Nayeemunnisa and Yasmeen, N. 1986. On the Presence of Calmodulin in the Brain of Control and Methyl Parathion-Exposed Developing Tadpoles of Frog, Rana cyanophlictis. Curr.Sci.(Bangalore) 55[11], 546-548.
  • Oyama, Y., Hori, N., Evans, M. L., Allen, C. N. & Carpenter, D. O. 1989. Electrophysiological estimation of the actions of acetylcholinesterase inhibitors on acetylcholine receptor and cholinesterase in physically isolated Aplysia neurones. Br J Pharmacol, 96, 573-82. DOI: 10.1111/j.1476-5381.1989.tb11855.x.
  • Pant, R. & Katiyar, S. K. 1983. Effect of malathion and acetylcholine on the developing larvae ofPhilosamia ricini (Lepidoptera: Saturniidae). Journal of Biosciences, 5, 89-95. DOI: 10.1007/BF02702598.
  • Rao, K. S. P. & Rao, K. V. R. 1984. Impact of methyl parathion toxicity and eserine inhibition on acetylcholinesterase activity in tissues of the teleost (Tilapia mossambica) — a correlative study. Toxicology Letters, 22, 351-356. DOI:
  • Ray, A., Liu, J., Karanth, S., Gao, Y., Brimijoin, S. & Pope, C. 2009. Cholinesterase inhibition and acetylcholine accumulation following intracerebral administration of paraoxon in rats. Toxicology and applied pharmacology, 236, 341-347. DOI: 10.1016/j.taap.2009.02.022.
  • Reddy, M. S., Jayaprada, P. & Rao, K. V. 1990. Impact of methylparathion and malathion on cholinergic and non-cholinergic enzyme systems of penaeid prawn, Metapenaeus monoceros. Biochem Int, 22, 769-79.
  • Soreq, H. & Seidman, S. 2001. Acetylcholinesterase--new roles for an old actor. Nat Rev Neurosci, 2, 294-302. DOI: 10.1038/35067589.
  • Stavinoha, W. B., Ryan, L. C. & Smith, P. W. 1969. Biochemical effects of an organophosphorus cholinesterase inhibitor on the rat brain. Ann N Y Acad Sci, 160, 378-82. DOI: 10.1111/j.1749-6632.1969.tb15859.x.
  • Verma, S. R., Tonk, I. P., Gupta, A. K. & Dalela, R. C. 1981. In vivo enzymatic alterations in certain tissues of Saccobranchus fossilis following exposure to four toxic substances. Environmental Pollution Series A, Ecological and Biological, 26, 121-127. DOI:
  • Wilson, B. W. 2001. CHAPTER 48 - Cholinesterases. In: KRIEGER, R. I. & KRIEGER, W. C. (eds.) Handbook of Pesticide Toxicology (Second Edition). San Diego: Academic Press.
  • Wilson, B. W. 2010. Cholinesterases. In: KRIEGER, R. (ed.) Hayes' Handbook of Pesticide Toxicology. Third ed. Amsterdam, The Netherlands: Elsevier.