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Relationship: 1857

Title

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

ACh Synaptic Accumulation leads to Activation, Muscarinic Acetylcholine Receptors

Upstream event

The causing Key Event (KE) in a Key Event Relationship (KER). More help

ACh Synaptic Accumulation

Downstream event

The responding Key Event (KE) in a Key Event Relationship (KER). More help

Activation, Muscarinic Acetylcholine Receptors

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 Neurodegeneration	adjacent	Moderate	High	Allie Always (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 Do not cite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
human	Homo sapiens	High	NCBI
zebrafish	Danio rerio	High	NCBI
rat	Rattus norvegicus	High	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	High

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

Acetylcholine (ACh) is a neurotransmitter within the central nervous system and peripheral nervous system that activates both muscarinic and nicotinic receptors (Haga, 2013). Muscarinic receptors are metabotropic and act using slower transmission signaling compared to the more direct ionotropic receptors (Miller and Yeh, 2016).

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

Evidence Map 2.0

ID	Experimental Design	Species	Upstream Observation	Downstream Observation	Citation (first author, year)	Notes

Evidence Map

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help

Title	First Author	Biological Plausibility	Dose Concordance	Temporal Concordance	Incidence Concordance

Biological Plausibility

Dose Concordance Evidence

Temporal Concordance Evidence

Incidence Concordance Evidence

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

There are no known uncertainties or inconsistencies 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

Quantitative Understanding of the Linkage

Captures information that helps to define how much change in the upstream KE, and/or for how long, is needed to elicit a detectable and defined change in the downstream KE. More help

Table 1. Summary of available quantitative data describing responses of mAChR activation by ACh. k₁ and k_-1 are the forward and reverse rate binding constants, respectively. K_d is the dissociation constant, IC₅₀ is the half maximal inhibitory concentration, and B_max is the maximal binding capacity.

Upstream Synaptic ACh Accumulation	Downstream Muscarinic Receptor Activation	Brief Summary	Species / Model	Reference
Upstream Synaptic ACh Accumulation	Downstream Muscarinic Receptor Activation	Brief Summary	Species / Model	Reference
[3H]-Acetylcholine	Non-specific mAChR (cerebral cortex tissue): k₁ = 0.034 nM^-1 min^-1 k_-1 = 1.04 min^-1 K_d = 35.2 ± 3.2 nM IC₅₀ = (many) B_max = 18.2 ± 1.0 fmol/mg tissue \| 318 ± 17 fmol/mg protein	Provides binding constants to various tissues in the rat brain and rat heart atrium, providing association and dissociation rate constants, K_d values, IC₅₀ values against various competing compounds, and B_max for radiolabeled acetylcholine.	Male Sprague-Dawley rats (250-350g)	Kellar et al. (1985)
Acetylcholine	M1 Receptor kinetic parameters fitted to Falkenburger et al. (2010) data: k₁ (k_f^L1) = 2.78 mM^-1 ms^-1 k_-1 (k_b^L1) = 2.15x10^-3 ms^-1	Computational model of a CA1 pyramidal neuron that incorporates mAChR activation through acetylcholine application, intracellular calcium dynamics, and its electrophysiological response. They provide the kinetics in response to acetylcholine application and provide the associated kinetic rate constants.	Computational model	Mergenthal et al. (2020)
[3H]-Acetylcholine	Non-specific mAChR: K_d = 20 nM B_max (maximum binding): 0.8-1.2 pmoles/mg protein	Using radiolabeled acetylcholine ([3H]acetylcholine), Sprague-Dawley rats, provides K_d and maximum binding values for acetylcholine to 'synaptic membrane' from brain tissue.	Sprague-Dawley rats (200-300g)	Uchida et al. (1978)

Response-response Relationship

Provides sources of data that define the response-response relationships between the KEs. More help

Time-scale

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

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

Muscarinic receptors are found in a wide variety of species, both vertebrates and invertebrates, and cholinergic transmissions occur at all stages in (Burke et al., 2017, Garcia et al., 2016, Miller and Yeh, 2016).