Aop: 204


A descriptive phrase which references both the Molecular Initiating Event and Adverse Outcome.It should take the form “MIE leading to AO”. For example, “Aromatase inhibition leading to reproductive dysfunction” where Aromatase inhibition is the MIE and reproductive dysfunction the AO. In cases where the MIE is unknown or undefined, the earliest known KE in the chain (i.e., furthest upstream) should be used in lieu of the MIE and it should be made clear that the stated event is a KE and not the MIE. More help

5-hydroxytryptamine transporter inhibition leading to increased reproductive success and population increase

Short name
A name that succinctly summarises the information from the title. This name should not exceed 90 characters. More help
5-HTT inhibition leading to population increase

Graphical Representation

A graphical representation of the AOP.This graphic should list all KEs in sequence, including the MIE (if known) and AO, and the pair-wise relationships (links or KERs) between those KEs. More help
Click to download graphical representation template Explore AOP in a Third Party Tool


The names and affiliations of the individual(s)/organisation(s) that created/developed the AOP. More help

Point of Contact

The user responsible for managing the AOP entry in the AOP-KB and controlling write access to the page by defining the contributors as described in the next section.   More help
Kellie Fay   (email point of contact)


Users with write access to the AOP page.  Entries in this field are controlled by the Point of Contact. More help
  • Kellie Fay


Provides users with information concerning how actively the AOP page is being developed, what type of use or input the authors feel comfortable with given the current level of development, and whether it is part of the OECD AOP Development Workplan and has been reviewed and/or endorsed. OECD Status - Tracks the level of review/endorsement the AOP has been subjected to. OECD Project Number - Project number is designated and updated by the OECD. SAAOP Status - Status managed and updated by SAAOP curators. More help
Author status OECD status OECD project SAAOP status
Under Development: Contributions and Comments Welcome 1.29 Under Development
This AOP was last modified on June 04, 2021 14:23

Revision dates for related pages

Page Revision Date/Time
Inhibition, 5-hydroxytryptamine transporter (5-HTT; SERT) September 16, 2017 10:15
Increased, valve movement December 03, 2016 16:37
Increase, cilia movement January 13, 2017 16:27
Induced parturition January 13, 2017 15:40
increased mantel display January 13, 2017 15:39
Increased, Reproductive Success December 03, 2016 16:37
Increased, Population December 03, 2016 16:37
Increased, serotonin (5-HT) September 16, 2017 10:15
Inhibition, 5-hydroxytryptamine transporter (5-HTT; SERT) leads to Increased, valve movement January 13, 2017 11:18
Inhibition, 5-hydroxytryptamine transporter (5-HTT; SERT) leads to Increase, cilia movement January 13, 2017 15:43
Inhibition, 5-hydroxytryptamine transporter (5-HTT; SERT) leads to increased mantel display January 13, 2017 15:44
increased mantel display leads to Induced parturition January 13, 2017 15:49
Increased, Reproductive Success leads to Increased, Population December 03, 2016 16:38
Induced parturition leads to Increased, Reproductive Success January 13, 2017 16:48
Inhibition, 5-hydroxytryptamine transporter (5-HTT; SERT) leads to Increased, serotonin (5-HT) December 03, 2016 16:37
Increased, serotonin (5-HT) leads to Increased, valve movement January 17, 2017 01:02
Increased, valve movement leads to Induced parturition January 30, 2017 12:23
Increase, cilia movement leads to Induced parturition January 30, 2017 12:24
Increased, serotonin (5-HT) leads to increased mantel display January 30, 2017 12:25
Increased, serotonin (5-HT) leads to Increase, cilia movement January 30, 2017 12:20


A concise and informative summation of the AOP under development that can stand-alone from the AOP page. The aim is to capture the highlights of the AOP and its potential scientific and regulatory relevance. More help

Anti-depressants such as fluoxetine inhibit the reuptake of 5-HT by blocking the 5-HTT, causing an increase in serotonin levels at neural junctions.  Movement-related endpoints in molluscs may be highly sensitive to 5-HTT inhibition, empirical evidence also supports a putative AO for reproductive health because serotonin is reported to control oocyte maturation, spawning and glochidia release (Ram 1993, Bringolf 2010, Meechonkit 2010,Lazarra 2012). Exposure of native freshwater mussels to fluoxetine induced premature release of glochidia resulting in non-viable larvae (Bringolf 2010), however most reports indicate increased serotinergic signaling results in the release of either viable gametes or glochidia.  Release is, in part, dependent on the water pumping rate and coordination with cilia, at least in some bivalves.   

AOP Development Strategy


Used to provide background information for AOP reviewers and users that is considered helpful in understanding the biology underlying the AOP and the motivation for its development.The background should NOT provide an overview of the AOP, its KEs or KERs, which are captured in more detail below. More help


Provides a description of the approaches to the identification, screening and quality assessment of the data relevant to identification of the key events and key event relationships included in the AOP or AOP network.This information is important as a basis to support the objective/envisaged application of the AOP by the regulatory community and to facilitate the reuse of its components.  Suggested content includes a rationale for and description of the scope and focus of the data search and identification strategy/ies including the nature of preliminary scoping and/or expert input, the overall literature screening strategy and more focused literature surveys to identify additional information (including e.g., key search terms, databases and time period searched, any tools used). More help

Summary of the AOP

This section is for information that describes the overall AOP. The information described in section 1 is entered on the upper portion of an AOP page within the AOP-Wiki. This is where some background information may be provided, the structure of the AOP is described, and the KEs and KERs are listed. More help


Molecular Initiating Events (MIE)
An MIE is a specialised KE that represents the beginning (point of interaction between a prototypical stressor and the biological system) of an AOP. More help
Key Events (KE)
A measurable event within a specific biological level of organisation. More help
Adverse Outcomes (AO)
An AO is a specialized KE that represents the end (an adverse outcome of regulatory significance) of an AOP. More help
Type Event ID Title Short name
MIE 619 Inhibition, 5-hydroxytryptamine transporter (5-HTT; SERT) Inhibition, 5-hydroxytryptamine transporter (5-HTT; SERT)
KE 1142 Increased, valve movement Increased, valve movement
KE 621 Increase, cilia movement Increase, cilia movement
KE 1257 Induced parturition Induced parturition
KE 1256 increased mantel display increased mantel display
KE 626 Increased, serotonin (5-HT) Increased, serotonin (5-HT)
AO 1163 Increased, Reproductive Success Increased, Reproductive Success
AO 1164 Increased, Population Increased, Population

Relationships Between Two Key Events (Including MIEs and AOs)

This table summarizes all of the KERs of the AOP and is populated in the AOP-Wiki as KERs are added to the AOP.Each table entry acts as a link to the individual KER description page. More help

Network View

This network graphic is automatically generated based on the information provided in the MIE(s), KEs, AO(s), KERs and Weight of Evidence (WoE) summary tables. The width of the edges representing the KERs is determined by its WoE confidence level, with thicker lines representing higher degrees of confidence. This network view also shows which KEs are shared with other AOPs. More help

Prototypical Stressors

A structured data field that can be used to identify one or more “prototypical” stressors that act through this AOP. Prototypical stressors are stressors for which responses at multiple key events have been well documented. More help

Life Stage Applicability

The life stage for which the AOP is known to be applicable. More help

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) can be selected.In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available. More help

Sex Applicability

The sex for which the AOP is known to be applicable. More help

Overall Assessment of the AOP

Addressess the relevant biological domain of applicability (i.e., in terms of taxa, sex, life stage, etc.) and Weight of Evidence (WoE) for the overall AOP as a basis to consider appropriate regulatory application (e.g., priority setting, testing strategies or risk assessment). More help

Domain of Applicability

Addressess the relevant biological domain(s) of applicability in terms of sex, life-stage, taxa, and other aspects of biological context. More help

Essentiality of the Key Events

The essentiality of KEs can only be assessed relative to the impact of manipulation of a given KE (e.g., experimentally blocking or exacerbating the event) on the downstream sequence of KEs defined for the AOP. Consequently, evidence supporting essentiality is assembled on the AOP page, rather than on the independent KE pages that are meant to stand-alone as modular units without reference to other KEs in the sequence. The nature of experimental evidence that is relevant to assessing essentiality relates to the impact on downstream KEs and the AO if upstream KEs are prevented or modified. This includes: Direct evidence: directly measured experimental support that blocking or preventing a KE prevents or impacts downstream KEs in the pathway in the expected fashion. Indirect evidence: evidence that modulation or attenuation in the magnitude of impact on a specific KE (increased effect or decreased effect) is associated with corresponding changes (increases or decreases) in the magnitude or frequency of one or more downstream KEs. More help

Evidence Assessment

Addressess the biological plausibility, empirical support, and quantitative understanding from each KER in an AOP. More help

Known Modulating Factors

Modulating factors (MFs) may alter the shape of the response-response function that describes the quantitative relationship between two KES, thus having an impact on the progression of the pathway or the severity of the AO.The evidence supporting the influence of various modulating factors is assembled within the individual KERs. More help

Quantitative Understanding

Optional field to provide quantitative weight of evidence descriptors.  More help

Considerations for Potential Applications of the AOP (optional)

Addressess potential applications of an AOP to support regulatory decision-making.This may include, for example, possible utility for test guideline development or refinement, development of integrated testing and assessment approaches, development of (Q)SARs / or chemical profilers to facilitate the grouping of chemicals for subsequent read-across, screening level hazard assessments or even risk assessment. More help


List of the literature that was cited for this AOP. More help