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Could our urge to fight actually feel rewarding?
A study published in Nature Communications suggests yes, and serotonin may hold the key to stopping it.
Most of us know that dopamine is involved in reward because of addiction research, and we know that serotonin can regulate emotions, as evidenced by the effects of antidepressants (SSRIs). However, how do these interact in the brain during aggression?
Researchers investigated this by the use of optogenetics, photometry (using light to control or record specific brain cells) and viral tools on mice (to genetically modify the cells and visualise or modify their activity). They recorded and modulated the activity of neurons in brain structures that communicate with nucleus accumbens, a structure involved in reward and motivation. These interventions where done, as they recorded fights mice.
They observed that serotonin signalling to nucleus accumbens could reduce the duration of attacks and that dopamine signalling neurons in the ‘reward pathway’ increase activity during attacks. While activating dopamine inputs directly had no effect on aggression, inhibition of D1-expressing neurons (a type of brain cell that responds to dopamine) reduced attack duration.
Taken together, this means that aggression has a rewarding effect and that serotonin signalling could suppress that activity and subsequently the behaviour. It may be that serotonin signaling supresses the rewarding effect of aggression. Think of it like an internal push-pull during aggression: dopamine makes the fight feel rewarding and encourages you, while serotonin pushes the brakes. Here, researchers managed to use advanced tools in a way that could push on the gas or the brakes during fighting.
The strength of this study is the demonstration of specific, targeted effects on aggressive behaviour by manipulating distinct circuits. Highlighting the importance of model organisms in investigations into mechanisms underlying brain function.
This study has revealed a microcircuitry involved in this fascinating behaviour in animals and a mechanistic basis for understanding how SSRIs may suppress aggression and boost impulse control. Further research into this microcircuitry could help elucidate the mechanisms underlying dysfunctions in aggression. There may be a benefit in studying the role of this microcircuit in impulse control in the future, as these behavioural results may have an alternative explanation.
Outside the scope of this study, could the rewarding effect of aggression be one of the facilitating factors for fighting competitions?
Declaration of AI use: The author used Lumo AI for spelling, grammar-checking and proofreading during the preparation of this article.
References
Zhang, Z., Touponse, G.C., Alderman, P.J. et al. Serotonin modulates nucleus accumbens circuits to suppress aggression in mice. Nat Commun 17, 2769 (2026). https://doi.org/10.1038/s41467-026-69254-x. Licensed under CC BY-NC-ND 4.0. Link: http://creativecommons.org/licenses/by-nc-nd/4.0/.
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