Why is Running Addictive?

Sometimes you will hear runners say, "I am addicted to running. I feel uncomfortable if I don't run for a day." Is running really addictive? The answer is: Yes. Most senior runners are addicted to running, especially those who participate in marathon long-distance running. Marathon is a very large amount of running. Running addiction is conducive to completing the 42-kilometer marathon. After ordinary runners become addicted to running, they will feel uncomfortable if they don't run for a day. For them, running becomes a magic medicine to relieve emotions and get a good mood.

On June 13, 2025, Katsuyuki Kaneda from Kanazawa University, Japan, published a study in Neuropsychopharmacology titled: "Medial nucleus accumbens dopamine receptors modulate motivation for wheel running in male mice." This research reveals that dopamine receptors in the medial nucleus accumbens regulate the motivation for wheel running in male mice.

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Overview

Abnormal motivation for natural rewards is a core feature of many mental health conditions, including behavioral addictions. Previous research, mainly using food reward tasks, has pinpointed the crucial role of the mesolimbic dopamine pathway in controlling motivated behaviors. However, most of these studies have focused solely on food rewards, limiting how much we can apply these findings to other natural rewards linked to behavioral addictions.

This study used a new wheel-running training reinforcement operant conditioning paradigm to systematically evaluate how rewarding wheel running is for rodents and its strong motivational properties. This method allowed the researchers to separately measure operant responses (i.e., appetitive behavior) and wheel running duration (i.e., consummatory behavior). This helped them deeply explore the role of dopamine signaling in the medial nucleus accumbens (mNAc) in motivating wheel running.

The results showed that systemically blocking both dopamine D1 and D2 receptors reduced appetitive behavior, but only D1 receptor blockage decreased consummatory behavior. Similarly, inhibiting mNAc neuron activity and blocking D1 and D2 receptors within this brain region significantly weakened appetitive behavior, with D1 receptor blockage specifically impairing consummatory behavior.

Fiber photometry further revealed that mNAc neural activity decreased while dopamine levels increased before appetitive behavior occurred. Conversely, after a cue indicated the wheel was available, both mNAc neural activity and dopamine levels increased. Additionally, systemic D1 receptor blockage reduced the decrease in mNAc neural activity observed during appetitive behavior.

In summary, these findings indicate that increased dopamine release and the resulting D1 receptor-dependent inhibition of mNAc neural activity are key mechanisms driving the motivation for wheel running. This research broadens our understanding of motivation beyond food rewards and offers insights into the neurobiology of behavioral addictions.

Fig.1 Establishing a Behavioral Paradigm to Quantify Appetitive and Consummatory Behaviors in Wheel Running Motivation.¹

Findings of the Study

In short, this research shows that activity in the medial nucleus accumbens (mNAc) and dopamine signaling (through D1 and D2 receptors) are super important for motivation when it comes to voluntarily running on a wheel. Specifically, the study found that dopamine release in the mNAc, acting through D1 receptors and causing changes in nerve cell activity, is crucial for driving this running behavior.

Future research needs to dig deeper into exactly how these changes in nerve cell activity happen and pinpoint the specific types of neurons in the mNAc involved. Doing so will help us better understand the brain basis of mental health conditions like major depression and behavioral addictions, which are often characterized by problems with motivation for natural rewards.

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Reference

1. Nishitani, Naoya et al. "Medial nucleus accumbens dopamine receptors modulate motivation for wheel running in male mice." Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 10.1038/s41386-025-02136-w. 12 Jun. 2025, doi:10.1038/s41386-025-02136-w. Distributed under Open Access license CC BY 4.0, without modification.