Dopamine Circuit in Brain Found to Drive Male Ejaculation

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https://neurosciencenews.com/dopamine-male-sexual-behavior-28519/

March 29, 2025

Summary: New research uncovers how dopamine in the ventral shell of the nucleus accumbens (vsNAc) governs the sexual behavior sequence in male mice, from sniffing to ejaculation. Using fiber photometry, scientists identified rhythmic dopamine activity during intromission that aligns with movement patterns and is regulated by acetylcholine inputs.

Crucially, the final intromission before ejaculation shows a distinct dopamine signal, and artificial stimulation of acetylcholine neurons during this phase triggers ejaculation. These insights not only deepen understanding of sexual behavior regulation but also hold potential for developing treatments for ejaculatory dysfunction linked to psychiatric conditions and medications.

Key Facts:

● Dopamine Timing: Rhythmic dopamine release in vsNAc tracks behavioral transitions.

● Acetylcholine Link: Acetylcholine neurons modulate dopamine rhythms that trigger ejaculation.

● Clinical Relevance: Findings may lead to new therapies for ejaculatory dysfunction in depression or medication use.

Male mice follow a stereotypical sequence of sexual behaviors, transitioning from initial interaction with an estrous female to ejaculation. This sequence includes sniffing, mounting, and intromission, all of which are crucial for reproductive success.

However, the specific brain mechanisms underlying these behavioral transitions remained unclear until now.

In this study, researchers demonstrated that dopamine, a key neurotransmitter in the brain’s reward system, plays a pivotal role in governing behavioral shifts. Using fiber photometry, they comprehensively measured dopamine input patterns to the nucleus accumbens, a region known for its substantial dopamine input.

Their findings showed that dopamine levels in a specific subregion—the ventral shell of the nucleus accumbens (vsNAc)—were closely linked to behavioral transitions.

Furthermore, rhythmic dopamine input to the vsNAc during intromission, which aligns with male movement patterns, was regulated by acetylcholine The study also revealed that the final intromission before ejaculation exhibited a distinct dopamine activity pattern compared to prior intromissions. Artificially stimulating acetylcholine neurons during intromission replicated this dopamine response, directly triggering ejaculation.

These findings provide the first evidence of a specific nucleus accumbens subregion playing a critical role in controlling sexual behavior and ejaculation.

Ejaculatory dysfunction is a known side effect of psychiatric disorders such as depression, as well as certain psychotropic medications innervation of the vsNAc.

The study also revealed that the final intromission before ejaculation exhibited a distinct dopamine activity pattern compared to prior intromissions. Artificially stimulating acetylcholine neurons during intromission replicated this dopamine response, directly triggering ejaculation.

These discoveries open new avenues for developing treatments for ejaculatory disorders and related conditions, potentially improving therapies for patients with psychiatric disorders or medication-induced dysfunction.