Published online 30 August 2002 | Nature | doi:10.1038/news020826-8


Identification of a potential ejaculation generator in the spinal cord

Rat study shows spinal-cord neurons control ejaculation.

Few researchers study ejaculation control in rats.Few researchers study ejaculation control in rats.© Science

Researchers have located the spinal-cord neurons that control ejaculation. The finding opens new avenues for treating premature ejaculation and problems with sexual function in paraplegic men.

Injecting male rats with a toxin that kills only one group of nerves in the spinal cord disrupts the very last step of their otherwise normal sexual behaviour, report researchers at the University of Cincinnati1. Encountering a willing female rat, the males still "act interested, get erections, chase her, mount her, and penetrate - they just never climax," says neuroscientist Lique Coolen.

Coolen targeted the lumbar spinothalamic neurons in the lower back because they are active only after a normal male rat ejaculates, and not simply at mounting or penetration.

Normally the brain is involved in the ejaculation reflex. But paraplegic men can climax even when the connection between the lower spinal chord and the brain is severed. So Coolen and other researchers had suspected that cells in the spinal cord generate the reflex.

"This ejaculation generator integrates sensory input from the penis with output to the muscle cells that cause ejaculation," says Coolen. These cells may also carry sensory information back to the brain after ejaculation.

Basic instinct

An estimated 30% of men have problems ejaculating at some time in their lives. Coolen is one of the few researchers to study this in lab animals.

Ejaculation is controlled by the lumbar spinothalamic cells.Ejaculation is controlled by the lumbar spinothalamic cells.© Science

"She's giving clinicians the basic information about what exactly is happening in the brain and spinal cord," says Marcel Waldinger, a psychiatrist at the University of Utrecht in the Netherlands.

He currently treats patients for premature ejaculation with antidepressant drugs such as Paxil and Prozac.

These drugs perform well in what Waldinger calls the "stopwatch test". But they have unwanted side-effects because they act on other areas of the brain, and their impact can last 24 hours.

Determining which chemicals activate the spinal neurons could improve treatments for male sexual dysfunction - or even simulate orgasm.

"It's wild speculation," warns Coolen. "But if we were to find the chemicals that contribute to the sensation of ejaculation and the pleasure associated with it, we may be able to find drugs that have the same effect." 

  • References

    1. Truitt, W.A. & Coolen, L. Identification of a potential ejaculation generator in the spinal cord. Science, 297, 1566 - 1569, (2002). | Article | ISI |