Men who were given an injection of a naturally occurring hormone showed enhanced activity in brain regions involved with sexual arousal and romantic love, decline in negative moods as well as helping treat some psychosexual disorders that commonly occur in patients with infertility, a study has found.

Kisspeptin has been linked to sexy and romantic feelings and is essential to the body's reproductive system.

"Our study indicates that kisspeptin plays a role in stimulating some of the emotions and responses that lead to sex and reproduction," said lead author Waljit Dhillo, Professor at Imperial College London.

"Kisspeptin boosts sexual and romantic brain activity as well as decreasing negative mood. This raises the interesting possibility that kisspeptin may have uses in treating psychosexual disorders and depression which are major health problems which often occur together," added Alexander Comninos from Imperial College London.

For the study, the team involved 29 healthy heterosexual young men who were given either an injection of kisspeptin or placebo who were shown a variety of images, including sexual and non-sexual romantic pictures of couples.

The findings demonstrated that men who received the injection of kisspeptin, had enhanced activity in structures in the brain typically activated by sexual arousal and romance.

This shows that kisspeptin boosts behavioural circuits associated with sex and love, the researchers said.

Further, the volunteers also underwent MRI scans where they were shown sexual and non-sexual romantic, negative, and neutral-themed images, and images of happy, fearful and neutral emotional faces.

Kisspeptin did not appear to alter emotional brain activity in response to neutral, happy or fearful-themed images.

However, when volunteers were shown negative images, kisspeptin did enhance activity in brain structures important in regulating negative moods, suggesting that then hormone might be used for treating depression, the researchers stated.

The study is detailed in the Journal of Clinical Investigation.