Hormone injection sparks love and sex regions in brain

The brain regions associated with sex and love can be enhanced by the naturally occurring hormone kisspeptin, according to new research. It raises the possibility of eventually treating psychosexual disorders and depression, two conditions that often occur together, through the development of a new kisspeptin-based therapy.

"Kisspeptin is a naturally occurring hormone, so it's present in all men and all women. And it's mainly found in the brain, especially in the centre of the brain in the area called the hypothalamus. At the moment we know that it works to control other reproductive hormones like testosterone and oestrogen using its actions at the centre point of the brain, in the hypothalamus. And we were interested in looking at how kisspeptin can affect other areas of the brain because there are receptors for this hormone in emotional areas of the brain," explained Dr. Alexander Comninos, first author of the study from Imperial College London.

In trials, 29 healthy young male volunteers were given an injection containing kisspeptin. They were then shown a variety of images while in an MRI scanner, including sexual and non-sexual romantic pictures of couples bonding. The same men were also administered a placebo during the two-stage controlled study.

Researchers analysing the brain responses of the men found that after the injection of kisspeptin, when viewing sexual or romantic images of couples, there was increased activity in structures in the brain typically activated by sexual arousal and romance.

"We used tasks to activate the sexual arousal centres of the brain and tasks to activate the romance sensors of the brain using images. And we observed that kisspeptin boosted the activity in sexual arousal and romantic circuits in the brain," said Comninos.

The researchers say the findings, published in the Journal of Clinical Investigation, show for the first time that the hormone that is vital in all of us to stimulate puberty can also alter the way that our brains behave.

"That's what the really exciting part of this study been - for the first time having a link between a hormone that's stimulating reproductive hormones, but also how our brains perceive sexual images," said lead author Professor Waljit Dhillo from Imperial College London.

During tests, kisspeptin did not appear to alter brain activity in response to neutral, happy or fear-inducing images. However, when volunteers were shown negative images, kisspeptin did spark activity in parts of the brain associated with regulating negative moods. Subsequent post-scan questionnaires revealed the men also felt a reduction in negative mood. As a result, the team is keen to investigate whether kisspeptin could have applications for treating depression.

Another potential therapy is an injection to treat sexual disorders which are psychological in origin. Most research into infertility focuses on the biological factors that make it difficult for couples to conceive a baby naturally. However, the team at Imperial believes the role the brain and emotion plays in this process is also very important. Medication like Viagra can trigger a physiological response, but a kisspeptin-derived therapy could treat the root cause of sexual disorder, said Prof. Dhillo.

"Viagra is very different. So Viagra will cause vasodilation, it will make the vessels essentially dilate, blood will go down to the genital area. So it's a completely different action, it's mechanical if you like. Whereas this is much more psychological in terms of its altering how we perceive sexual images in our brains. So it's a completely different mechanism of action," he said.

While kisspeptin offers the tantalising prospect of, in effect, 'mental Viagra', the scientists concede there's much more research needed.

"We've been able to show how kisspeptin does alter how we perceive those sexual images. And that's only in men. So, future study will need to be done with a larger group of patients, they'll need to be done in women, and they'll need to be done in patients with psycho-sexual disorders to see whether the same effects would happen. And there's no reason to suggest that they shouldn't, but obviously once those studies are done we'll have a clearer indication of the potential therapeutic benefits," added Dhillo. — Reuters