London, November 7: Researchers at the University of Groningen in the Netherlands have successfully tested a drug to reduce aggressiveness in feral rats, which had been trained to be violent.

Sietse de Boer of the university believes that his team’s work may open the door to future treatments for pathological violence in humans.

During the study, the researchers exposed rodents to feeble intruders rats that were bound to lose battle, each day for two or three weeks. Repeated victories over other rats caused the test animals to behave in a more violent manner.

The rats’ brains were then tested for levels of the neurotransmitter serotonin, as pathologically violent people have been found to have lower levels of serotonin metabolites in their spinal fluid.

Although brain levels of serotonin did not change in rats as a result of normal, 'appropriate' acts of aggression, de Boer found them that the levels did sink in his pathologically aggressive rats.

When the rats were administered S-15535, a compound that binds exclusively to a neuron 'autoreceptor' that acts to dampen the serotonin system, the rodents’ serotonin levels came back to normal.

According to de Boer, the compound seemed to work by ‘fixing’ the serotonin breaking system, which had become dysfunctional in the super-aggressive rats.

The compound reduced aggressiveness in rats without affecting other behaviour, and without making them lethargic or ‘spaced out’,

"I can’t imagine that we can pin such a complex behaviour as pathological violence in humans on one single receptor," Nature magazine quoted de Boer as saying.

The study, however, strongly suggests that the serotonin system plays an important role in abnormally violent behaviour, and that understanding the system is the first step to being able to control it.

The findings were presented at the Society for Neuroscience meeting in San Diego. (ANI)