Brain's fear response could treat anxiety, pain

Soldiers on the battlefield often experience pain considerably later than the time of the injury. The way the brain postpones pain in a terrifying situation is providing clues into new ways to treat fear, anxiety and pain, said Dr David Finn from Galway in Ireland today.

Speaking at the British Neuroscience Association annual meeting in Harrogate, in association with Neuroscience Ireland, Dr Finn and his team from the department of pharmacology and therapeutics at the National University of Ireland, reported studies of behavior in response to the action of endocannabinoids, substances in the brain that fine-tune a range of the body's functions and emotions. Their research in rats has shown that if the endocannabinoid signalling is blocked, fear and anxiety increased and lasted longer, whilst the suppression of pain normally observed in response to fear was abolished. Conversely, administration of drugs which prevent the breakdown of endocannabinoids enhances suppression of pain in response to fear. "If the endocannabinoid system is blocked, animals feel pain immediately, but if it is fully functioning, it suppresses the pain for a while," said Dr Finn.

Smoking cannabis may mimic the effects of the body's own endocannabinoids. Around 15 percent of people who smoke cannabis experience anxiety, suggesting that the cannabinoid system may represent a new way to treat anxiety disorders.

"Our research - and that of others - implies that if you can enhance endocannabinoids in the brain, this might be a route for treating phobias, stress and trauma associated with aversive memories and experiences. Ultimately, it might even help treat post-traumatic stress disorder," said Dr Finn. In certain situations, such as when soldiers are injured, the pain is suppressed. "Perhaps this delay has evolved to allow a person to carry on and get themselves to safety before the pain kicks in. We are now getting a handle on what mediates profound suppression of pain," he said.

From understanding the basic mechanisms of pain in relation to traumatic experiences, the goal would be to try and manipulate the system therapeutically. "But this is not so straightforward," said Dr Finn. "We have to find out whether fear is needed to induce the analgesic effect. Can you separate the two - and is it wise to?"

The next stage of his research, which is funded by Science Foundation Ireland and the Irish Health Research Board, will be to study further the brain regions involved and the chemical alterations in the brain during fear-induced pain suppression.

Finn D.
Endocannabinoid-mediated modulation of fear-related behaviour: sites and mechanisms of action
BNA meeting symposia 2007 Apr 2.