The stress hormone corticosterone could be developed into a treatment for post traumatic stress disorder .
The human body’s own natural stress hormone, corticosterone, could be developed into a treatment for post traumatic stress disorder (PTSD), report researchers at UT Southwestern Medical Centre, Texas, US.
The group used a mouse model of PTSD. Mice were placed in a box and administered a mild electric shock through the floor. The normal response of mice is to freeze with fear when they are placed back in the same box, a scenario commonly used to experimentally duplicate the experience of ’reliving’ a trauma, as seen in PTSD.
Mice injected with corticosterone immediately after the electric shock showed a significantly lower fear response when put back in the same environment.
’We can show experimentally that the original memory trace is still there, so we are not erasing these memories,’ explained Craig Powell, lead author of the study. ’We think that high levels of corticosterone stimulate the brain to make a new memory when the context of the trauma is re-experienced minus the trauma itself,’ he said. Repeating the non-traumatic experience in the same context consolidates this new memory, dampening the memory of the trauma in a process called ’extinction’.
Highly elevated levels of stress hormones, which occur naturally during trauma, may help to stimulate this process and prevent PTSD.
’It looks like we have found a way to chemically modulate this extinction process and directly affect specific fear behaviour,’ added Robert Greene, co-author of the study.
PTSD is triggered by a life-threatening event. The often debilitating symptoms include flashbacks, brought on by a reminder of the ordeal. Sufferers can experience flashbacks for years and some live with the symptoms for the rest of their lives. Patients are often treated with generic anti-anxiety drugs such as selective serotonin reuptake inhibitors (SSRIs). This work provides the hope of a specific PTSD drug, which is not currently available to patients.
’The administration of glucocorticoids could be time-locked to the reactivation of the memory,’ said Powell. ’So, if you imagine a psychotherapeutic situation, the patient is stimulated to relive the memory and this is time-locked with administration of the drug in order to stimulate this ’extinction’ process and lessen the intensity of the traumatic memory.’
Dominique de Quervain, from the division of psychiatry research at the University of Zurich, Switzerland cautioned that future study would be needed to show the optimal way of timing this treatment. ’Since traumatic memories in PTSD patients manifest as flashbacks and nightmares, these memories can be reactivated without psychotherapy,’ he said.
Since glucocorticoids are already in wide use, positive results from clinical trials, which have already begun, could see this new PTSD treatment immediately put into use. Victoria Gill
Cai et alJ.Neurosci, 2006, Doi: 10.1523/JNEUROSCI.2397-06.2006