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PTSD Symptoms Linked To Imbalance Between Serotonin And Substance P In Brain: Study

PTSD
Understanding the symptoms of PTSD soon after the distressing event is needed to develop better treatment says a new study by researchers at University of Vermont. Reuters

People with post-traumatic stress disorder have an imbalance between two neurochemical systems in the brain, serotonin and substance P, a new study suggests. The greater the imbalance, the more serious the symptoms, say researchers at Uppsala University and Karolinska Institutet.

While many of us will experience some trauma in our lives, most of us will not have the misfortune to suffer the long-lasting symptoms of post-traumatic stress disorder (PTSD). In fact, of those who have been involved in a car accident, rape, child abuse, torture, train wreck, plane crash, bombing, or natural disaster, only about one in 10 will develop PTSD, according to the National Institute of Mental Health. For some, the disorder may progress to extreme torment. Signs are grouped into three categories: re-experiencing symptoms, such as flashbacks occurring at any moment; avoidance symptoms, including feeling numb; and hyperarousal symptoms, such as feeling tense and unable to sleep.

Previous research shows altered brain anatomy and function in people diagnosed with PTSD. For the current study, investigators led by Professors Mats Fredrikson and Tomas Furmark focused on two neurochemical signaling systems — serotonin and substance P — and used brain scans to measure the relationship between them.

“Both these neurochemical systems have independently been implicated in stress and anxiety, but interactions between them might be crucial for human anxiety conditions,” wrote the researchers in their study.

What is Substance P?

Substance P is widely distributed throughout the brain, but still it is most closely associated with the transmission of pain information into the central nervous system. It also plays a role in the regulation of anxiety, stress, mood, and nausea, among other functions. By comparison, serotonin, famously, is linked to our feelings of happiness and well-being.

Using PET scans, Fredrikson, Furmark, and their colleagues examined the serotonin and substance P systems, both individually and as overlapping neurochemical configurations, in the brains of 16 patients with PTSD as well as 16 healthy volunteers. In particular, the team looked at the amygdala, center of our most primal emotions. Among the PTSD patients, they observed an increased number of receptors related to substance P, but not serotonin. Symptom severity was negatively related to serotonin availability in the amygdala, while receptor levels moderated this relationship, the researchers noted.

In fact, throughout the brain, aberrant "couplings" of these two neurochemical systems appeared to contribute to the pathophysiology of PTSD, explained the researchers.

Commonly, people with PTSD are prescribed selective serotonin re-uptake inhibitors (SSRIs), a kind of drug that directly impacts the serotonin system. However, these medicines do not work for everyone, wrote the researchers in their study.

“Restoring the balance between the serotonin and substance P systems could become a new treatment strategy for individuals suffering from traumatic incidents,” Dr. Andreas Frick, department of psychology, Uppsala University, stated in a press release. Though this avenue of research may quickly be explored, any resulting drugs would take time to develop, what with the necessary tests and scientific experiments. There may be hope for better medications as a result of this study, but it is further down the road.

Source: Frick A, Ahs F, Palmquist AM, et al. Overlapping expression of serotonin transporters and neurokinin-1 receptors in posttraumatic stress disorder: a multi-tracer PET study. Molecular Psychiatry. 2015.

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