Chronic Pain and Anxiety Linked By Neurotransmitter

A recent study provides insights into the link between chronic pain and anxiety. Experts believe the findings may offer a new approach to manage the conditions.

In the research, scientists discovered the body releases the same neurotransmitter in response to pain as it does for stress. Specifically, investigators determined the body releases the peptide neurotransmitter PACAP (pituitary adenylate cyclase activating polypeptide) both in response to stress and as a result of neuropathic pain.

Researchers believe this suggests that the PACAP neurotransmitter is responsible for both chronic pain and accompanying anxiety.

Investigators examined the expression of PACAP along one of the nervous system’s pathways to the brain — the spino-parabrachiomygdaloid tract — which travels from the spinal cord to the amygdala, the brain’s home base for emotional behavior.

Using models for chronic pain and anxiety, as well as models that can trace PACAP neurocircuits, the team members were able to observe where the stress and chronic pain pathways intersected.

“Chronic pain and anxiety-related disorders frequently go hand-in-hand,” said senior author Victor May, Ph.D., professor of neurological sciences at the University of Vermont (UVM). In a 2011 study, he and members of the research team found that PACAP was highly expressed in women exhibiting PTSD symptoms.

While May and his colleagues saw an increase in anxiety-related behaviors in models of chronic pain, the anxious behavior and pain hypersensitivity were significantly reduced when a PACAP receptor antagonist designed to block the response was applied.

“By targeting this regulator and pathway, we have opportunities to block both chronic pain and anxiety disorders,” said May.

May believes scientists can develop a small molecule compounds that can antagonize PACAP actions.

“This would be a completely different approach to using benzodiazepine and opioids — it’s another tool in the arsenal to battle chronic pain and stress-related behavioral disorders.”

Source: University of Vermont