Scientists have discovered that the neurotransmitter dopamine drops significantly during a migraine headache and then fluctuates at various times during the attack, according to a new PET (positron emission tomography) scan study at the University of Michigan (U-M).
The findings offer new insights into how dopamine-based migraine treatments work and also give scientists a better understanding of patients’ behavior during an attack. Dopamine is known to regulate emotion, motivation, and sensory perception.
Migraine patients are often given dopamine antagonists, drugs that block overactive dopamine receptors, to level off wild dopamine fluctuations and ease migraine attacks. But the link between dopamine and migraines has been a poorly understood therapeutic and research area, said Dr. Alex DaSilva, assistant professor at the U-M School of Dentistry and Center for Human Growth and Development.
For the study, the researchers measured the brain activity and dopamine levels of eight migraine sufferers during and between migraine attacks. They compared study participants to one another and also to a control group of eight healthy patients.
The findings show that when migraine patients were between headaches, their dopamine levels were as stable as the healthy patients, DaSilva said. But during an attack, the migraine patients’ dopamine levels dropped significantly.
“Dopamine is one of the main neurotransmitters controlling sensory sensitivity,” said study co-author Kenneth Casey, U-M professor emeritus of neurology. “Therefore, a drop in dopamine could produce increased sensory sensitivity so that normally painless or imperceptible sensory signals from skin, muscle, and blood vessels could become painful.”
This supports the theory held by some researchers that migraines are a periodic disorder characterized by sensory hypersensitivity during which light, sound, and odors may become abnormally intense, Casey says.
DaSilva says he was surprised when patients who were resting during their migraine attacks experienced a small dopamine spike and worsening symptoms when researchers applied warmth to their foreheads.
This condition in chronic pain patients is called allodynia — when a stimulus that normally wouldn’t cause pain does. DaSilva says the sudden small spike in dopamine was probably an aversive reaction to environmental stimulation.
This small fluctuation was only a partial recovery of dopamine, but it intensified patients’ suffering because the dopamine receptors were highly sensitive by then, and even a small recovery would trigger more nausea, vomiting, and other symptoms related to migraine, he says.
In addition to the pain of migraines, DaSilva says the fall in dopamine in general could also explain many common behaviors during an attack, such as withdrawal and isolation.
“This dopamine reduction and fluctuation during the migraine attack is your brain telling you that something is not going well internally, and that you need time to heal by forcing you to slow down, go to a dark room and avoid any kind of stimulation,” he said.
Source: University of Michigan