Dr. T.C. Theoharides and his research team have initiated superb investigations into the intersection of mast cell activation and neurological processes. Dr. Theoharides’ research strongly supports the hypothesis that some manifestations or subtypes of autism are due to allergy-like responses in the brain.
How is this possible?
Well, there’s a part of the brain called the diencephalon. The diencephalon includes the hypothalamus, thalamus, epithalamus, and the subthalamus. The hypothalamus sits above the brainstem. It regulates the release of hormones and the functions of the autonomic nervous system. Sensory input is first received and processed by the thalamus. All sensory input except smell goes through the thalamus first, before traveling on to the cortex of the brain; a part of the brain that is also involved in sensory processing, as well as cognition, language, and memory. The epithalamus contains the pineal gland, which secretes melatonin. The subthalamic nucleus is interconnected with that basal ganglia, which is central to controlling the motor functions and movements of the body.
Mast cells are abundant in the diencephalon. When mast cells are triggered, they release various substances called mediators. The best known mast cell mediator is histamine, which is involved in several allergic responses. But there are many lesser known mediators within mast cells that are just as potent as histamine.
There are a few different ways that mast cells can promote allergic like reactions in the brain. The first way is when a stressful event causes a person’s body to release something called corticotropin-releasing hormone (CRH). CRH stimulates mast cells in the brain, and the stimulated cells release their mediators. Since there are mast cells located at the blood brain barrier, this process of stimulation and mediator release can cause the blood brain barrier to become compromised or leaky. Once it becomes leaky, immune cells circulating in the body, that are supposed to stay outside the barrier, begin cross over into the brain. The immune cells that cross over stir up inflammation, which adds to the inflammation the mast cell mediators were already causing.
In autistic people, one often finds altered or extreme emotional responses to sensory stimuli, and mast cell activation can cause inflammation in the diencephalon, which is a relay station in sensory processing.
Here’s a very helpful talk by Dr. Theoharides that outlines a few other mechanisms that allow mast cells to be key players in the autistic experiences of people like me.
“Diencephalon.” Encyclopedia.com. http://www.encyclopedia.com/medicine/anatomy-and-physiology/anatomy-and-physiology/diencephalon Accessed January 2018.
Technical University of Munich (TUM). “Sensory function: Thalamus enhances, stores sensory information: Important brain network for processing sensory perceptions elucidated.” ScienceDaily. ScienceDaily, 21 January 2016. <www.sciencedaily.com/releases/2016/01/160121110929.htm>. Accessed January 2018.
Majewska, Ania. “Cerebral Cortex.” Els.net. http://www.els.net/WileyCDA/ElsArticle/refId-a0000090.html Updated January 2015. Accessed January 2018.
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