EVER wonder why you fear the dental chair? Or why you react immediately when you feel a dental tool on your gums or teeth?
Well, a new study makes interesting reading as it explains behavioral reaction to painful experiences.
It is well known that exposure to uncomfortable sensations elicits a wide range of appropriate and quick reactions, from reflexive withdrawal to more complex feelings and behaviors. To better understand the body’s innate response to harmful activity, researchers at the National Center for Complementary and Integrative Health (NCCIH) have identified activity in the brain that governs these reactions.
Using heat as the source of discomfort, experiments conducted at the NCCIH showed that bodily responses to pain are controlled by a neural pathway involving heightened activity in the spinal cord and two parts of the brainstem.
Results of the study were published in the journal Neuron.
“Much is known about local spinal cord circuits for simple reflexive responses, but the mechanisms underlying more complex behaviors remain poorly understood,” said Alexander T. Chesler, Ph.D., of the NCCIH and the senior author of the study. “We set out to describe the brain pathway that controls motor responses and involuntary behaviors when the body is faced with painful experiences.”
The NCCIH, in a press statement, describes how people respond to increasingly uncomfortable surfaces like a sandy beach on a hot day by lifting their feet, hopping, and eventually running to a water source. It says that laboratory experiments also show a predictable sequence of behaviors.
Experiments showed that the parts of a brainstem involved in this circuit are the parabrachial nucleus (PBNI) and the dorsal reticular formation in the medulla (MdD). A specific group of nerve cells in the PBNI is activated by standing on a hot surface, triggering escape responses through connections to the MdD.
The PBNI cells express a gene called Tac1, which codes for substances called tachykinins that participate in many functions in the body and contribute to multiple disease processes. The MdD cells involved in this circuit also express Tac1. A different group of cells in the PBNI participates in the aspects of the response to noxious heat that involve the forebrain.
Lest you get lost in all the technical jargons, Arnab Barik, Ph.D., postdoctoral fellow at NCCIH and one of the study’s authors, explains: “Our data provide evidence that the PBNI produces streams of information with distinct functional significance. The brainstem-spinal cord pathway identified in this study selectively controls pain response and elicits appropriate behaviors based on sensory input.”
Still lost? Dr. Chesler points out that the more this pathway is activated by harmful activity, the more it reacts, leading to dramatic behavioral responses.
Knowledge of this brain activity provides new insight into how the body responds to harmful, painful stimuli, the NCCIH says. The mechanism described in the study can help researchers better understand how pain is encoded in the brain.
More investigation of this circuit may increase understanding of how responses to pain are coordinated with other biological needs, such as feeding and reproduction. These findings may also offer opportunities to understand how the body becomes dysregulated during chronic pain.
The NCCIH’s mission is to define, through rigorous scientific investigation, the usefulness and safety of complementary and integrative health approaches and their roles in improving health and health care. It is part of the National Institutes of Health or NIH, the US medical research agency that includes 27 institutes and centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research and is investigating the causes, treatments and cures for both common and rare diseases./PN
Dr. Joseph D. Lim is the former Associate Dean of the UE College of Dentistry, former Dean of the College of Dentistry, National University, past president and honorary fellow of the Asian Oral Implant Academy, and honorary fellow of the Japan College of Oral Implantologists. Honorary Life Member of Thai Association of Dental Implantology. For questions on dental health, e-mail jdlim2008@gmail.com or text 0917-8591515.
