THE NEUROCHEMISTRY OF PAIN I.
Pain is not just a sensory experience - it is a full-body biochemical event. When you hurt your toe, get a paper cut, or receive an intense strike during impact play, your body does more than just notice it. It reacts, modulates, and adapts through a cascade of neurotransmitters and hormones - finely tuned by hundreds of thousands of years of evolution. This system helped your ancestors survive, and it’s the reason you’re here today reading these lines.
The First Responders: Glutamate & Substance P
As soon as nociceptors (pain receptors) in the skin detect a potentially harmful stimulus, they send signals to the central nervous system (the spine and the brain). The first chemicals that carry this pain message are:
Glutamate – Fast-acting and powerful, glutamate ensures the brain notices the pain right away (“F.ck! That hurt!”)
Substance P – A slower, longer-lasting neuropeptide that helps amplify and sustain the pain signal.
Pain is a full-body biochemical event based on the fine coordination of neurochemichals. The Second Wave: The Endogenous Opioid System
Very quickly after the initial reaction, the nervous system attempts to regulate the pain. If the situation is judged to be safe, meaningful, or manageable (see the role of consent & pre-session negotions here?!), the body activates its endogenous opioid system - your internal pain relief system:
Endorphins – Short for endogenous morphines, these powerful natural painkillers dull pain signals and start inducing pleasure.
Enkephalins & dynorphins – These opioid peptides mostly work in the spinal cord to mitigate pain signals before they reach full awareness.
These chemicals don’t just reduce pain - they can create euphoria, warmth, and partially altered states of consciousness. This is often referred to as the “pain high.” But they are not the only neurochemicals that are responsible for the experience.
Modulators and Mood Shifters: Serotonin & Norepinephrine
As the session continues, other systems come into the picture - especially those tied to mood, emotional meaning, and stress response.
Serotonin (5-HT) – Helps inhibit pain pathways and also stabilizes mood. When enough serotonin is in the system, people often report better sleep, improved energy, and a sense of emotional grounding that lasts for hours or days after a good session.
Norepinephrine (Noradrenaline) – Increases alertness and focus. In pain processing, norepinephrine plays a key role in descending inhibition - meaning it helps the brain tune down pain signals. People vary widely in their ability to use norepinephrine as a natural painkiller. Some (“adrenaline junkies”) enjoy sharp, unexpected strikes. Others dislike unpredictability and need a consistent rhythm to stay in their flow. Reading your person correctly and checking in with them helps.
Importantly, the balance of these neurotransmitters is state-dependent. A calm, trusting environment will help towards pain inhibition. Fear, stress, or unpredictability (the breaking of the flow) can increase the sensation of pain.
These neurochemicals each follow their own time course, which means that the timing of pain intensity needs to align with the body’s readiness. We will explore this in more detail in Part 2.