The Neurochemistry of Pain
Pain is not just a sensory experience - it’s 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 (your spine and brain). The first chemicals that carry this pain message are:
Glutamate – Fast-acting and powerful, glutamate ensures the brain notices the pain right away (“Ouch! That hurt!”)
Substance P – A slower, longer-lasting neuropeptide that helps amplify and sustain the pain signal.
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 block 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, or even 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. This is why it is so important to regularly check-in with your person to make sure they are still enjoying the experience. Their state will make it or break it for pain to turn into pleasure (or just stay annoying or painful).
Timing: The Course of a Pain Response
It is important to note that these chemicals have their own course of action. There is nothing much you as impact top can do to rush the release of these chemicals. Finding the individual pace is the key to a pleasurable experience.
You will notice from the table below, that endorphins only start to release after 2 minutes and they usually take up to 10 minutes (or longer) to reach their peak. There is no point hitting with full force before the endorphins kick in, because their body is simply not prepared to receive the impact and turn it into pleasure.
A brief summary of the neurochemistry of pain reaction.
The Long-Term Actors: Dopamine & Oxytocin
As the session unfolds and pain becomes integrated into a rhythm, new chemicals enter the scene:
Dopamine is part of the brain’s reward system. It’s linked to novelty, pattern recognition, and anticipation. During impact play, changing rhythm, pacing, or tools - all of which introduce novelty and prevent boredom - can increase dopamine release, keeping the person engaged and “high”.
Oxytocin - often called the “love and attachment hormone” - is released when trust is present, but they are also triggered via skin-to-skin touch, eye contact, and physical closeness. Oxytocin doesn't directly inhibit pain, but it buffers stress and contributes to a feeling of safety and emotional connection. This makes the body more willing to stay open, even to painful stimuli.
Reciprocal Effects
These neurochemicals don’t just follow mood - they create it too. The nervous system works both bottom-up (from body to mind) and top-down (from the mind to the body). That means pain, touch, sound, and connection all feed into a loop of experience and meaning.
For example:
A warm hand on the skin, a scratch, or even a firm hug can trigger oxytocin, which in turn helps buffer incoming pain and help the body stay open to the opioids.
The anticipation of pain - like “missing” a beat nearby - can stimulate norepinephrine, which can increase focus and help the body modulate pain (as long as the person stays relaxed and trusting).
This dual process helps explain why pain in a safe, well-calibrated setting can turn into pleasure, a powerful inner journey between body and soul.