THE ‘BRAIN PHARMACY’
Updated: Sep 21, 2020
Our natural pain relief: how it works and the kinds of things that influence it
If you are always trying to be normal, you will never know how amazing you can be.
Image by Ralf Kunze from Pixabay
In the post, THE BRAIN IN PAIN, we discussed how activity in the emotional and thinking parts of the brain and the connections between the two can become altered in pain. This impacts our experience of pain… how much and how it feels. We also explored how meditation can regulate the responses in the emotional brain, and improve the regulation that the thinking brain can have on the emotional brain and in turn, the pain we experience.
In this post, we delve further into the brain and explain some of the connections with our natural pain relieving system and how brain can influence whether we experience pain or not and if we do, how much. To do this let me introduce you to the pharmacy in your brain ….. downstream from the cortex lies the brain stem, and within it are areas called the periaqueductal grey (PAG) and rostro-ventral medulla (RVM). For some time now we’ve known that the PAG and RVM are key players in controlling how much pain relief (or not) we get in the presence of nociceptive signals.(1) Remember nociceptive signals are warning messages sent from our tissues to our brain. The ‘Brain Pharmacy’ releases natural painkillers (e.g. opiates, serotonin, noradrenalin, GABA) to reduce nociceptive signaling, (1,2) and therefore can reduce pain. It does so frequently in response to inflammation, injury or even threat of injury. It might not feel it when you’ve had an injury but the Brain Pharmacy will be active, working to keep your pain manageable. Importantly though, the Brain Pharmacy can also release neurotransmitters that can enhance nociceptive signaling and therefore increase pain. And so, depending on which chemicals are released, you may experience less or more pain.
The Brain Pharmacy can release natural painkillers to reduce pain. But it can also have the opposite effect. Thoughts and emotional responses have a big influence on which way it goes.
Like all good pharmacies, the Brain Pharmacy receives instructions or prescriptions about what to release and when to release it. At least some of these prescriptions come from the emotional and thinking parts of the brain.(3) While a very complex process involving many regions of the brain and nervous system, we now have growing evidence that when areas of the brain like the amygdala (part of the emotional brain) are highly active, they signal to the Brain Pharmacy to stop releasing pain relieving chemicals and instead release chemicals that actually enhance nociception, and thus the pain experience.(3) On the other hand, better mood (in experiments, these can be induced by pleasant odours) and attention away from pain can reduce pain unpleasantness and intensity. This is at least in part due to the release of pain-relieving chemicals from the ‘Brain Pharmacy’.(4)
The brain is pretty clever too because it can prioritise depending on threat and importance. In the presence of imminent danger (think soldiers at war, running away from danger) fear can cause the Brain Pharmacy can release high doses of painkillers.(3) We think the same happens when there’s something more important going on, like scoring a goal at a football final, getting through that big project at work, getting your study assignment completed, etc. In these situations, the brain focuses on what’s most important, often ignoring nociceptive signals from your tissues. The ‘Brain Pharmacy’ can release large doses of painkillers to get you through. The problem is it can’t do this for too long before it backfires. For example, while we get high doses of painkillers in the presence of imminent danger, in the presence of ongoing anxiety or chronic stress, the ‘Brain Pharmacy’ becomes less effective at releasing painkillers.(3) This seems to be the case for many people with persistent pain. Findings from functional MRI scans of the brain demonstrate increased signalling in the emotional brain in people with persistent pain, (5) greater protective responses (6) and reduced nociceptive inhibition.(7,8)
CAN YOGA PRACTICES IMPROVE OUR NATURAL PAIN RELIEF?
Meditation and yoga practices have the potential to reduce pain. Some of this happens through the way meditation helps us recognise and regulate our thoughts and our emotional responses (see previous post on THE BRAIN IN PAIN). Information specifically relating to our pain relieving system is somewhat lacking at this stage; however, two recent studies are worth mentioning.
In one experimental study, Zeidan and colleagues investigated whether mindfulness meditation could reduce pain responses more than placebo or sham meditation, and whether this was associated with different brain activation patterns.(9) They tested responses to painful heat in healthy people and found that mindfulness meditation (trained over 4 days) was more effective at reducing pain and unpleasantness in response to the painful heat stimuli than the control interventions. In addition, this was associated with increased activation of the thinking parts of the brain and reduced activation within areas associated with sensory processing.(9)
In a second study, Sharon and colleagues (10) attempted to investigate how meditation works to reduce pain…. what are the specific pathways? They exposed experienced mindfulness practitioners to painfully cold stimuli and compared pain intensity and unpleasantness ratings before and after meditation. The meditation resulted in a reduction in reported pain. Participants were then either given naloxone, a drug that blocks the body from releasing opioids, or a placebo drug and the trial was repeated. What they found was that the pain relieving effects of meditation were reduced after the naloxone but not the placebo, demonstrating that one way meditation works to give pain relief is through the body’s natural opioid system.
These studies were conducted on small samples of healthy people so we don’t know whether people with pain would respond in the same way, or if these results would hold up in bigger studies yet. However, finding ways to improve the effectiveness of our natural pain relieving system seems like a sensible thing to do, and mindfulness and meditation practices may be ways to do this. Remember that movement can be meditative too, so the use of physical practices (asanas) as a vehicle to a more meditative state may be useful for those who struggle to sit quietly.
Remember that movement can be meditative too, so the use of physical practices (asanas) as a vehicle to a more meditative state may be useful for those who struggle to sit quietly.
Nociception: detection of potential danger within the body
Nociceptive signaling: nerve impulses relayed within the body’s nociceptive system, that is, danger detection system
Emotional brain: AKA Limbic system: areas of the brain typically associated with emotional regulation and protective responses, for example, the amygdala, hippocampus and insula.
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3. Lumley MA, Cohen JL, Borszcz GS, et al. Pain and emotion: a biopsychosocial review of recent research. Journal of clinical psychology. 2011;67(9):942-968.
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5. Kupers R, Witting N, Jensen TS. Brain-Imaging Studies of Experimental and clinical Forms of Allodynia and Hyperalgesia In: Brune K, Handwerker H, eds. Hyperalgesia: Molecular Mechanisms and Clinical Implications. Seattle: IASP Press; 2004.
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7. Fingleton C, Smart KM, Doody CM. Exercise-induced Hypoalgesia in People With Knee Osteoarthritis With Normal and Abnormal Conditioned Pain Modulation. Clin J Pain. 2017;33(5):395-404.
8. Rabey M, Poon C, Wray J, Thamajaree C, East R, Slater H. Pro-nociceptive and anti-nociceptive effects of a conditioned pain modulation protocol in participants with chronic low back pain and healthy control subjects. Man Ther. 2015.
9. Zeidan F, Emerson NM, Farris SR, et al. Mindfulness Meditation-Based Pain Relief Employs Different Neural Mechanisms Than Placebo and Sham Mindfulness Meditation-Induced Analgesia. The Journal of neuroscience : the official journal of the Society for Neuroscience. 2015;35(46):15307-15325.
10. Sharon H, Maron-Katz A, Ben Simon E, et al. Mindfulness Meditation Modulates Pain Through Endogenous Opioids. The American journal of medicine. 2016;129(7):755-758.