In the early 1970s, researchers were studying how poppy-derived opiates, such as heroin and morphine, affect the brain. They uncovered receptors in the brain that only receive opioids, the class of drugs into which opiates fall. In considering why our brains might have opioid receptors, the researchers hypothesized that our bodies naturally produce substances like morphine and heroin. They were right! Read on to find out more in an exclusive excerpt from The Physiology of Yoga.
The term endorphin is a contraction of endogenous (meaning created within the body) and morphine. Morphine is used in painkillers like Vicodin (hydrocodone and acetaminophen) and fentanyl, as well as the street drug heroin. It is also chemically similar to the endorphins our bodies produce. They are produced by both the pituitary gland and the central nervous system, so they cannot be easily categorized into just one bodily system.
Endorphins function as both hormones and neurotransmitters. Researchers are still working to understand all the roles of endorphins. They are considered important in modulating pain and enhancing pleasure, thus promoting an overall sense of well-being. Endorphins play a vital role in pain modulation. Noxious stimuli are received from the peripheral nervous system. The brain decides then whether the experience of pain would be useful at that time. One of the ways the brain will slow down the messages of nociception from the peripheral nervous system is with endorphins transmitted along pathways with serotonin and noradrenaline as neurotransmitters (Akil et al. 1984).
Endorphins
It is believed that endorphins might alleviate depression, reduce anxiety and the stress response, increase self-esteem, and reduce body weight.
Endorphins are important in our natural reward circuits and are related to activities like eating, drinking, physical fitness, and sexual intercourse. They minimize pain and maximize pleasure, which helps us to continue functioning despite injury or stress. Endorphins are also considered responsible for producing the euphoric states experienced with sex, orgasm, listening to music, and eating certain foods like chocolate (Chaudhry and Gossman 2020). Some evidence has also shown that endorphins help reinforce social attachments (Machin and Dunbar 2011). Having strong social bonds certainly helps the survival of a species. Finally, endorphins help with childbirth, which can indeed be a rewarding but painful experience. Pregnant women’s endorphin levels rise beyond their normal levels, which may help ease some of the symptoms associated with pregnancy and childbirth (Cahill 1989).
Savasana
Of all the hormones, endorphins are the ones most commonly associated with physical activity, including yoga. The famous runner’s high refers to the reduction of anxiety and increased euphoria distance runners have reported in surveys and studies. In the 1980s, exercise scientists started attributing this feeling of blissfulness to endorphins after observing increased levels of these natural painkillers in people’s bloodstreams immediately following a run. However, more recent research has revealed that postexercise bliss is more likely due to a different compound: endocannabinoids.
Runner's High
Similar in chemical structure to cannabis, cannabinoids made by our bodies increase in number during pleasurable activities, such as orgasms, and also when we run. First exploring endocannabinoids in mice and more recently in humans, Siebers and colleagues (2021) recruited 63 experienced runners, both male and female, and randomly assigned half to receive naloxone, a drug that blocks the uptake of opioids, which includes endorphins. The other half received a placebo. Most of the subjects reported experiencing a runner’s high independent of whether they had taken naloxone or the placebo and all showed increased blood levels of endocannabinoids. This study provides strong evidence that the runner’s high previously associated with endorphins is more likely correlated with endocannabinoids, but more research is of course needed to confirm these findings. This study shows that even as recently as 2021, there was still much we did not fully understand about human physiology, and what we previously considered fact may not be so.
References:
Akil, H., S.J. Watson, E. Young, M.E. Lewis, H. Khachaturian, and J.M. Walker. 1984. “Endogenous Opioids: Biology and Function.” Annual Review of Neuroscience 7:223-255.
Cahill, C.A. 1989. “Beta-Endorphin Levels During Pregnancy and Labor: A Role in Pain Modulation?” Nursing Research 38 (4): 200-203.
Chaudhry, S.R., and W. Gossman. 2020. “Biochemistry, Endorphin.” StatPearls
Machin, A.J., and R.I.M. Dunbar. 2011. “The Brain Opioid Theory of Social Attachment: A Review of the Evidence.” Behaviour 148 (9/10): 985-1025. www.jstor.org/stable/23034206.
Siebers, M., S.V. Biedermann, L. Bindila, B. Lutz, and J. Fuss. 2021. “Exercise-Induced Euphoria and Anxiolysis Do Not Depend on Endogenous Opioids in Humans.” Psychoneuroendocrinology 126:105173.