Opioid receptors are responsible for different functions throughout the body that are controlled by brain activity. Often confused with glands, these receptors are actually proteins found on the surface of neurons. The American Society of Addiction Medicine reports that about 2.1 million people are addicted to opioid painkillers and 467,000 to heroin in the United States.

Opioid receptors, however, are affected by far more than just opioid drugs. These specific receptors are classed as four different types, including:

  • Delta
  • Kappa
  • Mu
  • Nociceptin

The delta receptor resides on the pontine nuclei, olfactory bulbs, amygdala, deep cortex, and also in peripheral sensory neurons. It controls analgesic, antidepressant, and convulsant effects, as well as dependency on substances. The kappa receptor, also found on peripheral sensory neurons, is mainly located on the hypothalamus, periaqueductal gray, claustrum, and the substantia gelatinosa in the spinal cord. Kappa opioid receptors control analgesic qualities, too, in addition to depression, anticonvulsant effects, dysphoria, sedation, stress, diuresis, neuroprotection, and dissociative functions.

Mu receptors are located on the thalamus, cortex, striosomes, periaqueductal gray, rostral ventromedial medulla, and the intestinal tract. They share physical dependency functioning with delta receptors and control respiratory depression and euphoria.

Last but not least, the nociception receptors are found in many of the same places as the kappa receptors, plus the cortex, amygdala, septal nuclei, habenula, hypothalamus, and hippocampus. Nociceptin opioid receptors control anxiousness, depression, and tolerance, as well as help to regulate appetite. This receptor is not as primary to substance abuse activities as the other three.

How Do Drugs Affect the Receptors?

Not surprisingly, many of the traits controlled by opioid receptors are common problems for substance abusers, such as mood issues. In fact, mood disorders like depression and anxiety occur in around 20 percent of all drug and alcohol abusers, per the Anxiety and Depression Association of America.

Different drugs act on opioid receptors in different ways. Opioid receptors are organically stimulated by chemicals like endorphins, but alternatively, drugs can activate them as well.


The most prominent substances that impact opioid receptors are opioids themselves. Heroin and prescription opioid pain relievers bind to opioid receptors, decreasing the receptors’ ability to perceive pain. In addition, many people experience a sense of euphoria initially after using, which generally wears off and leaves them feeling the polar opposite — down and depressed.

Aside from pain, the opioid receptors control reward centers, too. As substance abuse persists, the addict grows accustomed to the pleasurable feelings that come from using and her body begins to crave the substance in an effort to replicate that feeling over and over again.

Furthermore, addictive behaviors are controlled by opioid receptors. This subset of functions often overlaps with pain and reward systems. Pain in the form of physical, emotion, or mental discomfort can lead someone to substance abuse, which is encouraged by reward mechanisms.

Over long periods of abuse, receptors may grow to become dysfunctional and have problems processing even organic input from the user’s own body. Even after detoxing from these drugs, the receptors can take years to heal and restore to full functionality. Thus, many opioid abusers experience prolonged periods of withdrawal symptoms. Known as post-acute withdrawal syndrome, addicts can be plagued with symptoms of withdrawal up to even a decade after their last use. Around 75-90 percent of all substance abusers encounter some form of PAWS, though not every case is lengthy, Addiction Blog reports.

Benzodiazepines, Cannabinoids, and Alcohol

While opioids like painkillers and heroin certainly do a number on opioid receptors, other substances such as benzodiazepines, cannabinoids and alcohol do, too. In America, approximately 20.4 million people had misused benzos in their lifetime as of 2011, the Drug Enforcement Administration reports. Cannabinoids include drugs such as marijuana and Spice. According to the National Institute on Drug Abuse, around 4.2 million people in the US were abusing marijuana in 2013. All of these drugs can impact the functioning of opioid receptors, inhibiting the pain, reward, and addiction centers of the brain, and thereby often supporting the development of dependency.

Alcohol also has a strong impact on opioid receptors, as well. The mu and delta receptors are primarily affected by alcohol abuse. Being a depressant, this makes sense. Nationwide, around 17 million people are addicted to alcohol as of 2012, per the National Institute on Alcohol Abuse and Alcoholism.

Treatment Drugs

Even treatment drugs like methadone, buprenorphine, naloxone, and naltrexone have an impact on opioid receptors. Methadone is a full opioid agonist and fills receptors, fooling them into believing they are bound to opioids like morphine. Buprenorphine is only a partial agonist, but it still performs in the same way.

Naloxone — used mostly in attempts to reverse the effects of opioid overdose — binds to all three receptors, but in majority to the mu receptor. Finally, naltrexone is frequently used in the treatment of alcoholism as a means to subdue cravings, also by acting mainly on the mu receptor site.

Getting Help

If you find yourself succumbing to substance abuse time after time, despite attempts to stop, you aren’t out of options. There is somewhere to turn, and there are people who can help. The skilled professionals we have on staff here at Orlando Recovery Center can help you to achieve a sustained recovery. Call us today to learn more about how we can help.

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Medical Disclaimer

The Recovery Village aims to improve the quality of life for people struggling with a substance use or mental health disorder with fact-based content about the nature of behavioral health conditions, treatment options and their related outcomes. We publish material that is researched, cited, edited and reviewed by licensed medical professionals. The information we provide is not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be used in place of the advice of your physician or other qualified healthcare provider.