Hypoalgesia
Encyclopedia
Hypoalgesia or hypalgesia denotes a decreased sensitivity to painful stimuli.
Hypoalgesia occurs when nociceptive (painful) stimuli are interrupted or decreased somewhere along the path between the input (nociceptors), and the places where they are processed and recognized as pain
in the conscious mind. Hypoalgesic effects can be mild, such as massaging a stubbed toe to make it hurt less or taking aspirin to decrease a headache, or they can be severe, like being under strong anesthesia. Hypoalgesia can be caused by exogenous chemicals such as opioids, as well as by chemicals produced by the body in phenomena such as fear- and exercise- induced hypoalgesia. Hypoalgesia can also be associated with diseases, such as CIPA
or in less severe cases with diabetes or other diseases associated with hypertension
.
and central
nervous systems to decrease pain. Certain analgesics also work to decrease the source of the pain by working to decrease swelling and inflammation, as in the case of NSAIDs.
, codeine
, and opium
- that act on opioid receptor
s, which are located mainly in the central nervous system
.
Endogenous opioids types of opioids produced by the body specifically to modulate pain. They include endorphins, enkephalins, dynorphins and endomorphins. These peptides are especially important for modulating pain in response to the environment. These can be released in response to a number of things, including increased blood pressure, pain and danger. It has been found that endogenous opioids are at least partially responsible for phenomena like “Runner's high”, hypoalgesia in the fight-or-flight response, and even for the analgesic effects of acupuncture therapy. In all these cases, there is a certain level of signal processing that occurs in the CNS which leads to the release of these chemicals.
, are hereditary disorders where genes essential for the correct functioning of nociceptors no longer work. There are many diseases like this, and they all fall under the category of hereditary sensory autonomic neuropathies. Alternatively, some diseases affect other functions in your body, which can activate the pathways that cause hypoalgesia. This effect happens in people with diabetes and other diseases associated with hypertension
.
(HSAN), e.g. CIPA
, are hereditary disorders that are characterized by malfunctioning or nonfunctioning pain receptors. Most of these diseases are also associated with decreased temperature sensation as well. In some cases these diseases are also associated with other symptoms like mental retardation and diminished production of sweat and tears. Diseases like this can be very dangerous for the patients, because they are not able to judge what hurts, and therefore when they should stop doing something. A child with the disease might bite their finger clean off before they realized that what they were doing might harm them, or they might leave their hand on a hot stove without ever realizing it was on. Diseases like this show just how beneficial feeling pain is for our survival.
in patients can cause hypoalgesia. Diseases like diabetes, which are associated with hypertension are also associated with hypoalgesia. Just like in Exercise-Induced Hypoalgesia, the increased blood pressure of hypertension works as a signal to the body to release opioids and activate other pain modulation pathways. Also, although the area is not widely studied, there is evidence that this is not the only cause. Diseases may lead to activation of any of these mechanisms, just like diabetes causing hypertension. A full study of the pathways regulating pain is needed.
Hypoalgesia occurs when nociceptive (painful) stimuli are interrupted or decreased somewhere along the path between the input (nociceptors), and the places where they are processed and recognized as pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
in the conscious mind. Hypoalgesic effects can be mild, such as massaging a stubbed toe to make it hurt less or taking aspirin to decrease a headache, or they can be severe, like being under strong anesthesia. Hypoalgesia can be caused by exogenous chemicals such as opioids, as well as by chemicals produced by the body in phenomena such as fear- and exercise- induced hypoalgesia. Hypoalgesia can also be associated with diseases, such as CIPA
Congenital insensitivity to pain with anhidrosis
Congenital insensitivity to pain with anhidrosis is an extremely rare inherited disorder of the nervous system which prevents the sensation of pain, heat, cold, or any real nerve-related sensations ; however, patients can still feel pressure. CIPA is the fourth type of hereditary sensory and...
or in less severe cases with diabetes or other diseases associated with hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
.
Analgesics
Analgesics are a class of biochemicals that cause hypoalgesia. Analgesics can act on both the peripheralPeripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...
and central
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
nervous systems to decrease pain. Certain analgesics also work to decrease the source of the pain by working to decrease swelling and inflammation, as in the case of NSAIDs.
Opioids
Opioids refers to a specific group of analgesics - including morphineMorphine
Morphine is a potent opiate analgesic medication and is considered to be the prototypical opioid. It was first isolated in 1804 by Friedrich Sertürner, first distributed by same in 1817, and first commercially sold by Merck in 1827, which at the time was a single small chemists' shop. It was more...
, codeine
Codeine
Codeine or 3-methylmorphine is an opiate used for its analgesic, antitussive, and antidiarrheal properties...
, and opium
Opium
Opium is the dried latex obtained from the opium poppy . Opium contains up to 12% morphine, an alkaloid, which is frequently processed chemically to produce heroin for the illegal drug trade. The latex also includes codeine and non-narcotic alkaloids such as papaverine, thebaine and noscapine...
- that act on opioid receptor
Opioid receptor
Opioid receptors are a group of G protein-coupled receptors with opioids as ligands. The endogenous opioids are dynorphins, enkephalins, endorphins, endomorphins and nociceptin. The opioid receptors are ~40% identical to somatostatin receptors...
s, which are located mainly in the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
.
Endogenous opioids types of opioids produced by the body specifically to modulate pain. They include endorphins, enkephalins, dynorphins and endomorphins. These peptides are especially important for modulating pain in response to the environment. These can be released in response to a number of things, including increased blood pressure, pain and danger. It has been found that endogenous opioids are at least partially responsible for phenomena like “Runner's high”, hypoalgesia in the fight-or-flight response, and even for the analgesic effects of acupuncture therapy. In all these cases, there is a certain level of signal processing that occurs in the CNS which leads to the release of these chemicals.
Exercise induced hypoalgesia
There has been a great deal of research examining the link between exercise and hypoalgesia. Many studies have shown the direct link between the two by subjecting patients to exercise and rating their pain responses, but despite the great deal of research, the mechanism of action is still poorly understood. It has been shown that the triggering mechanism for the hypoalgesic effects is the increase in blood pressure that accompanies a good workout. The body senses the increased blood pressure, and it is hypothesized that in response, endogenous opioids are released. This hypothesis is well supported in human research, and it has been verified that it plays a part, but animal research implies that other mechanisms are also involved.Fear induced hypoalgesia
Fear induced hypoalgesia is another example of a mechanism controlled by opioids. It is postulated that fear is a defense mechanism that has evolved over time to provide protection. In the case of hypoalgesia, a decreased response to pain would be very beneficial in a situation where an organism’s life was at stake, since feeling pain would be a hindrance rather than a help. It has been well documented that fear does cause a decrease in pain response, however much like the exercise induced hypoalgesia, the exact mechanisms of action are not well understood. Studies have shown that opioids are definitely involved in the process, yet opiates alone do not completely explain the analgesic response. What the other mechanisms of action are is still unknown.Diseases
It has been demonstrated that many diseases can cause hypoalgesia. Some diseases, like CIPACongenital insensitivity to pain with anhidrosis
Congenital insensitivity to pain with anhidrosis is an extremely rare inherited disorder of the nervous system which prevents the sensation of pain, heat, cold, or any real nerve-related sensations ; however, patients can still feel pressure. CIPA is the fourth type of hereditary sensory and...
, are hereditary disorders where genes essential for the correct functioning of nociceptors no longer work. There are many diseases like this, and they all fall under the category of hereditary sensory autonomic neuropathies. Alternatively, some diseases affect other functions in your body, which can activate the pathways that cause hypoalgesia. This effect happens in people with diabetes and other diseases associated with hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
.
Hereditary neuropathies
Hereditary sensory and autonomic neuropathiesHereditary sensory and autonomic neuropathy
Hereditary sensory and autonomic neuropathy or hereditary sensory neuropathy is a condition used to describe any of the types of this disease which inhibit sensation.They are less common than Charcot-Marie-Tooth disease....
(HSAN), e.g. CIPA
Congenital insensitivity to pain with anhidrosis
Congenital insensitivity to pain with anhidrosis is an extremely rare inherited disorder of the nervous system which prevents the sensation of pain, heat, cold, or any real nerve-related sensations ; however, patients can still feel pressure. CIPA is the fourth type of hereditary sensory and...
, are hereditary disorders that are characterized by malfunctioning or nonfunctioning pain receptors. Most of these diseases are also associated with decreased temperature sensation as well. In some cases these diseases are also associated with other symptoms like mental retardation and diminished production of sweat and tears. Diseases like this can be very dangerous for the patients, because they are not able to judge what hurts, and therefore when they should stop doing something. A child with the disease might bite their finger clean off before they realized that what they were doing might harm them, or they might leave their hand on a hot stove without ever realizing it was on. Diseases like this show just how beneficial feeling pain is for our survival.
Hypoalgesia and hypertension
Many studies have shown that hypertensionHypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
in patients can cause hypoalgesia. Diseases like diabetes, which are associated with hypertension are also associated with hypoalgesia. Just like in Exercise-Induced Hypoalgesia, the increased blood pressure of hypertension works as a signal to the body to release opioids and activate other pain modulation pathways. Also, although the area is not widely studied, there is evidence that this is not the only cause. Diseases may lead to activation of any of these mechanisms, just like diabetes causing hypertension. A full study of the pathways regulating pain is needed.