Hyperalgesia (ˌhaɪpərælˈdʒiːziə or -siə; 'hyper' from Greek ὑπέρ (huper, “over”), '-algesia' from Greek algos, ἄλγος (pain)) is an abnormally increased sensitivity to pain, which may be caused by damage to nociceptors or peripheral nerves and can cause hypersensitivity to stimulus.
Prostaglandins E and F are largely responsible for sensitizing the nociceptors. Temporary increased sensitivity to pain also occurs as part of sickness behavior, the evolved response to infection.
Hyperalgesia can be experienced in focal, discrete areas, or as a more diffuse, body-wide form. Conditioning studies have established that it is possible to experience a learned hyperalgesia of the latter, diffuse form.
The focal form is typically associated with injury, and is divided into two subtypes:
Primary hyperalgesia describes pain sensitivity that occurs directly in the damaged tissues.
Secondary hyperalgesia describes pain sensitivity that occurs in surrounding undamaged tissues.
Opioid-induced hyperalgesia may develop as a result of long-term opioid use in the treatment of chronic pain. Various studies of humans and animals have demonstrated that primary or secondary hyperalgesia can develop in response to both chronic and acute exposure to opioids. This side effect can be severe enough to warrant discontinuation of opioid treatment.
Hyperalgesia is induced by platelet-activating factor (PAF) which comes about in an inflammatory or an allergic response. This seems to occur via immune cells interacting with the peripheral nervous system and releasing pain-producing chemicals (cytokines and chemokines).
One unusual cause of focal hyperalgesia is platypus venom.
Long-term opioid (e.g. heroin, morphine) users and those on high-dose opioid medications for the treatment of chronic pain, may experience hyperalgesia and experience pain out of proportion to physical findings, which is a common cause for loss of efficacy of these medications over time.
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Allodynia is a condition in which pain is caused by a stimulus that does not normally elicit pain. For example, bad sunburn can cause temporary allodynia, and touching sunburned skin, or running cold or warm water over it, can be very painful. It is different from hyperalgesia, an exaggerated response from a normally painful stimulus. The term is from Ancient Greek άλλος állos "other" and οδύνη odúnē "pain".
Neuropathic pain is pain caused by damage or disease affecting the somatosensory system. Neuropathic pain may be associated with abnormal sensations called dysesthesia or pain from normally non-painful stimuli (allodynia). It may have continuous and/or episodic (paroxysmal) components. The latter resemble stabbings or electric shocks. Common qualities include burning or coldness, "pins and needles" sensations, numbness and itching. Up to 7-8% of the European population is affected, and in 5% of persons it may be severe.
The Interleukin-1 family (IL-1 family) is a group of 11 cytokines that plays a central role in the regulation of immune and inflammatory responses to infections or sterile insults. Discovery of these cytokines began with studies on the pathogenesis of fever. The studies were performed by Eli Menkin and Paul Beeson in 1943–1948 on the fever-producing properties of proteins released from rabbit peritoneal exudate cells. These studies were followed by contributions of several investigators, who were primarily interested in the link between fever and infection/inflammation.
Explores the pharmacology of pain, including transduction, sensitizing agents, opioid receptor agonists, NSAIDs, and neuropathic pain treatments.
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Background Mechanical hyperalgesia and allodynia incidence varies considerably amongst neuropathic pain patients. This study explored whether sensory or psychological factors associate with mechanical hyperalgesia and brush allodynia in a human experimenta ...
In naive individuals, the administration of bacterial lipopolysaccharide (LPS) provokes a rapid systemic increase in pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-6, inducing an acute phase response inc ...
Intrathecal implants of adrenal chromaffin cells are known to release analgesic substances such as catecholamines and opioid peptides. In the present study, bovine chromaffin cells were encapsulated in a permselective polymer membrane which protects the ce ...