Itch, pain, and metaesthetic sensation

Abstract

Itch is one of the alarm sensations that human beings have phylogenetically evolved for a defense purpose. Many theories and evidences regarding the biological, pathophysiological, and clinical aspects have been given, but an update on the neuroanatomy paths and consequent treatments is required. Some chemicals that are released after skin injury and facilitate the inflammatory process can induce itch or pain or basically lead to a sensitization of the nociceptor response. In clinical practice, the present authors note a continuum of sensations from touch to pain, among which many metaesthetic sensations can be described, even if the patients themselves cannot precisely define them. The specificity of itch neurons is therefore based on their spinal connections to the itch pathway rather than on unique peripheral receptors. The ambiguity of "itch unit" discharge to pruritics and algogens may be solved by the central inhibition of itch by pain: it is common knowledge that scratching relieves itching. Conversely, centrally acting pain-inhibiting opioids enhance itch by disinhibition. The relation between itch and pain is interesting in its clinical and physiopathological aspects in order to select appropriate treatment.

Psychological disorders in patients with lichen simplex chronicus: A comparative study with normal population

“…Since this difference in perception is most probably because of a central processing, this may be proposed as one potential portal of psychological factors to contribute in the pathogenesis of LSC. [22][23][24] Chronic pruritus of unknown etiology has been considered as a 'somatoform' disorder in some clinical situations. 25 In this p o l i s h a n n a l s o f m e d i c i n e x x x ( 2 0 1 6 ) x x x -x x x regard, concordance of other somatic symptoms, as was noted in LSC patients in the current study, is not unexpected.…”

Development of an in vitro coculture of primary sensitive pig neurons and keratinocytes for the study of cutaneous neurogenic inflammation

“…Here, we found that we could increase the secretion of SP in cells exposed to trypsin. Similarly, incubation of the cocultured cells with papain, a cysteine protease known for its ability to induce neurogenic inflammation in a manner independent of PAR2 activation (45)(46)(47)(48)(49), also increased SP secretion in vitro. Collectively, these results indicate that our model adequately mimics the in vivo activation and modification of SP secretion.…”

Innovative Neurophysiological Methods in Itch Research: Long-latency Evoked Potentials after Electrical and Thermal Stimulation in Patients with Atopic Dermatitis

“…Key words: pruritus; atopic dermatitis; somatosensory evoked potentials; long-latency evoked potentials to thermal stimulation; CHEPS; thin sensory fibres. Pruritus or itch is defined as a cutaneous sensation that provokes a desire to scratch (1,2). Pruritus is one of the most common symptoms of skin diseases, and is thus of increasing interest.…”