The discovery of a specialized neuronal pathway for itch has markedly improved our understanding of itch processing under physiological conditions. However, the complex interactions of pain and itch are only partly understood. This review focuses on the neurophysiological mechanisms involved in clinical and experimental itch conditions. There is emerging evidence that similar patterns of periph...

Patients with chronic itch are diagnosed and treated by dermatologists. However, itch is a neural sensation and some forms of chronic itch are the presenting symptoms of neurological diseases. Dermatologists need some familiarity with the most common neuropathic itch syndromes to initiate diagnostic testing and to know when to refer to a neurologist. This review summarizes current knowledge, ad...

OF THE DISSERTATION Molecular mechanisms of itch sensations By Seungil Kim Doctor of Philosophy in Biology and Biomedical Sciences (Developmental Biology) Washington University in St. Louis, 2011 Associate Professor James Skeath, Chairperson Itch is a sensation which causes scratching response to protect skin against external harmful reagents. Acute itch arises in short time period after insect...

Opioid receptors in the central nervous system are important modulators of itch transmission. In this study, we examined the effect of mixed-action opioid butorphanol on histamine itch, cowhage itch, and heat pain in healthy volunteers. Using functional MRI, we investigated significant changes in cerebral perfusion to identify the critical brain centers mediating the antipruritic effect of buto...

Protease-activated receptors (PARs) have been implicated in a variety of physiological functions, as well as somatosensation and particularly itch and pain. Considerable attention has focused on PARs following the finding they are upregulated in the skin of atopic dermatitis patients. The present review focuses on recent studies showing that PARs are critically involved in itch and sensitizatio...

Itch, or pruritus, is an important clinical problem whose molecular basis has yet to be understood. Recent work has begun to identify genes that contribute to detecting itch at the molecular level. Here we show that Pirt, known to play a vital part in sensing pain through modulation of the transient receptor potential vanilloid 1 (TRPV1) channel, is also necessary for proper itch sensation. Pir...

Opioids such as morphine numb pain but often concomitantly induce itch. Liu et al. (2011) now separate the sensation of itch from opioid-induced analgesia, showing that in a subset of spinal neurons, morphine directly induces itch by signaling through a heteromer of opioid- and itch-mediating G protein-coupled receptors.

Sequence similarities exist between terminal inverted repeats (TIRs) of some miniature inverted-repeat transposable element (MITE) families isolated from a wide range of organisms, including plants, insects, and humans, and TIRs of DNA transposons from the pogo family. We present here evidence that one of these MITE families, previously described for Arabidopsis thaliana, is derived from a larg...

Despite its clinical importance, the underlying neural mechanisms of itch sensation are poorly understood. In many diseases, pruritus is not effectively treated with antihistamines, indicating the involvement of nonhistaminergic mechanisms. To investigate the role of small myelinated afferents in nonhistaminergic itch, we tested, in psychophysical studies in humans, the effect of a differential...