Scratching

Soma

Neuroscience

Acoustics

Sensation

Physics

Psychology

Medicine

Trends in Neurosciences

Multiple neural pathways and molecular mechanisms responsible for producing the sensation of itch have recently been identified, including histamine-independent pathways. Physiological, molecular, behavioral and brain imaging studies are converging on a description of these pathways and their close association with pain processing. Some conflicting results have arisen and the precise relationship between itch and pain remains controversial. A better understanding of the generation of itch and of the intrinsic mechanisms that inhibit itch after scratching should facilitate the search for new methods to alleviate clinical pruritus (itch). In this review we describe the current understanding of the production and inhibition of itch. A model of itch processing within the CNS is proposed. Multiple neural pathways and molecular mechanisms responsible for producing the sensation of itch have recently been identified, including histamine-independent pathways. Physiological, molecular, behavioral and brain imaging studies are converging on a description of these pathways and their close association with pain processing. Some conflicting results have arisen and the precise relationship between itch and pain remains controversial. A better understanding of the generation of itch and of the intrinsic mechanisms that inhibit itch after scratching should facilitate the search for new methods to alleviate clinical pruritus (itch). In this review we describe the current understanding of the production and inhibition of itch. A model of itch processing within the CNS is proposed. an electrophysiological technique used to identify the location of an axon that is far from its soma. A small current is injected near the axon, generating an action potential that travels retrogradely toward the cell body. A recording electrode records the action potential as it invades the soma. This technique permits investigators to functionally characterize a neuron and determine the projection target of its axon. the membrane depolarization of primary afferent terminals due to signal transduction can spread to the far-reaching branches of the peripheral axon. The spreading depolarization leads to the release of peptides and neurotransmitters within the peripheral tissues, and can have effects on blood vessels and immune cells in the skin causing neurogenic inflammation. the spicules covering the pod of the tropical legume Mucuna pruriens. Contained within these spicules is the proteolytic enzyme mucunain and also serotonin. These spicules produce itch and sensations of pricking and burning pain when inserted into the skin. a proto-oncogene belonging to the immediate-early gene family of transcription factors. Immunological identification of c-Fos protein can be used as an indicator of neural activity. the hypothesis that a specific quality of sensation (e.g. hot, cold, itch or pain) is encoded by a dedicated group of neurons that respond to and encode a single quality and signal that quality in series to the brain. related to the neural mechanisms involved in the detection, encoding and transmission of noxious stimuli (from Latin nocere, to injure). the hypothesis that qualities of sensation are encoded by polymodal neurons that transmit information about a particular quality via the temporal pattern or frequency of discharge of action potentials. the hypothesis that qualities of sensation are encoded by multiple polymodal neurons. By virtue of being active simultaneously, subsets of these neurons are able to generate information about the specific quality of sensation. related to the neural mechanisms involved in the detection, encoding and transmission of the sensation of itch or itch behavior (from Latin prurire, to itch). these neuropeptides are released from peripheral terminals and central terminals of nociceptive neurons during ongoing signal transduction. Both play a role in neurogenic inflammation and pain. The receptor for substance P is neurokinin-1 and for CGRP is the CGRP receptor. a family of diversely functioning six-transmembrane polypeptide subunits with intracellular N- and C-termini that assemble as tetramers to form cation-permeable pores. TRP channels are involved in sensory transduction of a wide variety of stimuli and are expressed throughout the body including on sensory nerve terminals in the skin.

The multiple pathways for itch and their interactions with pain