2023
Volume 23, Number 2/3, pp. 57-60
Thermal hyperalgesia and mechanical allodynia in itch: TRPA1 and TRPV1 channels
Merab G. Tsagareli1 and Earl Carstens2
1Ivane Beritashvili Centre for Experimental Biomedicine, Tbilisi, Georgia
2University of California at Davis, USA
Allodynia and hyperalgesia are prominent symptoms in patients with neuropathic and inflammatory pain and itch (pruritus). The respective corresponding phenomena of alloknesis and hyperknesis are also present in the context of pruritus. Like pain, acute itch is a warning signal for the body to scrape off insects or plant spicules from the skin surface or to dig out invasive parasites. The pathological consequences of itching affect the quality of life just as much as pain. Chronic pruritus conditions such as atopic dermatitis, allergic contact dermatitis or psoriasis pose a significant socioeconomic burden. Itching is encoded by two main neural pathways: histaminergic and non-histaminergic. Here we review the latest evidence on thermal hyperalgesia and mechanical allodynia induced by histamine and non-histaminergic pruritogens, with a respective involvement of transient receptor potential (TRP) channels TRPV1 and TRPA1 in itch sensation. Principal conclusion of these data is that antagonists of these TRP channels may be useful in the clinical management of increased pain and allodynia, which may be symptomatic in patients with chronic pruritus.
Keywords: analgesia, inflammation, nociception, pain, paw withdrawal, pruritus