Itch, also known as pruritus, is the uncomfortable sensation that triggers the desire to scratch. Its pathogenesis is characterized by histaminergic and nonhistaminergic pathways, transmitted via G protein-coupled receptors and transient receptor potential channels [1,4]. In the skin, it is primarily transmitted by unmyelinated type C and thinly myelinated type Aδ nerve fibers, and the crosstalk between the immune and neural systems modulates its transmission [1]. Itch is a significant factor affecting the quality of life, being associated with various etiologies such as dermatologic, systemic, paraneoplastic, neuropathic, and psychogenic conditions [2]. Genetic models, especially KO/CKO mouse models, can be valuable for studying the molecular, neural, and immune mechanisms of Itch [4].

No specific findings from KO/CKO mouse models or other loss-of-function experiments were presented in the provided abstracts.

In conclusion, Itch is a complex sensation with its pathogenesis involving multiple pathways and systems. While the lack of KO/CKO mouse model findings in the given references limits a deeper understanding from this aspect, the knowledge of its general mechanisms helps in understanding the biological importance of Itch. Understanding Itch is crucial for addressing various conditions where itch is a prominent symptom, such as atopic dermatitis, chronic pruritus, and lichen simplex chronicus [1,2,3,5].

References:

1. Sutaria, Nishadh, Adawi, Waleed, Goldberg, Rebecca, Choi, Justin, Kwatra, Shawn G. 2021. Itch: Pathogenesis and treatment. In Journal of the American Academy of Dermatology, 86, 17-34. doi:10.1016/j.jaad.2021.07.078. https://pubmed.ncbi.nlm.nih.gov/34648873/

2. Roh, Youkyung S, Choi, Justin, Sutaria, Nishadh, Kwatra, Shawn G. 2021. Itch: Epidemiology, clinical presentation, and diagnostic workup. In Journal of the American Academy of Dermatology, 86, 1-14. doi:10.1016/j.jaad.2021.07.076. https://pubmed.ncbi.nlm.nih.gov/34428534/

3. Tominaga, Mitsutoshi, Takamori, Kenji. 2022. Peripheral itch sensitization in atopic dermatitis. In Allergology international : official journal of the Japanese Society of Allergology, 71, 265-277. doi:10.1016/j.alit.2022.04.003. https://pubmed.ncbi.nlm.nih.gov/35624035/

4. Yosipovitch, Gil, Rosen, Jordan Daniel, Hashimoto, Takashi. . Itch: From mechanism to (novel) therapeutic approaches. In The Journal of allergy and clinical immunology, 142, 1375-1390. doi:10.1016/j.jaci.2018.09.005. https://pubmed.ncbi.nlm.nih.gov/30409247/

5. Ju, Teresa, Vander Does, Ashley, Mohsin, Noreen, Yosipovitch, Gil. 2022. Lichen Simplex Chronicus Itch: An Update. In Acta dermato-venereologica, 102, adv00796. doi:10.2340/actadv.v102.4367. https://pubmed.ncbi.nlm.nih.gov/36250769/