Sun YG, Zhao ZQ, Meng XL et al.Science 2009;325:1531–4.
Itch is a sensation that is thought to be a submodality or subquality of pain, but it is not known whether these two sensations are controlled by distinct neural circuits. The current authors carried out an investigation in mice to determine this by selective ablation of the gastrin-releasing peptide receptor (GRPR) in lamina I neurons of the spinal cord. They found that ablation of GRPR in these neurons significantly decreased the scratching response, implicating GRPR-positive neurons in the response to itch.
Itch is a frequent sensation among humans that can be a considerable nuisance. Similar to pain, it is a sensation that is controlled by the brain and that can only be localized in the skin or the mucosa. Itch evokes an itch reflex and it usually resolves quickly after brief scratching. The itch and the subsequent scratching help remove irritants from the skin. However, in persons with a skin disease it sometimes becomes the major symptom for which treatment is sought. Moreover, the scratching reflex adds to the damage and inflammation of the skin. Almost all dermatoses can be accompanied by this poorly understood sensation, but severe pruritus without a skin disease may also be encountered.