Problem:
Question 1: What exactly at the molecular level is itching?
Question 2: What physiological function does itching serve, if any?
I can't remember the reference but a PLCb3 null mice lost the itch phenotype, so presumably it is mediated by the Gq-PLCbeta pathway through a cell surface GPCR. Since a physical action of scratching relieves it,
Question: Could it be a case of a mechanosensitive channel at work?