Sex Differences in Scratching Behaviors Induced by Intradermal Injections of Pruritogenic Chemicals in C57BL/6 Mice

Pruritus is an individual unpleasant sensation of human sensory nervous system. In the physiological condition it excerts a self-protective mechanism to protect the skin against external harmful agents. Pruritoceptive itch is also a major symptom of skin disease and a common reason for consulting a dermatologist in clinic. It has been well known that both histamine-dependent and histamine-independent pathways mediate acute and chronic itch sensations. Previous studies have showed common neural pathways partially shared by itch and pain sensation, and significant sex differences in pain sensation. However, sex difference in itch sensation has not been given too much attention as the majority of itch studies were done in male mice or rats till now. In the present study, we compared the scratching behaviors induced by pruritogenic agents in male and female C57BL/6 mice. The results showed that both males and females exhibited scratching behaviors in response to the intradermal injection of histamine-dependent and histamine-independent pruritogenic chemicals. Moreover, the number of scratching behaviors in response to compound 4880 and chloroquine were significantly higher in females. These results suggested that sex differences occured in histamine-dependent compound 4880-induced and histamine-independent chloroquine-induced itch sensations, but not in histamine-independent SLIGRL-NH2-induced itch sensation.