Skin reactivity to substance P, not to neurokinin A, is increased in allergic asthmatics

The tachykinins substance P (SP) and neurokinin A are believed to be major mediators of neurogenic inflammation. To determine whether the skin reactivity to tachykinins is increased in asthmatics, we examined the erythemas and wheals induced by intradermal injections of SP, the C-terminal peptide SP6-11, the N-terminal peptide SP1-9 and neurokinin A (10(-7)-10(-5) M) in 10 allergic asthmatics and 9 normal subjects. SP and SP1-9 induced both erythemas and wheals in a concentration-dependent manner in allergic asthmatics and in normal subjects, whereas SP6-11 and neurokinin A induced only wheals in both groups. SP induced greater erythemas and wheals in allergic asthmatics than in normal subjects. However, the wheals induced by neurokinin A were not significantly different between the two groups. SP1-9 also induced greater erythemas and wheals in allergic asthmatics than in normal subjects, whereas the wheals induced by SP6-11 were not significantly different between the two groups. Therefore, the increased skin reactivity to SP was dependent on the N-terminal peptide but not on the C-terminal peptide. We conclude that the skin reactivity to SP but not to neurokinin A is increased in allergic asthmatics.