Neurogenic inflammation caused by wool fabric in the rat; possible mediation by substance P

We have measured plasma extravasation in response to stimulation of the rat hind footpad with wool fabric. The stimulus was delivered using a constantly weighted disc of wool rotating at 4 revolutions per minute for 30 min on the base of blisters induced by vacuum. The protein content of prestimulated blister base perfusate was 38 +/- 2 micrograms/ml in a 30-min collection. With stimulation this increased to 80 +/- 10 micrograms/ml (P less than 0.001; Student's paired t-test). No increase in plasma extravasation was observed in adult animals pretreated as neonates with capsaicin indicating that the plasma extravasation observed was neurogenically mediated. Plasma extravasation was also observed with substance P added to the perfusate. The threshold for substance P-induced plasma extravasation was 2 X 10(-11) mol/30 min. These results suggest that neurogenic inflammation induced by the mechanical stimulus of wool fabric may be mediated by substance P. This reaction may be involved in wool-induced prickle and itch noted in some individuals.