Neuropeptide- and capsaicin-induced histamine release in skin monitored with the microdialysis technique.

Abstract

Mast cells are thought to be involved in neurogenic inflammation in skin, and numerous neuropeptides are known to degranulate mast cells. We monitored histamine release in skin in situ with the microdialysis method after skin challenge with neuropeptide injections (10 microM substance P, vasoactive intestinal peptide and calcitonin gene-related peptide), capsaicin injection (30 microM) and 0.1% capsaicin cream with a moist compress. Fractions were collected for 15 min each at 3.0 microliter/min. One hour after insertion of the probe, the baseline histamine level was 4.5 +/- 4.5 nM (mean +/- SD, n = 20). Substance P (250 pmol) induced histamine release peak (66.1 +/- 52.5 nM, n = 8) in the 0-15 or 15-30 min fraction. Thereafter, the histamine concentration declined steadily and rapidly and no second rise was observed. A single substance P injection was sufficient to induce major histamine release in three out of four experiments