NEUROPEPTIDE DEPLETION BY CAPSAICIN DOES NOT PREVENT MUCOSAL MAST-CELL ACTIVATION IN THE RAT AT WEANING

Substance P release by enteric nerves could be an initiating factor fo r mucosal mast cell (MMC) activation that is associated with weaning i n the rat. Capsaicin, which depletes substance P from enteric nerves, should therefore prevent MMC degranulation. Rat pups received either c apsaicin (50 mg/kg) or vehicle control subcutaneous injections at 3 an d 6 days of life. Capsaicin-treated and control litters were killed at 16, 18, 20, 22, 24 and 26 days of life. MMC activation was measured b y serum levels of rat mast cell protease II (RMCPII). Intestinal devel opment was assessed by microdissection to measure villus area, crypt l ength and crypt cell production rate. RMCPII levels were similar in ca psaicin-treated and control rats and peaked at day 22 of life, and int estinal development was not retarded by capsaicin treatment. We conclu de that substance P release is unlikely to be an initiating factor for the MMC activation that is associated with weaning.