THE EFFECTS OF 4 NEUROPEPTIDES ON THE DEGRANULATION OF MUCOSAL MAST-CELLS FROM SHEEP

Isolated mucosal mast cells (MMC) were used to examine the ability of four neuropeptides, substance P, vasoactive intestinal peptide, beta-e ndorphin and somatostatin, to release mediators in the presence or abs ence of parasite antigen. None of the neuropeptides induced the releas e of sheep mast cell protease (SMCP) or histamine from MMC of helminth -immune sheep in the absence of parasite antigen. Incubation of immune MMC with 100 and 1.0 mu g/mL parasite antigen induced 32.1 and 15.5% specific SMCP release, respectively. While the neuropeptides did not a ugment SMCP release at 100 mu g/mL parasite antigen, significant enhan cement (40-98%) of SMCP release at 1 mu g/mL antigen was obtained by e ach neuropeptide at concentrations from 10(-8) to 10(-12) mol/L. The r esults provide additional support for modulation of MMC degranulation by neural activity in sheep and, to our knowledge, this is the first d emonstration that the threshold antigen concentration for allergic res ponses may also be lowered by neuropeptides to render the reaction mor e sensitive to antigen.