The Schultz‐Dale response of the longitudinal muscle strip preparation of guinea‐pig ileum

Abstract

1 The mast-cell distribution in the various layers of the ileum has been described. 2 Histamine-content, anaphylactic histamine-release and the anaphylactic dose-response curve of the full-thickness ileum and of the longitudinal muscle strip have been measured and compared. 3 Tetrodotoxin 10⁻⁷ g/ml had no obvious effect on the anaphylactic dose-response curve of either preparation. This suggests that the plexus is not of any great importance in the Schultz-Dale reaction. 4 Exposure of the longitudinal muscle strip to octylamine 10⁻³ g/ml for 1 min reduced the mast cell content by 95–100%. After this treatment the dose-response curve to antigen was eliminated, although the muscle still responded to small doses of histamine and to anaphylactic mediators. Pre-treatment of antibody with octylamine did not impair passive sensitization and subsequent response to antigenic challenge. This suggests that the classical Schultz-Dale reaction in the strip is mediated mainly by mast cells, and possibly other cells, and is probably not due to a direct effect of the antigen-antibody reaction on the smooth muscle. 5 The typical three-phase anaphylactic response (quick contraction, quick relaxation, slow contraction) of full-thickness ileum is discussed and compared with the predominantly two-phase response of the longitudinal muscle strip. No evidence was found for the release of a relaxation-factor. It is suggested that the initial fast phase may be due to mediators released from mast cells among the longitudinal muscle fibres, and the sustained contraction to a second wave of mediators reaching the longitudinal muscle from deeper layers of the ileum.