Abstract
A study was made of the PCA reaction in rat hind paw for analysis of the mechanisms of the anaphylactic release of mediators in vivo. Also studied was the function of cyclic AMP in the anaphylactic release of histamine during PCA induced in rats with homologous and heterologous antibody. A close correlation was seen among edema formation, histamine release and decrease of cyclic AMP during homologous and heterologous PCA. Theophylline, epinephrine and isoproterenol increased the cyclic AMP level and strongly inhibited edema formation and histamine release, in all animals. Aminopyrine and trasylol also increased the cyclic AMP level but aminopyrine did not inhibit either edema formation or histamine release in case of heat labile homocytotropic antibody induced PCA in rats and trasylol did not inhibit histamine release in any animal. Methysergide and mepyramine strongly inhibited histamine release but did not alter cyclic AMP levels. Thus, the increase of the cyclic AMP level did not always inhibit the histamine release during PCA in rats. It has also been demonstrated that the PCA reaction in rat hind paw is a suitable model for studying the mechanisms of the anaphylactic release of mediators in vivo.
