“…Although it is well known that (1-adrenoceptor agonists do not inhibit mediator release from rat mast cells [16,17], (1-adrenoceptor agonists are potent inhibitors of histamine release in human lung fragments [6,7,18,19], dispersed human lung mast cells [9,20,21], human skin slices [19], dispersed human skin mast cells [4], and in in vivo studies of human skin [22][23][24], (1-adrencrgic receptor activation also inhibits antigen-induced peptidoleukotricne genera tion by human lung fragments [19] and dispersed lung mast cells [9,20,21], Ketotifen is a derivative of the tricyclic compound, benzocycloheptathiophcne, that differs markedly in its chem ical structure from any of the classic antihistamines [25,26], Ketotifen (10-200 \iM) inhibits histamine release from rat peritoneal mast cells using non-immunologic stimuli [27][28][29][30]. Ketotifen also inhibits the release of histamine and slow-reacting substance of anaphylaxis (SRS-A) leukotrienes from peripheral human leukocytes induced by both immunogenic (anti-IgE) and non-immunogenic (cal cium ionophore A23187) stimuli [31][32][33].…”