SRS, PGF, and histamine were administered intravenously or as aerosols to artificially ventilated guineapigs in order to assess their capacity to affect tracheal insufflation pressure measured by means of Konzett-Rössler technique. Independently of route of administration all three compounds increased tracheal insufflation pressure, SRS being the most potent one. Bilateral cervical vagotomy did not alter the effect. Relative to histamine SRS and PGF were considerably more active by aerosol administration than by intravenous injection. The aerosols had little or no effect on systemic blood pressure. On intravenous injection, histamine decreased and SRS adn PGF increased arterial blood pressure in a dose-dependent fashion. The airway effects of histamine were correlated to those on blood pressure whereas with SRS and PGF this was not seen when the blood pressure effects were marked. Preadministration of adrenaline or isoprenaline as aerosols antagonized the increase in insufflation pressure, but not the effects on blood pressure, produced by intravenously injected histamine of PGF.

It is concluded that SRS, PGF and histamine on intravenous or aerosol administration increase tracheal insufflation pressure in the guinea-pig mainly by an action on airway tone. The data emphasize that SRS is a potent bronchoconstricting agent, possibly of pathophysiological significance in guinea-pig anaphylaxis.