5-Hydroxytryptamine receptor subtypes participating in pulmonary edema in dogs

The present study was undertaken to evaluate the effects of 5-hydroxytryptamine on pulmonary vascular resistances and vascular permeability with respect to the 5-hydroxytryptamine receptor subtypes. Left lower lobe of lungs isolated from the dog was perfused with constant heights of arterial and venous blood reservoirs and was maintained at zone III condition (pulmonary venous pressure greater than airway pressure). Drugs were administered into blood reservoir (1 l of total blood volume). Infusion of 5-hydroxytryptamine (100 micrograms/min) increased the pulmonary pre- and post-capillary resistances, but did not change the filtration coefficient. In the presence of ketanserin (10 mg), the infusion of 5-hydroxytryptamine caused an increase in filtration coefficient that was prevented by methysergide (30 mg). ICS 205-930 (10 mg) did not prevent such an increase in filtration coefficient. Infusion of 5-carboxamidotryptamine (100 micrograms/min) increased the filtration coefficient as well as both pre- and post-capillary resistances. These results suggested that the 5-HT1-like receptor mediates the increase in pulmonary vascular permeability.