Heterogeneous responses of canine basilar and middle cerebral arteries to serotonin at normal and high CO₂ tension

Abstract

The responses of basilar arteries (BAs) to serotonin were attenuated by high$P_{CO_2 }$ (86±1 mm Hg) and the pH matched acidotic solution ($P_{CO_2 }$ 37±1 mm Hg), whereas the responses of middle cerebral arteries (MCAs) were not. High$P_{CO_2 }$ decreased the basal tone of both arteries, and the changes in basal tone due to high$P_{CO_2 }$ were not influenced by 3×10⁻⁷ M imipramine, 10⁻⁵ M pargyline or 10⁻⁴ M aspirin. The responses of BAs to serotonin were attenuated by high$P_{CO_2 }$ in the presence of imipramine, pargyline and aspirin. The responses of MCAs to serotonin were not influenced by high$P_{CO_2 }$ in the presence of pargyline and aspirin, but attenuated by high$P_{CO_2 }$ in the presence of imipramine.