Acute hypotensive action of 2-(2,6-dichlorophenylamino)-2-imidazoline hydrochloride (St 155) after infusion into the cat's vertebral artery

Low doses (0.25–2.0 μg/kg) of 2-(2, 6-dichlorophenylamino)-2-imidazoline-hydrochloride were infused into the vertebral artery of anesthetized cats. A considerable, dose-dependent decrease in blood pressure developed suddenly towards the end of the infusion. The same low doses hardly affected blood pressure when given intravenously. The hypotensive effect, observed after infusion into the vertebral artery is in agreement with the presumed central mechanism of action of the drug. In most animals the infusion of 1 μg/kg 2-(2, 6-dichlorophenylamino)-2-imidazoline-hydrochloride into the verterbral artery reduced the carotid occlusion reflex considerably, probably also via a central mechanism. The chemo-receptor component of the reflex seemed to be affected more by the drug than the baroreceptor component.