The delayed pressor response to small doses of intravenous noradrenaline in conscious rabbits.

1. Noradrenaline, infused intravenously at low rates into conscious rabbits, can sustain a moderate elevation of blood pressure of 20-40 mm Hg. The most effective dose range is 0.1-0.5 mug.kg(-1).min(-1).2. Toxic manifestations and tachyphylaxis occur at higher infusion rates, but have also been seen at infusion rates within this range.3. The highest sustained rise of blood pressure was obtained after initially low infusion rates had been gradually increased over a period of 2-4 weeks.