“…In cats, dogs, monkeys, rabbits and rats intravenous injection of clonidine between 2 and 10 pg kg-l produces a shortacting pressor response of 1 to 2 min duration which is superceded by a sustained depressor response accompanied by bradycardia which may last up to 2 h (Boissier, Giudicelli & others, 1968;Constantine & McShane, 1968;Nayler, Price & others, 1968;Rand & Wilson, 1968;Bolme & Fuxe, 1971). The brief rise in blood pressure is the result of peripheral vasoconstriction and is discussed in section (b) below.…”