Peripheral actions of hexamethonium in relation to the decreasing effects of repeated doses on the blood pressure of anaesthetized rats.

When hexamethonium was given intravenously to anaesthetized rats, the depressor response produced by successive doses became less. This effect was not related to the duration of anaesthesia and the possible recovery of cardiovascular reflex activity. When the rat's own blood was perfused at constant rate through one hind limb, successive doses of hexamethonium reduced the hind-limb perfusion pressure to the same extent each time, but their effect on the blood pressure of the remainder of the animal became less. When the hind limb was perfused at constant rate with blood from a separate donor rat, hexamethonium in the donor blood produced a very small increase in the vasoconstrictor response to noradrenaline in the innervated hind limb but not in the denervated hind limb.