Effects of i.a. lignocaine on adrenaline-induced vasoconstriction

The effects of i.a. administered lignocaine on the in vivo response of the vascular bed supplied by the lingual, external maxillary and posterior auricular branches of the common carotid artery were studied in the rat. Infusions of lignocaine in concentrations of 10-1000 micrograms ml-1 administered at the rate of 0.05 ml min-1 for 10 min did not affect vascular resistance or arterial pressure in the common carotid artery. However, following such infusions, the increase of vascular resistance caused by bolus doses of adrenaline (20-120 ng in 0.1 ml) was inhibited, indicating lignocaine-adrenaline antagonism. Responses to adrenaline remained significantly depressed 60 min after the termination of a 100-micrograms ml-1 or higher lignocaine infusion.