EFFECTS OF I.A. LIGNOCAINE ON ADRENALINE-INDUCED VASOCONSTRICTION

The effects of i.a. administered lignocaine on the in vivo responseof the vascular bed supplied by the lingual, external maxillaryand posterior auricular branches of the common carotid arterywere studied in the rat. Infusions of lignocaine in concentrationsof 10–1000 µg ml^–1 administered at the rateof 0.05 ml min^–1 for 10 min did not affect vascular resistanceor arterial pressure in the common carotid artery. However,following such infusions, the increase of vascular resistancecaused by bolus doses of adrenaline (20–120 ng in 0.1ml) was inhibited, indicating lignocaine-adrenaline antagonism.Responses to adrenaline remained significantly depressed 60min after the termination of a 100-µg ml^–1 or higherlignocaine infusion. ^* Present address: Turner Dental School, University of Manchester,Bridgeford Street, Manchester M15.