Effects of local anaesthetics on responses of human saphenous vein and bovine coronary artery to neurotransmitters, acetylcholine, noradrenaline and 5-hydroxytryptamine

The effects of 5 different local anaesthetics, lignocaine, etidocaine, prilocaine, mepivacaine, bupivacaine, and 3 different neurotransmitters, acetylcholine (ACh), noradrenaline (NA), 5-hydroxytryptamine (5-HT) on tone and contractility of human saphenous vein and bovine coronary artery were studied and compared in vitro. The experiments were carried out to see if there were species or tissue differences in the action of local anaesthetics and neurotransmitters at vascular smooth muscle, i.e. saphenous vein and coronary artery. Another important aspect was to see if local anaesthetics modified cholinergic (ACh), adrenergic (NA) and serotoninergic (5-HT) responses in vascular smooth muscle. Among the local anaesthetics studied, lignocaine and etidocaine produced prolonged relaxations, whereas prilocaine, mepivacaine, bupivacaine produced contractions in the saphenous vein and coronary artery. High concentrations of the latter drugs produced relaxations in the blood vessels. Among the local anaesthetics, lignocaine produced differential effects on saphenous vein and coronary artery, its effect on the latter was 3 times larger than on the saphenous vein. ACh, NA and 5-HT contracted the saphenous vein. In the coronary artery, ACh and 5-HT contracted whereas NA relaxed the vessel. On a molar basis, ACh was less effective than NA in contracting the saphenous vein. 5-HT was equipotent on both the saphenous vein and coronary artery. Lignocaine reduced ACh, NA and 5-HT-induced contractions in the saphenous vein and those of ACh and 5-HT in the coronary artery, and shifted the control curves, non-competitively, to the right. The relaxation produced by NA in the coronary artery was enhanced by lignocaine.(ABSTRACT TRUNCATED AT 250 WORDS)