The effects of lignocaine on actions of the venom from the yellow scorpion"Leiurus quinquestriatus" in vivo and in vitro

Fatani, A.J., Harvey, A.L., Furman, B.L., and Rowan, E.G. The effects of li gnocaine on actions of the venom from the yellow scorpion, Leiurus quinques triatus, in vivo and in vitro. Toxicon, 19. Many toxins from scorpion venom s activate sodium channels, thereby enhancing neurotransmitter release. The aim of the present work was to determine if the in vivo and in vitro effec ts of Leiurus quinquestriatus venom (Lee) could be ameliorated by lignocain e, a sodium channel blocker. In urethane anaesthetised rabbits, LQQ venom ( 0.5 mg kg(-1), i.v.) caused initial hypotension and bradycardia followed by hypertension, pulmonary oedema, electrocardiographic changes indicating co nduction defects, ischaemia, infarction, and then hypotension and death. Li gnocaine (1 mg kg(-1) i.v. bolus initially, followed by i.v. infusion of 50 mu g kg(-1) min(-1)) significantly attenuated the majority of the venom-ev oked effects and reduced mortality. Addition of LQQ Venom (1, 3 and 10 mu g ml(-1)) to chick biventer cervicis, guinea pig ileum, and rat vas deferens preparations, increased the height of electrically-induced twitches, eleva ted resting tension, and caused autorhythmic oscillations. Lignocaine (3 x 10(-4)-1.2 x 10(-3) M) greatly attenuated these venom-evoked actions in the three preparations. Antagonists of appropriate neurotransmitters were also tested to determine the contribution of released transmitters to Lee effec ts. Atropine significantly decreased the venom-elicited effects on guinea p ig ileum preparations, while prazosin and guanethidine significantly reduce d the venom's actions on rat vas deferens. In chick biventer cervicis prepa rations, tubocurarine and hexamethonium significantly;attenuated the venom- induced effects. This study supports the hypothesis that many effects of Le e venom involve the release of neurotransmitters and maybe ameliorated by t reatment with lignocaine. (C) 2000 Elsevier Science Ltd. All rights reserve d.