Abstract
The crude venom from the scorpion
L. quinquestriatus (H and E) as well as the dialysed venom and the diffusate obtained from the venom stimulated the spontaneously contracting rat uterus. The crude venom was fractionated electrophoretically into 18 protein fractions. Only one fraction, which moved towards the cathode, had a stimulant effect on the spontaneously contracting rat uterus. The same fraction, obtained after exhaustive dialysis of the venom, was devoid of the stimulant effect. The lipid extracted from the venom had no stimulant effect and the delipidated venom was as powerful as the crude venom in stimulating rat uterine muscle. Paper chromatography of the diffusate of the venom showed that one fraction, having an
R
f
equal to that of 5-hydroxytryptamine, was responsible for the stimulant effect. The action of this fraction on the rat uterus was blocked by methysergide. Injection of this fraction into pregnant female rats precipitated abortion early in pregnancy. It is concluded that 5-hydroxytryptamine contained in the venom induces abortion early in pregnancy and may be responsible for abortion observed in women stung by this scorpion during the first trimester.