C Pharmacology & Toxicology 2000, 86, 149–155. Copyright C Printed in Denmark . All rights reserved ISSN 0901-9928 Neurotoxic Effects of Three Fractions Isolated from Tityus serrulatus Scorpion Venom Ana Leonor A. Nencioni 1,3 , Fa ´tima F. Carvalho 1,3 , Ivo Lebrun 2 , Valquiria A. Coronado Dorce 1 and Maria Regina L. Sandoval 1 1 Laboratory of Pharmacology, 2 Laboratory of Biochemistry and Biophysics, Butantan Institute and 3 Laboratory of Pharmacology, School of Veterinary Medicine, Sa ˜o Paulo University, Sa ˜o Paulo, SP, Brazil (Received July 27, 1999; Accepted November 2, 1999) Abstract: Scorpion venoms contain low molecular weight basic polypeptides, neurotoxins, that are the principal toxic agents. These toxins act on ion channels, promoting a derangement that may result in an abnormal release of neurotrans- mitters. In the present study we investigated some of the effects of the F, H and J fractions isolated from Tityus serrulatus scorpion venom on the central nervous system of rodents. The venom was partially purified by gel filtration chromatogra- phy. The neurotoxic effect of these fractions was studied on convulsive activity after intravenous injection, and on electro- graphic activity and neuronal integrity of rat hippocampus when injected directly into this brain area. The results showed that intravenous injection of the F and H fractions induced convulsions, and intrahippocampal injection caused electro- graphic seizures in rats and neuronal damage in specific hippocampal areas. Fraction J injected intravenously reduced the general activity of mice in the open field but induced no changes when injected into the brain. These results suggest that scorpion toxins are able to act directly on the central nervous system promoting behavioural, electrographic and histologi- cal modifications. Tityus serrulatus and Tityus bahiensis are the most poison- ous scorpion species occurring in Brazil, being responsible for the largest part of sting incidents (von Eickstedt et al. 1996). Small quantities of hyaluronidase, phospholipase, low molecular weight substances such as serotonin or hista- mine, and neurotoxins, have been found in the chemical composition of scorpion venoms (Couraud & Jover 1983). Scorpion toxins are low molecular weight basic polypep- tides consisting of single chains bound by disulfide bridges and each scorpion venom has many neurotoxins (Co- uraud & Jover 1983). A large number of scorpion neur- otoxins are specifically able to modify the normal function of sodium channels (Catterall 1980; Couraud & Jover 1983; De Lima & Martin Eauclaire 1995). Other scorpion toxins act by blocking potassium channels (Castle et al. 1989). Thus, the change in function of ion channels caused by scorpion venom or isolated toxins may be responsible for the elicited convulsions, an important effect mainly ob- served in children in severe cases of envenomation. Studies with Centruroides sculpturatus scorpion venom have shown epileptiform waves when the venom is applied to the cer- ebral cortex (Allon & Woody 1983) and intracerebroventric- ular injection of Leiurus quinquestriatus scorpion venom in- duces convulsions (Osman et al. 1973). Experiments carried out in our laboratory with T. serrulatus scorpion venom have shown epileptiform activity in cerebral recordings of Author for correspondence: Valquiria A. C. Dorce, Laboratory of Pharmacology, Butantan Institute, Av. Dr. Vital Brasil, 1500, 05503–900 Sa ˜o Paulo SP, Brazil (fax π55 11 815 1505, e-mail vdorce/usp.br). rats after venom injection into the hippocampus (Sandov- al & Dorce 1993). The venom fractions are composed by toxins that must be responsible, at least in part, for the convulsive effect ob- served with whole venom. Since these toxins are important not only for the pathophysiology of envenomation but also as neurological tools for studying convulsive activity, the present study was undertaken to investigate the ability of three of the fractions isolated from T. serrulatus venom on convulsive activity by analysing their effects on the electro- graphic activity and neuronal integrity of the rat hippocam- pus. The open field study was also used but only to quantify possible alterations in general activity. Materials and Methods Male Swiss Webster mice, 20–22 g, and male Wistar rats, 200–250 g, were used. The animals which arrived at the laboratory 7 days before the beginning of the experiments, were housed 6 to a cage and maintained at 22∫2æ on a 12/12 hr light dark cycle (lights on from 7 a.m. to 7 p.m.) with free access to chow and water. The animals used in this study were maintained in accordance with the guidelines of the Department of Pathology at the Sa ˜o Paulo Univer- sity School of Veterinary Medicine, which are based on the guide- lines for animal care prepared by the Committee on Care and Use of Laboratory Animal Resources, National Research Council, USA. Dried Tityus serrulatus scorpion venom was obtained from the Arthropod Laboratory of the Butantan Institute and partially puri- fied by gel filtration chromatography. Sephadex G-50M (0.8¿150 cm) and G-25F (0.6¿120 cm) columns were equilibrated and the samples eluted with 0.02 M ammonium bicarbonate, pH 8.0, at room temperature (see legend to fig. 1A, 1B). Based on previous