Effects of a toxin isolated from Tityus bahiensis scorpion venom on the hippocampus of rats

The objective of the present study was to determine the effects of a toxin from T. bahiensis scorpion venom on the hippocampus of rats. This toxin, called Tb V-4, was chosen since it shows remarkable convulsive activity. Male Wistar rats weighing 250g were used. The toxin (1.0μg/μl) was injected into the hippocampus. The animals were then submitted to electroencephalographic and behavioral examinations or to microdialysis to determine the levels of neurotransmitters. The location of the implanted guide cannulae and electrodes was checked histologically. The number of cells in the CA1, CA3 and CA4 areas of the hippocampus was determined by light microscopy. Changes in the concentration of cytosolic free calcium were evaluated by confocal microscopy. The toxin evoked behavioral alterations such as wet dog shakes, myoclonus, yawning and orofacial automatisms. Electroencephalographic recordings exhibited alterations such as isolated or grouped spikes and epileptic-like discharges. Injection of the toxin augmented glutamate concentration in the extracellular fluid in some animals. There was also a decrease in the number of pyramidal cells, mainly in the CA1 and CA4 areas for some rats. In some slices of the hippocampus, an increase in intracellular calcium mobilization was seen. The present results suggest that the Tb V-4 toxin may be responsible for the epileptic and behavioral effects observed with the crude venom. We suggest that the convulsive and degenerative effects induced by the toxin could be due to the enhanced release of excitatory amino acids involved in the most important pathways of the hippocampus.