Tityustoxin and toxin-gamma are neurotoxins, purified from the venom of scorpion Tityus srrulatus, that act on the voltage-sensitive sodium channel delaying the inactivation or activating the channel, respectively. We have determined and compared the effect of both toxins on the elicited release of acetylcholine from rat brain cortical slices. Tityustoxin showed a linear concentration-dependent effect, but toxin-gamma did not show the same behaviour. Tetrodotoxin 1.2 mu M was able to block the effects of both toxins. Med Sci Res 26:583-584 (C) 1998 Lippincott Williams & Wilkins.