Most of the polypeptides constituent of scorpion venoms appear to interfere with the function of ion channels.In the present study,sharp intracellular recordings were made under the current clamp condition on F1 cells of Helix aspersa;/I>.Following extracellular application of the Buthotus schach scorpion toxin extracts(T3 and T6), and kaliotoxin(KTX),a well-known scorpion neurotoxin,either alone or in combination with diltiazem,an L-type calcium channel blocker,changes in the firing pattern and properties of Ca²⁺ spikes were assessed and compared to control values.While application of kaliotoxin(1μM)in calcium Ringer led to a significant reduction in the firing frequency and the duration of calcium spikes and increase in the AHP amplitude,the RMP and AP amplitude did not significantly change.Bath perfusion of T3(1 μM) significantly depolarized the RMP and reduced the frequency and AP amplitude.The AHP amplitude increased.The mean duration of Ca²⁺ spike almost remained unchanged.When diltiazem(1 μM) was added to the bath solution containing T3, F1 cells became further depolarized.The firing frequency and mean duration of spikes significantly reduced.The AHP amplitude decreased.Application of T6(1 μM)led to a significant reduction in the firing frequency and duration of spikes. Its application also caused a remarkable increase in the AHP amplitude. The RMP shifted toward hyperpolarized voltage.Blockade of L-type Ca²⁺ channels by diltiazem(1 μM) in the presence of T6 led to a significant hyperpolarization of cells and further prolongation of action potential.Moreover,the firing frequency was significantly increased,but the AHP amplitude was decreased.Taken together,these findings suggest that two neurotoxin extracts from Buthotus schach affect neuronal excitability and Ca²⁺ spikes properties almost identical to kaliotoxin.