Venom from Anemesia species of spider modulates high voltage-activated Ca2+ currents from rat cultured sensory neurones and excitatory post synaptic currents from rat hippocampal slices

The actions of crude venom from Anemesia species of spider were investigate d in cultured dorsal root ganglion neurones from neonatal rats and hippocam pal slices. Using mass spectrometry (MALDI-TOF MS), 10-12 distinct peptides with masses between about 3 and 10 kDa were identified in the crude spider venom. At a concentration of 5 mug/ml crude Anemesia venom transiently enh anced the mean peak whole cell voltage-activated Ca2+ current in a voltage- dependent manner and potentiated transient increases in intracellular Ca2triggered by 30 mM KCI as measured using Fura-2 fluorescence imaging. Addit ionally, 5-8 mug/ml Anemesia venom increased the amplitude of glutamatergic excitatory postsynaptic currents evoked in hippocampal slices. omega -Cono toxin GVIA (1 RM) prevented the increase in voltage-activated Ca2+ currents produced by Anemesia venom. This attenuation occurred when the cone shell toxin was applied before or after the spider venom. Anemesia venom (5 mug/m l) created no significant change in evoked action potentials but produced m odest but significant inhibition of voltage-activated K+ currents. At a con centration of 50 mug/ml Anemesia venom only produced reversible inhibitory effects, decreasing voltage-activated Ca2+ currents. However, no significan t effects on Ca2+ currents were observed with a concentration of 0.5 mug/ml . The toxin(s) in the venom that enhanced Ca2+ influx into sensory neurones was heat-sensitive and was made inactive by boiling or repetitive freeze-t hawing. Boiled venom (5 mug/ml) produced significant inhibition of voltage- activated Ca2+ currents and freeze-thawed venom inhibited Ca2+ transients m easured using Fura-2 fluorescence. Our data suggest that crude Anemesia ven om contains components, which increased neuronal excitability and neurotran smission, at least in part this was mediated by enhancing Ca2+ influx throu gh N-type voltage-activated Ca2+ channels. (C) 2001 Harcourt Publishers Ltd .