Effects of alpha-dendrotoxin and dendrotoxin K on extracellular excitatoryamino acids and on electroencephalograph spectral power in the hippocampusof anaesthetised rats

Dendrotoxins, important pharmacological tools for studying K+ channels, are potently convulsant in the central nervous system and evidence suggests th at different members of the dendrotoxin family may act at pre- or post-syna ptic sites, Using a combination of intrahippocampal infusion, microdialysis and electroencephalograph (EEG) recording, we have compared the effects of alpha -dendrotoxin and dendrotoxin K on extracellular levels of excitatory amino acids in anaesthetised rats. Our findings show that although infusio n of 35 pmol of both peptides was associated with elevated extracellular as partate and glutamate, these increased levels were more sustained with dend rotoxin K. Furthermore, there was EEG evidence of an associated transient f unctional change consistent with an action on pre-synaptic K+ channels. In contrast, infusion of cr-dendrotoxin produced only a brief effect on amino acid levels and no evidence of a functional consequence. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.