This study investigated the behavioural and anticonvulsant effects of 
voltage-sensitive calcium channel blockers in DBA/2 mice. Omega-Conotoxin MVIIC 
(0.1, 0.3 micrograms ICV/mouse) and omega-agatoxin IVA (0.1, 0.3, 1 micrograms 
ICV), which act predominantly at P- and/or Q-type calcium channels, prevented 
clonic and tonic sound-induced seizures in this animal model of reflex epilepsy 
(ED50 values with 95% confidence limits for protection against clonic 
sound-induced seizures were 0.09 (0.04-0.36) micrograms ICV and 0.09 (0.05-0.15) 
micrograms ICV respectively and against tonic seizures 0.07 (0.03-0.16) 
micrograms ICV and 0.08 (0.04-0.13) micrograms ICV, respectively). The N-type 
calcium channel antagonists omega-conotoxin GVIA and omega-conotoxin MVIIA were 
also tested in this model. Omega-Conotoxin GVIA was anticonvulsant in DBA/2 
mice, but only at high doses (3 micrograms ICV prevented tonic seizures in 60% 
of the animals; 10 micrograms ICV prevented clonic seizures in 60% and tonic 
seizures in 90% of the animals), whereas omega-conotoxin MVIIA did not inhibit 
sound-induced seizures in doses up to 10 micrograms ICV. Both omega-conotoxin 
GVIA and omega-conotoxin MVIIA induced an intense shaking syndrome in doses as 
low as 0.1 microgram ICV, whereas omega-conotoxin MVIIC and omega-agatoxin IVA 
did not produce shaking at any of the doses examined. Finally, omega-conotoxin 
GI (0.01-1 microgram ICV) and alpha-conotoxin SI (0.3-30 micrograms ICV), which 
both act at acetylcholine nicotinic receptors, were not anticonvulsant and did 
not induce shaking in DBA/2 mice. These results confirm that blockers of N- and 
P-/Q-type calcium channels produce different behavioural responses in animals. 
The anticonvulsant effects of omega-conotoxin MVIIC and omega-agatoxin IVA in 
DBA/2 mice are consistent with reports that P- and/or Q-type calcium channel 
blockers inhibit the release of excitatory amino acids and are worthy of further 
exploration.