Abstract
Effects of conantokin-T, a 21 amino acid peptide toxin isolated from the fish-hunting cone snail Conus tulipa, on the high-voltage-activated Ca 2+ channel currents were studied in acutely dissociated rat hippocampal CA1 neurons using whole-cell voltage clamp-recording technique with 5 mM Ba 2+ as the charge carrier. Conantokin-T inhibited the whole-cell Ba 2+ current (I(Ba)) in a concentration-dependent manner. The nimodipine (20 μM) and ω-agatoxin-IVA (0.2 μM) block of I(Ba) were abolished in the presence of conantokin-T (3 μM); however, conantokin-T (3 μM) did not affect the block of I(Ba) induced by 3 μM ω-conotoxin-GVIA. These results indicate that conantokin-T is a potent but wide-spectrum Ca 2+ channel antagonist.