INHIBITION OF CALCIUM CHANNELS IN RAT HIPPOCAMPAL CA1 NEURONS BY CONANTOKIN-T

Effects of conantokin-T, a 21 amino acid peptide toxin isolated from t he fish-hunting cone snail Conus tulipa, on the high-voltage-activated Ca2+ channel currents were studied in acutely dissociated rat hippoca mpal CA1 neurons using whole-cell voltage clamp-recording technique wi th 5 mM Ba2+ as the charge carrier. Conantokin-T inhibited the whole-c ell Ba2+ current (I-Ba) in a concentration-dependent manner. The nimod ipine (20 mu M) and omega-agatoxin-IVA (0.2 mu M) block of I-Ba were a bolished in the presence of conantokin-T (3 mu M); however, conantokin -T (3 mu M) did not affect the block of I-Ba induced by 3 mu M omega-c onotoxin-GVIA. These results indicate that conantokin-T is a potent bu t wide-spectrum Ca2+ channel antagonist. Copyright (C) 1996 Elsevier S cience Ireland Ltd.