TY - JOUR
T1 - Brain voltage-sensitive calcium channel subtypes differentiated by ω-conotoxin fraction GVIA
AU - Reynolds, I. J.
AU - Wagner, J. A.
AU - Snyder, S. H.
AU - Thayer, S. A.
AU - Olivera, B. M.
AU - Miller, R. J.
PY - 1986
Y1 - 1986
N2 - We have studied the voltage-activated influx of Ca2+ into synaptosomes. Rapid 45Ca2+ influx into synaptosomes, measured at 1 sec, was blocked by predepolarization and by low concedntrations of cadmium (IC50, 1 μM), as anticipated for voltage-sensitive calcium channels (VSCCs). However, fluxes were insensitive to dihydropyridine drugs that block or activate VSCCs, including nitrendipine, Bay K 8644, and (+)- and (-)-PN202-791. Phenylalkylamine calcium antagonists, including verapamil and desmethoxyverapamil, blocked 45Ca2+ uptake in a nonspecific fashion. The peptide ω-conotoxin fraction GVIA (ω-CgTx GVIA) blocked 45Ca2+ uptake in a biphasic fashion, with a 30% reduction at 50 pM toxin and a further decrease at concentrations > 5 nM. The toxin inhibited neurotransmitter release from synaptosomes in nanomolar concentrations, corresponding to its low-affinity effects on 45Ca2+ influx. ω-CgTx GVIA also inhibited depolarization-induced increases in intracellular Ca2+ concentration in single hippocampal and striatal neurons. These findings indicate that ω-CgTx GVIA blocks VSCCs in both cell bodies and nerve terminals and that the predominant form of VSCC in nerve terminals is the dihydropyridine-insensitive N type.
AB - We have studied the voltage-activated influx of Ca2+ into synaptosomes. Rapid 45Ca2+ influx into synaptosomes, measured at 1 sec, was blocked by predepolarization and by low concedntrations of cadmium (IC50, 1 μM), as anticipated for voltage-sensitive calcium channels (VSCCs). However, fluxes were insensitive to dihydropyridine drugs that block or activate VSCCs, including nitrendipine, Bay K 8644, and (+)- and (-)-PN202-791. Phenylalkylamine calcium antagonists, including verapamil and desmethoxyverapamil, blocked 45Ca2+ uptake in a nonspecific fashion. The peptide ω-conotoxin fraction GVIA (ω-CgTx GVIA) blocked 45Ca2+ uptake in a biphasic fashion, with a 30% reduction at 50 pM toxin and a further decrease at concentrations > 5 nM. The toxin inhibited neurotransmitter release from synaptosomes in nanomolar concentrations, corresponding to its low-affinity effects on 45Ca2+ influx. ω-CgTx GVIA also inhibited depolarization-induced increases in intracellular Ca2+ concentration in single hippocampal and striatal neurons. These findings indicate that ω-CgTx GVIA blocks VSCCs in both cell bodies and nerve terminals and that the predominant form of VSCC in nerve terminals is the dihydropyridine-insensitive N type.
UR - http://www.scopus.com/inward/record.url?scp=0022998368&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0022998368&partnerID=8YFLogxK
U2 - 10.1073/pnas.83.22.8804
DO - 10.1073/pnas.83.22.8804
M3 - Article
C2 - 2430302
AN - SCOPUS:0022998368
SN - 0027-8424
VL - 83
SP - 8804
EP - 8807
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 22
ER -