Tityustoxin-mediated Na+ influx is more efficient than KCl depolarisation in promoting Ca(2+)-dependent glutamate release from synaptosomes.
The scorpion venom toxin, tityustoxin (TsTX), causes rapid, dose-dependent increases in intracellular free Ca2+ ([Ca2+]i) and glutamate release in rat cerebrocortical synaptosomes. These effects are completely abolished by the Na+ channel blocker tetrodotoxin (TTX). The increase in [Ca2+]i is completely dependent on extracellular Ca2+ but the increased glutamate release has both Ca(2+)-dependent and -independent components. Comparison of the effects of TsTX with those of depolarising concentrations of KCl reveals that TsTX is more effective, both in raising [Ca2+]i and promoting Ca(2+)-dependent and -independent glutamate release. These data suggest that the Ca(2+)-dependent glutamate release caused by TsTX is only partly due to Ca2+ entry through voltage-sensitive Ca2+ channels.
Romano-Silva
M A
MA
Institute of Psychiatry, London, UK.
Ribeiro-Santos
R
R
Gomez
M V
MV
Moraes-Santos
T
T
Brammer
M J
MJ
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism*; D018698:Glutamic Acid; D066298:In Vitro Techniques; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology*; D009498:Neurotoxins / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012604:Scorpion Venoms / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology
D005971:Glutamates; D009467:Neuromuscular Depolarizing Agents; D009498:Neurotoxins; D012604:Scorpion Venoms; C003609:tityustoxin; D018698:Glutamic Acid; D013779:Tetrodotoxin; D011189:Potassium Chloride; D012964:Sodium; D002118:Calcium