Effect of tetracaine on veratrine-mediated influx of sodium into rat brain synaptosomes.
Depolarization of synaptosomes with veratrine (0.1 mg/ml) or 50 mmol/l of KCl results in the release of radioactivity from 14C-choline loaded synaptosomes with partial dependence on external Ca2+. Like tetrodotoxin, tetracaine prevented veratrine but not KCl action, with a half-maximal effect at approximately 10(-5) mol/l of anesthetic. A similar half-maximal value was obtained for tetracaine blockade of veratrine-stimulated tetrodotoxin-sensitive 22Na influx into synaptosomes, complete blockage being achieved at 10(-4) mol/l. At this concentration tetracaine failed to modify Ca2+ channels measured by KCl-induced 45Ca uptake. Microviscosity of a lipid bilayer in synaptic membranes evaluated with 5- and 16-doxylstearate spin labels decreased at tetracaine concentrations exceeding 10(-3) mol/l. It is suggested that Na+ channels of synaptosomes are blocked by direct action of anesthetic or through changes in the channel annular lipids.
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D013574:Synaptosomes / Q000378:metabolism*; D013748:Tetracaine / Q000494:pharmacology*; D014702:Veratrine / Q000494:pharmacology*
D013748:Tetracaine; D012964:Sodium; D014702:Veratrine; D000109:Acetylcholine; D002118:Calcium