Ruthenium red inhibits the voltage-dependent increase in cytosolic free calcium in cortical synaptosomes from guinea-pig.
Effects of ruthenium red (RuR) on adenylates, plasma membrane potential (delta psi p) and cytosolic free calcium concentration ([Ca2+]c) in cortical synaptosomes from guinea-pig were investigated. Ten micromoles of RuR did not affect either energy levels as indicated by ATP/ADP ratio or the basal delta psi p. The resting [Ca2+]c in the presence of RuR was unchanged, but above 5 microM it inhibited by more than 50% of the voltage-activated increase in [Ca2+]c by K+-depolarization. In another experiment the potencies of 10 microM RuR and 100 microM verapamil to inhibit high K+-induced increase in [Ca2+]c were compared. It was found that either produced 59% inhibition and this inhibition was not potentiated by the substances together (65% inhibition). The extent of depolarisation of delta psi p by high external K+ was independent of the presence of RuR. RuR blocked only 20% of the increase in [Ca2+]c by veratridine treatment, indicating that Ca2+ accumulation into synaptosomal cytoplasm by veratridine involves some additional mechanisms other than depolarisation of delta psi p. The mechanism of inhibition of evoked release of neurotransmitters by RuR is discussed.
Taipale
H T
HT
National Public Health Institute, Department of Environmental Hygiene and Toxicology, Kuopio, Finland.
Kauppinen
R A
RA
Komulainen
H
H
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects; D002540:Cerebral Cortex / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D004560:Electricity; D006168:Guinea Pigs; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000037:antagonists & inhibitors / Q000494:pharmacology; D012428:Ruthenium / Q000494:pharmacology*; D012430:Ruthenium Red / Q000494:pharmacology*; D009435:Synaptic Transmission / Q000187:drug effects; D013574:Synaptosomes / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology
D012430:Ruthenium Red; D000244:Adenosine Diphosphate; D014701:Veratridine; D012428:Ruthenium; D000255:Adenosine Triphosphate; D014700:Verapamil; D011188:Potassium; D002118:Calcium