Changes of the membrane potential in striatal synaptoneurosome, synaptosome and membrane sac preparations induced by glutamate, kainate and aspartate as measured with a cyanine dye DiS-C2-(5).
The effects of glutamate, kainate and aspartate on the membrane potential of striatal synaptoneurosome, synaptosome and membrane sac preparations were studied by using a potential sensitive cyanine dye DiS-C2-(5). Excitatory amino acids glutamate and aspartate had a depolarizing effect on synaptoneurosomes. 7.9 microM glutamate and 2.8 microM aspartate produced a half-maximal response. Depolarizations induced by glutamate and aspartate were dependent on the concentration of extracellular sodium ions, a maximal response occurred at around 40 mM of external Na+. Kainate induced a dual effect on synaptoneurosomes. In a standard Na+-based medium a hyperpolarization, likely due to inhibition of a presynaptic sodium-dependent glutamate uptake, predominated over a postsynaptic kainate receptor-mediated depolarization that was observed when electrogenic glutamate uptake was inhibited. This interpretation was supported by results obtained with synaptosome and membrane sac preparations. In a standard Na+-based medium kainate had a hyperpolarizing effect on synaptosomes while in the membrane sac preparation kainate induced a depolarization.
Heinonen
E
E
Neurobiology Research Unit, University of Helsinki, Finland.
Akerman
K E
KE
Panula
P
P
D000818:Animals; D001224:Aspartic Acid / Q000494:pharmacology*; D003342:Corpus Striatum / Q000502:physiology*; D004225:Dithiazanine; D005456:Fluorescent Dyes; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D006168:Guinea Pigs; D007608:Kainic Acid / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D013574:Synaptosomes / Q000187:drug effects / Q000502:physiology*
D005456:Fluorescent Dyes; D005971:Glutamates; D001224:Aspartic Acid; D018698:Glutamic Acid; D004225:Dithiazanine; D007608:Kainic Acid