Extracellular alkaline transients mediated by glutamate receptors in the rat hippocampal slice are not due to a proton conductance.
1. The ionic mechanism of extracellular alkaline transients mediated by alpha-amino-3-hydroxy-5-methylisoxazolate-4-propionic acid (AMPA) receptor channels was studied in the rat hippocampal slice (area CA1) by means of H(+)-, Ca(2+)- and Na(+)-selective microelectrodes. 2. Alkaline transients mediated by selective synaptic activation of AMPA receptors were coupled to a transient fall in extracellular Ca2+ ([Ca2+]o). 3. Removal of [Ca2+]o blocked the alkaline transient evoked by microinjection of AMPA, but had little effect on the simultaneous tetrodotoxin-resistant fall in extracellular Na+ ([Na+]o). 4. Alkaline transients evoked by microinjection of gamma-aminobutyric acid (GABA) were not affected by removal of [Ca2+]o. GABA had no effect on [Na+]o. 5. The present results indicate that activity-induced glutamatergic alkaline transients in the hippocampal slice are due to an influx of Ca2+, and not to a conductive movement of H+ ions across glutamate-gated cation channels.
Paalasmaa
P
P
Department of Zoology, University of Helsinki, Finland.
Taira
T
T
Voipio
J
J
Kaila
K
K
D000136:Acid-Base Equilibrium / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D046508:Culture Techniques; D005110:Extracellular Space / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D051381:Rats; D018091:Receptors, AMPA / Q000502:physiology; D017470:Receptors, Glutamate / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D007473:Ion Channels; D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D005680:gamma-Aminobutyric Acid; D012964:Sodium; D002118:Calcium