title: Effects of kainic acid on brain calcium fluxes studied in vivo and in vitro.
abstract: The effect of in vivo administration of kainic acid into the rabbit hippocampus was studied with brain dialysis and subsequent determination of the Ca2+ concentration in the dialysate. When included in the perfusing medium, kainic acid as well as veratridine induced a decrease in extracellular Ca2+. The effect of kainic acid (but not of veratridine) was insensitive to tetrodotoxin. In vitro studies revealed no effect of kainic acid on 45Ca2+ uptake by isolated astrocytes, but showed an enhancement of synaptosomal 45Ca2+ accumulation. This was, however, only 25% of the stimulatory effect of high K+ depolarization. Glutamate activated synaptosomal Ca2+ uptake, whereas dihydrokainate had no effect. The uptake evoked by kainate and glutamate was independent of the K+ level in the medium which indicates the involvement of other than voltage-sensitive Ca2+ channels. The results confirm previous finding that kainic acid promotes the uptake of Ca2+ in brain cells. Kainate affects Ca2+ fluxes pre- and postsynaptically. Presynaptic Ca2+ influx may be mediated by chemically gated mechanisms.
authors.forename: J W
authors.initials: JW
authors.lastname: Lazarewicz
authors.forename: A
authors.initials: A
authors.lastname: Lehmann
authors.forename: H
authors.initials: H
authors.lastname: Hagberg
authors.forename: A
authors.initials: A
authors.lastname: Hamberger
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D004357:Drug Synergism; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D007608:Kainic Acid / Q000031:analogs & derivatives / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism; D011817:Rabbits; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology
chemical_list: D005971:Glutamates; D018698:Glutamic Acid; D013779:Tetrodotoxin; C020889:dihydrokainic acid; D014701:Veratridine; D011188:Potassium; D007608:Kainic Acid; D002118:Calcium