Glutamate-induced cytoplasmic Ca2+ transients in neurones isolated from the rat dorsal cochlear nucleus.
Extracellular application of glutamate elicited cytoplasmic Ca2+ transients in freshly dissociated rat neurones of the dorsal cochlear nucleus (DCN) (identified as pyramidal cells) with half-maximal concentration of 513 micromol/l while saturating doses (5 mmol/l) of this neurotransmitter caused transients of 46.1 +/- 3.0 nmol/l on an average. The genesis of these glutamate-evoked Ca2+ transients required extracellular Ca2+. When [Mg2+]o was 1 mmol/l, the NMDA receptor antagonist AP5 (100 micromol/l) had no effects while 100 micromol/l CNQX and 10 micromol/l NBQX, inhibitors of the AMPA receptors, greatly decreased the glutamate-induced Ca2+ transients (a decrease of 92 and 57%, respectively). When facilitating the activation of the NMDA receptors (50 micromol/l glycine, 20 micromol/l [Mg2+]o) in the presence of 100 micromol/l CNQX, Ca2+ transients of 55.4 +/- 13.1 nmol/l could be produced. Block of the voltage-gated Ca2+ channels (200 micromol/l Cd2+) decreased the Ca2+ transients to approx. 50%. The data indicate that under our control experimental circumstances the glutamate-induced Ca2+ transients of the isolated DCN neurones are produced mainly by Ca2+ entry through voltage-gated Ca2+ channels and AMPA receptors. However, when the activation of the NMDA receptors may take place, these receptors also contribute significantly to the genesis of the glutamate-evoked cytoplasmic [Ca2+] elevations.
Department of Physiology, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary.
A
A
Pór
Cs
C
Harasztosi
Z
Z
Rusznák
G
G
Szucs
D000818:Animals; D000831:Animals, Newborn; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology*; D002478:Cells, Cultured; D017626:Cochlear Nucleus / Q000187:drug effects* / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D018698:Glutamic Acid / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D018091:Receptors, AMPA / Q000187:drug effects / Q000378:metabolism; D017470:Receptors, Glutamate / Q000187:drug effects / Q000378:metabolism
D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D018698:Glutamic Acid