Glutamate and N-acetylaspartylglutamate block HVA calcium currents in frog olfactory bulb interneurons via an mGluR2/3-like receptor.
1. We investigated the glutamate-mediated modulation of voltage-activated calcium currents in cultured interneurons of the olfactory bulb of Xenopus laevis, with the use of standard patch-clamp whole-cell recordings. 2. Glutamate and N-acetylaspartylglutamate (NAAG) activated (2S,1'R,2'R,3'R)-2-(2,3-dicarboxy-cyclopropyl)glycin-sens iti ve metabotropic glutamate receptors at olfactory bulb interneurons and thereby inhibited calcium influx through presynaptic voltage-gated calcium channels. 3. The glutamate- or NAAG-mediated blockage of calcium channels showed indistinguishable dose-response curves, with K1/2 = 388 and 350 nM for glutamate and NAAG, respectively. At saturating concentrations of glutamate or NAAG, approximately 40% of the maximum calcium currents were blocked. 4. It is concluded that glutamate, which excites interneurons at olfactory bulb reciprocal synapses, also causes a reduction of gamma-aminobutyric acid-mediated feedback inhibition at these synapses by activating a metabotropic-glutamate-receptor-2/3-like receptor.
Physiologisches Institut, Universität Göttingen, Germany.
J
J
Bischofberger
D
D
Schild
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002478:Cells, Cultured; D003521:Cyclopropanes / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology*; D018698:Glutamic Acid / Q000494:pharmacology*; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006719:Homovanillic Acid / Q000378:metabolism*; D007395:Interneurons / Q000187:drug effects / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D009830:Olfactory Bulb / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013569:Synapses / Q000187:drug effects / Q000502:physiology; D014981:Xenopus
D002121:Calcium Channel Blockers; D003521:Cyclopropanes; D004151:Dipeptides; D018094:Receptors, Metabotropic Glutamate; C082313:2-(2,3-dicarboxycyclopropyl)glycine; C027172:isospaglumic acid; D018698:Glutamic Acid; D005998:Glycine; D006719:Homovanillic Acid