Glutamate and N-acetyl-aspartyl-glutamate block HVA calcium currents in frog olfactory bulb interneurons via an mGluR2/3-like receptor. Bischofberger, Josef and Detlev Schild. Physiologisches Institut, Universit[umlaut]at G[diaeresis]ottingen, Humboldtallee 23, D37073 G[diaeresis]ottingen, FRG, T. 49-551-395915, F. 49- 551-395923, sd@helena.ukps.gwdg.de.
APStracts 3:0108N, 1996.
SUMMARY AND CONCLUSIONS
1. We have investigated the glutamate-mediated modulation of voltage activated calcium currents in cultured interneurons of the olfactory bulb of Xenopus laevis using standard patch clamp whole-cell recordings. 2. Glutamate and N- acetylaspartylglutamate (NAAG) activated DCGIV-sensitive 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 about 40% of the maximum calcium currents was blocked. 4. It is concluded that glutamate, which excites interneurons at OB reciprocal synapses, also causes a reduction of GABA-mediated feedback inhibition at these synapses by activating a mGluR2/3-like receptor. 

Received 30 January 1996; accepted in final form 9 May 1996.
APS Manuscript Number J66-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 June 96