TWO TYPES OF NETWORK OSCILLATIONS IN NEOCORTEX MEDIATED BY DISTINCT
GLUTAMATE RECEPTOR SUBTYPES AND NEURONAL POPULATIONS.
Flint, Alexander C. Alexander C. and Barry W. Connors.
Department of Neuroscience, Brown University, Providence, RI 02912.
APStracts 2:0332N, 1995.
SUMMARY AND CONCLUSIONS
1. Two distinct forms of spontaneous synchronous oscillations were
investigated with field potential recordings in slices of rat somatosensory
cortex in vitro . 2. The first type of synchronous oscillation was activated
by low extracellular [Mg 2+ ], and had dominant frequencies of 8-12 Hz. It was
reversibly abolished by the NMDA receptor antagonist d-2-amino-5-
phosphonovaleric acid (AP-5), and was relatively unaffected by the non-NMDA
receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX). The duration of
oscillatory events was increased by blocking GABA A receptors with bicuculline
or by activating metabotropic glutamate receptors with trans -1-
aminocyclopentane-1,3-dicarboxylic acid ( trans -ACPD). 3. A second form of
synchronous oscillation was activated by acute application of kainic acid (10
[mu]M), had dominant frequencies of 1-5 Hz, and was reversibly abolished by
DNQX. Low concentrations of domoic acid mimicked the effects of kainate, but
[alpha]-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) or
quisqualic acid did not, suggesting a role for the GluR5-7 and KA1-2 glutamate
receptor subunits. 4. Surgical isolation of cortical layers showed that
spontaneous NMDA receptor-dependent oscillations originated within layer 5
exclusively, but kainate receptor-dependent oscillations were uniquely
generated by neurons in layers 2/3. 5. Our results suggest that neocortical
neurons in layers 2/3 and layer 5 can independently generate two distinct
forms of rhythmic population activity, each dependent upon activation of a
different subtype of glutamate receptor.
Received 25 September 1995; accepted in final form 6 November 1995.
APS Manuscript Number J637-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95