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Characterization of striatal activity in conscious rats: Contribution of NMDA and AMPA/kainate receptors to both spontaneous and glutamate‐driven firing
Author(s) -
Sandstrom Michael I.,
Rebec George V.
Publication year - 2003
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/syn.10142
Subject(s) - cnqx , kainate receptor , ampa receptor , nmda receptor , glutamate receptor , chemistry , neuroscience , excitatory postsynaptic potential , striatum , nbqx , pharmacology , inhibitory postsynaptic potential , psychology , receptor , biology , biochemistry , dopamine
Single‐unit activity in the striatum of unrestrained, conscious rats was characterized by extracellular recording in combination with iontophoresis. To avoid the confounding effect of motor‐related changes in firing rate, measurements were restricted to periods when animals were at quiet rest. Recording electrodes were lowered stepwise through 4.0 mm of anterior striatum in 36 equal ventral movements of 111 μm to assess the ratio of spontaneously active vs. silent neurons. Spontaneous activity was assessed at each step followed by iontophoretic glutamate (GLU) application to expose silent neurons. Eleven such experimental sessions resulted in a total of 100 spontaneously active and 264 silent neurons, indicating that without overt movement the large majority (72.7%) of striatal cells are silent. Spontaneously active neurons, moreover, discharged at low rates (4.85 ± 0.85 spikes/s). In separate experiments, both the AMPA/kainate (CNQX: 6‐cyano‐2,3‐dihydroxy‐7‐nitro‐quinoxaline disodium salt) and NMDA (AP5: D‐(‐)‐2‐amino‐5‐phosphonovaleric acid) GLU‐receptor antagonists blocked the activity of most spontaneously active (83% CNQX, 69% AP5), and GLU‐stimulated silent (68% CNQX, 98% AP5) units. Collectively, our results are consistent with an overall low level of striatal activity in the absence of strong excitatory input. When neuronal activity is initiated, however, it appears that both NMDA and AMPA/kainate receptors are critical for maintaining continuous impulse activity. Synapse 47:91–100, 2003. © 2002 Wiley‐Liss, Inc.