Non-NMDA-mediated transmission of somatosensory-evoked potentials in the rat thalamus

Somatosensory-evoked potentials (SEPs) were recorded from the somatosensory cortex of pentobarbital-anesthetized rats, in response to single electrical stimulation of the contralateral forelimb. The effects of microapplication of the selective N-methyl-D-aspartate (NMDA) antagonist, (-)-2-Amino-7-phosphonoheptanoate (AP7), and of the specific non-NMDA antagonist, 6,7-Dinitro-quinoxaline-2,3-dione (DNQX), in the ventrobasal thalamic nucleus on the amplitudes and latencies of cortical potentials were measured. The injection of DNQX resulted in a decrease in amplitude and an increase in the latency of cortical SEPs. These effects were a) dose dependent over the range 0.1 to 1.0 nmol, b) specific for non-NMDA receptors, and c) site specific. In contrast, microapplications of AP7 did not affect the SEPs. The present findings support the hypothesis that non-NMDA receptors in the ventrobasal thalamic nucleus are involved in the transmission of cortical SEPs.