title: N-methyl-D-aspartate receptors contribute to excitatory postsynaptic potentials of cat lateral geniculate neurons recorded in thalamic slices.
abstract: Neurons of the cat's dorsal lateral geniculate nucleus were recorded intracellularly to study the contribution of N-methyl-D-aspartate (NMDA) receptors to excitatory postsynaptic potentials (EPSPs) and low-threshold calcium spikes. EPSPs were evoked by stimulation of retinogeniculate axons in the optic tract and/or corticogeniculate axons in the optic radiations; EPSPs from both sources were similar. These EPSPs had one or two components, and the second component had several characteristics of NMDA receptor-mediated events. For example, EPSP amplitude decreased when neurons were hyperpolarized and increased when stimulus frequency was increased; these EPSPs could also be blocked reversibly by application of the selective NMDA receptor antagonist DL-2-amino-5-phosphonovaleric acid (APV). We also studied the influence of NMDA receptors on low-threshold calcium spikes, which are large, voltage- and calcium-dependent depolarizations that are often accompanied by high-frequency action potential discharge. APV blocked synaptically activated low-threshold calcium spikes, but APV had no effect on low-threshold calcium spikes that were elicited by current injection. Therefore, APV does not appear to have a direct effect on the T-type calcium channel that is involved in generation of low-threshold calcium spikes. The voltage and frequency dependence of the NMDA receptor-mediated component of the EPSPs, as well as its ability to trigger low-threshold calcium spikes, provide for complex signal processing in the lateral geniculate nucleus.
authors.affiliation: Howard Hughes Medical Institute, State University of New York, Stony Brook, NY 11794-5230.
authors.forename: H E
authors.initials: HE
authors.lastname: Scharfman
authors.forename: S M
authors.initials: SM
authors.lastname: Lu
authors.forename: W
authors.initials: W
authors.lastname: Guido
authors.forename: P R
authors.initials: PR
authors.lastname: Adams
authors.forename: S M
authors.initials: SM
authors.lastname: Sherman
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D001369:Axons / Q000502:physiology; D002118:Calcium / Q000494:pharmacology; D002415:Cats; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000187:drug effects; D005829:Geniculate Bodies / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials; D016202:N-Methylaspartate; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000502:physiology*; D013569:Synapses / Q000502:physiology*; D013788:Thalamus / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology
chemical_list: D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D001224:Aspartic Acid; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate; D002118:Calcium