Biomaterial Database

The relationship between light-evoked synaptic excitation and spiking behaviour of salamander retinal ganglion cells. 1995

J S Diamond, and D R Copenhagen

Department of Physiology, University of California, San Francisco 94143-0730, USA.

1. Light-evoked input-output characteristics of ganglion cells in dark-adapted tiger salamander retina were studied in the slice preparation using patch-clamp techniques. Excitatory postsynaptic currents (EPSCs), isolated by blocking inhibitory inputs and evoked by a range of light stimulus intensities, were recorded under whole-cell voltage clamp. Spike responses, evoked by the same light intensities, were recorded extracellularly from the same cells using the cell-attached patch-clamp technique. 2. When N-methyl-D-aspartate (NMDA) receptor-mediated input was blocked by the competitive NMDA antagonist DL-2-amino-5-phosphonoheptanoate (AP7), light-evoked EPSC amplitude and peak firing rate were reduced at all light intensities. In both cases, the data obtained in the presence of AP7 scaled linearly to control data, indicating that NMDA and non-NMDA receptors are activated in the same proportions across the entire 2 log unit stimulus response range of these ganglion cells. 3. The relationship between light-evoked spike frequency and light-evoked EPSC amplitude was linear. The slope of the light-evoked synaptic current-spike frequency relationship was close to the slope of the injected current-spike frequency relationship, indicating that synaptic current and injected current drive spiking in a similar manner. The linearity of the synaptic current-spike frequency relationship was not compromised when NMDA input was blocked by AP7. 4. Light-evoked voltage responses, recorded under whole-cell current clamp, revealed that the average membrane potential during a spike response was depolarized only slightly with increased firing rate. Once the membrane potential surpassed spike threshold, it was maintained by the voltage-gated, spike-generating conductances at a depolarized plateau upon which action potentials were fired. The potential of this plateau varied only slightly with spike frequency. We conclude that the voltage control exerted by the spike-generating currents in ganglion cells prevents a substantial response-dependent decrease in the electrical driving force of the excitatory currents, obviating the need for the voltage-independent synaptic efficacy provided by the combination of NMDA and non-NMDA inputs.

UI	MeSH Term	Description	Entries
D009474	Neurons	The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.	Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D010775	Photic Stimulation	Investigative technique commonly used during ELECTROENCEPHALOGRAPHY in which a series of bright light flashes or visual patterns are used to elicit brain activity.	Stimulation, Photic,Visual Stimulation,Photic Stimulations,Stimulation, Visual,Stimulations, Photic,Stimulations, Visual,Visual Stimulations
D005074	Evoked Potentials, Visual	The electric response evoked in the cerebral cortex by visual stimulation or stimulation of the visual pathways.	Visual Evoked Response,Evoked Potential, Visual,Evoked Response, Visual,Evoked Responses, Visual,Potential, Visual Evoked,Potentials, Visual Evoked,Response, Visual Evoked,Responses, Visual Evoked,Visual Evoked Potential,Visual Evoked Potentials,Visual Evoked Responses
D000557	Ambystoma	A genus of the Ambystomatidae family. The best known species are the axolotl AMBYSTOMA MEXICANUM and the closely related tiger salamander Ambystoma tigrinum. They may retain gills and remain aquatic without developing all of the adult characteristics. However, under proper changes in the environment they metamorphose.	Amblystoma,Ambystoma tigrinum,Tiger Salamander,Amblystomas,Ambystomas,Salamander, Tiger,Salamanders, Tiger,Tiger Salamanders
D000596	Amino Acids	Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.	Amino Acid,Acid, Amino,Acids, Amino
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D012165	Retinal Ganglion Cells	Neurons of the innermost layer of the retina, the internal plexiform layer. They are of variable sizes and shapes, and their axons project via the OPTIC NERVE to the brain. A small subset of these cells act as photoreceptors with projections to the SUPRACHIASMATIC NUCLEUS, the center for regulating CIRCADIAN RHYTHM.	Cell, Retinal Ganglion,Cells, Retinal Ganglion,Ganglion Cell, Retinal,Ganglion Cells, Retinal,Retinal Ganglion Cell
D013569	Synapses	Specialized junctions at which a neuron communicates with a target cell. At classical synapses, a neuron's presynaptic terminal releases a chemical transmitter stored in synaptic vesicles which diffuses across a narrow synaptic cleft and activates receptors on the postsynaptic membrane of the target cell. The target may be a dendrite, cell body, or axon of another neuron, or a specialized region of a muscle or secretory cell. Neurons may also communicate via direct electrical coupling with ELECTRICAL SYNAPSES. Several other non-synaptic chemical or electric signal transmitting processes occur via extracellular mediated interactions.	Synapse
D015763	2-Amino-5-phosphonovalerate	The D-enantiomer is a potent and specific antagonist of NMDA glutamate receptors (RECEPTORS, N-METHYL-D-ASPARTATE). The L form is inactive at NMDA receptors but may affect the AP4 (2-amino-4-phosphonobutyrate; APB) excitatory amino acid receptors.	2-Amino-5-phosphonopentanoic Acid,2-Amino-5-phosphonovaleric Acid,2-APV,2-Amino-5-phosphonopentanoate,5-Phosphononorvaline,d-APV,dl-APV,2 Amino 5 phosphonopentanoate,2 Amino 5 phosphonopentanoic Acid,2 Amino 5 phosphonovalerate,2 Amino 5 phosphonovaleric Acid,5 Phosphononorvaline
D016194	Receptors, N-Methyl-D-Aspartate	A class of ionotropic glutamate receptors characterized by affinity for N-methyl-D-aspartate. NMDA receptors have an allosteric binding site for glycine which must be occupied for the channel to open efficiently and a site within the channel itself to which magnesium ions bind in a voltage-dependent manner. The positive voltage dependence of channel conductance and the high permeability of the conducting channel to calcium ions (as well as to monovalent cations) are important in excitotoxicity and neuronal plasticity.	N-Methyl-D-Aspartate Receptor,N-Methyl-D-Aspartate Receptors,NMDA Receptor,NMDA Receptor-Ionophore Complex,NMDA Receptors,Receptors, NMDA,N-Methylaspartate Receptors,Receptors, N-Methylaspartate,N Methyl D Aspartate Receptor,N Methyl D Aspartate Receptors,N Methylaspartate Receptors,NMDA Receptor Ionophore Complex,Receptor, N-Methyl-D-Aspartate,Receptor, NMDA,Receptors, N Methyl D Aspartate,Receptors, N Methylaspartate