Biomaterial Database

Desensitizing glutamate receptors shape excitatory synaptic inputs to tiger salamander retinal ganglion cells. 1995

P D Lukasiewicz, and J E Lawrence, and T L Valentino

Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110-1093, USA.

AMPA/kainate (KA) receptors mediate a component of ganglion cell excitatory postsynaptic currents (EPSCs). We investigated whether desensitization at these receptors contribute to the shape of transient EPSCs in ON-OFF ganglion cells. Whole-cell, voltage-clamp recordings were made from ganglion cells in the retinal slice or in isolation. EPSCs were evoked by either stimulating the slice with light or puffing K+ at the outer plexiform layer (OPL). The AMPA/KA receptor-mediated component of the EPSCs was isolated by including NMDA receptor antagonists in the bath. Strychnine and picrotoxin blocked inhibitory inputs. In isolated ganglion cells, cyclothiazide (10 microM), which blocks desensitization in non-NMDA receptors, enhanced both the amplitude and the duration of currents evoked by puffs of AMPA or glutamate. EPSCs evoked by K(+)-puffs in the OPL were also enhanced by cyclothiazide (30 microM). When AMPA/KA receptors were blocked with NBQX (10 microM), no enhancement of the EPSCs by cyclothiazide was observed, indicating that cyclothiazide did not act presynaptically. Cyclothiazide also enhanced the amplitude and duration of both the ON and OFF light-evoked (L-) EPSCs recorded in ON-OFF ganglion cells. Current-voltage relationships showed the enhancement was not voltage dependent. When control and enhanced responses where normalized, it was observed that the rate of desensitization of both the ON and OFF L-EPSCs was decreased by cyclothiazide. Cyclothiazide selectively enhanced the AMPA/KA receptor-mediated component of ganglion cells EPSCs, suggesting that desensitization of AMPA/KA receptors shape transient L-EPSCs.

UI	MeSH Term	Description	Entries
D008027	Light	That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.	Light, Visible,Photoradiation,Radiation, Visible,Visible Radiation,Photoradiations,Radiations, Visible,Visible Light,Visible Radiations
D003981	Diazoxide	A benzothiadiazine derivative that is a peripheral vasodilator used for hypertensive emergencies. It lacks diuretic effect, apparently because it lacks a sulfonamide group.	Hyperstat,Proglycem
D004594	Electrophysiology	The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
D005971	Glutamates	Derivatives of GLUTAMIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the 2-aminopentanedioic acid structure.	Glutamic Acid Derivatives,Glutamic Acids,Glutaminic Acids
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
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
D001581	Benzothiadiazines	Heterocyclic compounds of a ring with SULFUR and two NITROGEN atoms fused to a BENZENE ring. Members inhibit SODIUM-POTASSIUM-CHLORIDE SYMPORTERS and are used as DIURETICS.
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
D017470	Receptors, Glutamate	Cell-surface proteins that bind glutamate and trigger changes which influence the behavior of cells. Glutamate receptors include ionotropic receptors (AMPA, kainate, and N-methyl-D-aspartate receptors), which directly control ion channels, and metabotropic receptors which act through second messenger systems. Glutamate receptors are the most common mediators of fast excitatory synaptic transmission in the central nervous system. They have also been implicated in the mechanisms of memory and of many diseases.	Excitatory Amino Acid Receptors,Glutamate Receptors,Receptors, Excitatory Amino Acid,Excitatory Amino Acid Receptor,Glutamate Receptor,Receptor, Glutamate