Biomaterial Database

Synaptic transmission at N-methyl-D-aspartate receptors in the proximal retina of the mudpuppy. 1985

P D Lukasiewicz, and J S McReynolds

The effects of excitatory amino acid analogues and antagonists on retinal ganglion cells were studied using intracellular recording in the superfused mudpuppy eyecup preparation. Aspartate, glutamate, quisqualate (QA), kainate (KA) and N-methylaspartate (NMA) caused depolarization and decreased input resistance in all classes of ganglion cells. The order of sensitivity was QA greater than or equal to KA greater than NMA greater than aspartate greater than or equal to glutamate. All of these agonists were effective when transmitter release was blocked with 4 mM-Co2+ or Mn2+, indicating that they acted at receptor sites on the ganglion cells. At a concentration of 250 microM, 2-amino-5-phosphonovalerate (APV) blocked the responses of all ganglion cells to NMA, but not to QA or KA, indicating that NMA acts at different receptor sites from QA or KA. Responses to bath-applied aspartate and glutamate were reduced slightly or not at all in the presence of APV, indicating that they were acting mainly at non-NMDA (N-methyl-D-aspartate) receptors. In all ganglion cells 250 microM-APV strongly suppressed the sustained responses driven by the 'on'-pathway but not those driven by the 'off'-pathway. In most on-off ganglion cells the transient excitatory responses at 'light on' and 'light off' were not reduced by 500 microM-APV. APV-resistant transient excitatory responses were also present in some on-centre ganglion cells. APV did not block the transient inhibitory responses in any class of ganglion cells. At concentrations which blocked the sustained responses of ganglion cells, APV did not affect the sustained responses of bipolar cells, indicating that it acted at sites which were post-synaptic to bipolar cells. The simplest interpretation of these results is that the transmitter released by depolarizing bipolar cells acts at NMDA receptors on sustained depolarizing amacrine and ganglion cells. It may act at non-NMDA receptors at synapses which produce transient excitatory responses, but this could not be proved. The transmitter released by hyperpolarizing bipolar cells does not appear to act at NMDA receptors on any post-synaptic cells.

UI	MeSH Term	Description	Entries
D009337	Necturus	A genus of the Proteidae family with five recognized species, which inhabit the Atlantic and Gulf drainages.	Mudpuppy,Mudpuppies
D009435	Synaptic Transmission	The communication from a NEURON to a target (neuron, muscle, or secretory cell) across a SYNAPSE. In chemical synaptic transmission, the presynaptic neuron releases a NEUROTRANSMITTER that diffuses across the synaptic cleft and binds to specific synaptic receptors, activating them. The activated receptors modulate specific ion channels and/or second-messenger systems in the postsynaptic cell. In electrical synaptic transmission, electrical signals are communicated as an ionic current flow across ELECTRICAL SYNAPSES.	Neural Transmission,Neurotransmission,Transmission, Neural,Transmission, Synaptic
D011956	Receptors, Cell Surface	Cell surface proteins that bind signalling molecules external to the cell with high affinity and convert this extracellular event into one or more intracellular signals that alter the behavior of the target cell (From Alberts, Molecular Biology of the Cell, 2nd ed, pp693-5). Cell surface receptors, unlike enzymes, do not chemically alter their ligands.	Cell Surface Receptor,Cell Surface Receptors,Hormone Receptors, Cell Surface,Receptors, Endogenous Substances,Cell Surface Hormone Receptors,Endogenous Substances Receptors,Receptor, Cell Surface,Surface Receptor, Cell
D012160	Retina	The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent.	Ora Serrata
D000200	Action Potentials	Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.	Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential
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
D001224	Aspartic Acid	One of the non-essential amino acids commonly occurring in the L-form. It is found in animals and plants, especially in sugar cane and sugar beets. It may be a neurotransmitter.	(+-)-Aspartic Acid,(R,S)-Aspartic Acid,Ammonium Aspartate,Aspartate,Aspartate Magnesium Hydrochloride,Aspartic Acid, Ammonium Salt,Aspartic Acid, Calcium Salt,Aspartic Acid, Dipotassium Salt,Aspartic Acid, Disodium Salt,Aspartic Acid, Hydrobromide,Aspartic Acid, Hydrochloride,Aspartic Acid, Magnesium (1:1) Salt, Hydrochloride, Trihydrate,Aspartic Acid, Magnesium (2:1) Salt,Aspartic Acid, Magnesium-Potassium (2:1:2) Salt,Aspartic Acid, Monopotassium Salt,Aspartic Acid, Monosodium Salt,Aspartic Acid, Potassium Salt,Aspartic Acid, Sodium Salt,Calcium Aspartate,Dipotassium Aspartate,Disodium Aspartate,L-Aspartate,L-Aspartic Acid,Magnesiocard,Magnesium Aspartate,Mg-5-Longoral,Monopotassium Aspartate,Monosodium Aspartate,Potassium Aspartate,Sodium Aspartate,Aspartate, Ammonium,Aspartate, Calcium,Aspartate, Dipotassium,Aspartate, Disodium,Aspartate, Magnesium,Aspartate, Monopotassium,Aspartate, Monosodium,Aspartate, Potassium,Aspartate, Sodium,L Aspartate,L Aspartic Acid
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