Biomaterial Database

Transmission along and between rods in the tiger salamander retina. 1978

F S Werblin

1. The electrical pathways that couple the rods and that link the outer segments of the rods to the coupled network, were evaluated. Two separate micro-electrodes were inserted into the inner or outer segments of the same or neighbouring rods under visual control. Current was passed through one electrode, and the resulting potential recorded with the other. 2. The input resistance, measured at the inner or outer segment in a rod in the network, is strongly outward rectifying. It is typically near 40 Momega when the membrane is hyperpolarized 10 mV or more by extrinsic current, less than 10 Momega when the membrane is depolarized by 5 mV or more, and near 30 Momega at the no-current level. 3. When current is injected into the outer segment, the response in the inner segment is nearly identical with that at the outer segment, suggesting that the resistance coupling the segments is not high relative to the input resistance of the rod in the network. 4. Under voltage clamp the light response current for a rod in the network is of constant magnitude for potential levels between -80 and -20 mV. This suggests that there is little or no measurable light elicited conductance change associated with the response, possibly a consequence of coupling between rods. 5. The rod response increases with increasing diameter of a concentric test flash up to about 200 micron, or about 16 rod diameters. 6. When current is injected into one rod, the response in its immediate neighbours is between a quarter and one tenth that recorded in the injected rod for all potential levels in the injected rod. 7. The membrane time constant, measured in a rod in the network, is proportional to the voltage-dependent input resistance at 0.16 msec/Momega. With assumptions about the geometry of the rod network this represents a membrane capacitance of 1.5 muF/cm2. 8. The data can be approximated by a network model of square array. The model predicts that: the outer segment contributes less than half the current for the total rod response, the membrane resistance of an individual rod is greater than twice the measured input resistance for the rod in the network, near 60 Momega, and the coupling resistance for each arm of the network is about 4 times the individual rod resistance, near 240 Momega.

UI	MeSH Term	Description	Entries
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D008959	Models, Neurological	Theoretical representations that simulate the behavior or activity of the neurological system, processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.	Neurologic Models,Model, Neurological,Neurologic Model,Neurological Model,Neurological Models,Model, Neurologic,Models, Neurologic
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
D010786	Photoreceptor Cells	Specialized cells that detect and transduce light. They are classified into two types based on their light reception structure, the ciliary photoreceptors and the rhabdomeric photoreceptors with MICROVILLI. Ciliary photoreceptor cells use OPSINS that activate a PHOSPHODIESTERASE phosphodiesterase cascade. Rhabdomeric photoreceptor cells use opsins that activate a PHOSPHOLIPASE C cascade.	Ciliary Photoreceptor Cells,Ciliary Photoreceptors,Rhabdomeric Photoreceptor Cells,Rhabdomeric Photoreceptors,Cell, Ciliary Photoreceptor,Cell, Photoreceptor,Cell, Rhabdomeric Photoreceptor,Cells, Ciliary Photoreceptor,Cells, Photoreceptor,Cells, Rhabdomeric Photoreceptor,Ciliary Photoreceptor,Ciliary Photoreceptor Cell,Photoreceptor Cell,Photoreceptor Cell, Ciliary,Photoreceptor Cell, Rhabdomeric,Photoreceptor Cells, Ciliary,Photoreceptor Cells, Rhabdomeric,Photoreceptor, Ciliary,Photoreceptor, Rhabdomeric,Photoreceptors, Ciliary,Photoreceptors, Rhabdomeric,Rhabdomeric Photoreceptor,Rhabdomeric Photoreceptor Cell
D004553	Electric Conductivity	The ability of a substrate to allow the passage of ELECTRONS.	Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
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
D014562	Urodela	An order of the Amphibia class which includes salamanders and newts. They are characterized by usually having slim bodies and tails, four limbs of about equal size (except in Sirenidae), and a reduction in skull bones.	Amphiuma,Caudata,Eel, Congo,Salamanders,Congo Eel,Congo Eels,Eels, Congo,Salamander
D066298	In Vitro Techniques	Methods to study reactions or processes taking place in an artificial environment outside the living organism.	In Vitro Test,In Vitro Testing,In Vitro Tests,In Vitro as Topic,In Vitro,In Vitro Technique,In Vitro Testings,Technique, In Vitro,Techniques, In Vitro,Test, In Vitro,Testing, In Vitro,Testings, In Vitro,Tests, In Vitro,Vitro Testing, In