Biomaterial Database

Na(+)-activated K+ channels and voltage-evoked ionic currents in brain stem and parasympathetic neurones of the chick. 1991

S E Dryer

Department of Biological Science, Florida State University, Tallahassee 32306-3050.

1. Patch-clamp and computer-modelling techniques were used to study the activation of Na(+)-activated K+ channels (IK(Na] in dissociated neurones from the embryonic chick ciliary ganglion and the embryonic chick brain stem. 2. Numerical solutions of diffusion equations suggested that Na+ accumulation as a result of Na+ influx through voltage-sensitive Na+ channels (INa) is insufficient to allow for alteration in the gating of IK(Na) channels. 3. Whole-cell recordings using two independent micropipettes were made from chick ciliary-ganglion neurones. These showed that transient outward currents were present only when there were clear indications of incomplete voltage clamp. 4. Single-electrode whole-cell recordings from ciliary-ganglion neurones showed that transient tetrodotoxin (TTX)-sensitive outward currents were present, but only when partial TTX blockade produced significant alterations in the kinetics of INa. In cells that were properly voltage clamped, there was no effect of TTX on the kinetics of INa or on voltage-evoked outward currents. 5. Examination of the relationship between peak INa and the command potential showed that transient outward currents were only present in neurones that showed sharp deviations from the behaviour expected of a cell that is adequately voltage clamped. Transient outward currents were not present in cells that were adequately voltage clamped. 6. Application of TTX to isolated outside-out patches obtained from ciliary ganglion neurones eliminated voltage-evoked inward currents but had no effect on outward currents. 7. Isolated inside-out patches obtained from ciliary-ganglion neurones did not contain IK(Na) channels. These patches usually contained Ca(2+)-activated K+ channels (IK(Ca] with a unitary conductance of around 200 pS when [K+]o = 150 mM and [K+]i = 75 mM. 8. Two-electrode whole-cell recordings from cultured brain stem neurones showed that transient outward currents were present only when there were clear indications of incomplete voltage clamp. 9. Application of TTX caused blockade of inward but not outward currents in brain stem neurones voltage clamped with a single whole-cell pipette. TTX had no effect on the kinetics of INa. Application of TTX to outside-out patches isolated from the same cells blocked only the inward currents. 10. Isolated inside-out patches obtained from brain stem neurones contained IK(Na) channels that could be activated by exposure of the cytoplasmic face of the patch membrane to 75 mM-Na+. These channels had a predominant conductance state of around 100 pS when [K+]o = 150 mM and [K+]i = 75 mM. The IK(Na) channels were not activated by 1 mM-Ca2+.(ABSTRACT TRUNCATED AT 400 WORDS)

UI	MeSH Term	Description	Entries
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
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
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D001933	Brain Stem	The part of the brain that connects the CEREBRAL HEMISPHERES with the SPINAL CORD. It consists of the MESENCEPHALON; PONS; and MEDULLA OBLONGATA.	Brainstem,Truncus Cerebri,Brain Stems,Brainstems,Cerebri, Truncus,Cerebrus, Truncus,Truncus Cerebrus
D002478	Cells, Cultured	Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.	Cultured Cells,Cell, Cultured,Cultured Cell
D002642	Chick Embryo	The developmental entity of a fertilized chicken egg (ZYGOTE). The developmental process begins about 24 h before the egg is laid at the BLASTODISC, a small whitish spot on the surface of the EGG YOLK. After 21 days of incubation, the embryo is fully developed before hatching.	Embryo, Chick,Chick Embryos,Embryos, Chick
D003198	Computer Simulation	Computer-based representation of physical systems and phenomena such as chemical processes.	Computational Modeling,Computational Modelling,Computer Models,In silico Modeling,In silico Models,In silico Simulation,Models, Computer,Computerized Models,Computer Model,Computer Simulations,Computerized Model,In silico Model,Model, Computer,Model, Computerized,Model, In silico,Modeling, Computational,Modeling, In silico,Modelling, Computational,Simulation, Computer,Simulation, In silico,Simulations, Computer
D005726	Ganglia, Parasympathetic	Ganglia of the parasympathetic nervous system, including the ciliary, pterygopalatine, submandibular, and otic ganglia in the cranial region and intrinsic (terminal) ganglia associated with target organs in the thorax and abdomen.	Parasympathetic Ganglia,Ciliary Ganglion,Ganglion, Parasympathetic,Otic Ganglia,Pterygopalatine Ganglia,Submandibular Ganglia,Ciliary Ganglions,Ganglia, Otic,Ganglia, Pterygopalatine,Ganglia, Submandibular,Ganglias, Otic,Ganglias, Pterygopalatine,Ganglias, Submandibular,Ganglion, Ciliary,Ganglions, Ciliary,Otic Ganglias,Parasympathetic Ganglion,Pterygopalatine Ganglias,Submandibular Ganglias
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
D012964	Sodium	A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.	Sodium Ion Level,Sodium-23,Ion Level, Sodium,Level, Sodium Ion,Sodium 23