Biomaterial Database

Calcium currents in hair cells isolated from the cochlea of the chick. 1990

P A Fuchs, and M G Evans, and B W Murrow

Department of Physiology, University of Colorado Health Sciences Center, Denver 80262.

1. Calcium currents were characterized in tall hair cells isolated from the chick's cochlea to determine what types of Ca2+ channels existed and if these varied in cells with differing voltage responses to current injection. 2. Whole-cell, tight-seal recordings showed that the current-voltage relation of cochlear hair cells of the chick was dominated by K+ current. However, when outward K+ current was blocked it was found that all hair cells had a smaller, maintained inward current. 3. This inward current was a Ca2+ current since it required Ca2+ in the external medium, could also be carried by Ba2+, and was blocked reversibly by 5 mM-Co2+ and by Ni2+ and Cd2+ at micromolar concentrations. The Ca2+ channels were opened at membrane potentials positive to -50 mV, and the current was maximal near 0 mV. 4. The dihydropyridine BayK8644 (0.5 microM) produced a voltage-dependent increase of inward current. Ten micromolar nifedipine partially blocked the inward current. The outward Ca2(+)-activated K+ current was also reduced in the presence of 10 microM-nifedipine. These effects of dihydropyridines were completely reversible. 5. The Ca2+ current had rapid activation kinetics, reaching steady-state levels within 1 ms. If all outward currents were completely blocked the Ca2+ current showed no inactivation during depolarization lasting 200 ms. 6. No differences in voltage activation range, pharmacology, or kinetics of the Ca2+ current were found in tall hair cells from apical and basal regions of the cochlea. This is in contrast to the marked differences in K+ currents amongst cells from these two widely separated regions of the cochlea.

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
D009543	Nifedipine	A potent vasodilator agent with calcium antagonistic action. It is a useful anti-anginal agent that also lowers blood pressure.	Adalat,BAY-a-1040,Bay-1040,Cordipin,Cordipine,Corinfar,Fenigidin,Korinfar,Nifangin,Nifedipine Monohydrochloride,Nifedipine-GTIS,Procardia,Procardia XL,Vascard,BAY a 1040,BAYa1040,Bay 1040,Bay1040,Monohydrochloride, Nifedipine,Nifedipine GTIS
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D002586	Cesium	A member of the alkali metals. It has an atomic symbol Cs, atomic number 55, and atomic weight 132.91. Cesium has many industrial applications, including the construction of atomic clocks based on its atomic vibrational frequency.	Caesium,Caesium-133,Cesium-133,Caesium 133,Cesium 133
D002645	Chickens	Common name for the species Gallus gallus, the domestic fowl, in the family Phasianidae, order GALLIFORMES. It is descended from the red jungle fowl of SOUTHEAST ASIA.	Gallus gallus,Gallus domesticus,Gallus gallus domesticus,Chicken
D004553	Electric Conductivity	The ability of a substrate to allow the passage of ELECTRONS.	Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
D006198	Hair Cells, Auditory	Sensory cells in the organ of Corti, characterized by their apical stereocilia (hair-like projections). The inner and outer hair cells, as defined by their proximity to the core of spongy bone (the modiolus), change morphologically along the COCHLEA. Towards the cochlear apex, the length of hair cell bodies and their apical STEREOCILIA increase, allowing differential responses to various frequencies of sound.	Auditory Hair Cells,Cochlear Hair Cells,Auditory Hair Cell,Cell, Cochlear Hair,Cells, Cochlear Hair,Cochlear Hair Cell,Hair Cell, Auditory,Hair Cell, Cochlear,Hair Cells, Cochlear
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
D001464	Barium	An element of the alkaline earth group of metals. It has an atomic symbol Ba, atomic number 56, and atomic weight 138. All of its acid-soluble salts are poisonous.
D001498	3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester	A dihydropyridine derivative, which, in contrast to NIFEDIPINE, functions as a calcium channel agonist. The compound facilitates Ca2+ influx through partially activated voltage-dependent Ca2+ channels, thereby causing vasoconstrictor and positive inotropic effects. It is used primarily as a research tool.	BK-8644,Bay R5417,Bay-K-8644,Bay-K-8644, (+)-Isomer,Bay-K-8644, (+-)-Isomer,Bay-K-8644, (-)-Isomer,Bay-K8644,Bay-R-5417,BK 8644,BK8644,Bay K 8644,Bay K8644,Bay R 5417,BayK8644,BayR5417,R5417, Bay