scholarly journals Effects of L-glutamate on the anomalous rectifier potassium current in horizontal cells of Carassius auratus retina.

1985 ◽  
Vol 358 (1) ◽  
pp. 169-182 ◽  
Author(s):  
A Kaneko ◽  
M Tachibana
Keyword(s):  
Potassium Current ◽  
Carassius Auratus ◽  
Horizontal Cells ◽  
Anomalous Rectifier

Ionic currents of cultured horizontal cells isolated from white perch retina

1986 ◽  
Vol 55 (3) ◽  
pp. 499-513 ◽  
Author(s):  
E. M. Lasater
Keyword(s):  
White Perch ◽  
Slow Component ◽  
Outward Current ◽  
Ionic Currents ◽  
Cell Types ◽  
Horizontal Cells ◽  
Inward Current ◽  
Whole Cell Patch Clamp ◽  
Anomalous Rectifier ◽  
K Concentration

Horizontal cells from the retinas of white perch were isolated and maintained in cell culture for 3 days to 3 wk. Four morphologically distinct types of horizontal cells could be identified in culture and were labeled types H1, H2, H3, and H4. Whole-cell patch-clamp techniques were used to study the ionic currents present in the four cell types. In all cells, depolarizing commands above threshold elicited a fast-inward current followed by an outward current. The fast-inward current was abolished by tetrodotoxin (TTX) or 0 Na+ Ringer's, indicating the current was carried by Na+. In H1, H2, and H3 cells, the outward current, carried by K+, consisted of two components: a transient current (IA), blockable with 4-aminopyridine (4-AP), tetraethylammonium (TEA), or intracellular cesium and a sustained current that could be blocked with TEA. The H4 cell had only the sustained current. An inward rectifying K+ current (anomalous rectifier) was observed in the four cell types. The current was sensitive to the extracellular K+ concentration. Its activation showed two components: an instantaneous component and a slower component. The slow component becomes faster with greater hyperpolarizations. The four cell types possessed a small, sustained Ca2+ current that, under normal conditions, was masked by the inward Na+ current and outward K+ currents.

scholarly journals Mitochondrial KATP channels stabilize intracellular Ca2+ during hypoxia in retinal horizontal cells of goldfish (Carassius auratus)

2021 ◽  
Author(s):  
Michael W. Country ◽  
Michael G. Jonz
Keyword(s):  
Carassius Auratus ◽  
Katp Channels ◽  
Horizontal Cells ◽  
Hypoxia Tolerance ◽  
Dependent Manner ◽  
Cellular Mechanisms ◽  
Atp Production ◽  
Goldfish Carassius Auratus ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Mitochondrial Katp Channels

Neurons of the retina require oxygen to survive. In hypoxia, neuronal ATP production is impaired, ATP-dependent ion pumping is reduced, transmembrane ion gradients are dysregulated, and [Ca2+]i increases enough to trigger excitotoxic cell death. Central neurons of the common goldfish (Carassius auratus) are hypoxia-tolerant, but little is known about how goldfish retinas withstand hypoxia. To study the cellular mechanisms of hypoxia tolerance, we isolated retinal interneurons (horizontal cells; HCs), and measured intracellular Ca2+ concentration ([Ca2+]i) with Fura-2. Goldfish HCs maintained [Ca2+]i throughout 1 h of hypoxia, whereas [Ca2+]i increased irreversibly in HCs of the hypoxia-sensitive rainbow trout (Oncorhynchus mykiss) with just 20 min of hypoxia. Our results suggest mitochondrial ATP-dependent K+ channels (mKATP) are necessary to stabilize [Ca2+]i throughout hypoxia. In goldfish HCs, [Ca2+]i increased when mKATP was blocked with glibenclamide or 5-HD, whereas an mKATP agonist (diazoxide) prevented [Ca2+]i from increasing in hypoxia in trout HCs. We showed that hypoxia protects goldfish HCs via mKATP channels. Glycolytic inhibition with 2-deoxyglucose increased [Ca2+]i, which was rescued by hypoxia in an mKATP-dependent manner. We found no evidence of plasmalemmal KATP channels in patch-clamp experiments. Instead, we confirmed the involvement of KATP in mitochondria with TMRE imaging, as hypoxia rapidly (<5 min) depolarized mitochondria in an mKATP-sensitive manner. We conclude that mKATP channels initiate a neuroprotective pathway in goldfish HCs to maintain [Ca2+]i and avoid excitotoxicity in hypoxia. This model provides novel insight into the cellular mechanisms of hypoxia tolerance in the retina.

Sustained and transient potassium currents of cultured horizontal cells isolated from white bass retina

1990 ◽  
Vol 64 (6) ◽  
pp. 1758-1766 ◽  
Author(s):  
J. M. Sullivan ◽  
E. M. Lasater
Keyword(s):  
Potassium Current ◽  
Potassium Currents ◽  
Calcium Currents ◽  
Horizontal Cells ◽  
Delayed Rectifier ◽  
White Bass ◽  
A Value ◽  
Outward Potassium Current ◽  
A Current

1. Horizontal cells (HCs) are second-order neurons in the retina that receive direct photoreceptor input. They rest at around -20 mV in the dark, because of the continuous release of neurotransmitter from photoreceptors. HCs respond to light with graded hyperpolarizations, which can reach -70 to -80 mV in the presence of very bright stimuli. 2. HCs from the retinas of white bass were isolated and maintained in culture. Potassium currents in three morphological types of HCs--H1, H2, and H4--were studied in culture with whole-cell, patch-clamp techniques, when sodium and calcium currents were blocked. 3. A transient outward potassium current (IA), with many characteristics of the A-current, was found in all H2s and H4s but only occasionally in H1s. The threshold for activation of this current was around -40 mV, a value more depolarized than usual for the A-current. The peak IA was typically smaller than 300 pA when the membrane was stepped from a holding potential of -70 mV to a command potential of -10 mV, the upper limit of the in vivo range of HC membrane potentials. Steady-state inactivation is expected to reduce the magnitude of IA in vivo. 4. A sustained outward potassium current (IK) was found in all types of HCs. This sustained potassium current did not activate until the membrane was stepped to potentials above -10 mV, a value much more depolarized than those reported for the delayed rectifier current in other neurons. As a result, IK is absent over the in vivo operating range of these cells. 5. No calcium-dependent potassium current was found in any cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Sign in / Sign up

Export Citation Format

Share Document