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Titolo:
Calcium-activated potassium current clamps the dark potential of vertebrate rods
Autore:
Moriondo, A; Pelucchi, B; Rispoli, G;
Indirizzi:
Univ Ferrara, Dept Biol, I-44100 Ferrara, Italy Univ Ferrara Ferrara Italy I-44100 ra, Dept Biol, I-44100 Ferrara, Italy
Titolo Testata:
EUROPEAN JOURNAL OF NEUROSCIENCE
fascicolo: 1, volume: 14, anno: 2001,
pagine: 19 - 26
SICI:
0953-816X(200107)14:1<19:CPCCTD>2.0.ZU;2-8
Fonte:
ISI
Lingua:
ENG
Soggetto:
HAIR-CELLS; K+ CHANNELS; CONE PHOTORECEPTORS; HIPPOCAMPAL-NEURONS; AMBYSTOMA-TIGRINUM; TIGER SALAMANDER; LIGHT RESPONSE; INNER SEGMENT; CONDUCTANCE; MUSCLE;
Keywords:
charybdotoxin; ionic channels; KCa; photoreceptor; salamander;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
28
Recensione:
Indirizzi per estratti:
Indirizzo: Pelucchi, B Univ Ferrara, Dept Biol, Via L Borsari 46, I-44100 Ferrara, Italy Univ Ferrara Via L Borsari 46 Ferrara Italy I-44100 ra, Italy
Citazione:
A. Moriondo et al., "Calcium-activated potassium current clamps the dark potential of vertebrate rods", EUR J NEURO, 14(1), 2001, pp. 19-26

Abstract

Vertebrate photoreceptors respond to light with a graded hyperpolarizationfrom a membrane potential in the dark of approximate to -35 mV. The present work investigates the physiological role of the Ca2+-activated K+ currentin the photovoltage generation in mechanically isolated rods from salamander retina. Membrane current or voltage in isolated rods was recorded from light- and dark-adapted rods under voltage- or current-clamp conditions, respectively. In light-adapted rods of the salamander, selective blockade of Ca2+-activated K+ channels by means of charybdotoxin depolarized the plasma membrane of current-clamped rods by approximate to 30 mV, from a resting potential of approximate to -35 mV. A similar depolarization was observed if external Ca2+ (1 mm) was substituted with Ba2+ or Sr2+. Under control conditions, the injection of currents of increasing amplitude (up to -100 pA, tomimic the current entering the rod outer segment) could not depolarize themembrane potential beyond a saturating value of approximate to -20 mV. However, in the presence of charybdotoxin, rods depolarized up to +20 mV. In experiments with dark-adapted current-clamped rods, charybdotoxin perfusion lead to transient depolarizations up to 0 mV and steady-state depolarizations of approximate to 5 mV above the dark resting potential. Finally, the recovery phase of the voltage response to a flash of light in the presence ofcharybdotoxin showed a transient overshoot of the membrane potential. It was concluded that Ca2+-activated K+ current is necessary for clamping the rod photovoltage to values close to the dark potential, thus allowing faithful single photon detection and correct synaptic transmission.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 25/11/20 alle ore 18:23:44