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Título
Ionic currents in dispersed chemoreceptor cells of the mammalian carotid body
Año del Documento
1989
Editorial
The Rockefeller University Press
Descripción
Producción Científica
Documento Fuente
Journal of General Physiology, 1989, vol. 93. p. 979-999
Résumé
Ionic currents of enzymatically dispersed type 1 and type 11 cells of the carotid body have been studied using the whole cell variant of the patch-clamp technique. Type 11 cells only have a tiny, slowly activating outward potassium cur rent. By contrast, in every type 1 chemoreceptor cell studied we found (a) sodium,
(b) calcium, and (e) potassium currents. (a) The sodium current has a fast activation time course and an activation threshold at --40 mV. At ali voltages inactivation follows a single exponential time course. The time constant of inactivation is 0.67 ms at O mV. Half steady state inactivation occurs at a membrane potential of
--50 mV. (b) The calcium current is almost totally abolished when most of the extemal calcium is replaced by magnesium. The activation threshold of this cur rent is at --40 mV and at O mV it reaches a peak amplitude in 6-8 ms. The calcium current inactivates very slowly and only decreases to 27% of the maximal value at the end of 300-ms pulses to 40 mV. The calcium current was about two times larger when barium ions were used as charge carriers instead of calcium ions. Barium ions also shifted 15-20 mV toward negative voltages the conductance vs. voltage curve. Deactivation kinetics of the calcium current follows a biphasic time course well fitted by the sum of two exponentials. At -80 mV the slow com ponent has a time constant of 1.3 ± 0.4 ms whereas the fast component, with an amplitude about 20 times larger than the slow component, has a time constant of
0.16 ± 0.03 ms. These results suggest that type 1 cells have predominantly fast deactivating calcium channels. The slow component of the tails may represent the activity of a small population of slowly deactivating calcium channels, although other possibilities are considered. (e) Potassium current seems to be mainly due to the activity of voltage-dependent potassium channels, but a small percentage of calcium-activated channels may also exist. This current activates slowly, reaches a peak amplitude in 5-1O ms, and thereafter slowly inactivates. Inactivation is almost complete in 250-300 ms. The potassium current is reversibly blocked by tetraeth ylammonium. Under current-clamp conditions type I cells can spontaneously fire large action potentials.
Palabras Clave
Cuerpo carotídeo
Quimiorreceptores
Carotid body
Chemoreceptors
ISSN
0022-1295
Revisión por pares
SI
Version del Editor
Propietario de los Derechos
© 1989 The Rockefeller University Press
Idioma
eng
Derechos
openAccess
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