In:
Neuroendocrinology, S. Karger AG, Vol. 77, No. 3 ( 2003), p. 162-176
Abstract:
Measurements of electrical activity and intracellular Ca 〈 sup 〉 2+ 〈 /sup 〉 levels were performed in perforated-patch clamped GH 〈 sub 〉 3 〈 /sub 〉 cells to determine the contribution of large-conductance calcium-activated K 〈 sup 〉 + 〈 /sup 〉 (BK) channels to action potential repolarization and size of the associated Ca 〈 sup 〉 2+ 〈 /sup 〉 oscillations. By examining the dependence of action potential (AP) duration on extracellular Ca 〈 sup 〉 2+ 〈 /sup 〉 levels in the presence and the absence of the specific BK channel blocker paxilline, it is observed that plateau-like action potentials are associated to low densities of paxilline-sensitive currents. Extracellular Ca 〈 sup 〉 2+ 〈 /sup 〉 increases or paxilline additions are not able to largely modify action potential duration in cells showing a reduced expression of BK currents. Furthermore, specific blockade of these currents with paxilline systematically elongates AP duration, but only under conditions in which short APs and/or prominent BK currents recorded under voltage-clamp mode are present in the same cells. Our data indicate that in GH 〈 sub 〉 3 〈 /sub 〉 cells, BK channels act primarily ending the action potential and suggest that by contributing to fine-tuning cellular electrical properties and hence intracellular Ca 〈 sup 〉 2+ 〈 /sup 〉 variations, BK channels may play an important role on time- and cell-dependent modulation of physiological outputs in adenohypophyseal cells.
Type of Medium:
Online Resource
ISSN:
0028-3835
,
1423-0194
Language:
English
Publisher:
S. Karger AG
Publication Date:
2003
detail.hit.zdb_id:
1483028-0
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