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The Journal of Neuroscience, August 1, 2001, 21(15):5397-5405
Gap Junctions Mediate Electrical Signaling and
Ensuing Cytosolic Ca2+ Increases between Chromaffin
Cells in Adrenal Slices: A Role in Catecholamine Release
Agnès O.
Martin,
Marie-Noëlle
Mathieu,
Claude
Chevillard, and
Nathalie C.
Guérineau
Institut National de la Santé et de la Recherche
Médicale (INSERM) U469, Centre National de la Recherche
Scientifique/INSERM de Pharmacologie et d'Endocrinologie, 34094 Montpellier CEDEX 5, France
In adrenal chromaffin cells, a rise in cytosolic calcium
concentration ([Ca2+]i) is a key event in the
triggering of catecholamine exocytosis after splanchnic nerve
activation. Action potential- or nicotine-induced [Ca2+]i transients are well described in
individual chromaffin cells, but whether they remain spatially confined
to the stimulated cell or propagate to adjacent cells is not yet known.
To address this issue, the spatiotemporal organization of electrical
and associated Ca2+ events between chromaffin cells
was investigated using the patch-clamp technique and real-time confocal
imaging in rat acute adrenal slices. Spontaneous or electrically evoked
action potential-driven [Ca2+]i transients were
simultaneously detected in neighboring cells. This was likely
attributable to gap junction-mediated electrotonic communication, as
shown by (1) the bidirectional reflection of voltage changes monitored
between cell pairs, (2) Lucifer yellow (LY) diffusion between cells
exhibiting spontaneous synchronized [Ca2+]i
transients, and (3) the reduction of LY diffusion using the uncoupling
agent carbenoxolone. Furthermore, transcripts encoding two connexins
(Cx36 and Cx43) were found in single chromaffin cells. This gap
junctional coupling was activated after a synaptic-like application of
nicotine that mediated synchronous multicellular [Ca2+]i increases. In addition, nicotinic
stimulation of a single cell triggered catecholamine release in coupled
cells, as shown by amperometric detection of secretory events.
Functional coupling between chromaffin cells in situ may
represent an efficient complement to synaptic transmission to amplify
catecholamine release after synaptic stimulation of a single excited
chromaffin cell.
Key words:
electrical propagation; gap junction coupling; rat
adrenal slices; chromaffin cells; real-time confocal microscopy; catecholamine release; nicotinic stimulation
Copyright © 2001 Society for Neuroscience 0270-6474/01/21155397-09$05.00/0
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