Document Detail


Spontaneous ryanodine-receptor-dependent Ca2+-activated K+ currents and hyperpolarizations in rat medial preoptic neurons.
MedLine Citation:
PMID:  20457857     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The aim of the present study was to clarify the identity of slow spontaneous currents, the underlying mechanism and possible role for impulse generation in neurons of the rat medial preoptic nucleus (MPN). Acutely dissociated neurons were studied with the perforated patch-clamp technique. Spontaneous outward currents, at a frequency of approximately 0.5 Hz and with a decay time constant of approximately 200 ms, were frequently detected in neurons when voltage-clamped between approximately -70 and -30 mV. The dependence on extracellular K(+) concentration was consistent with K(+) as the main charge carrier. We concluded that the main characteristics were similar to those of spontaneous miniature outward currents (SMOCs), previously reported mainly for muscle fibers and peripheral nerve. From the dependence on voltage and from a pharmacological analysis, we concluded that the currents were carried through small-conductance Ca(2+)-activated (SK) channels, of the SK3 subtype. From experiments with ryanodine, xestospongin C, and caffeine, we concluded that the spontaneous currents were triggered by Ca(2+) release from intracellular stores via ryanodine receptor channels. An apparent voltage dependence was explained by masking of the spontaneous currents as a consequence of steady SK-channel activation at membrane potentials > -30 mV. Under current-clamp conditions, corresponding transient hyperpolarizations occasionally exceeded 10 mV in amplitude and reduced the frequency of spontaneous impulses. In conclusion, MPN neurons display spontaneous hyperpolarizations triggered by Ca(2+) release via ryanodine receptors and SK3-channel activation. Thus such events may affect impulse firing of MPN neurons.
Authors:
Göran Klement; Michael Druzin; David Haage; Evgenya Malinina; Peter Arhem; Staffan Johansson
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-03-24
Journal Detail:
Title:  Journal of neurophysiology     Volume:  103     ISSN:  1522-1598     ISO Abbreviation:  J. Neurophysiol.     Publication Date:  2010 May 
Date Detail:
Created Date:  2010-05-12     Completed Date:  2010-08-25     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0375404     Medline TA:  J Neurophysiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2900-11     Citation Subset:  IM    
Affiliation:
Department of Integrative Medical Biology, Section for Physiology, Umeå University, Umeå, Sweden.
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MeSH Terms
Descriptor/Qualifier:
Animals
Caffeine / pharmacology
Calcium / metabolism*
Calcium Channel Agonists / pharmacology
Cells, Cultured
Central Nervous System Agents / pharmacology
Extracellular Space / metabolism
Intracellular Space / drug effects,  metabolism
Macrocyclic Compounds / pharmacology
Male
Membrane Potentials / drug effects,  physiology*
Neurons / drug effects,  physiology*
Oxazoles / pharmacology
Patch-Clamp Techniques
Potassium / metabolism*
Preoptic Area / drug effects,  physiology*
Rats
Rats, Sprague-Dawley
Ryanodine / pharmacology
Ryanodine Receptor Calcium Release Channel / metabolism*
Time Factors
Chemical
Reg. No./Substance:
0/Calcium Channel Agonists; 0/Central Nervous System Agents; 0/Macrocyclic Compounds; 0/Oxazoles; 0/Ryanodine Receptor Calcium Release Channel; 0/xestospongin C; 15662-33-6/Ryanodine; 58-08-2/Caffeine; 7440-09-7/Potassium; 7440-70-2/Calcium

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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