Suppression of potassium channels elicits calcium-dependent plateau potentials in suprachiasmatic neurons of the rat

Article Article scientifique Article Suppression of potassium channels elicits calcium-dependent plateau potentials in suprachiasmatic neurons of the rat eng 2005 author Pierson P. M. author Liu Xinhuai 510980 author Raggenbass Mario 24721 50-59 10.1016/j.brainres.2004.12.020 15725401 0006-8993 By using whole-cell recordings in acute and organotypic hypothalamic slices, we found that following K+ channel blockade, sustained plateau potentials can be elicited by current injection in suprachiasmatic neurons. In an attempt to determine the ionic basis of these potentials, ion-substitution experiments were carried out. It appeared that to generate plateau potentials, calcium influx was required. Plateau potentials were also present when extracellular calcium was replaced by barium, but were independent upon an increase in the intracellular free calcium concentration. Substitution of extracellular sodium by the impermeant cation N-methyl-D-glucamine indicated that sodium influx could also contribute to plateau potentials. To gain some information on the pharmacological profile of the Ca++ channels responsible for plateau potentials, selective blocker of various types of Ca++ channel were tested. Plateau potentials were unaffected by isradipine, an L-type Ca++ channel blocker. However, they were slightly reduced by omega-conotoxin GVIA and omega-agatoxin TK, blockers of N-type and P/Q-type Ca++ channels, respectively. These data suggest that R-type Ca++ channels probably play a major role in the genesis of plateau potentials. We speculate that neurotransmitters/neuromodulators capable of reducing or suppressing potassium conductance(s) may elicit a Ca++-dependent plateau potential in suprachiasmatic neurons, thus promoting sustained firing activity and neuropeptide release. Animals Barium/metabolism/pharmacology Calcium/metabolism/pharmacology Calcium Channel Blockers/pharmacology Calcium Channels/drug effects/ physiology Calcium Channels, R-Type/drug effects/physiology Calcium Signaling/drug effects/ physiology Chelating Agents/pharmacology Electric Stimulation Extracellular Fluid/metabolism Magnesium/metabolism/pharmacology Male Membrane Potentials/drug effects/physiology Neurons/drug effects/ metabolism Organ Culture Techniques Patch-Clamp Techniques Potassium Channel Blockers/ pharmacology Potassium Channels/drug effects/ physiology Rats Rats, Sprague-Dawley Sodium/metabolism/pharmacology Suprachiasmatic Nucleus/drug effects/ metabolism Dewey 616.8 53 Département de neurosciences fondamentales 21A false Brain research 1036 1-2 34de6b55-495a-49bc-a19e-b29e3ac497d1 Article Restricted file1.pdf 316187 application/pdf restrictedAccess Faculté de médecine / Section de médecine fondamentale / Département de neurosciences fondamentales

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Suppression of potassium channels elicits calcium-dependent plateau potentials in suprachiasmatic neurons of the rat	Brain research			2005	606	0

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Liu, Xinhuai