Abstract
Muscarinic and alpha-adrenergic suppression of current through Ca2+ channels was studied in adult rat superior cervical ganglion neurons using whole-cell and cell-attached configurations of the patch-clamp technique. Oxotremorine methiodide suppressed ICa by both a rapid (much less than 1 s) and a slow (greater than 4 s) process, whereas norepinephrine suppressed ICa only by a rapid process. The slow muscarinic suppression could be prevented by adding 20 mM BAPTA, a Ca2+ chelator, to the recording pipette, whereas the adrenergic suppression was not affected. Muscarinic, but not alpha-adrenergic, receptors can couple to Ca2+ channels by a second messenger capable of diffusing into an on-cell patch. This signal seems not to be carried by intracellular Ca2+, cGMP, cAMP, or protein kinase C.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Calcium Channels / physiology*
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Egtazic Acid / pharmacology
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Electric Conductivity / drug effects
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Ganglia, Sympathetic / physiology*
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In Vitro Techniques
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Male
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Membrane Potentials / drug effects
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Neurons / physiology*
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Norepinephrine / pharmacology
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Oxotremorine / pharmacology
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Phorbol 12,13-Dibutyrate / pharmacology
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Rats
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Rats, Inbred Strains
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Receptors, Adrenergic, alpha / drug effects
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Receptors, Adrenergic, alpha / physiology*
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Receptors, Muscarinic / drug effects
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Receptors, Muscarinic / physiology*
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Second Messenger Systems*
Substances
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Calcium Channels
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Receptors, Adrenergic, alpha
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Receptors, Muscarinic
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Phorbol 12,13-Dibutyrate
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Egtazic Acid
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Oxotremorine
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1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
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Norepinephrine