Abstract
We studied inhibition of N-type Ca2+ channels in rat superior cervical ganglion neurons by substance P (SP) and somatostatin-14 (Som). In whole-cell clamp, 70 of 82 acutely dissociated neurons showed inhibition (mean 37%) by 500 nM SP, and 54 of 61 showed inhibition by 240 nM Som (mean 57%). Pertussis toxin (PTX) blocked Som but not SP inhibition; intracellular dialysis with 2 mM GDP-beta-S attenuated inhibition with either peptide. Inhibition was voltage dependent with Som but not with SP. Neurokinin A (1 microM) or B was without effect, implicating NK1 tachykinin receptors. In cell-attached patches with bath-applied drugs, to test for a diffusible messenger, inhibition by SP or Som was only 8%. Thus, SP signaling is voltage independent and PTX insensitive; Som inhibition is voltage dependent and PTX sensitive; and both are membrane delimited.
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 / drug effects*
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Calcium Channels / physiology
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Dialysis
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Egtazic Acid / analogs & derivatives
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Egtazic Acid / pharmacology
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Electric Conductivity
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GTP-Binding Proteins / physiology*
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Ganglia, Sympathetic / cytology*
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Guanosine Diphosphate / analogs & derivatives
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Guanosine Diphosphate / pharmacology
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Male
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Neurons / drug effects
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Neurons / physiology*
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Pertussis Toxin
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Rats
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Rats, Sprague-Dawley
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Receptors, Neurokinin-2
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Receptors, Neurotransmitter / physiology
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Second Messenger Systems / physiology
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Somatostatin / pharmacology*
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Substance P / pharmacology*
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Thionucleotides / pharmacology
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Virulence Factors, Bordetella / pharmacology
Substances
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Calcium Channels
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Receptors, Neurokinin-2
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Receptors, Neurotransmitter
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Thionucleotides
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Virulence Factors, Bordetella
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Guanosine Diphosphate
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Substance P
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Somatostatin
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Egtazic Acid
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guanosine 5'-O-(2-thiodiphosphate)
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Pertussis Toxin
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GTP-Binding Proteins
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1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid