Abstract
Growth cones of isolated neurons B5 of Helisoma were voltage clamped in the whole-cell configuration. Depolarization of growth cones to -20 mV or greater activated a high-voltage-activated (HVA) calcium current. Addition of the neuropeptide FMRFamide (1 microM), which causes a presynaptic inhibition of synaptic transmission, reversibly reduced the calcium current magnitude. This inhibitory effect is mediated by a pertussis toxin (PTX)-sensitive G protein. Dialysis with the non-hydrolyzable GTP analogs GTP gamma S and Gpp(NH)p caused FMRFamide's effect to become irreversible. Dialysis with GDP beta S or preincubation with PTX prevented FMRFamide from reducing the calcium current. Thus, one role of growth cone G proteins is to modulate ion channels in growth cone membrane which in turn may control growth cone motility.
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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Axons / drug effects
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Axons / physiology*
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Calcium / metabolism*
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Calcium Channels / drug effects
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Calcium Channels / physiology
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Cells, Cultured
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FMRFamide
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GTP-Binding Proteins / antagonists & inhibitors*
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GTP-Binding Proteins / physiology
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Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
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Guanosine Diphosphate / analogs & derivatives
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Guanosine Diphosphate / pharmacology
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Guanylyl Imidodiphosphate / pharmacology
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Ion Channel Gating / drug effects*
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Neurons / drug effects
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Neurons / physiology
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Neurons / ultrastructure
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Neuropeptides / pharmacology
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Pertussis Toxin*
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Snails / physiology*
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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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Neuropeptides
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Thionucleotides
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Virulence Factors, Bordetella
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Guanosine Diphosphate
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Guanylyl Imidodiphosphate
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Guanosine 5'-O-(3-Thiotriphosphate)
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FMRFamide
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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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Calcium