Modulation of growth cone calcium current is mediated by a PTX-sensitive G protein.
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.
Man-Son-Hing
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Department of Zoology and Genetics, Iowa State University, Ames 50011.
Haydon
P G
PG
D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D019835:FMRFamide; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000502:physiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D009479:Neuropeptides / Q000494:pharmacology; D037342:Pertussis Toxin; D012908:Snails / Q000502:physiology*; D013873:Thionucleotides / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D015220:Calcium Channels; D009479:Neuropeptides; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D006153:Guanosine Diphosphate; D006165:Guanylyl Imidodiphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019835:FMRFamide; C023427:guanosine 5'-O-(2-thiodiphosphate); D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D002118:Calcium