Calcium current modulation in frog sympathetic neurones: L-current is relatively insensitive to neurotransmitters

J Physiol. 1992 Oct;456:107-23. doi: 10.1113/jphysiol.1992.sp019329.

Abstract

1. Neurotransmitters (noradrenaline, NA; chicken II luteinizing hormone-releasing hormone, LHRH) and activators of G proteins (GTP-gamma-S and AlF3) partially inhibit calcium current in bullfrog sympathetic neruones. Activation of the remaining current is slowed and shifted to more positive voltages. 2. The N-type calcium current appears to be the type modulated, since approximately 90% of peak current is blocked by omega-conotoxin (omega CgTx) and modulation is not affected by nisoldipine. 3. Calcium current at relatively negative voltages (-30 to -50 mV) is resistant to transmitter modulation. The current at such voltages is also resistant to omega CgTx, suggesting that it results from a different type of calcium channel. 4. The omega CgTx-resistant current includes dihydropyridine (DHP)-sensitive and DHP-resistant components. The omega CgTx- and DHP-resistant current is inhibited by transmitter agonist, but the DHP-sensitive (L-type) current is not. 5. In cells dialysed with a low concentration of calcium buffer (0.1 mM-BAPTA), transmitters still inhibit N-current incompletely. However, L-current was partially inhibited (approximately 10%) by LHRH, NA and the muscarinic agonist oxotremorine-M (OXO-M).

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aluminum / pharmacology
  • Aluminum Compounds*
  • Animals
  • Calcium Channels / drug effects*
  • Dose-Response Relationship, Drug
  • Fluorides / pharmacology
  • Ganglia, Sympathetic / physiology*
  • Gonadotropin-Releasing Hormone / pharmacology
  • Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
  • In Vitro Techniques
  • Neurotransmitter Agents / pharmacology*
  • Nifedipine / pharmacology
  • Norepinephrine / pharmacology
  • Peptides, Cyclic / pharmacology
  • Rana catesbeiana
  • omega-Conotoxin GVIA

Substances

  • Aluminum Compounds
  • Calcium Channels
  • Neurotransmitter Agents
  • Peptides, Cyclic
  • Gonadotropin-Releasing Hormone
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • omega-Conotoxin GVIA
  • Aluminum
  • Nifedipine
  • Fluorides
  • Norepinephrine
  • aluminum fluoride