Proctolin activates a slow, voltage-dependent sodium current in motoneurons of the lobster cardiac ganglion

Neurosci Lett. 1989 Nov 20;106(1-2):105-11. doi: 10.1016/0304-3940(89)90210-3.


The two-electrode voltage-clamp technique was used to study the ionic basis of the slow depolarization caused by the neuropeptide proctolin. At negative membrane potentials, proctolin caused a dose-dependent slow inward current. This current reversed and became outward at membrane potentials positive to 0 to +20 mV. Current-voltage curves also showed the response to be voltage-dependent, with a reversal potential at positive membrane potentials. The response was blocked in sodium-free solutions. Solutions with reduced sodium concentration caused a shift of the reversal potential in a manner expected for a response that is largely sodium-dependent. We conclude that proctolin causes an inward current by increasing a voltage-dependent cation conductance that is predominantly permeable to sodium.

MeSH terms

  • Animals
  • Ganglia / drug effects
  • Ganglia / physiology*
  • In Vitro Techniques
  • Membrane Potentials / drug effects
  • Motor Neurons / drug effects
  • Motor Neurons / physiology*
  • Nephropidae / physiology*
  • Neuropeptides*
  • Oligopeptides / pharmacology*
  • Sodium / physiology*


  • Neuropeptides
  • Oligopeptides
  • proctolin
  • Sodium