5-HT1A receptors increase excitability of spinal motoneurons by inhibiting a TASK-1-like K+ current in the adult turtle

J Physiol. 2003 Apr 15;548(Pt 2):485-92. doi: 10.1113/jphysiol.2002.037952. Epub 2003 Mar 7.

Abstract

The modulatory effects of serotonin mediated by 5-HT1A receptors in adult spinal motoneurons were investigated by intracellular recordings in a slice preparation from the turtle. In current-clamp mode, activation of 5-HT1A receptors by 8-OH-DPAT led to depolarization and an increase in input resistance in most motoneurons but caused hyperpolarization and a decrease in input resistance in the remaining smaller fraction of cells. When slices were preincubated in medium containing the 5-HT1A receptor antagonist WAY-100635, 8-OH-DPAT had no effect. In voltage-clamp mode, with 1 mM CsCl in the bathing medium, 8-OH-DPAT consistently inhibited a leak current that was sensitive to extracellular acidification and anandamide, a TASK-1 channel blocker. In medium with a low pH, as in the presence of anandamide, 8-OH-DPAT had no effect. Our results show that activation of 5-HT1A receptors contributes to the excitatory effect of serotonin on spinal motoneurons by inhibition of a TASK-1 potassium channel leading to depolarization and increased input resistance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 8-Hydroxy-2-(di-n-propylamino)tetralin / pharmacology
  • Animals
  • Arachidonic Acids / pharmacology
  • Electrophysiology
  • Endocannabinoids
  • In Vitro Techniques
  • Membrane Potentials / physiology
  • Motor Neurons / physiology*
  • Nerve Tissue Proteins / drug effects
  • Nerve Tissue Proteins / physiology*
  • Patch-Clamp Techniques
  • Polyunsaturated Alkamides
  • Potassium Channel Blockers / pharmacology*
  • Potassium Channels / drug effects
  • Potassium Channels / physiology*
  • Potassium Channels, Tandem Pore Domain*
  • Receptor, Serotonin, 5-HT1A / physiology*
  • Serotonin / pharmacology
  • Serotonin Receptor Agonists / pharmacology
  • Spinal Cord / cytology
  • Spinal Cord / physiology*
  • Turtles / physiology*

Substances

  • Arachidonic Acids
  • Endocannabinoids
  • Nerve Tissue Proteins
  • Polyunsaturated Alkamides
  • Potassium Channel Blockers
  • Potassium Channels
  • Potassium Channels, Tandem Pore Domain
  • Serotonin Receptor Agonists
  • Receptor, Serotonin, 5-HT1A
  • potassium channel subfamily K member 3
  • Serotonin
  • 8-Hydroxy-2-(di-n-propylamino)tetralin
  • anandamide