5-HT1A receptors increase excitability of spinal motoneurons by inhibiting a TASK-1-like K+ current in the adult turtle.
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.
Perrier
Jean-François
JF
Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark. perrier@mfi.ku.dk
Alaburda
Aidas
A
Hounsgaard
Jørn
J
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology; D004594:Electrophysiology; D063388:Endocannabinoids; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000502:physiology; D009046:Motor Neurons / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D053284:Polyunsaturated Alkamides; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D024683:Potassium Channels, Tandem Pore Domain; D044282:Receptor, Serotonin, 5-HT1A / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*; D014426:Turtles / Q000502:physiology*
D001095:Arachidonic Acids; D063388:Endocannabinoids; D009419:Nerve Tissue Proteins; D053284:Polyunsaturated Alkamides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; D017366:Serotonin Receptor Agonists; D044282:Receptor, Serotonin, 5-HT1A; C420132:potassium channel subfamily K member 3; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; C078814:anandamide