5-HT1A receptors modulate small-conductance Ca2+-activated K+ channels.
Small-conductance calcium-activated potassium channels (SK) are responsible for the medium afterhyperpolarisation (mAHP) following action potentials in neurons. Here we tested the ability of serotonin (5-HT) to modulate the activity of SK channels by coexpressing 5-HT1A receptors with different subtypes of SK channels (SK1, SK2, and SK3) in Xenopus laevis oocytes. SK channels were activated by intracellular injection of Cd2+. Subsequent activation of 5-HT1A receptors by 8-OH-DPAT always produced an inhibition of the SK current, showing the existence of a specific pathway between the receptor and the ion channel. To investigate the physiological relevance of this pathway, we characterized the mAHP present after action potentials in spinal motoneurons recorded in a slice preparation from the lumbar spinal cord of the adult turtle. By performing current and voltage clamp recordings, we showed that 8-OH-DPAT specifically inhibited the fraction of the AHP mediated by SK channels. We conclude that the activity of SK channels is modulated by activation of serotonergic receptors.
Grunnet
Morten
M
MFI, Panum Institute, Copenhagen University, Copenhagen, Denmark.
Jespersen
Thomas
T
Perrier
Jean-François
JF
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D003001:Cloning, Molecular; D005260:Female; D006801:Humans; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology*; D051381:Rats; D044282:Receptor, Serotonin, 5-HT1A / Q000187:drug effects / Q000502:physiology*; D011994:Recombinant Proteins / Q000187:drug effects / Q000378:metabolism; D014982:Xenopus laevis
D024681:Potassium Channels, Calcium-Activated; D011994:Recombinant Proteins; D044282:Receptor, Serotonin, 5-HT1A; D001030:Apamin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin