Neuronal inhibition by the peptide FMRFamide involves opening of S K+ channels.
Neurotransmitters modulate the activity of ion channels through a variety of second messengers, including cyclic AMP, cyclic GMP and the products of phosphatidylinositol breakdown. Little is known about how different transmitters acting through different second-messenger systems interact within a cell to regulate single ion channels. We here describe the reciprocal actions of serotonin and the molluscan neuropeptide, FMRFamide, on individual K+ channels in Aplysia sensory neurons. In these cells, serotonin causes prolonged all-or-none closure of a class of background conductance K+ channels (the S channels) through cAMP-dependent protein phosphorylation. Using single-channel recording, we have found that FMRFamide produces two actions on the S channels; it increases the probability of opening of the S channels via a cAMP-independent second-messenger system and it reverses the closures of S channels produced by serotonin or cAMP.
D000818:Animals; D001048:Aplysia / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D004553:Electric Conductivity; D019835:FMRFamide; D005724:Ganglia / Q000166:cytology / Q000502:physiology; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials; D009419:Nerve Tissue Proteins / Q000502:physiology*; D009433:Neural Inhibition; D009474:Neurons / Q000502:physiology; D011188:Potassium / Q000502:physiology*; D012701:Serotonin / Q000502:physiology*
D007473:Ion Channels; D009419:Nerve Tissue Proteins; D012701:Serotonin; D019835:FMRFamide; D000242:Cyclic AMP; D011188:Potassium