Potentiation of GABA(A) receptor-mediated Cl-current by urotensin peptides in identified Aplysia neurons.
Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the vertebrate and invertebrate central nervous systems, including those of molluscs. The effects of extracellularly applied urotensin peptides (urotensin I (UI) and urotensin II (UII)) on the GABA-induced Cl- current recorded from identified neurons (R9 and R12) of Aplysia kurodai were investigated using voltage-clamp and pressure ejection techniques. Focal application of 100 nM UI and UII potentiated the GABA-induced Cl- current without affecting the resting membrane conductance and holding current. The increase was completely reversible. The GABA-induced Cl- current also was potentiated by bath-applied UI and UII (5-10 nM). The potentiating effects of UI and UII on the GABA-induced Cl- current were concentration-dependent and completely reversible. These results suggest that neurotensin peptides may decrease neuronal excitability by potentiating the GABA(A) receptor-mediated Cl- current in the neurons of mammalian and invertebrate central nervous systems.
Sawada
M
M
Department of Physiology, Shimane Medical University, Izumo, Japan.
Ichinose
M
M
D000818:Animals; D001048:Aplysia; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000502:physiology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology*; D014579:Urotensins / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D018118:Chloride Channels; D011963:Receptors, GABA-A; D014579:Urotensins; D005680:gamma-Aminobutyric Acid; C029676:urotensin I; C029677:urotensin II