title: The role of GABAergic neuron on NMDA- and SP-induced phase delays in the suprachiasmatic nucleus neuronal activity rhythm in vitro.
abstract: Gamma-aminobutyric acid (GABA), and its biosynthetic enzyme, glutamic decarboxylase, are widely distributed in the suprachiasmatic nucleus (SCN). In the present study, we examined the role of the GABA(A) receptor on in vitro SCN responses to photic-like signals. We found that 100microM GABA(A) receptor antagonist bicuculline partially blocked field potentials evoked by optic nerve stimulation. NMDA- and SP-induced phase shifts of SCN neuronal activity rhythms, were blocked with 10microM bicuculline. Application of 100microM bicuculline alone induced phase advance of SCN neuronal activity rhythm. These results show that NMDA- and SP-induced phase shifts are blocked by bicuculline and suggest GABA has an important role as neurotransmitter in the neuronal network regulating phase shifts of the circadian clock.
authors.affiliation: Advanced Photonic Bioimaging Center, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido 060-8638, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Hamada
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Shibata
mesh_terms: D000200:Action Potentials; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002940:Circadian Rhythm; D004558:Electric Stimulation; D005071:Evoked Potentials; D058787:GABA-A Receptor Antagonists; D066298:In Vitro Techniques; D016202:N-Methylaspartate / Q000494:pharmacology*; D009474:Neurons / Q000502:physiology*; D009900:Optic Nerve / Q000502:physiology; D051381:Rats; D011963:Receptors, GABA-A / Q000502:physiology*; D013373:Substance P / Q000494:pharmacology*; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*
chemical_list: D058787:GABA-A Receptor Antagonists; D011963:Receptors, GABA-A; D013373:Substance P; D016202:N-Methylaspartate; D001640:Bicuculline