title: Interruption of pacemaker signals is mediated by GABAergic inhibition of the pacemaker nucleus in the African electric fish Gymnarchus niloticus.
abstract: The wave-type African weakly electric fish Gymnarchus niloticus produces electric organ discharges (EODs) from an electric organ in the tail that is driven by a pacemaker complex in the medulla, which consists of a pacemaker nucleus, two lateral relay nuclei and a medial relay nucleus. The prepacemaker nucleus (PPn) in the area of the dorsal posterior nucleus of the thalamus projects exclusively to the pacemaker nucleus and is responsible for EOD interruption behavior. The goal of the present study is to test the existence of inhibition of the pacemaker nucleus by the PPn. Immunohistochemical results showed clear anti-GABA immunoreactive labeling of fibers and terminals in the pacemaker nucleus, but no apparent anti-glycine immunoreactivity anywhere in the pacemaker complex. GABA injection into the pacemaker nucleus could induce EOD interruptions that are comparable to the interruptions induced by glutamate injection into the PPn. Application of the GABA(A) receptor blocker bicuculline methiodide reversibly eliminated the effects of stimulation of the PPn. Thus the EOD interruption behavior in Gymnarchus is mediated through GABAergic inhibition of the pacemaker nucleus by the PPn.
authors.affiliation: Department of Biology, Gilmer Hall, University of Virginia, P.O. Box 400328, Charlottesville, VA 22904-4328, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Masashi
authors.initials: M
authors.lastname: Kawasaki
mesh_terms: D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D001683:Biological Clocks / Q000502:physiology*; D004555:Electric Fish / Q000502:physiology*; D004557:Electric Organ / Q000502:physiology*; D004567:Electrodes, Implanted; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D018756:GABA Antagonists / Q000494:pharmacology; D007150:Immunohistochemistry; D008839:Microelectrodes; D009412:Nerve Fibers / Q000502:physiology; D017729:Presynaptic Terminals / Q000502:physiology; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology; D013569:Synapses / Q000187:drug effects / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000008:administration & dosage / Q000494:pharmacology / Q000502:physiology*
chemical_list: D018756:GABA Antagonists; D011963:Receptors, GABA-A; D005680:gamma-Aminobutyric Acid; D001640:Bicuculline