title: Prolonged initiation latency in Morris water maze learning in rats with ibotenic acid lesions to medial striatum: effects of systemic and intranigral muscimol administration.
abstract: The contribution of the rat striatonigral GABAergic system to spatial navigation was investigated in this study. We first tested the effects of ibotenic acid lesions of the striatum on place navigation performance in Morris water maze. Medial but not lateral striatal lesions produced a significant increase of escape latency, and this deficit was clarified as mainly caused by a marked increase of initiation latency rather than of thigmotaxis time (experiment 1). Next we tested the effects of systemic (0.5 mg/kg) and intranigral (2.0 ng/side) administrations of muscimol, a GABA receptor agonist, on the place navigation deficits produced by medial striatal lesions. Systemic muscimol administration significantly ameliorated the increase of initiation latency, while intranigral administration was not sufficiently effective (experiment 2). The results suggest that neural circuits containing medial striatal neurons play an essential role in place navigation performance probably through some movement preparation processes that precede movement execution, and the GABAergic system may be involved in this initiation process, although whether it is the striatonigral GABAergic system that is involved remains unclear.
authors.affiliation: University of Tsukuba Graduate School of Comprehensive Human Sciences, Tsukuba, Ibaraki 305-8575, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Shirakawa
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ichitani
mesh_terms: D000818:Animals; D018690:Excitatory Amino Acid Agonists / Q000008:administration & dosage; D018755:GABA Agonists / Q000008:administration & dosage; D007051:Ibotenic Acid / Q000008:administration & dosage; D007275:Injections, Intravenous; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology*; D008845:Microinjections; D009118:Muscimol / Q000008:administration & dosage; D017072:Neostriatum / Q000187:drug effects / Q000502:physiology*; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects; D013028:Space Perception / Q000187:drug effects / Q000502:physiology; D013037:Spatial Behavior / Q000187:drug effects / Q000502:physiology; D013378:Substantia Nigra / Q000187:drug effects / Q000502:physiology*; D013550:Swimming
chemical_list: D018690:Excitatory Amino Acid Agonists; D018755:GABA Agonists; D007051:Ibotenic Acid; D009118:Muscimol