GABAergic mediation of indirect transsynaptic control over basal and spatial memory testing-induced activation of septo-hippocampal cholinergic activity in mice.
A neurochemical study of the transsynaptic interactions established between septal GABAergic interneurones and cholinergic septo-hippocampal neurones was conducted using mice. The effects of acute in vivo injections of either muscimol (20-500 ng/0.2 microliter), bicuculline (100 ng-1 micrograms/0.2 microliter) or saline vehicle (0.2 microliter) into the medial septum on septo-hippocampal cholinergic activity were evaluated using measures of hippocampal high affinity choline uptake at 30 min post-injection in two main groups of mice. The first (quiet control) remained in their home cages during the post-injection period whereas the second (active) were submitted, 10 min following injection to a 20-min period of spatial working memory testing in an 8-arm radial maze. Intraseptal injections of either muscimol or bicuculline produced significant (25-50%) inhibition of hippocampal cholinergic activity in quiet conditions (basal) as compared to intact or saline-injected mice. In the active groups, whereas memory testing induced significant cholinergic activation (+15-20%) in intact and saline injected mice at 30 s post-test no significant memory testing-induced activation was observed in either muscimol or bicuculline-injected mice at any dose. The role of septal GABAergic interneurones in the indirect transsynaptic control over the basal and activated states of septo-hippocampal cholinergic activity is discussed with respect to the concept that these complex neuronal interactions contribute to the physiological mechanisms involved in the modulation of working memory performance.
Durkin
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URA CNRS 339, Université de Bordeaux I-UFR de Biologie, Talence, France.
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D001931:Brain Mapping; D002799:Cholinergic Fibers / Q000187:drug effects / Q000502:physiology*; D004193:Discrimination Learning / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005106:Exploratory Behavior / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D007267:Injections; D008297:Male; D011939:Mental Recall / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009118:Muscimol / Q000494:pharmacology; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D009949:Orientation / Q000187:drug effects / Q000502:physiology; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology*; D012153:Retention, Psychology / Q000187:drug effects / Q000502:physiology; D012688:Septum Pellucidum / Q000187:drug effects / Q000502:physiology*; D013028:Space Perception / Q000187:drug effects / Q000502:physiology*; D013377:Substantia Innominata / Q000187:drug effects / Q000502:physiology; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D011963:Receptors, GABA-A; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D001640:Bicuculline