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Projections from the nucleus incertus (NI) to the septum have been implicated in the modulation of hippocampal theta rhythm. In this study we describe a previously uncharacterized projection from the septum to the NI, which may provide feedback modulation of the ascending circuitry. Fluorogold injections into the NI resulted in retrograde labeling in the septum that was concentrated in the horizontal diagonal band and areas of the posterior septum including the septofimbrial and triangular septal nuclei. Double-immunofluorescent staining indicated that the majority of NI-projecting septal neurons were calretinin-positive and some were parvalbumin-, calbindin-, or glutamic acid decarboxylase (GAD)-67-positive. Choline acetyltransferase-positive neurons were Fluorogold-negative. Injection of anterograde tracers into medial septum, or triangular septal and septofimbrial nuclei, revealed fibers descending to the supramammillary nucleus, median raphe, and the NI. These anterogradely labeled varicosities displayed synaptophysin immunoreactivity, indicating septal inputs form synapses on NI neurons. Anterograde tracer also colocalized with GAD-67-positive puncta in labeled fibers, which in some cases made close synaptic contact with GAD-67-labeled NI neurons. These data provide evidence for the existence of an inhibitory descending projection from medial and posterior septum to the NI that provides a "feedback loop" to modulate the comparatively more dense ascending NI projections to medial septum and hippocampus. Neural processes and associated behaviors activated or modulated by changes in hippocampal theta rhythm may depend on reciprocal connections between ascending and descending pathways rather than on unidirectional regulation via the medial septum.
Pubmed ID: 25269409 RIS Download
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This monoclonal targets parvalbumin
View all literature mentionsThis polyclonal targets Calbindin D-28k
View all literature mentionsThis monoclonal targets Synaptophysin
View all literature mentionsThis monoclonal targets Calbindin D-28k
View all literature mentionsThis monoclonal targets Calretinin (CR)
View all literature mentionsThis polyclonal targets Fluorescent Gold?? (hydroxystibamidine)
View all literature mentionsThis polyclonal targets Choline Acetyltransferase (ChAT)
View all literature mentionsCompact 3rd edition of The Rat Brain Atlas of Paxinos & Watson published in 1997, it is the most widely used stereotaxic reference system for rat brain. The illustrations and nomenclature of the atlas have become standard tools used by almost all research neuroscientists who deal with anatomy, physiology, or function. It has been subsequently updated, with the 6th edition being the most recent. The 3rd edition is the most recent one available online for free. The program runs in Adobe Acrobat Reader.
View all literature mentionsSoftware for image capture, processing and analysis with Leica fluorescence and confocal microscopes.
View all literature mentionsThis polyclonal targets Choline Acetyltransferase (ChAT)
View all literature mentionsThis monoclonal targets Synaptophysin
View all literature mentionsThis monoclonal targets Calretinin (CR)
View all literature mentionsThis monoclonal targets parvalbumin
View all literature mentionsThis polyclonal targets Calbindin D-28k
View all literature mentionsThis polyclonal targets Fluorescent Gold?? (hydroxystibamidine)
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