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In vitro activation of the medial septum—Diagonal band complex generates atropine‐sensitive and atropine‐resistant hippocampal theta rhythm: An investigation using a complete septohippocampal preparation
Author(s) -
Goutagny Romain,
Manseau Frédéric,
Jackson Jesse,
Danik Marc,
Williams Sylvain
Publication year - 2008
Publication title -
hippocampus
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.767
H-Index - 155
eISSN - 1098-1063
pISSN - 1050-9631
DOI - 10.1002/hipo.20418
Subject(s) - hippocampal formation , diagonal band of broca , neuroscience , bicuculline , muscarinic acetylcholine receptor , hippocampus , chemistry , theta rhythm , muscarinic antagonist , carbachol , picrotoxin , antagonist , basal forebrain , cholinergic , psychology , receptor , biochemistry , stimulation
The medial septum and diagonal band complex (MS‐DB) is believed to play a key role in generating theta oscillations in the hippocampus, a phenomenon critical for learning and memory. Although the importance of the MS‐DB in hippocampal theta rhythm generation is generally accepted, it remains to be determined whether the MS‐DB alone can generate hippocampal oscillations or is only a transducer of rhythmic activity from other brain areas. Secondly, it is known that hippocampal theta rhythm can be separated into an atropine‐sensitive and insensitive component. However, it remains to be established if the MS‐DB can generate both types of rhythm. To answer these questions, we used a new in vitro rat septohippocampal preparation placed in a hermetically separated two side recording chamber. We showed that carbachol activation of the MS‐DB generated large theta oscillations in the CA1 and CA3 regions of the hippocampus. These oscillations were blocked by applying either the GABA A receptor antagonist bicuculline or the AMPA/kainate antagonist DNQX to the hippocampus. Interestingly, the application of the muscarinic receptor antagonist atropine produced only a partial decrease in the amplitude, without modification of the frequency, of theta. These results show for the first time, that upon optimal excitation, the MS‐DB alone is able to generate hippocampal oscillations in the theta frequency band. Moreover, these MS‐DB generated theta oscillations are mediated by muscarinic and nonmuscarinic receptors and have a pharmacological profile similar to theta rhythm observed in awake animals. © 2008 Wiley‐Liss, Inc.