Document Detail

Multiple hypothalamic sites control the frequency of hippocampal theta rhythm.
MedLine Citation:
PMID:  12722977     Owner:  NLM     Status:  MEDLINE    
Stimulation of a neural pathway originating in the brainstem reticular formation, with synapses in the medial hypothalamus, activates the hippocampal theta rhythm. The frequency of reticular-elicited theta is determined in the medial supramammillary nucleus (mSuM) completely in anaesthetised rats, but only partially when the animal is awake. We tested other medial hypothalamic sites for their capacity to control theta frequency in awake rats. Blockade of sodium channels (1 microl fast infusion of the local anaesthetic procaine, experiment 1) or increased inhibition by GABA (Chlordiazepoxide [CDP], experiment 2) was found to reduce or increase the frequency of reticular-elicited theta, depending on the precise site of injection, in the region of the dorsomedial hypothalamic nucleus (DMH) and the posterior hypothalamic nucleus (PH). A band of null sites for CDP was located in the region of the ventral border of PH and dorsal border of mSuM. Using 0.5 and 1 microl CDP, and slow infusions (experiment 3), it was found that effective PH sites were also separate from mSuM in the rostrocaudal direction. In experiment 4, the DMH/PH region was mapped with unilateral and bilateral slow infusions of 0.5 microl CDP. CDP significantly reduced frequency in medial (periventricular) and dorsal PH, but not DMH. Bilateral injections appeared to generally sum the usual effects of unilateral injection, producing effects of intermediate size. However, the absolute frequency change in any given site, or with any pair of sites, did not exceed 1 Hz, which is similar to what is seen with single injections in mSuM. Overall, it appears that at, any one time, theta frequency may be determined by a complex interplay between distinct but interacting modulatory regions in the medial hypothalamus.
Mary-Anne Woodnorth; Rachel J Kyd; Barbara J Logan; Mark A Long; Neil McNaughton
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Hippocampus     Volume:  13     ISSN:  1050-9631     ISO Abbreviation:  Hippocampus     Publication Date:  2003  
Date Detail:
Created Date:  2003-04-30     Completed Date:  2003-06-10     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9108167     Medline TA:  Hippocampus     Country:  United States    
Other Details:
Languages:  eng     Pagination:  361-74     Citation Subset:  IM    
Department of Psychology and Centre for Neuroscience, University of Otago, Dunedin, New Zealand.
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MeSH Terms
Action Potentials / drug effects,  physiology*
Chlordiazepoxide / pharmacology
Dorsomedial Hypothalamic Nucleus / cytology,  drug effects,  physiology
Functional Laterality / drug effects,  physiology
GABA Modulators / pharmacology
Hippocampus / cytology,  drug effects,  physiology*
Hypothalamus / cytology,  drug effects,  physiology*
Hypothalamus, Posterior / cytology,  drug effects,  physiology
Neural Pathways / cytology,  drug effects,  physiology*
Neurons / drug effects,  physiology*
Pons / physiology
Procaine / pharmacology
Rats, Sprague-Dawley
Reticular Formation / physiology
Sodium Channel Blockers / pharmacology
Synaptic Transmission / drug effects,  physiology
Theta Rhythm / drug effects*
Reg. No./Substance:
0/GABA Modulators; 0/Sodium Channel Blockers; 58-25-3/Chlordiazepoxide; 59-46-1/Procaine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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