High frequency oscillations in hippocampus and amygdala [Elektronische Ressource] : modulation by ascending systems / vorgelegt von Alexei Ponomarenko

Tjeerdstra

Sujets

• Psychologie

Informations

• Publié par: heinrich-heine-universitat_dusseldorf
• Publié le: 01 janvier 2003
• Nombre de lectures: 13
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

High-frequency oscillations in hippocampus and amygdala:
modulation by ascending systems








Inaugural-Dissertation
zur
Erlangung des Doktorgrades der
Mathematisch-Naturwissenschaftlichen Fakultät
der Heinrich-Heine Universität Düsseldorf




vorgelegt von
Alexei Ponomarenko
aus Petropavlovsk-Kamchatsky






Düsseldorf
2003

























Gedruckt mit der Genehmigung der Mathematisch-Naturwissen-

schaftlichen Fakultät der Heinrich-Heine-Universität Düsseldorf




Referent: Prof. Dr. H.L. Haas

Korreferent: Prof. Dr. J.P. Huston

Tage der mündlichen Prüfung: 18.07, 21.07, 22.07.2003.
2
CONTENTS

Summary 4
Introduction 5
Literature review
1. Anatomical organisation of the hippocampus and amygdala
Hippocampal formation 6
Amygdaloid complex: nuclei and its external connections 9
Anatomical basis of amygdaloid processing 11
The dorsal endopiriform nucleus 14
2. Oscillatory patterns of hippocampus and amygdaloid complex
Hippocampal ripples 15
Network and cellular mechanisms of ripple oscillations 18
Epileptogenesis: ultrafast ripples 22
Theta oscillations: sites and mechanisms 23
Pharmacology of theta oscillations 27
Interneurons and theta-rhythm 29
Interneuron network gamma 30
Oscillations in the amygdaloid complex 33
3. Memory processing during sleep
Evidence from behavioral studies 37
Physiological correlates of trace consolidation during
sleep: synchrony and reactivation 38
Sleep and neuromodulators 41
Regional brain activation during sleep and biochemical correlates 42
Dreams and memory 42
Sleep-deprivation: waking-promoting substances 43
4. The Histaminergic system
Anatomy 44
Histamine receptors 46
Hisminergic modulation of NMDA-receptors 48
Electrophysiological effects of histamine in hippocampus 49
Neurophysiological actions of histamine: reinforcement and learning 50

3
Hypotheses 52
Methods
Animals 53
Surgery 53
Histology 54
Recording and data processing 54
Drugs 59
Statistical analysis 60
Results
1. Sleep-related dynamics of ripples after stimulant-induced waking
Ripple rebound in different treatment groups 61
Recovery of ripple occurrence during SWS 62
PS-related dynamics of ripple rebound decay 63
2. On the role of GABA-receptors in the mechanisms of ripples:
effects of benzodiazepine-site ligands 71
3. The histaminergic system shapes synchronization in the hippocampus 76
4. High-frequency synchronization in the basolateral amygdala (BL) and dorsal
endopiriform nucleus (EPN)
Common firing patterns of the BL and EPN 77
High-frequency oscillations in the BL and EPN 78
Discussion
Methodological considerations 86
Sleep-related dynamics of ripple oscillations 86
Benzodiazepine pharmacology of ripple oscillations 89
Histaminergic modulation of synchronization in the hippocampus 90
High-frequency oscillations in the BL and EPN 92
Conclusions 94
Reference list 95
Appendix 115



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4
SUMMARY
Long-term potentiation (LTP), a cellular and network-module for the engram-formation, is
mostly elicited by high-frequency stimulation of hippocampal fiber-bundles. High-frequency
oscillations (200 Hz, „ripples") are naturally induced by synchronous discharge of a large
number of CA3 pyramidal neurons and the subsequent excitation of many CA1 pyramidal
cells and interneurons. These oscillatory patterns are believed to represent an intrinsic
network mechanism of the hippocampus and the physiological LTP stimulus. Ripples were
recorded in freely behaving rats by microwire electrode arrays. The atypical waking-
promoting agent modafinil, amphetamine and natural sleep deprivation evoked a profound
(>200%) increase of ripple occurrence in comparison with the pre-drug slow-wave sleep
episode. The duration of waking but not the type of treatment determined the sleep-related
increase of ripple numbers. The number of ripples decreased within individual slow wave
sleep (SWS) episodes, the duration of a SWS episode predicted the ripple occurrence decay
dynamics during the following episode. Paradoxical sleep (PS) or waking episodes (W) acted
to reduce elevated ripple numbers but evoked an increase of ripple occurrence when this had
been low at the beginning of PS.
Benzodiazepines are known to potentiate GABAergic transmission, they diminished
ripple oscillations. The benzodiazepine antagonist flumazenil also reduced the number of
ripples. The modulation of GABA -transmission by benzodiazepines, zolpidem and A
diazepam, reduced amplitude and frequency of ripples; zoplidem elevated ripple duration.
The histaminergic system exerted divergent effects upon ripple oscillations: systemic
administration of an antagonist of H -receptors elevated the number of ripples, whilst an 1
antagonist of H -receptors produced a transient suppression. 2
In the basolateral amygdaloid (BL) and endopiriform nuclei (EPN) local field
potentials and single-unit activities were recorded in parallel with the hippocampal EEG.
Units from both EPN and BL exhibited similar irregular firing patterns with bursts and mean
firing rates <1 Hz. Neuronal activity in both BL and EPN was phase-locked with high-
frequency (~200 Hz) field oscillations with a lower numbers of cycles and smaller amplitudes
than hippocampal ripples. Both these EEG patterns and neuronal f