electrophysiological characterization of p300 event-related potentials in a rat model of alzheimer's

93 Pages·2012·2.45 MB·English

by  Joachim Ahlbeck

2012

Aalborg University

H. Lundbeck A/S

Joachim Ahlbeck

[ELECTROPHYSIOLOGICAL
CHARACTERIZATION OF P300 EVENT-
RELATED POTENTIALS IN A RAT MODEL
OF ALZHEIMER’S DISEASE]
This page is intentionally left blank.
Aalborg University
Institute of Health Science and Technology, Fredrik Bajers Vej 7D, DK-9220 Aalborg East
TITLE: ELECTROPHYSIOLOGICAL CHARACTERIZATION OF P300 EVENT-RELATED POTENTIALS IN A
RAT MODEL OF ALZHEIMER’S DISEASE
PROJECTGROUP:
11gr950
GROUPMEMBERS:
Joachim Ahlbeck

SUPERVISORS:
Aalborg University: Parisa Gazerani
H. Lundbeck A/S: Jesper Frank Bastlund
H. Lundbeck A/S: Bettina Clausen
SEMESTER:
9-10th
PROJECTPERIOD:
01/08-2011 to 01/06-2012
PUBLICATIONS:
12
PAGES:
87

Abstract:
Background: Alzheimer’s disease (AD) is an incurable and debilitating neurodegenerative disease
characterized by a progressive loss of cognitive and bodily functions. The disease is associated with
accumulation of toxic peptides and cholinergic degeneration in the brain. Event-related potentials (ERPs)
are measured by electroencephalography (EEG) and have been widely studied in AD patients, since ERPs
represent an objective measure of brain processing. The P300 ERP is of particular interest because a
compromised P300 is commonly associated with the loss of cognitive function in AD. A rodent model of
P300 would be useful in developing new pharmacological compounds that affect the cognitive system.
Methods: ERPs were recorded by EEG from hippocampus, auditory cortex, parietal cortex, and
frontal/prelimbic cortex during an auditory discrimination paradigm in rats. Three experiments were
conducted using two different experimental setups. A total of three sessions were analyzed. 1: Sensory
paradigm with no discrimination of tones, 2: discrimination paradigm, and 3: scopolamine (0.1mg/kg) /
saline treated rats in the discrimination paradigm for each experiment.
Results: No P300 could be identified during experiment 1 (Three tone discrimination). A clearly defined
P300 developed in hippocampus in experiment 2+3 and prelimbic cortex in experiment 3 with a latency of
170-180ms during discrimination training of the rats in experiment 2 and 3 (Two tone discrimination).
Scopolamine increased latency in hippocampus in experiment 2 similar to what is seen in humans providing
evidence that the P300 observed in the rats are translatable to the P300 seen in humans.
Conclusion: A method to evoke a P300 in rats was established. The P300 identified in rat hippocampus
shows similar features to the human P300 and would be useful in studying new compounds that affect the
cognitive function in AD. The prelimbic cortex also showed a trend towards mimicking human P300 but
further studies are required to validate this.
This page is intentionally left blank.
Preface
This master thesis in Medicine with Industrial Specialization - Translational Medicine, is based on
experimental work performed at H. Lundbeck A/S, Copenhagen, in the period of August 2011 to June 2012.
The study consists of three experiments. The first experiment was conducted in the time period of
September 2011 to November 2011. The second experiment was conducted in the time period of January
2012 to April 2012. The third experiment was started in May 2012 and is expected to end by June 2012.
The second experiment had to be postponed due to a viral infection in the animal facilities requiring
disinfection of the entire site from end of November to medio January. The third experiment was
conducted in the late stage of the project period to validate findings from experiment 2. Data retrieved
from experiment 3 are currently being analyzed and only key findings are shown in this report.
Acknowledgement
Huge thanks to my advisors Parisa Gazerani, Associate Professor at Aalborg University, Jesper Frank
Bastlund, Principal Scientist at H. Lundbeck A/S, and Bettina Clausen, Ph.D. Student at H. Lundbeck A/S, for
their support and guidance throughout the project. Also thanks to Steven C. Leiser, Senior Research
Scientist at H. Lundbeck A/S US division and Søren Ellegaard, owner of Ellegaard Systems A/S for helping me
developing the procedures and experimental setup that was used. Also thanks to H. Lundbeck A/S for giving
me the opportunity to conduct this project. Further thanks to all my colleagues at H. Lundbeck A/S for
being open-minded, helpful, and allowing me to join in their meetings, seminars, and other projects.
This page is intentionally left blank.
Introduction to Alzheimer’s disease

Table of Contents
1 Introduction to Alzheimer’s disease ............................................................................................. 5
1.1 The cause of Alzheimer’s disease ......................................................................................... 5
1.2 Symptoms and diagnosis ....................................................................................................... 6
1.3 Medical management of Alzheimer’s disease ....................................................................... 6
1.4 Biomarkers of AD ................................................................................................................. 7
1.5 Electroencephalography ........................................................................................................ 8
1.5.1 Event-related potentials ............................................................................................................ 8
1.5.2 P300 in Alzheimer’s disease .................................................................................................... 10
1.5.3 Rodent models of P300 ERPs ................................................................................................... 11
1.6 Rodent models of Alzheimer’s disease ............................................................................... 13
2 Aim ............................................................................................................................................. 13
3 Methods ...................................................................................................................................... 14
3.1 Experiment 1 ....................................................................................................................... 14
3.1.1 Subjects .................................................................................................................................... 14
3.1.2 Surgical preparation ................................................................................................................ 14
3.1.3 Behavioral procedures ............................................................................................................. 15
3.1.4 Recording ................................................................................................................................. 16
3.1.5 Data analyses ........................................................................................................................... 16
3.2 Experiment 2 ....................................................................................................................... 17
3.2.1 Subjects .................................................................................................................................... 17
3.2.2 Surgical preparation ................................................................................................................ 17
3.2.3 Behavioral procedures ............................................................................................................. 17
3.2.4 Recording ................................................................................................................................. 19
3.2.5 Data analyses ........................................................................................................................... 19
3.3 Experiment 3 ....................................................................................................................... 19
3.3.1 Subjects .................................................................................................................................... 19
3.3.2 Surgical preparation ................................................................................................................ 20
3.3.3 Behavioral procedures ............................................................................................................. 20
3.3.4 Recording ................................................................................................................................. 20
3.3.5 Data analyses ........................................................................................................................... 20
3.4 Methodological considerations and validation .................................................................... 20
4 Results......................................................................................................................................... 23
4.1 Experiment 1 ....................................................................................................................... 23
4.1.1 Sensory vs. normal paradigm .................................................................................................. 24

1/87
Introduction to Alzheimer’s disease

4.1.2 Saline vs. Scopolamine treatment ........................................................................................... 26
4.2 Experiment 2 ....................................................................................................................... 28
4.2.1 Validation of tones .................................................................................................................. 28
4.2.2 Peak development ................................................................................................................... 28
4.2.3 Sensory vs. Discrimination paradigm ...................................................................................... 32
4.2.4 Saline vs. Scopolamine treatment ........................................................................................... 40
4.3 Experiment 3 ....................................................................................................................... 48
4.3.1 Sensory vs. discrimination paradigm ....................................................................................... 49
5 Discussion ................................................................................................................................... 53
5.1 Experiment 1 ....................................................................................................................... 53
5.2 Experiment 2 and 3.............................................................................................................. 54
6 Conclusion .................................................................................................................................. 58
7 Future perspectives ..................................................................................................................... 58
8 Appendix: ................................................................................................................................... 59
8.1 Protocols .............................................................................................................................. 59
8.1.1 Protocol for electrode operation in rats:................................................................................. 59
8.1.2 Rat weight control protocol ..................................................................................................... 68
8.1.3 Experiment 1 – Setup .............................................................................................................. 68
8.1.4 Experiment 1 – Protocols ........................................................................................................ 70
8.1.5 Experiment 2 – Setup .............................................................................................................. 72
8.1.6 Experiment 2 – Protocols ........................................................................................................ 73
8.2 Results ................................................................................................................................. 76
8.2.1 Experiment 1 – Auditory sensory paradigm ............................................................................ 76
8.2.2 Experiment 1 - Difficult peak localization on surface electrodes ............................................ 77
8.2.3 Experiment 1 – Lever artifact .................................................................................................. 77
8.2.4 Experiment 2 – Auditory sensory paradigm – Tone validation ............................................... 78
9 Reference List ............................................................................................................................. 82

2/87
Introduction to Alzheimer’s disease

List of abbreviations:
Aβ Amyloid-β
ACh Acetylcholine
AChEI Acetylcholine Esterase Inhibitor
AD Alzheimer’s disease
ADAS-Cog Alzheimer’s disease Assessment Scale – Cognitive subscale
APOE Apolipoprotein E
APP Amyloid Precursor Protein
CSF Cerebrospinal Fluid
EEG Electroencephalography
ERP Event-Related Potential
FDG-PET Fludeoxyglucose Positron Emission Tomography
MCI Mild Cognitive Impairment
MMSE Mini-Mental State Examination
MRI Magnetic Resonance Imaging
NFT Neurofibrillary Tangles
NMDA N-Methyl-D-Aspartate
qEEG Quantitative Electroencephalography
S.C. Subcutaneously

3/87
Introduction to Alzheimer’s disease

This page is intentionally left blank.

4/87