The Effect of Cigarette Smoke Maintained at 10 – 32 Part Per Million of Carbon Monoxide on the Hippocampus of Wistar Rats

The Effect of Cigarette Smoke Maintained at 10 – 32 Part Per Million of Carbon Monoxide on the Hippocampus of Wistar Rats.

ABSTRACT  

Memory and Learning are diverse and complex entities attracting numerous studies with different findings, some even contrasting each other. This study was conducted to make a contribution towards unravelling this reality. Behavioural studies using the Morris Water Maze task was elicited in Wistar rats which were grouped for weight and sex (nmale=18; n female =12).

Reference or latency time recordings for three (3) training at the start of the experiment and after a 5week period of exposure to cigarette smoke (in case of exposed Rats) or 5weeks training free period (in case of non-exposed Rats). Analysis of the time recordings suggest that there is a significant decrease (p≤0.05) for the control male Wistar rats unlike the insignificant(p≥0.05) change obtained for the control and experimental female and experimental male.

Similarly, assessment of the histological section of the hippocampus of the Male Wistar rats from both tissue sections and hippocampal cell suspension was done. Cell counting of normal and Pyknotic pyramidal cells was done using Image J software. Analysis of the cell count suggests a significantly higher (p≤0.05) count in the Exposed Males only, for both the normal and pyknotic pyramidal cells compared to the counts of the Control Male rats.

In conclusion, male Wistar rats tend to retain Reference memory of Morris Water Maze Task for a longer time (5 weeks in this case) compared to female Wistar rats. Similarly, cigarette smoke maintained at 10-32ppm of Carbon Monoxide for 4 days in a week for 5 weeks suffices in disrupting the memory capabilities of the Wistar rats. With a corresponding level of higher rates of Pyknotic pyramidal cell. 

TABLE OF CONTENTS

Title page ………………………………………………………………………………………………………… i
Declaration ……………………………………………………………………………………………………… ii
Certification ……………………………………………………………………………………………………… iii
Dedication ………………………………………………………………………………………………………… iv
Acknowledgements ……………………………………………………………………………………………. v
Abstract…………………………………………………………………………………………………………….. vi
Table of contents ……………………………………………………………………………………………… vii
List of tables …………………………………………………………………………………………………….. xii
List of figures……………………………………………………………………………………………………… xiii
List of Plates ……………………………………………………………………………………………………… xiv
Abbreviations …………………………………………………………………………………………. ……….. xvi

CHAPTER ONE
1.0 Introduction …………………………………………………………………………………………………. 1
1.1 Background…………………………………………………………………………………1
1.2 Statement of Problem . …………………………………….………………………….. 4
1.3 Study Hypothesis… ….………………………………………………………………… 4
1.4 Justification . ……………………………….…………………….…………………… 5
1.5 Aim ……………………………….………………………………………………… 6
1.6 Objectives …………………………………………………………………………… 6

CHAPTER TWO
2.0 Literature Review …………………………………………………………………… 7
2.1 Anatomy of Hippocampus ………………………….…………. …………………….. 7
2.2 Place Cells of The Hippocampus ………………………………………………….…11
2.3 Memory And Spatial Memory ….……………………………………………………12
2.4 Memory Systems And Models ……………………..…………………………………15
2.4.1 Atkinson- Shiffrin Model ……………………………………………………………15
2.4.2 Working Memory Model …………………………………………………………..17
2.5 Studies Relating Hippocampus to Memory ….……………………………………….19
2.6 Electrophysiology of Memory ………………………………………………………20
2.6.1 SRR And Hippocampal Memory Consolidation ……………………………………27
2.7 Memory Task For Rats …………………….…………………………………………28
2.7.1 Morris Water Maze Task ……………………………………………………………28
2.8 Cigarette / Cigarette Smoke ………………………………………………………….31
2.8.1 Carbon Monoxide ……………………………………..……………………………32
2.8.1.1 CO And L.T.P …………………………………………………………………….35
2.8.2 Nicotine …………………………………..…………………………………………..37
2.8.2.1 Nicotine And Cognition …………………………………………………………38
2.8.2.2 Nicotine And Hippocampus ………………….………………………………….39
2.8.3 Hydrogen Sulphide …………………………….…………………………………40
2.8.4 Tar ………………………………………………………………………………….42
2.8.5 Polynuclear Aromatic Hydrocarbon ……………………………………………….42
2.8.6 Chlorinated Dioxins And Furans ……………………………………………………42
2.8.7 Cigarette Smoke In The Environment …………………………………………….43
2.8.7.1 Cigarette Smoke Exposure & Hippocampus ………………………………………49

CHAPTER THREE
3.0 MATERIALS AND METHOD ………………………………………………………52
3.1 Materials …………..…………………………………………………………………52
3.1.1 Rats ……………………………………………………………………………… 52
3.1.2 Carbon Monoxide Meter ……………….…………………………………………52
3.1.3 Nicotine Screen Strip ……………………………………………………………..53
3.1.4 Commercial Available Cigarette (Aspen) .………………………………………..53
3.1.5 Morris Water Maze Training Tank ………………………………………………………..58
3.1.6 Fabricated chamber for static exposure …. …………………………………………58
3.1.7 Microscope …… ………………………………………………………………… 58
3.1.8 Neuber Improved Bright Lines Counting Chamber…………………………………61
3.2 Method ……………………………………………………………………………………. 61
3.2.1 Morris Water Maze Task ………………………………………………………. 62
3.2.2 Tissue Preparation For Cell Suspension ………………………………………….65
3.2.2.1 Preparation of hippocampal cell suspension……………………………………..…68
3.2.3 Preparation of Histological Slides ..…………………………………………………71
3.2.4 Assessment of The Slides of the Hippocampus ……………………………………71
3.2.5 Statistical Analysis ………………………………………………………………72

CHAPTER FOUR
4.0 Result ……………………………….……………………………………. 73
4.1 Physical Observation ……………………………………………………………73
4.2 Morris Water Maze ………………………………………………………………………..78
4.3 Cell Count of Hippocampal Cell Suspension … …………………………………… 81
4.4 Cell Count of Slides …………………………….…………………………………..82
4.5 Histological Observations of M &G Stained Slides ………………………………………89

CHAPTER FIVE
5.0 Discussion ……………………………..…………………………………………92
5.1 Physical Characteristics …..…………………………………………………….…92
5.2 Morris Water Maze …………………………………………………………….…92
5.3 Cell Count ……………………………………………………………………..94
5.3.1 Cell Count for Hippocampal Suspension ………………………………………………………… 94
5.3.2 Cell Count of Slides ……………………………………………………………….94
5.3.3 Discussion on Cell Count ………………………………………………………..94
5.4 Summary and Conclusion ….……………………………………………………….. 95
5.4.1 Summary ……………………………………………………………………………..95
5.4.2 Conclusion …………………………………………………………………………..96
5.5 Recommendations …………………………………………………………………..97
References …………………………………………………………………………98
Appendix …………………………………………………………………………117

INTRODUCTION  

Memory is a complex, diverse and heterogeneous entity and in recent decades, it has become one of the principal pillars of a branch of science called cognitive neuroscience, an interdisciplinary link between cognitive psychology and neuroscience. In psychology, memory is an organism’s ability to store, retain and recall information. Tulving and Craik (2000) define memory as ‘the ability to recollect past events and to bring learned facts and ideas back to mind’.

An adequate definition of memory must incorporate other aspects of this complex phenomenon including, both conscious and non-conscious aspects of memory. Memory is ‘the demonstration that behaviour has been altered as a consequence of the previous storage of information at some point in time ranging from a few seconds to several decades’ (Jonathan, 2002). For descriptive purpose, memory could be viewed from the perspectives of duration, temporal and information type.

The duration perspective has the following entities: Sensory memory, which is the memory that corresponds approximately to the initial 200 – 500 milliseconds after an item is perceived. The ability to look at an item and remember what it looked like with just a second of observation or memorization is an example of sensory memory (Sperling, 1960). While, a short-term memory is the memory that allows recall for a period of several seconds to a minute without rehearsal.

Long-term memory can store much larger quantities of information for potentially unlimited duration sometimes a whole life span. The capacity can xix also approach infinity (unlimited). Memory could be viewed from temporal direction of the information to be remembered, this address whether the content to be remembered is in the past, “retrospective memory”, or whether the content to be remembered is in the future, “prospective memory”.  

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StudentsandScholarship Team.