targeting the trace amine-associated receptor 1 in psychomotor stimulant addiction

203 Pages·2016·4.75 MB·English

TARGETING THE TRACE AMINE-ASSOCIATED
RECEPTOR 1 IN PSYCHOMOTOR STIMULANT
ADDICTION

A thesis submitted in partial fulfilment of the
requirements for the Degree of
Doctor of Philosophy in Psychology
at the University of Canterbury
By Yue Pei

University of Canterbury
2016
ABSTRACT
Psychomotor stimulant drugs, such as cocaine and amphetamine-type substances, including
amphetamine and methamphetamine (METH), are potent central nervous system (CNS)
stimulants with highly addictive potential. They are widely used and abused around the
world, generating a staggering burden on society and the individual’s family, yet no specific
medications have been found to safely facilitate detoxification and promote quicker recovery
from chronic stimulant abuse. The mainstay pharmacological approach for stimulant
addiction has largely relied on directly altering neurotransmission of the classic monoamines,
especially dopamine (DA), which is a key mediator of psychostimulant’s effects. However,
progress has been hindered by the limited efficaciousness and potential non-specific side
effects associated with direct manipulation of the DA system. The newly discovered trace
amine-associated receptor 1 (TAAR1) has gained increasing attention as a novel target for the
pharmacological development of new addiction treatments. TAAR1 belongs to a family of G
protein-coupled receptors (GPCRs) and is activated by trace amines (TAs), a group of
endogenous amines that are intimately related to the classic monoamines. TAAR1 shares
overlapping CNS distribution with the major monoaminergic pathways and is directly
activated by some psychostimulants including METH. Early evidence from in vitro
preparations and in vivo transgenic studies indicated an important role of TAAR1 in the
regulation of DA transmission and psychostimulant action, leading to the hypothesis that
pharmacological targeting of TAAR1 may present a promising avenue for addiction
treatment. However, due to the unavailability of highly selective TAAR1 agonists until very
recently, a direct assessment of this hypothesis has been difficult. The goal of the present
thesis is to investigate systematically the potential therapeutic effectiveness of TAAR1-based
agents in clinically-relevant animal models of addiction. Specifically, we will examine the
ability of newly generated TAAR1 selective partial and full agonists to modulate key
abuse-related behavioural and neurochemical effects of cocaine and METH. This is
accomplished across three major sets of experiments, with 10 experiments in total. The
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findings obtained from the current work provide evidence of highly favourable properties of
TAAR1 agonists, consistent with an efficacious anti-addiction medication, and support the
candidacy of TAAR1 as a pharmacological target for the treatment of stimulant addiction.

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TABLE OF CONTENTS

ABSTRACT ............................................................................................................................... ii
TABLE OF CONTENTS .......................................................................................................... iv
ACKNOWLEDGEMENTS ................................................................................................... viii
LIST OF FIGURES ................................................................................................................... x
ABBREVIATIONS .................................................................................................................. xi
1 Psychostimulant Addiction ................................................................................................. 1
1.1 Psychomotor Stimulant and Its Addiction - Concept and Definition.......................... 1
1.2 A Worldview of Psychomotor Stimulant Use - Prevalence and Impact ..................... 2
1.3 Behavioural Theories of Addiction ............................................................................. 4
1.3.1 A conceptual framework ...................................................................................... 4
1.3.2 Motivation and opponent process theory ............................................................. 6
1.3.3 Allostatic model ................................................................................................... 9
1.3.4 Incentive-sensitization theory ............................................................................ 10
1.4 Neurobiology of Addiction and the Role of Dopamine (DA) ................................... 12
1.4.1 Acute reinforcement/reward of psychostimulants ............................................. 12
1.4.2 Voluntary drug-seeking ..................................................................................... 16
1.4.3 Compulsive drug-seeking .................................................................................. 17
1.4.4 Negative withdrawal state .................................................................................. 20
1.4.5 Summary ............................................................................................................ 21
1.5 Current Treatment and Problems .............................................................................. 22
1.5.1 Antidepressants .................................................................................................. 23
1.5.2 DA replacement agonists - releasers .................................................................. 24
1.5.3 DA replacement agonists - uptake inhibitors ..................................................... 24
1.5.4 DA replacement agonists - atypical DA uptake inhibitors ................................ 25
1.5.5 DA receptor ligands ........................................................................................... 27
1.5.6 GABAergic agents ............................................................................................. 29
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1.5.7 Other medications .............................................................................................. 29
1.5.8 Summary ............................................................................................................ 29
2 Targeting Trace Amine-Associated Receptor 1 (TAAR1) to Treat Psychostimulant
Addiction.................................................................................................................................. 31
2.1 Trace Amines ............................................................................................................ 32
2.2 Identification of TAAR Family ................................................................................. 36
2.3 Expression, Signalling, and Pharmacology of TAAR1............................................. 37
2.4 Functional Interaction of TAAR1 with Brain Monoamine Systems......................... 40
2.5 Target TAAR1 to Treat Stimulant Addiction ........................................................... 44
2.6 The Present Work ...................................................................................................... 48
2.6.1 Experiment set one ............................................................................................. 48
2.6.2 Experiment set two ............................................................................................ 50
2.6.3 Experiment set three .......................................................................................... 52
3 TAAR1 Activation Modulates Psychostimulant-Induced Locomotor Activity and
Neuronal Plasticity ................................................................................................................... 55
3.1 Introduction ............................................................................................................... 55
3.2 Materials and Methods .............................................................................................. 56
3.2.1 Subjects .............................................................................................................. 56
3.2.2 Pharmacological agents ..................................................................................... 56
3.2.3 Apparatus ........................................................................................................... 57
3.2.4 Behavioural procedures (experiments 1 and 2) ................................................. 57
3.2.5 Immunohistochemistry and microscopy (experiment 2 cont.) .......................... 58
3.2.6 Statistical analysis .............................................................................................. 59
3.3 Results and Summary ................................................................................................ 59
3.3.1 Experiment 1 results .......................................................................................... 59
3.3.2 Experiment 1 summary ...................................................................................... 60
3.3.3 Experiment 2 results .......................................................................................... 61
3.3.4 Experiment 2 summary ...................................................................................... 64
3.4 Discussion ................................................................................................................. 64
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4 TAAR1 Activation Reduces the Reinforcing Efficacy of Psychostimulants ................... 74
4.1 Introduction ............................................................................................................... 74
4.2 Materials and Methods .............................................................................................. 76
4.2.1 Subjects .............................................................................................................. 76
4.2.2 Pharmacological agents ..................................................................................... 76
4.2.3 Catheter implantation surgery ............................................................................ 76
4.2.4 Self-administration apparatus ............................................................................ 77
4.2.5 Cocaine dose-response training and test (experiment 3) ................................... 77
4.2.6 Cocaine PR test (experiment 4) ......................................................................... 78
4.2.7 METH PR test (experiment 5) ........................................................................... 79
4.2.8 Food PR test (experiments 4 and 5 cont.) .......................................................... 79
4.2.9 FSCV equipment (experiment 6) ....................................................................... 80
4.2.10 Tissue preparation .............................................................................................. 80
4.2.11 FSCV recordings ................................................................................................ 81
4.2.12 Statistical analysis .............................................................................................. 82
4.3 Results and Summary ................................................................................................ 82
4.3.1 Experiment 3 results .......................................................................................... 82
4.3.2 Experiment 3 summary ...................................................................................... 85
4.3.3 Experiment 4 results .......................................................................................... 85
4.3.4 Experiment 4 summary ...................................................................................... 88
4.3.5 Experiment 5 results .......................................................................................... 89
4.3.6 Experiment 5 summary ...................................................................................... 93
4.3.7 Experiment 6 results .......................................................................................... 93
4.3.8 Experiment 6 summary ...................................................................................... 95
4.4 Discussion ................................................................................................................. 95
5 TAAR1 Activation Prevents Relapse to Drug Seeking .................................................. 102
5.1 Introduction ............................................................................................................. 102
5.2 Materials and Methods ............................................................................................ 103
5.2.1 Subjects ............................................................................................................ 103
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5.2.2 Pharmacological agents ................................................................................... 103
5.2.3 Catheter implantation surgery .......................................................................... 104
5.2.4 Apparatus ......................................................................................................... 104
5.2.5 Context-induced relapse of cocaine seeking (experiment 7) ........................... 104
5.2.6 Food assay (experiment 7 cont.) ...................................................................... 105
5.2.7 Cocaine-primed reinstatement of drug seeking (experiment 8) ....................... 105
5.2.8 METH-primed reinstatement of drug seeking (experiment 9) ........................ 106
5.2.9 Substitution assay (experiment 10) .................................................................. 106
5.2.10 Statistical analysis ............................................................................................ 107
5.3 Results and Summary .............................................................................................. 107
5.3.1 Experiment 7 results ........................................................................................ 107
5.3.2 Experiment 7 summary .................................................................................... 111
5.3.3 Experiment 8 results ........................................................................................ 111
5.3.4 Experiment 8 summary .................................................................................... 113
5.3.5 Experiment 9 results ........................................................................................ 114
5.3.6 Experiment 9 summary .................................................................................... 116
5.3.7 Experiment 10 results ...................................................................................... 117
5.3.8 Experiment 10 summary .................................................................................. 118
5.4 Discussion ............................................................................................................... 120
6 General Discussion ......................................................................................................... 128
6.1 Summary of Study ................................................................................................... 128
6.2 Physiology and Regulatory Effects of TAAR1 Activation ..................................... 131
6.3 TAs vs. Selective TAAR1 Agonists ........................................................................ 136
6.4 Non-Drug Related Effects of TAAR1 Agonists ..................................................... 138
6.5 Limitations and Future Directions........................................................................... 141
6.6 Conclusion ............................................................................................................... 144
7 REFERENCES ............................................................................................................... 146
8 APPENDIX A................................................................................................................. 183

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ACKNOWLEDGEMENTS

First and foremost, I would like to express my sincere gratitude to my primary supervisor Dr
Juan J. Canales for his invaluable expertise, guidance, and encouragement throughout my
postgraduate years, especially for the enormous support and patience during my 12-month
visit to the UK where I collected important data and gained experience. Juan you have set a
fine example of what an enthusiastic and successful scientist is like, and this will always
motivate me for my future pursuing of an academic career. I feel extremely privileged to have
been your student and simply cannot imagine a better supervisor.
I would also like to deeply thank my secondary supervisor, Professor Randolph Grace, for his
continuing feedback, advice, and encouragement throughout the PhD, as well as the
invaluable support he has provided during my laboratory work. I really enjoyed our long talks
that have broadened my thoughts and stimulated new perspectives for my thesis.
I am thankful to all of the laboratory staff, Neroli Harris, Silvana De Freitas, and Kate
Freeman, for their excellent care of the animals. I would also like to thank Glenn Lewis for
building up some experimental equipment and Gerard Mesman for assistance with sorting out
computer issues. Thank you also to the psychology department administration staff, who
were always helpful and supportive. I thank my fellow labmates for the stimulating
discussions, helping with each other at the busiest time of our experiments, and providing
important suggestions during my preparation for conference presentations.
Sincere thanks must go to the people in the University of Leicester for the fruitful
collaboration and valuable advices. I’m deeply thankful to Dr Claire Gibson, the head of
department of Neuroscience, Psychology & Behaviour, for providing me with the opportunity
to conduct research there. I would particularly like to acknowledge Dr Aman Asif-Malik,
who has assisted with my research in every possible way. Aman thank you a million for your
expertise on voltammetry, stimulating discussion, and great sense of humour. Your patience,
motivation, enthusiasm, and passion make you a great mentor that will keep inspiring me in
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my life. I would also like to thank staff in the Centre Research Facility, who provided good
care for the animals, without which it would not be possible to complete this research.
Acknowledgement must also go to the University of Canterbury for providing me with a
scholarship to finance my studies and to Roche for generously providing the TAAR1
compounds for my experiments and funding for my visit to the UK.
The last word of acknowledgement I have saved for my dear family and boyfriend for their
love, support, and sacrifices. Without them, this thesis would never have been written. They
have been with me all these years, witnessed my laughs and tears, and made these time most
unforgettable memory of my life.

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LIST OF FIGURES

Figure 1.1 Stages of impulse control disorder and compulsive disorder related to the
sources of reinforcement .......................................................................................... 5
Figure 1.2 The spiralling addiction cycle from the psychiatric-motivational perspective ........ 6
Figure 1.3 The affective dynamics of the opponent process ..................................................... 8
Figure 1.4 The opponent process theory relevant to addiction .................................................. 8
Figure 1.5 The allostatic model of drug addiction ..................................................................... 9
Figure 1.6 The mesocorticolimbic dopaminergic pathways .................................................... 15
Figure 1.7 The striato-nigro-striatal loop for the transition to compulsive drug seeking ........ 18
Figure 1.8 Neuroadaptations in the brain circuitry for the three stages of addiction cycle ..... 22
Figure 2.1 Signalling of trace amine-associated receptor 1 (TAAR1) at a DA synapse ......... 39
Figure 3.1 RO5203648 time-dependently modulated METH-induced locomotion ................ 60
Figure 3.2 Compound M altered subsequent locomotor response to a METH probe ............. 62
Figure 3.3 Compound M modulated the effects of repeated METH on
brain gene inducibility ........................................................................................... 63
Figure 4.1 RO5203648 and RO5256390 shifted the cocaine dose-response
curve downward ..................................................................................................... 84
Figure 4.2 RO5203648 differentially regulated the reinforcing efficacy of
cocaine and food .................................................................................................... 87
Figure 4.3 RO5263397 reduced the reinforcing efficacy for METH ...................................... 90
Figure 4.4 RO5263397 increased the reinforcing efficacy for food ........................................ 92
Figure 4.5 RO5263397 reduced METH-induced DA outflow in slices of rat NAc core ........ 94
Figure 5.1 RO5203648 suppressed context-induced relapse of cocaine seeking .................. 108
Figure 5.2 RO5203648 delayed food intake only at the high dose ........................................ 109
Figure 5.3 RO5256390 suppressed context-induced relapse of cocaine seeking .................. 110
Figure 5.4 RO5256390 affected food intake only at the high dose ....................................... 111
Figure 5.5 RO5203648 prevented cocaine-primed reinstatement of cocaine seeking ........... 114
Figure 5.6 RO5263397 prevented METH-primed reinstatement of METH seeking ............ 117
Figure 5.7 RO5263397 did not sustain responding when substituted for METH ................. 119

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