University of Wollongong Research Online University of Wollongong Thesis Collection University of Wollongong Thesis Collections 2014 The effect of Neuregulin 1 on PCP induced alterations of locomotion, neurotransmission and cell growth as relevant for schizophrenia Martin Engel University of Wollongong Recommended Citation Engel, Martin, The effect of Neuregulin 1 on PCP induced alterations of locomotion, neurotransmission and cell growth as relevant for schizophrenia, Doctor of Philosophy thesis, School of Medicine, University of Wollongong, 2014. http://ro.uow.edu.au/theses/4395 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] The effect of Neuregulin 1 on PCP induced alterations of locomotion, neurotransmission and cell growth as relevant for schizophrenia Martin Engel This thesis is presented as part of the requirement for the Award of the Degree Doctor of Philosophy from the University of Wollongong School of Medicine July, 2014 CERTIFICATION I, Martin Engel, declare that this thesis, submitted in partial fulfilment of the re- quirements for the award of Doctor of Philosophy, in the School of Medicine, Uni- versity of Wollongong, is wholly my own work unless otherwise referenced or acknowledged. The document has not been submitted for qualifications at any other academic institution. Martin Engel 23rd of July 2014 II ABSTRACT Schizophrenia is a serious psychiatric disorder causing a wide range of devastating impairments. A combination of several genetic and environmental factors is consid- ered to result in a range of neurobiological changes underlying the symptom spec- trum of schizophrenia. Differences in the γ-aminobutyric acid (GABA)ergic, glu- tamatergic and dopaminergic neurotransmitter systems have been most consistently observed in patients with schizophrenia. Current pharmacological treatment options for patients with schizophrenia are, however, still limited in their ability to address the range of symptoms and identified neurobiological differences. Substantial evidence from human studies has linked the neurotrophic factor neuregu- lin 1 (NRG1) to the pathophysiology of schizophrenia, with further support from an- imal studies. Acute NRG1 signalling has been shown to affect GABAergic and glu- tamatergic neurotransmission in vitro in the prefrontal cortex (PFC) and hippocam- pus, two regions strongly linked to the symptomatology of schizophrenia. Due to the acute signalling properties of NRG1 in attenuating schizophrenia-relevant neuro- transmission, a therapeutic potential of the NRG1 signalling system for the treatment of schizophrenia has been hypothesized, but never explored. In the present PhD thesis I assessed the possible antipsychotic-like characteristics of NRG1 treatment on schizophrenia-relevant behavioural and molecular impairments focusing on GABAergic and glutamatergic signalling. I modelled schizophrenia-like impairments in adult male mice by acute phencyclidine (PCP). Acute PCP treatment in mice has been shown to induce a wide spectrum of schizophrenia-relevant symp- toms, including hyperlocomotion, impaired sensorimotor gating and neurotransmis- sion impairments. This treatment paradigm is therefore widely used as a first step in antipsychotic drug development studies. In my first study, I examined the effects of concurrent NRG1 and PCP treatment on locomotor activity and sensorimotor gating. Central and peripheral NRG1 admin- istration dose-dependently prevented PCP-induced hyperlocomotion and prepulse inhibition impairment. Advancing on these findings, I then studied the effects of NRG1 application on acute neurotransmission in the presence of PCP by microdialy- sis in the PFC and hippocampus of freely moving mice. In the PFC, NRG1 reduced glutamate and glycine levels, while combined NRG1 and PCP treatment triggered an increase in extracellular glycine. In the hippocampus, PCP treatment triggered a sig- III nificant increase in GABA levels without affecting glutamate or glycine. The GABA increase was not observed following combined NRG1 and PCP treatment, suggesting that NRG1 prevented the PCP effect. An increase in glycine was again observed fol- lowing combined treatment, here accompanied by a reduction in glutamate levels. In my final study, I treated cells from primary frontal cortex cultures with NRG1 in the presence of PCP, measuring components of the GABAergic system relevant to the pathophysiology of schizophrenia. PCP changed the mRNA expression of GABA producing enzymes and the calcium binding protein parvalbumin. Combined treat- ment with NRG1 dose-dependently prevented these PCP-induced expression changes in the frontal cortex cells. Prevention of PCP-induced hyperlocomotion and PPI impairments demonstrates a clear involvement of the NRG1 signalling pathway in neuronal circuits relevant for spontaneous behaviour. The region specific influence of NRG1 on glutamate and glycine levels confirms the involvement of NRG1-ERBB signalling in adult excitato- ry neurotransmission. Furthermore, preventing the PCP-induced GABA increase in the hippocampus provides support for a functional role in inhibitory neurotransmitter signalling. An involvement of NRG1 in the regulation of inhibitory neurotransmis- sion was further supported by in vitro frontal cortex experiments where NRG1 treat- ment prevented changes to GABA producing enzymes. The combined outcomes of my experiments provide initial support for potential anti- psychotic-like characteristics of NRG1 treatment in a mouse model with induced schizophrenia-relevant behavioural and molecular impairments. The observed effica- cy of peripherally administered NRG1 to prevent PCP-induced behavioural deficits indicates its potential as a new therapy for schizophrenia patients. Exploring the con- sequences of long-term NRG1 treatment on a broader spectrum of behavioural per- formance and molecular changes, particularly of the dopaminergic system, will be required to advance on the present findings and take the next step towards a potential suitability of NRG1 treatment in a clinical setting. IV ACKNOWLEDGEMENTS I would like to acknowledge and thank all the people who have taken part, assisted and supported me throughout the journey of my PhD. First and foremost, I would like to thank my supervisors Elisabeth Frank and Xu-Feng Huang, who have made this PhD project possible. For their support me despite the unexpected start, through many turns and changes, from early Monday mornings till late Sunday nights, from Amsterdam to Wollongong, from a skype call in Cardiff to presentations on three continents, who supported the idea before the first data point was anywhere in sight. My collaborators Tim Karl, Andrew Jenner and Lezanne Ooi, who have joined along the way from different groups and institutes: thank you for your constant support and giving me the opportunity to learn new methods and strategies for scientific investi- gations. Vincenzo Crunelli, Angelique Hoolahan and Simon Kaja, for the valuable scientific discussions and helpful advice, despite having no stakes in the project, but only wanting to see me progress. Thank you to the owners of the many hands that have helped me day in and day out, particularly Tracy, Maria, Zhixiang, the CTN and IHMRI team, for providing and maintaining an atmosphere I was happy to return to, even when I left it less than 12 hours ago. Thank you to my fellow PhD students who made surviving the endless hours in the lab bearable, with great company and hot chocolate, especially Peta, Na- talie, Jess, Colin and Amy. And finally, to all my family and friends, especially Louise, for tolerating my spend- ing so many late nights and weekends in the lab. My sincere gratitude for your good humour, support and acceptance while I completed this project! V TABLE OF CONTENTS CERTIFICATION ...................................................................................................... II ABSTRACT ............................................................................................................... III ACKNOWLEDGEMENTS ........................................................................................ V TABLE OF CONTENTS ........................................................................................... VI LIST OF FIGURES .................................................................................................... X LIST OF TABLES .................................................................................................... XII List of abbreviations ................................................................................................ XIII 1 Introduction ............................................................................................................... 1 1.1 Schizophrenia ............................................................................................... 1 1.1.1 The symptoms of schizophrenia .............................................................. 1 1.1.2 The neurobiology of schizophrenia .......................................................... 2 1.1.3 Current Pharmacological Treatment Situation of Schizophrenia ............. 9 1.1.4 Current attempts in targeting GABA for treating schizophrenia ........... 12 1.2 Neuregulin 1 and ERBB4 signalling .......................................................... 13 1.2.1 ERBB4 ................................................................................................... 13 1.2.2