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The Suprachiasmatic Nucleus of the Domestic Chicken

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The Suprachiasmatic Nucleus of the Domestic Chicken THE SUPRACHIASMATIC NUCLEUS OF THE DOMESTIC CHICKEN, Gallus domesticus A Dissertation by ELIZABETH LAYNE CANTWELL Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY December 2005 Major Subject: Zoology THE SUPRACHIASMATIC NUCLEUS OF THE DOMESTIC CHICKEN, Gallus domesticus A Dissertation by ELIZABETH LAYNE CANTWELL Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Vincent M. Cassone Committee Members, David J. Earnest Susan S. Golden Mark J. Zoran Head of Department, Vincent M. Cassone December 2005 Major Subject: Zoology iii ABSTRACT The Suprachiasmatic Nucleus of the Domestic Chicken, Gallus domesticus. (December 2005) Elizabeth Layne Cantwell, B.A., University of Virginia Chair of Advisory Committee: Dr. Vincent M. Cassone The avian circadian system is composed of multiple inputs, oscillators and outputs. Among its oscillators is a hypothalamic structure presumed to be homologous to the primary circadian pacemaker in mammals, the suprachiasmatic nucleus (SCN). The SCN in avian species is poorly defined: two structures in the hypothalamus, the medial SCN (mSCN) and visual SCN (vSCN), have been referred to in the literature as the SCN. The present studies were designed to answer one central question: where is the avian homolog to the mammalian SCN? Uptake of 2-[14C]-deoxyglucose (2DG), an indicator of glucose metabolism, fluctuates in the mSCN and vSCN in both a daily and circadian manner. These data indicate a possible role in the circadian system for both the vSCN and the mSCN. Additionally, several visual structures display daily fluctuations of 2DG uptake, two of which exhibit circadian variations, supporting previous studies indicting circadian regulation of the visual system. Efferents and afferents of the mSCN and vSCN were identified and compared to those of rodents. While the mSCN bears a stronger resemblance to the rodent SCN in its efferent connections than the vSCN, afferents of both are comparable. The total number of mSCN and vSCN neuronal connections far exceeds that of the rodent SCN. A subset of iv these connections is strikingly similar to those of the rodent SCN, while others are found to connect these two nuclei to the visual system. These data further support the involvement of both the mSCN and vSCN in the circadian and visual systems. Suprachiasmatic organization was addressed using classical techniques. Though loosely similar in location to the mammalian SCN, the mSCN is cyto- and chemoarchitecturally different, while the vSCN bears more similarity to the mammalian SCN in this regard. A unique astrocytic bridge exists between the mSCN and vSCN, suggesting a role for astrocytes in the circadian system. Finally, the vSCN efferent to the medial nucleus of Edinger-Westphal was verified using a technique that may advance future studies of avian of circadian organization. The current data and the available literature were considered in the development of a working model of the avian SCN. v ACKNOWLEDGMENTS I would first like to thank my advisor, Vinnie “Soul Crusher” Cassone, for sticking with me throughout my graduate career and for having “Git ’r done” at the top of the list. You helped me see the forest, encouraged me to think more critically, and motivated me when I needed it. I feel more prepared to move forward in my career than I ever thought possible, due in large part to your efforts. Knowing that I’ve made you proud means more to me than I think you’ll ever know. I would also like to thank my committee members, Dave Earnest and Susan Golden, and Mark Zoran, who were always great sources of wisdom and encouragement. I must also thank Dave, for his gift of Cholera toxin in the eleventh hour, and Mark, for helping me with iontophoretic injections and for dreaming with me about some experiments I hope to accomplish in the future. Thanks also to Tom Champney, a founding member of my committee, for his advice and support early in my graduate career. I have been lucky to have many supportive friends and labmates throughout my graduate career. I’d especially like to thank Arjun Natesan, Michael Gonzales, Jayna Ditty, Jen McGoogan and Kathryn Craven for their many pep talks. Heather Fugger was a great source of support throughout the writing process—sharing an office with you kept me sane. Jiffin Paulose helped me polish my defense and listened to it more times than any good person should have to. Paul Bartell really came through for me at crunch time and helped me strengthen my writing. The members of the Manson lab, my second home, have been a constant source of comic relief, particularly Arjan Bormans, who vi took me to the emergency room occasionally. I’d like to thank Jen Peters, my lunch buddy, for our many deep conversations and commiserations. I’d like to thank Jen and Kevin Leiner for their friendship and for dancing with me to “You are my sunshine”. Finally, I’d like to thank Shelby, Bobber, Gretchen and Roscoe for their healing powers. I’d like to thank my husband, Brian Cantwell, for his love and support. You’ve done more than your fair share for quite some time now, while keeping me going. There are truly no words that adequately describe how much you’ve helped me or how much you mean to me. Finally, I’d like to thank my mother. You always encouraged me in my aspirations and prodded me along when I was feeling like I might not be able to achieve them. You wouldn’t let me beat myself up when I was feeling low. I’d have never gotten through this without your love, guidance and support, which have been constant throughout my entire life. You’re my given, and I love you very much. vii TABLE OF CONTENTS Page ABSTRACT................................................................................................................ iii ACKNOWLEDGMENTS........................................................................................... v TABLE OF CONTENTS............................................................................................ vii LIST OF FIGURES..................................................................................................... ix LIST OF TABLES ...................................................................................................... xi NOMENCLATURE.................................................................................................... xii CHAPTER I INTRODUCTION............................................................................... 1 Formal Properties of Circadian Rhythms...................................... 1 The Vertebrate Circadian System ................................................. 3 The Avian Circadian System......................................................... 4 The Putative Avian Suprachiasmatic Nucleus .............................. 9 Visual System Pathways............................................................... 12 Objectives and Significance.......................................................... 13 II DAILY AND CIRCADIAN FLUCTUATION IN 2-DEOXY[14C]- GLUCOSE UPTAKE IN CIRCADIAN AND VISUAL SYSTEM STRUCTURES OF THE CHICK BRAIN: EFFECTS OF EXOGENOUS MELATONIN ........................................................... 16 Introduction................................................................................... 16 Materials and Methods.................................................................. 19 Results........................................................................................... 24 Discussion..................................................................................... 31 viii CHAPTER Page III THE CHICKEN SUPRACHIASMATIC NUCLEI: EFFERENT AND AFFERENT CONNECTIONS.................................................. 37 Introduction................................................................................... 37 Materials and Methods.................................................................. 41 Results........................................................................................... 49 Discussion..................................................................................... 82 IV THE CHICKEN SUPRACHIASMATIC NUCLEI: AUTORADIOGRAPHIC AND IMMUNOHISTOCHEMICAL ANALYSIS ......................................................................................... 98 Introduction................................................................................... 98 Materials and Methods.................................................................. 101 Results........................................................................................... 104 Discussion..................................................................................... 113 V DATA INDICATE THAT INTRAVITREAL INJECTION OF PSEUDORABIES VIRUS BARTHA RETROGRADELY INFECTS THE SUPRACHIASMATIC COMPLEX OF THE CHICK.............. 124 Introduction................................................................................... 124 Materials and Methods.................................................................. 126 Results........................................................................................... 129 Discussion..................................................................................... 136 VI CONCLUSIONS................................................................................. 140 LITERATURE CITED ..............................................................................................
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