Functional Morphology of Gustatory Centers in the Brain of the Channel Catfish, Ictalurus Punctatus

Louisiana State University LSU Digital Commons LSU Historical Dissertations and Theses Graduate School 1991 Functional Morphology of Gustatory Centers in the Brain of the Channel Catfish, Ictalurus Punctatus. Charles Franklin Lamb IV Louisiana State University and Agricultural & Mechanical College Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_disstheses Recommended Citation Lamb, Charles Franklin IV, "Functional Morphology of Gustatory Centers in the Brain of the Channel Catfish, Ictalurus Punctatus." (1991). LSU Historical Dissertations and Theses. 5254. https://digitalcommons.lsu.edu/gradschool_disstheses/5254 This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Historical Dissertations and Theses by an authorized administrator of LSU Digital Commons. For more information, please contact [email protected]. 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MI 4X I Oft FUNCTIONAL MORPHOLOGY OF GUSTATORY CENTERS IN THE BRAIN OF THE CHANNEL CATFISH, ICTALURUS PUNCTATUS A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and A(,.ri cultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Zoology and Physiology by Charles Franklin Lamb IV B.A., Humboldt State University, 1983 M.S., Louisiana State University, 1986 December 1991 Acknowledgements This dissertation would not have been possible without the understanding tutelage of Dr. John Caprio, who supported this project both intellectually and financially. Others deserving grateful acknowledgement Include Dr. Dominique Homberger for providing the impetus to develop a critical consideration for the context within whicli scientific research is performed, Drs. Jagmeet Kanwal, Takayuki Marui, and Tomio Hayama for their help with technical aspects during the initial stages of this project, and Drs. Tom Finger, Harold Silverman, George Strain, Peter Johnsen. and William Herke for reviewing the manuscript and providing constructive criticism. I also thank Mr. Ron Bouchard for his time and effort in the darkroom, and the LSU Life Sciences Microscopy Facility (supported in part by LSU Board of Regents Academic Enhancement Grant LEQSF ENHBS1) for the light microphotography. This project was supported by NIH grant NS- 14819 and NSF grant BNS 8819772 to Dr. John Caprio. On a more per onal note, I thank my parents, Charles and Barbara Lamb, for their persistent admonishments on the permanence of education and the pursuance of elusive goals, and my wife, Judy Lamb, for her support and patience throughout the process. It is to these people that this dissertation is dedicated, not as a culminating triumph but as a struggling first step. i i Table of Contents Page Acknowledgements . .................................................... il List of Tables .... iv List of Figures ........................................................ v Abst ract .............................................................. vii Chapter I : Int roduction ...................................................... i Chapter II: Convergence of Oral and Extraoral Information In th> Superior Secondary Gustatory Nucleus .......... 7 Chapter III: Diencephalic Gustatory Connections ..................... 37 Chapter IV: Taste and Tactile Responsiveness in the Posterior Diencephalon ................................ 90 Chapter V: Summary ................................................. 125 References ...................................................................... 129 Appendix A: Abbreviations for Figures and Tables ................. 143 Appendix B: Curriculum Vitae ....................................... 146 Vita .................................................................. 150 i i i List of Tables Chapter 11: 11.1, Receptive fields of neurons in the superior secondary gustatory nucleus .......... Chapter III: 111.1, Descr*ption of gustatory nuclei in the inferior lobe ........................ 111.2, Summary of HRP-labeling of gustatory connections in the inferior lobe Chapter IV: IV.1. Response characteristics of neurons from gustatory nuclei In the Inferior lobe List of Figures Page Chapter 11 : II. 1. Horizontal section through the nGS ................... 15 II. 2. Schematic of response locations in the nGS .......... 17 11.3. Marked electrode locations of two units .............. 20 11.4. Taste responses of a unit from the medial nGS ........ 21 11.5. Bimodal responses of a unit from the central nGS ..... 23 11.6. HRP-labeled projections from the facial and vagal lobes in the medulla to the nGS ...................... 25 Chapter III: 111.1. Transverse sections through the caudal inf er i or lobe .......................................... 46 111.2. Schematic of nuclei in the caudal inferior lobe ..... 47 111.3. Tertiary gustatory efferents in the inferior lobe .... 51 111.4. HRP-laleled cells in the nucleus lobobulbaris ........ 54 111.5. Nucleus lobobulbaris celIs in three dimens ions ....... 55 111.6. Longitudinal terminal fields of the inferior lobe .... 59 111.7. HRP-labeled tertiary gustatory cells and fibers ..... 60 111.8. Summary of connect ions of the caudal nucleus centralis (ltfLI) ............................. 61 111.9. Summary of connections of the rostromedial nucleus centralis ..................................... 63 v List of Figures (cont.) Page Chapter III (cont.): III. 10. HRP inject ion in the nucleus centralIs ............... 6 5 111 . 11 . HRP-labeled cells in different nuclei of the Inferior lobe following injections in the nucleus centralis .................................... 67 111.12. Summary of connections of the rostrolateral nucleus centralis .................................... 69 111.13. HRP-labeled cells in the inferior lobe following injections in the telencephalon ..................... 71 111.14. Summary of connections between the caudal inferior lobe and the primary and secondary gustatory nuclei ..................................... 75 111.15. Schematic of diencephalic gustatory connect ions ..... 81 Chapter IV: IV.1. Schematic of connections between the primary and secondary gustatory nuclei and the inferior lobe .... 92 IV.2. Marked electrode locations of six units from the Infer ior lobe ......................................... 100 IV.3. Bimodal responses of a unit from the medial nucleus centralis .................................... 104 IV.4. Bimodal responses of a unit from the caudal nucleus lobobulbaris ................................. 106 IV.5. Taste responses of a unit from the caudal nucleus lobobulbaris .......................................... 109 IV.6. Tactile responses of two units from the rostrolateral nucleus lobobulbaris ............ Ill IV.7. Tactile responses of a unit from the rostral lateral thalamic nucleus ............................. 114 IV.8. Bimodal responses of a unit from the rostral lateral thalamic nucleus ............................. 115 vi Abstract Gustatory nuclei in the isthmic region of the metencephalon and in the posterior diencephalon of the channel catfish, Ictalurus punctatus. were examined anatomically and electrophysiologica1ly. Neurons in the superior secondary gustatory nucleus (nGS) responded to taste and tactile stimulation of large peripheral receptive fields (RFs) that often included the epithelia of the oropharyngeal cavity and whole extraoral body surface. Taste responses to amino acids and nucleotides were dose dependent, with detected thresholds from micromolar to millimolar concentrations. The RF organization within the nGS did not display the somatotopy present in the medullary gustatory nuclei. Anatomical labeling of secondary

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