The Brain Stem in a Lizard, Varanus Exanthematicus

ISBN-13: 9783540179481 / Angielski / Miękka / 1987 / 168 str.

Hendrik J. Ten Donkelaar; Gesineke C. Bangma; Heleen A. Barbas-Henry

Opis

With the introduction of modern neuroanatomical tract-tracing techniques (e. g. , Heimer and RoBards 1981; Mesulam 1982) and immunohistochemical methods (e. g. , Cuello 1983) powerful tools to study the circuitry of the central nervous system in vertebrates became available. These techniques have also been widely applied in "lower" vertebrates. A major task of comparative neurobiology is to sample the variations that exist in the brains of living taxa and to recognize common morphological patterns and their adaptive significance (Northcutt 1978, 1981). Reptiles, with their great variation in form and locomotion, are particularly interesting objects for neurobiologic research. They were the first vertebrates to be truly terrestrial and each reptilian radiation has solved many of the major obstacles to successful land invasion in strikingly different ways (Gans 1974). Among reptiles, the most encephalized species (as regards brain- body weight relationship, e. g. , Jerison 1973; Ebbesson and Northcutt 1976; Platel1979) are the dracomorphs (e. g. teiids, varanids and iguanids). The brains of dracomorphs can best be described as the most complex among living lizards with increase in both size and differentiation of most sensory modalities (North- cutt 1978). In the present study, the structure and fiber connections of the brain stem of such a highly developed dracomorph, the savanna monitor lizard, Varanus exanthematicus (Fig. 1), are analyzed. The brain stem plays a key role within the central nervous system.

Spis treści

1 Introduction.- 2 Materials and Techniques.- 2.1 Cytoarchitectonic Analysis.- 2.2 Immunohistochemical Procedures.- 2.3 Tract-Tracing Studies.- 2.3.1 Anterograde Degeneration Studies.- 2.3.2 Horseradish Peroxidase Retrograde and Anterograde Transport Studies.- 2.3.3 Retrograde Fluorescent Tracer Studies.- 2.3.4 Anterograde [3H] Leucine Tracing Studies.- 3 Gross Anatomy.- 3.1 The Brain Stem.- 3.2 The Cranial Nerves.- 4 Spinal Projections to the Brain Stem.- 4.1 The Dorsal Column Nucleus and its Afferent and Efferent Connections.- 4.2 Fiber Systems Ascending in the Lateral Funiculus.- 4.2.1 The Spinal Lemniscus.- 4.2.1.1 Spinorhombencephalic Projections.- 4.2.1.2 Spinomesencephalic Projections.- 4.2.1.3 Spinothalamic Projections.- 4.2.2 Spinocerebellar Projections.- 5 Organization and Connections of the Sensory Trigeminal Nuclei.- 5.1 Cytoarchitecture.- 5.2 Primary Afferents.- 5.3 Central Trigeminal Projections.- 6 The Solitary Tract and Related Nuclei.- 6.1 Cytoarchitecture : Viscerosensory Nuclei.- 6.2 Primary Afferents.- 6.3 Central Visceral and Taste Pathways.- 7 Cranial Nerve Motor Nuclei.- 7.1 Somatomotor Nuclei.- 7.2 Branchiomotor Nuclei.- 7.3 Visceromotor Nuclei.- 8 The Vestibular Nuclear Complex and Related Structures.- 8.1 Cytoarchitecture.- 8.2 Primary Afferents.- 8.3 Central Vestibular Projections.- 8.3.1 The Fasciculus Longitudinalis Medialis.- 8.3.2 Vestibulospinal Pathways.- 9 Acoustic Projections.- 9.1 Primary Acoustic Projections and Nuclei.- 9.2 The Superior Olive.- 9.3 The Torus Semicircularis.- 10 Visual Input to the Brain Stem.- 10.1 The Tectum Mesencephali.- 10.1.1 Tectal Lamination.- 10.1.2 Tectal Afferents.- 10.1.2.1 Visual Input.- 10.1.2.2 Nonvisual Afferents.- 10.1.3 Tectal Efferents.- 10.1.3.1 Ascending Tectal Efferents.- 10.1.3.2 Descending Tectal Efferents.- 10.2 The Nucleus of the Basal Optic Root.- 10.3 The Isthmic Nuclei.- 11 Forebrain Projections to the Brain Stem.- 11.1 Notes on the Organization of the Reptilian Forebrain.- 11.2 Basal Ganglia Projections to the Brain Stem.- 11.2.1 The Substantia Nigra and Ventral Tegmental Area.- 11.3 Diencephalic Projections to the Brain Stem.- 11.3.1 Thalamic Projections to the Brain Stem.- 11.3.2 Hypothalamic Projections to the Brain Stem.- 11.4 The Habenulointerpeduncular Tract.- 11.4.1 The Nucleus Interpeduncularis.- 12 Cerebellar Connections.- 12.1 Notes on the Cerebellar Cortex.- 12.2 The Cerebellar Nuclei.- 12.3 Afferent Connections of the Cerebellum.- 12.3.1 Spinal Afferents.- 12.3.2 Rhombencephalic Afferents.- 12.3.2.1 Vestibular Afferents.- 12.3.2.2 The Nucleus Prepositus Hypoglossi.- 12.3.2.3 The Inferior Olive.- 12.3.2.4 Other Rhombencephalic Afferents.- 12.3.3 Mesencephalic Afferents.- 12.3.4 Prosencephalic Afferents.- 12.4 Efferent Connections of the Cerebellum.- 12.4.1 Corticonuclear Projections.- 12.4.2 Projections of the Cerebellar Nuclei.- 12.4.3 The Red Nucleus.- 13 The Reticular Formation.- 13.1 Cytoarchitecture.- 13.2 Monoaminergic and Peptidergic Components.- 13.2.1 Distribution of Catecholamine Neurons in the Brain Stem.- 13.2.2 Distribution of Serotonin-Containing Neurons in the Brain Stem.- 13.2.3 Peptidergic Components.- 13.3 Ascending Projections.- 13.3.1 Ascending Projections of the Brain Stem Reticular Formation.- 13.3.2 Ascending Monoaminergic Systems in the Reptilian Reticular Formation.- 13.4 Descending Projections.- 13.4.1 Reticulospinal Projections.- 13.4.2 Descending Monoaminergic Projections to the Spinal Cord.- 13.4.2.1 Raphespinal Projections.- 14 Concluding Remarks.- 14.1 Ascending Projections.- 14.2 Descending Projections to the Brain Stem.- 14.3 Descending Projections from the Brain Stem.- 14.4 Cerebellar Connections.- 14.4.1 Cerebellar Afferents.- 14.4.2 Cerebellar Efferents.- 14.5 Research Perspectives.- Acknowledgments.- References.