Introduction 9

University of Groningen The basic neural circuitry for sexual behavior van der Horst, Veronica Gerarda Johanna Maria IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 1996 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): van der Horst, V. G. J. M. (1996). The basic neural circuitry for sexual behavior: Pathways and plasticity. [S.n.]. Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license. More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne- amendment. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date: 10-10-2021 The basic neural circuitry for sexual behavior; Pathways and plasticity ISBN 90 367 0670 x Drukkerij: Print Partners Ipskamp, Enschede RIJKSUNIVERSITEIT GRONINGEN The basic neural circuitry for sexual behavior; Pathways and plasticity Proefschrift ter verkrijging van het doctoraat in de Medische Wetenschappen aan de Rijksuniversiteit Groningen op gezag van de Rector Magnificus, dr. F. van der Woude, in het openbaar te verdedigen op woensdag 25 september 1996 des namiddags te 2.45 uur door Veronica Gerarda Johanna Maria van der Horst geboren op 21 mei 1969 te Heeze Promotor: Prof. dr. G. Holstege Promotion Committtee: Prof. dr. D. Kernell University of Groningen, Groningen Prof. dr. D.W. Pfaff Rockefeller University, New York Prof. dr. H.J. Ralston III University California San Francisco, San Francisco Prof. dr. J. Voogd Erasmus University, Rotterdam Paranymphs: Dr. D.D. Ralston Drs. M.C. van der Horst Run hard, be strong, think big Contents General introduction 9 Chapter 1 Distinct cell groups in the lumbosacral cord of the cat project to different areas in the periaqueductal gray 17 Chapter 2 The organization of lumbosacral motoneuronal cell groups innervating hindlimb, pelvic floor and axial muscles in the cat 43 Chapter 3 Caudal medullary pathways to lumbosacral motoneuronal cell groups in the cat: evidence for direct projections possibly representing the final common pathway for lordosis 79 Chapter 4 Nucleus retroambiguus projections to lumbosacral motoneuronal cell groups in the male cat, possibly representing the final common pathway for mounting behavior 99 Chapter 5 Estrogen induces axonal outgrowth in the nucleus retroambiguus-lumbosacral motoneuronal pathway in the adult female cat 113 General discussion 129 References 145 Abbreviations 158 Summary 159 Samenvatting 160 Dankwoord 163 List of publications 164 Curriculum vitae 165 General introduction General introduction 9 General introduction General introduction The somatic and emotional motor systems Motoneurons All motor activities, for example running, Motor system reaching, jumping, writing, talking, drinking, and Voluntary motor Emotional motor mating, require the activation of specific sets of striated system system and smooth muscles. The striated muscles are innervated Lateral Medial Lateral Medial by somatic motoneurons, whereas the smooth muscles eye, neck, specific axial and proximal emotional are innervated by sympathetic or parasympathetic body movements behaviors preganglionic motoneurons. Each muscles, or even independent gain setting systems movements of including triggering muscle compartment, is innervated by its own group of the extremities mechanisms of rhythmical and other motoneurons. Somatic motoneuronal cell groups spinal reflexes innervating muscles of the head are located in the brain Basic system (premotor interneurons) stem, those of the remaining parts of the body in the ventral horn of the spinal cord (lamina IX of Rexed, 1954; see Fig. 1). The axial muscles of the neck and back are innervated by motoneurons in the medial part of the ventral horn throughout the ventral horn, whereas Motoneurons those innervating the muscles of the extremities are located in the lateral ventral horn of the cervical and Figure 2 Schematic overview of the three subdivisions of the lumbosacral enlargements. Sympathetic preganglionics motor system (from Holstege, 1996). are present in the lateral horn of the thoracic and upper lumbar cord (see Cabot, 1996 for review), whereas The basic premotor interneuronal system The in- parasympathetic preganglionics are located in certain dividual components of the voluntary or emotional motor brain stem nuclei, and in the sacral cord (see Holstege, system reach the motoneurons via direct projections, or 1996 for review). All somatic and autonomic moto- indirectly via interneurons (see Fig. 2). Propriospinal neuronal cell groups are controlled by other structures premotor interneurons are located in the intermediate in the central nervous system (CNS), and together they zone of the spinal cord (Rexed’s laminae V to VIII; see form the “motor system” (Holstege, 1991; Fig. 2). Fig. 1). Premotor interneurons for the somatic motoneurons in the brain stem are located in the caudal pontine and medullary lateral tegmental field, which can be considered as the rostral extent of the spinal Rexed's laminae I to X intermediate zone (Holstege et al., 1977). However, premotor interneurons are not necessarily located in II I close proximity to their target motoneurons, but can also III be found at significant distances. Examples are the C2 Dorsal horn IV interneurons projecting to C8 (see Holstege, 1988), and V the pontine M-region neurons projecting to bladder X VI preganglionic motoneurons in the sacral cord (see Blok VII and Holstege, 1996). Together, all these premotor interneuronal cell groups constitute the “basic motor IX system” (Fig. 2; Holstege, 1991; 1996). VIII Ventral horn IX The voluntary motor system Part of our behavior is first sacral under control of the so-called “voluntary motor system” IX segment (S1) (Fig. 2). Examples are goal directed motor activities such as reaching and writing. The lateral component of the Figure 1 Schematic drawing of a transverse section of the voluntary motor system specifically involves the first sacral segment of the spinal cord, showing the laminar supraspinal control of goal directed movements of subdivisions in the gray matter according to Rexed (1954). especially the distal limb muscles, but also the orofacial 11 General introduction Dorsal Midbrain Rostral Caudal periaqueductal gray Ventral Nucleus Lumbosacral retroambiguus motoneurons L4-S1 Dorsal Ventral Figure 3 Schematic representation of the central nervous system in sagittal view (at the top) , and transverse view (at the bottom. The location of the periaqueductal gray, the nucleus retroambiguus, and motoneuronal cell groups in the lumbosacral segments of the spinal cord is indicated in gray. and tongue muscles during speech. It consists of the The emotional motor system Not all behavioral patterns cortico- and rubrospinal tracts, which act on laterally are voluntary. Crying, laughing and fear reactions for located motoneurons either directly, or via interneurons example are not mediated by the voluntary motor of the basic motor system (see Kuypers, 1981; Holstege, system, but by other structures in the CNS, which have 1996). been defined as the “emotional motor system” (Holstege, Postural control, involving axial and proximal muscles, 1991). Similar to the somatic motor system, the is controlled by cortico-, interstitio-, tecto-, vestibulo-, emotional motor system can be divided into a medial and reticulospinal tracts. Apart from the medial and a lateral component, corresponding to their location corticospinal tract, these pathways originate from the in the CNS. The lateral component is involved in specific medial tegmentum of the rostral midbrain, caudal pons, motor activities such as vocalization (=production of and medulla. They form the medial part of the voluntary sound; Holstege, 1989; Zhang, 1992; Davis et al., 1996), motor system, and act on medially located motoneurons, micturition (Holstege et al., 1986; Blok and Holstege, but mostly via the premotor interneurons of the basic 1996), bloodpressure control (Lovick, 1993; 1996), and motor system (see Kuypers, 1981; Holstege, 1996). mating (Pfaff et al., 1994). These activities are controlled Limbic system Pedunculopontine Periaqueductal gray and cuneiform nuclei (PAG) Ventral 1/3 of caudal pontine Barrington's subretrofacial nucleus and medullary medial tegmentum nucleus nucleus retroambiguus sympathetic sensory neurons motoneurons and parasympathetic sympathetic motoneurons of the motoneurons of the spinal cord T1-T2 C4-T8 preganglionics in the premotor interneurons preganglionics preganglionics larynx, iliopsoas, laminae intermediolateral lamina X in the dorsal horn in the in the in the pharynx, adductor

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