A Neurosecretory System in the Brain of the Lancelet,Branchiostoma lanceolatum

Abstract

Obermiiller-Wildn, H . 1979. A neurosecretory system in the brain of the lancelet, Branchiostoma lanceolatum. (Department of Zoology, University of Stockholm, Sweden.) -Acta zool. (Stockh.) 60( 3) : 187-196.Ultrastructural and histochemical studies indicate a neurosecretory system exists in the lancelet brain with basal properties resembling a primitive hypothalamic system. A nucleus of secreting neurons, containing peptide granules (115 nm), is prominent in the dorsal walls of the brain. The axons establish contacts with the ventral brain surface,, probably releasing their secretory product out of the brain. The neurons are innervated by dopaminergic "boutons en passant" often very active with a high number of electron translucent vesicles as well as dense-core vesicles (90 nm) . Ventrally located cellbodies containing what are probably secretory peptide granules (110 nm) establish contacts with their basal processes on the ventral brain surface.

Distribution of GABA immunoreactivity in the central and peripheral nervous system of amphioxus (Branchiostoma lanceolatum pallas)

“…Nevertheless, very little is known about the distribution of neuroactive substances in the nervous system of amphioxus, although histological and histofluorescent studies have found putative neurosecretory and monoaminergic neurons in the brain (Obermü ller-Wilén, 1979;Obermü llerWilén and van Veen, 1981). Furthermore, the presence of neurons immunoreactive to several neuropeptides has been reported in adult amphioxus (calcitonin and pancreatic polypeptide, Van Norden, 1984;met-enkephalin, Uemura et al, 1990;vasopressin/vasotocin, oxytocin, FMRFamide peptide, angiotensin II, urotensin I, and cholecystokinin-gastrin, Uemura et al, 1994;FMRFamide peptide, Pestarino and Lucaroni, 1996), and immunocytochemical studies of larval amphioxus have also demonstrated the presence of serotoninergic neurons (Holland and Holland, 1993).…”

“…The remarkable simplicity of arrangement of the amphioxus nervous system is thought to be primitive (Bone, 1960a). Most of our knowledge of the morphology of the amphioxus nervous system is based on light microscopic studies with classical neurohistological methods (Rohde, 1888;Retzius, 1891;Hesse, 1898;Joseph, 1904;Stendell, 1914;Bone, 1960a), although some authors have investigated the ultrastructure of the brain vesicle (Welsch, 1968;Meves, 1973;Anadón, 1976;Obermü ller-Wilén, 1976, 1979Obermü ller-Wilén and van Veen, 1981;Watanabe and Yoshida, 1986;Ruiz and Anadón, 1991b,c;Lacalli et al, 1994;Lacalli, 1996a), the spinal cord (Eakin and Westfall, 1962;Flood, 1966Flood, , 1968Guthrie, 1975;Vigh-Teichmann and Vigh, 1983;Anadón, 1989, 1991a,c), and peripheral nerves and sensory cells (Peters, 1963;Bone and Best, 1978;Baatrup, 1981Baatrup, , 1982. Recent ultrastructural studies performed in early larvae (Lacalli et al, 1994;Lacalli, 1996a,b), together with studies of the expression in the neural tube of genes implicated in the control of the axial patterning during embryonic development (Holland et al, 1992Holland, 1996;Holland and García-Ferná ndez, 1996), have provided new landmarks that facilitate comparison of the regions of the rostral nerve cord of amphioxus with the main regions of the vertebrate brain (Lacalli, 1996b).…”

Neuronal organization of the brain in the adult amphioxus (Branchiostoma lanceolatum): A study with acetylated tubulin immunohistochemistry

“…The chemically identified neurons reported to date for this brain region comprise the c-opsin-expressing photoreceptors in the frontal eye of the larval brain (Vopalensky et al, 2012) and populations of small dorsal GABAergic cells (Anad on et al, 1998) and small serotonergic cells (Oberm€ uller-Wil en and van Veen, 1981;Moret et al, 2004) described for adults. The caudal region of the vesicle also contains the neurosecretory cells reported by Oberm€ uller-Wil en (1979, 1984 using electron microscopy, which were not detected in ATimmunostained series, suggesting again that these short axon neurons had scant tubulin in the cytoskeleton. Cells expressing amphioxus vasotocin have also been reported for the caudal brain vesicle via in situ hybridization (Kubokawa et al, 2010), which is in good agreement with Oberm€ uller-Wil en's ultrastructural observations.…”

“…Cells expressing amphioxus vasotocin have also been reported for the caudal brain vesicle via in situ hybridization (Kubokawa et al, 2010), which is in good agreement with Oberm€ uller-Wil en's ultrastructural observations. The amphioxus neurosecretory system appears to release neurohormones directly to the "pial" surface of the brain (Oberm€ uller-Wil en, 1979, 1984. The presence of these cells and the discharge region in the caudal region of the brain vesicle suggest that it corresponds to the neurosecretory preoptic region and hypothalamus of fishes, actually considered as belonging to the secondary prosencephalon (Puelles and Rubenstein, 2003).…”

“…As noted above, the "infundibulum" is located in a region considered homologous to the rhombencephalon, which is unlike the vertebrate hypophysis. Moreover, the neurosecretory system described by Oberm€ uller-Wil en (1979) is located in the brain vesicle (i.e., the putative diencephalon homologue). Ekhart et al (2003) suggested that the Rohde nucleus cells might be neuroendocrine neurons on the basis of the abundance of Nissl bodies in the perikaryon and the conspicuous nucleolus.…”