title: Relationships between radial glial progenitors and 5-HT neurons in the paraventricular organ of adult zebrafish - potential effects of serotonin on adult neurogenesis.
abstract: In non-mammalian vertebrates, serotonin (5-HT)-producing neurons exist in the paraventricular organ (PVO), a diencephalic structure containing cerebrospinal fluid (CSF)-contacting neurons exhibiting 5-HT or dopamine (DA) immunoreactivity. Because the brain of the adult teleost is known for its neurogenic activity supported, for a large part, by radial glial progenitors, this study addresses the origin of newborn 5-HT neurons in the hypothalamus of adult zebrafish. In this species, the PVO exhibits numerous radial glial cells (RGCs) whose somata are located at a certain distance from the ventricle. To study relationships between RGCs and 5-HT CSF-contacting neurons, we performed 5-HT immunohistochemistry in transgenic tg(cyp19a1b-GFP) zebrafish in which RGCs are labelled with GFP under the control of the cyp19a1b promoter. We show that the somata of the 5-HT neurons are located closer to the ventricle than those of RGCs. RGCs extend towards the ventricle cytoplasmic processes that form a continuous barrier along the ventricular surface. In turn, 5-HT neurons contact the CSF via processes that cross this barrier through small pores. Further experiments using proliferating cell nuclear antigen or 5-bromo-2'-deoxyuridine indicate that RGCs proliferate and give birth to 5-HT neurons migrating centripetally instead of centrifugally as in other brain regions. Furthermore, treatment of adult zebrafish with tryptophan hydroxylase inhibitor causes a significant decrease in the number of proliferating cells in the PVO, but not in the mediobasal hypothalamus. These data point to the PVO as an intriguing region in which 5-HT appears to promote genesis of 5-HT neurons that accumulate along the brain ventricles and contact the CSF.
authors: Neuroendocrine Effects of Endocrine Disruptors, IRSET, Case 1302, INSERM U1085, Université de Rennes 1, Campus de Beaulieu, Rennes cedex, 35 042, France; Laboratorio de Ictiofisiología y Acuicultura, Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús (IIB-INTECH. CONICET-UNSAM), Chascomús, Argentina.
authors: María Rita
authors: MR
authors: Pérez
authors: Elisabeth
authors: E
authors: Pellegrini
authors: Joel
authors: J
authors: Cano-Nicolau
authors: Marie-Madeleine
authors: MM
authors: Gueguen
authors: Dounia
authors: D
authors: Menouer-Le Guillou
authors: Yohann
authors: Y
authors: Merot
authors: Colette
authors: C
authors: Vaillant
authors: Gustavo M
authors: GM
authors: Somoza
authors: Olivier
authors: O
authors: Kah
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D063928:Ependymoglial Cells / Q000166:cytology / Q000378:metabolism*; D058953:Neural Stem Cells / Q000166:cytology / Q000378:metabolism*; D055495:Neurogenesis; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology / Q000378:metabolism*; D059326:Serotonergic Neurons / Q000166:cytology / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*; D015027:Zebrafish
chemical_list: D012701:Serotonin
keywords: dopamine; fish; hypothalamus; radial glial cell; serotonin