Relationships between radial glial progenitors and 5-HT neurons in the paraventricular organ of adult zebrafish: Potential effects of serotonin on adult neurogenesis

MARÍA R. PÉREZ; ELISABETH PELLEGRINI; JOEL CANO-NICOLAU; MARIE MADELAINE GUEGUEN; DOUNIA MENOUER; YOHANN MEROT; COLETTE VAILLANT; GUSTAVO M. SOMOZA; OLIVIER KAH

EUROPEAN JOURNAL OF NEUROSCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2013 vol. 38 p. 3292 - 3301

0953-816X

In non-mammalian vertebrates, serotonin (5HT)-producing neurons exist in theparaventricular organ (PVO), a diencephalic structure containing cerebrospinal fluid(CSF)-contacting neurons exhibiting serotonin or dopamine (DA) immunoreactivity.Because the brain of adult teleosts is known for its neurogenic activity supported, fora large part, by radial glial progenitors, this study addresses the origin of newborn5HT neurons in the hypothalamus of adult zebrafish. In this species, the PVOexhibits numerous radial glial cells (RGC) whose soma are located to a certaindistance of the ventricle. To study relationships between RGC and 5-HT CSFcontactingneurons, we performed 5-HT immunohistochemistry in transgenictg(cyp19a1b-GFP) zebrafish in which RGC are labelled by GFP under the control ofthe cyp19a1b promoter. We show that the soma of the 5-HT neurons are locatedcloser to the ventricle than those of RGCs. RGCs extend towards the ventriclescytoplasmic processes that form a continuous barrier along the ventricular surface.In turn, 5-HT neurons contact the CSF via processes that cross this barrier throughsmall pores. Further experiments using PCNA or BrdU indicate that RGC proliferateand give birth to 5-HT neurons migrating centripetally, instead of centrifugally as inother brain regions. Furthermore, treatment of adult zebrafish with tryptophanhydroxylase inhibitor causes a significant decrease in the number of proliferatingcells in the PVO, but not in the mediobasal hypothalamus. These data point to thePVO as an intriguing region where 5-HT appears to promote genesis of 5-HTneurons that accumulate along the brain ventricles and contact the CSF.