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

ELISABETH PELLEGRINI; MARÍA RITA PÉREZ; MARIE MADELAINE GUEGUEN; COLETTE VAILLANT; GUSTAVO M. SOMOZA; OLIVIER KAH

Rouen

Congreso; 17th Annual Meeting of the LARC-neuroscience network.; 2013

The paraventricular organ (PVO) is a diencephalic structure found in non- mammalian vertebrates and containing a large number of cerebrospinal fluid (CSF) contacting neurons, exhibiting serotonin (5-HT) immunoreactivity. In zebrafish, the PVO also possesses numerous radial glial cells (RGC) whose soma, in contrast to other brain regions, are located to a certain distance of the ventricle. These cells are also known to express brain aromatase, a product of the cyp19a1b gene. In order to study the relationships between RGC and 5-HT CSF-contacting neurons, we performed 5-HT immunohistochemistry in transgenic zebrafish in which RGC are labelled by GFP under the control of the cyp19a1b promoter The data show that the soma of the 5-HT neurons are located closer to the ventricle than those of the RGCs. RGCs extend towards the ventricles cytoplasmic processes that form along the ventricular surface a continuous barrier. In turn, 5-HT neurons contact the CSH by means of processes that cross this barrier through small pores. Further experiments using PCNA or BrdU indicate that RGC proliferate and give birth to 5-HT neurons. Treatment of zebrafish with a tryptophan hydroxylase inhibitor causes a significant decrease in the number of proliferating cells in the PVO. Altogether, these data further 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 are in contact with the CSF.