Does serotonin modulate the neurogenic activity of the caudal hypothalamus in adult zebrafish (Danio rerio)?

PÉREZ, MR; VAILLANT, C; SOMOZA, GM; KAH, O

Lille

Congreso; 14th Annual Meeting of the LARC- Neuroscience network.; 2010

Vincent Prévot (Chair). LARC- Neuroscience

The monoamines (histamine, dopamine, noradrenaline and serotonine) are involved in a variety of physiological and behavioral processes in vertebrates. In adult mammals, there are indications that serotonine (5-HT) levels influence neurogenesis in the hippocampus and subventricular zone. These observations potentially correlate with neurodegenerative disorders, such as Parkinson?s disease, Alzheimer?s disease, schizophrenia or depression. In most vertebrates, except mammals, the caudal hypothalamic region contains numerous cerebrospinal fluid (CSF)-contacting neurons that express 5-HT. This so called paraventicular organ (PVO) is extremely developed in fish where such neurons are found along the the third ventricle and its lateral and posterior recesses. This area also exhibits a significant proliferative activity and a high number of aromatase-positive progenitor radial glial cells in adult fish. This intriguing situation raises the question of the potential functional links between monoamines, estrogen production and neurogenesis in these regions. In order to examiner the relationship between the 5-HT in the neurogenesis, was we investigated whether alterations in levels of these neurotransmitters are associated with changes in the proliferation in the caudal hypothalamus in adult zebrafish. Using immunohistochemistry in cyp19a1b-GFP (Aromatase B) transgenic zebrafish line, which expresses GFP in radial glial cells, the precise distribution of the 5-HT and DA expressing cells was compared with that of aromatase expression in the periventricular cell layers of the nucleus of the posterior recess (NRP), the most caudal extension of the diencephalic ventricle. Subsequently, pharmacological treatments were performed with p-chlorophenylalanine (pCPA), inhibitor of the tryptophan hydroxylase, the limiting enzyme of 5-HT synthesis. Following injection, fish were sacrificed, their brains removed and fixed for immunohistochemistry processing. Cell proliferation in the treated and control groups were monitored by counting PCNA positive cells. Exposure of fish to pCPA decreases the number of ir-PCNA cells. These results, although preliminary, indicate that 5HT levels can modulate cell proliferation in the caudal hypothalamus of adult zebrafish.