Abstract
Urotensin-II-related peptide (URP) is an eight amino-acid neuropeptide recently isolated from rat brain and considered as the endogenous ligand for the GPR14 receptor. Using single and double immunohistochemical labelling, in situ hybridization and ultrastructural immunocytochemistry, we explored the cellular and subcellular localization of URP in the male rat brain. URP peptide was detected in numerous varicose fibres of the median eminence (ME) and organum vasculosum laminae terminalis (OVLT) as well as in neuronal cell bodies of the medial septal nucleus and diagonal band of Broca where corresponding mRNA were also detected. Combining in situ hybridization with immunohistochemistry, we showed that cell bodies of the rat anterior hypothalamus contained both URP mRNA and GnRH peptide. In addition, double ultrastructural immunodetection of URP and GnRH peptides clearly revealed, in the median eminence, the co-localization of both peptides in the same neuronal processes in the vicinity of fenestrated portal vessels. This remarkable cellular and subcellular distribution led us to test the effect of URP on the GnRH-induced gonadotrophins release in the anterior pituitary, and to discuss its putative role at the level of the median eminence.
Highlights
In vertebrate, sexual maturation and reproduction are governed by the gonadotrophin-releasing hormone (GnRH) system which regulates the function of gonads [1,2,3]
We have showed in a preliminary study that Urotensin II-related peptide (URP) and its corresponding mRNA were present within GnRH neurones in male mouse hypothalamus proposing this peptide, for the first time, as a novel hypothalamus neuroendocrine peptide [12]
Using GnRH immunohistochemistry combined with URP mRNA in situ hybridization, we showed that cell bodies containing both GnRH peptide and URP-mRNA were detected in the anterior hypothalamus, in the same areas where URP
Summary
Sexual maturation and reproduction are governed by the gonadotrophin-releasing hormone (GnRH) system which regulates the function of gonads [1,2,3]. Regulation of GnRH neurones activity is complex and is controlled by several excitatory and inhibitory transsynaptic inputs [1,3,4,5,6,7] These synaptic regulatory mechanisms lead to a function-related structural plasticity of the GnRH system involving neuronal-glialendothelial interactions (see for review [8]), so allowing an answer adapted by the system to the physiological situations. Neuroendocrine GnRH neurones are known to present a various pattern of chemical phenotype, expressing some neuropeptides such as galanin [9,10], cholecystokinin and neurotensin [11]. Interest of UII function in the mammalian central nervous system has only emerged very recently with the discovery of its potential role in sleep or behaviour (see for reviews in [19,20])
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