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.
Subject(s)
Gonadotropin-Releasing Hormone/metabolism , Hypothalamus/metabolism , Neurons/metabolism , Peptide Hormones/metabolism , Animals , Base Sequence , Cells, Cultured , DNA Primers , Hypothalamus/cytology , Immunohistochemistry , In Situ Hybridization , Male , Microscopy, Electron , Rats , Rats, Sprague-Dawley , Rats, Wistar , Subcellular Fractions/metabolismABSTRACT
Urotensin-II (UII), a 12 amino acid peptide, was discovered in the teleost fish neurosecretory cells located in the caudal portion of the spinal cord and which project to a neurohemal gland called the urophysis. The distribution of UII and of its prepro-UII mRNA is not limited to fish and was found for example in the rat spinal cord. In view of the potential interest of obtaining transgenic mice, we have therefore characterized the distribution of mouse pro-UII mRNA and UII immunoreactivity, by in situ hybridization and immunohistochemistry, respectively, in the mouse spinal cord. A population of UII-like immunoreactive cell bodies was located in the ventral horn of the different segments. These cells displayed all the features of motoneurons, as confirmed by a double immunohistochemical labelling showing the co-occurrence of UII and vesicular acetylcholine transporter, and by electron microscope immunocytochemistry. Retrograde labelling of motoneurons innervating the bulbocavernosus penile muscle showed that some of them contained UII. In situ hybridization histochemistry revealed that pro-UII mRNA was located in some ventral horn neuronal perikarya. The pro-UII mRNA-containing cell bodies possessed the same motoneuron characteristics, confirming the results of the immunohistochemical studies and showing that the gene of mouse UII is expressed in a subpopulation of motoneurons in the spinal cord. Our results support the assumption that UII peptide characterized as endocrine in fish is also expressed within mammalian motoneurons.
Subject(s)
Spinal Cord/metabolism , Urotensins/biosynthesis , Animals , Fluorescent Antibody Technique , Immunohistochemistry , In Situ Hybridization , Male , Mice , Mice, Inbred C57BL , Mice, Transgenic , Microscopy, Confocal , Microscopy, Immunoelectron , Motor Neurons/metabolism , Peroxidases/metabolism , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , Sexual Behavior, Animal/physiology , Urotensins/geneticsABSTRACT
Urotensin-II-related peptide (URP) is an eight-amino-acid peptide recently isolated from rat brain and considered as the endogenous ligand for the urotensin-II receptor. Immunohistochemical treatment of mouse brain sections with anti-URP antibodies revealed numerous immunopositive fibres in the median eminence and vascular organ of the lamina terminalis as well as labelled cell bodies, mainly in the preoptic area. In consecutive serial sections, in situ hybridization demonstrated URP-mRNA in neuronal perikarya. Double-immunofluorescence labelling showed a co-localization of URP and GnRH in fibres and cell bodies. These results suggest the existence of URP as a novel hypothalamic neuroendocrine peptide co-localized and possible co-released with GnRH.
