Urotensin II in the central nervous system of the frog Rana ridibunda: immunohistochemical localization and biochemical characterization

Abstract

Urotensin II (UII) is traditionally regarded as a product of the neurosecretory cells in the caudal portion of the spinal cord of jawed fishes. A peptide related to UII has been recently isolated from the frog brain, thereby providing the first evidence that UII is also present in the central nervous system of a tetrapod. In the present study, we have investigated the distribution of UII-immunoreactive elements in the brain and spinal cord of the frog Rana ridibunda by immunofluorescence using an antiserum directed against the conserved cyclic region of the peptide. Two distinct populations of UII-immunoreactive perikarya were visualized. The first group of positive neurons was found in the nucleus hypoglossus of the medulla oblongata, which controls two striated muscles of the tongue. The second population of immunoreactive cell bodies was represented by a subset of motoneurons that were particularly abundant in the caudal region of the cord (34% of the motoneuron population). The telencephalon, diencephalon, mesencephalon, and metencephalon were totally devoid of UII-containing cell bodies but displayed dense networks of UII-immunoreactive fibers, notably in the thalamus, the tectum, the tegmentum, and the granular layer of the cerebellum. In addition, a dense bundle of long varicose processes projecting rostrocaudally was observed coursing along the ventral surface of the brain from the midtelencephalon to the medulla oblongata. Reversed-phase high-performance liquid chromatography analysis of frog brain, medulla oblongata, and spinal cord extracts revealed that, in all three regions, UII-immunoreactive material eluted as a single peak which exhibited the same retention time as synthetic frog UII. Taken together, these data indicate that UII, in addition to its neuroendocrine functions in fish, is a potential regulatory peptide in the central nervous system of amphibians.

International Union of Basic and Clinical Pharmacology. XCII. Urotensin II, Urotensin II–Related Peptide, and Their Receptor: From Structure to Function

“…1). Unlike many other neuropeptides, UII is not found in hypothalamic neurons, but is almost exclusively produced in motoneurons of the frog brainstem and spinal cord (Chartrel et al, 1996). The identification of UII in the frog brain confirmed that 1) UII is produced in extra-urophysial nervous tissues and 2) urotensinergic systems exist in vertebrate phyla outside the fish lineage (Conlon et al, 1997;Conlon, 2008;Vaudry et al, 2010).…”

“…Specifically, in the European green frog, UII immunoreactivity is found in neurons of the hypoglossal nucleus of the medulla oblongata, which controls tongue muscles, and in a subpopulation of motoneurons of the spinal cord, particularly abundant in the caudal region (Chartrel et al, 1996). In the brain of rodents, UII is primarily expressed in brainstem nuclei including the dorsal motor nucleus of the vagus, the hypoglossal nucleus, the trigeminal motor nucleus, the facial motor nucleus, the abducens nucleus, and the trigeminal motor nucleus (Coulouarn et al, 1999;Dun et al, 2001;Dubessy et al, 2008).…”

MOLECULAR EVOLUTION OF GPCRS: Somatostatin/urotensin II receptors

“…The highest levels of expression of the UII gene are found in the CNS, specifically in motor neurons (Chartrel et al 1998, Coulouarn et al 1998, 1999, Dun et al 2001, Pelletier et al 2002, Egginger et al 2006. However, the bulk of all research into the UII-ergic system has mainly focused on the peripheral effects as the receptor is expressed predominantly in the periphery, in the cardiorenal system (Tal et al 1995, Ames et al 1999, Matsushita et al 2001, Elshourbagy et al 2002.…”

“…http://jme.endocrinology-journals.org DOI: 10.1530/JME-13-0274 (Chartrel et al 1998, Coulouarn et al 1998, 1999, Dun et al 2001, Pelletier et al 2002, Egginger et al 2006. Notably, UII mRNA is detected early in the formation of the rat embryonic ventral neural tube, at a developmental stage coincident with the differentiation of motor neurons (Coulouarn et al 2001).…”

Urotensin II Modulates Rapid Eye Movement Sleep through Activation of Brainstem Cholinergic Neurons

“…Urotensin II (UII) is a neuropeptide that was initially isolated from urophysis extracts of several species of fish (Pearson et al, 1980), with a core structure that is conserved through mollusks to mammals (Conlon et al, 1996(Conlon et al, , 1997Chartrel et al, 1998;Coulouarn et al, 1998Coulouarn et al, , 1999. UII has potent vasoconstrictor activity in the periphery (Russell et al, 2001;Bohm and Pernow, 2002).…”