title: Neuromedin-U is regulated by the circadian clock in the SCN of the mouse.
abstract: Neuromedin-U (NMU) has been reported to drive several physiological or behavioural responses following i.c.v. injection of the peptide into the third ventricle of rodent brains. Many of these responses are mediated through a change in corticotrophin-releasing factor (CRF) output from the paraventricular nucleus (PVN). A number of the physiological or behavioural responses are regulated in a circadian manner, e.g. feeding. We have previously reported NMU gene expression in the suprachiasmatic nucleus (SCN) and NMU-2 receptor expression in the PVN, dorsal medial hypothalamus (DMH) and other regions of the mouse brain. We therefore hypothesized that NMU would be regulated by the circadian clock and may consequently drive a circadian rhythm of CRF expression in the PVN. Here we report that NMU is regulated in a circadian manner with peak expression during the light phase of a light-dark cycle. In C3H mice held in constant darkness, the NMU rhythm free runs with a period predicted by the free running period of locomotor activity in this mouse. The NMU mRNA transcript colocalizes with cells expressing AVP in the SCN and shows a coincident rhythm of expression with AVP. On the other hand, CRF did not express a circadian rhythm of expression in a light-dark cycle, although a rhythm was evident in constant darkness with a peak of expression prior to the rise of NMU in the same conditions. This would suggest that the circadian rhythm in NMU expression in the SCN does not drive a circadian rhythm in CRF in the PVN to be translated into physiological and behavioural responses mediated by NMU.
authors.affiliation: Molecular Endocrinology Group, Aberdeen Centre for Energy Regulation and Obesity (ACERO), Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, UK.
authors.forename: E Scott
authors.initials: ES
authors.lastname: Graham
authors.forename: Pauline
authors.initials: P
authors.lastname: Littlewood
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Turnbull
authors.forename: Julian G
authors.initials: JG
authors.lastname: Mercer
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Morgan
authors.forename: Perry
authors.initials: P
authors.lastname: Barrett
mesh_terms: D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D003346:Corticotropin-Releasing Hormone / Q000096:biosynthesis; D003624:Darkness; D005786:Gene Expression Regulation / Q000502:physiology; D051379:Mice; D008809:Mice, Inbred C3H; D009479:Neuropeptides / Q000096:biosynthesis*; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*
chemical_list: D009479:Neuropeptides; C056900:neuromedin U; D003346:Corticotropin-Releasing Hormone