Neuromedin U is involved in nociceptive reflexes and adaptation to environmental stimuli in mice

• Published in: Biochemical and biophysical research communications 2004-10, Vol.323 (2), p.615-620
• Main Authors: Nakahara, Keiko, Kojima, Masayasu, Hanada, Reiko, Egi, Yutaka, Ida, Takanori, Miyazato, Mikiya, Kangawa, Kenji, Murakami, Noboru
• Format: Article
• Language: English
• Subjects: Adaptation; Adaptation, Physiological - drug effects; Animals; Dose-Response Relationship, Drug; Environment, Controlled; Formaldehyde - pharmacology; Heart Rate - drug effects; Hot Temperature; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Motor Activity - drug effects; Neuromedin U; Neuropeptides - administration & dosage; Neuropeptides - deficiency; Neuropeptides - metabolism; Pain; Pain - chemically induced; Pain - physiopathology; Pain Measurement - drug effects; Pain Measurement - methods; Physical Stimulation - methods; Reflex; Reflexes; Stress
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2004.08.136

Following our recent observations of inactivity and slowed movement in neuromedin U knockout (NMU KO) mice, we compared nociceptive reflexes and environmental adaptation in NMU KO and wild-type mice. Hot plate and formalin tests revealed that reflexes to heat and pain were significantly decreased in NMU KO mice. Conversely, intracerebroventricular injection of NMU into wild-type mice stimulated nociceptive reflexes in a dose-dependent manner. After NMU injection, increased c-Fos expression was observed in a wide range of locations in hypothalamus, brainstem, and spinal cord. NMU mRNA expression increased in the spinal cord, but not in the hypothalamus, 2 and 4h after formalin injection. When their light–dark cycle was advanced or retarded by 5h, NMU KO mice required a longer time to re-entrain into the new light–dark cycle than did wild-type mice. Wild-type mice displayed increased blood pressure after their environmental temperature was changed from 23 to 37°C, whereas no such increase was observed in NMU KO mice. Blood corticosterone levels were significantly increased after 10min of immobilization stress in wild-type mice, but not in NMU KO mice. These results suggest that endogenous NMU may be involved in reflexes and adaptation to environmental stimuli.