Possible involvement of orexin in the stress reaction in rats.
We examined whether corticotropin-releasing factor (CRF) was involved in orexin-induced grooming and face-washing behaviors, and whether orexin was involved in the stress reaction. Administration of alpha-helical CRF, CRF antagonist, alone had no behavioral effect, but it blocked the orexin-induced grooming and face-washing behaviors in rats. The level of corticosterone increased in a dose-dependent manner 15 min after icv injection of orexin, and it remained high for at least 60 min. In 2-month-old rats, 1 h of immobilization stress increased orexin mRNA levels, but not the melanin-concentrating hormone (MCH) mRNA, in the lateral hypothalamic area (LHA). In 6-month-old rats, 30 min of cold stress increased the expression of orexin mRNA in the LHA. Unlike in the 2-month-old rats, immobilization stress did not change orexin mRNA expression in 6-month-old rats. These results suggest that CRF is involved in orexin-induced behaviors, and that orexin may play an important role in some stress reactions.
Ida
T
T
Department of Veterinary Physiology, Faculty of Agriculture, Miyazaki, 889-2155, Japan.
Nakahara
K
K
Murakami
T
T
Hanada
R
R
Nakazato
M
M
Murakami
N
N
D000818:Animals; D001070:Appetitive Behavior / Q000187:drug effects*; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology*; D003080:Cold Temperature; D003345:Corticosterone / Q000097:blood; D003346:Corticotropin-Releasing Hormone / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000494:pharmacology*; D007026:Hypothalamic Area, Lateral / Q000378:metabolism*; D007028:Hypothalamic Hormones / Q000096:biosynthesis; D007103:Immobilization; D007276:Injections, Intraventricular; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008543:Melanins / Q000096:biosynthesis; D009479:Neuropeptides / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology*; D000068797:Orexins; D010907:Pituitary Hormones / Q000096:biosynthesis; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D013312:Stress, Physiological / Q000378:metabolism*
D002352:Carrier Proteins; D007028:Hypothalamic Hormones; D047908:Intracellular Signaling Peptides and Proteins; D008543:Melanins; D009479:Neuropeptides; D000068797:Orexins; D010907:Pituitary Hormones; D012333:RNA, Messenger; C019463:melanin-concentrating hormone; D003346:Corticotropin-Releasing Hormone; D003345:Corticosterone