Chronic intracerebroventricular administration of orexin-A to rats increases food intake in daytime, but has no effect on body weight.
Orexins are recently identified neuropeptides, and have been shown to increase food intake when administered intracerebroventricularly. We examined the effects of chronic administration of orexin in rats by continuous intracerebroventricular administration by means of an osmotic minipump. Continuous administration of orexin-A (0.5 nmol/h) for 7 days in rats resulted in a significant increase in food intake in the daytime. Daytime food intake increased to 180% of the control value. However, it resulted in a slight decrease nighttime food intake as compared with vehicle-treated rats. The total amount of food intake per day was almost comparable with that of vehicle-administered rats. The gain of body weight and blood glucose, total cholesterol and free fatty acid levels were normal. Chronic orexin-A treatment did not cause obesity in rats. We observed abnormal behavior during the daytime after starting administration of orexin-A; these rats kept awake during the daytime. Our present observation showed that continuous administration of orexin-A could not overcome the regulation of energy homeostasis and body weight. However, orexin-A might be implicated in short-term, immediate regulation of feeding behavior.
Yamanaka
A
A
Department of Pharmacology, Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, Japan.
Sakurai
T
T
Katsumoto
T
T
Yanagisawa
M
M
Goto
K
K
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects; D002352:Carrier Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D002552:Cerebral Ventricles / Q000187:drug effects / Q000502:physiology*; D002784:Cholesterol / Q000097:blood; D002940:Circadian Rhythm / Q000187:drug effects*; D002149:Energy Intake / Q000187:drug effects; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005247:Feeding Behavior / Q000187:drug effects*; D007263:Infusions, Parenteral; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D009479:Neuropeptides / Q000008:administration & dosage / Q000494:pharmacology*; D000068797:Orexins; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014280:Triglycerides / Q000097:blood
D001786:Blood Glucose; D002352:Carrier Proteins; D005230:Fatty Acids, Nonesterified; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins; D014280:Triglycerides; D002784:Cholesterol