Feeding and activity induced by orexin A in the lateral hypothalamus in rats.
Orexin A injected into the lateral hypothalamus (LH) stimulates feeding and activates neurons in brain sites regulating feeding and arousal. The feeding effects of orexin A have been demonstrated during the light cycle, a time when rats are normally resting, and the effect of orexin A on activity after injection into the LH has not been previously measured. Thus, it is unclear whether LH orexin A-induced feeding is secondary to enhanced arousal. To address this, LH-cannulated rats habituated to a running wheel were injected with either orexin A (1000 pmol) or vehicle during light and dark cycles. Food intake and running wheel rotations were measured for 2 h. Spontaneous physical activity (SPA) was also measured during the dark cycle. During the light cycle, orexin A in the LH stimulated feeding in the presence and absence of a running wheel and increased number of running wheel rotations in the presence and absence of food. During the dark cycle, orexin A in the LH induced SPA (+/- presence of food), but had no effect on feeding. These data show that LH orexin A stimulation of feeding is not always coincident with increased activity, suggesting that feeding induced by LH-injected orexin A is not consequent to enhanced arousal.
Kotz
Catherine M
CM
Veterans Affairs Medical Center, One Veterans Drive, Research Service (151), Minneapolis, MN 55417, USA. kotzx004@umn.edu
Teske
Jennifer A
JA
Levine
James A
JA
Wang
ChuanFeng
C
D000818:Animals; D002352:Carrier Proteins / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000502:physiology*; D004435:Eating / Q000187:drug effects*; D007026:Hypothalamic Area, Lateral / Q000187:drug effects* / Q000502:physiology; D007276:Injections, Intraventricular / Q000379:methods; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D009479:Neuropeptides / Q000494:pharmacology*; D000068797:Orexins; D051381:Rats; D017207:Rats, Sprague-Dawley
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins