Food cues and ghrelin recruit the same neuronal circuitry.
BACKGROUND
Cues that are associated with the availability of food are known to trigger food anticipatory activity (FAA). This activity is expressed as increased locomotor activity and enables an animal to prepare for maximal utilization of nutritional resources. Although the exact neural network that mediates FAA is still unknown, several studies have revealed that the medial hypothalamus is involved. Interestingly, this area is responsive to the anorexigenic hormone leptin and the orexigenic hormone ghrelin that have been shown to modulate FAA. However, how FAA is regulated by neuronal activity and how leptin and ghrelin modulate this activity is still poorly understood.


OBJECTIVE
We aimed to examine how the total neuronal population and individual neurons in the medial hypothalamus respond to cue-signaled food availability in awake, behaving rats. In addition, ghrelin and leptin were injected to investigate whether these hormones could have a modulatory role in the regulation of FAA.


METHODS
Using in vivo electrophysiology, neuronal activity was recorded in the medial hypothalamus in freely moving rats kept on a random feeding schedule, in which a light cue signaled upcoming food delivery. Ghrelin and leptin were administered systemically following the behavioral paradigm.


RESULTS
The food-predictive cue induced FAA as well as a significant increase in neural activity on a population level. More importantly, a sub-population of medial hypothalamic neurons displayed highly correlated identical responses to both ghrelin and FAA, suggesting that these neurons are part of the network that regulates FAA.


CONCLUSIONS
This study reveals a role for ghrelin, but not leptin, signaling within medial hypothalamus in FAA on both a population level and in single cells, identifying a subset of neurons onto which cue information and ghrelin signaling converge, possibly to drive FAA.
Rudolf Magnus Institute of Neuroscience, Department of Neuroscience and Pharmacology, University Medical Centre Utrecht, Utrecht, The Netherlands. g.vanderplasse@umcutrecht.nl
G
G
van der Plasse
M
M
Merkestein
M C M
MC
Luijendijk
M
M
van der Roest
H G M
HG
Westenberg
A B
AB
Mulder
R A H
RA
Adan
D000818:Animals; D059031:Anticipation, Psychological / Q000187:drug effects; D001522:Behavior, Animal; D003463:Cues; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology*; D054439:Ghrelin / Q000378:metabolism* / Q000494:pharmacology; D007031:Hypothalamus / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D020738:Leptin / Q000378:metabolism* / Q000494:pharmacology; D008297:Male; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology*; D009478:Neuropeptide Y / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D054439:Ghrelin; D047908:Intracellular Signaling Peptides and Proteins; D020738:Leptin; D009478:Neuropeptide Y