The effects of bilateral lesions of the mesencephalic trigeminal sensory nucleus on nocturnal feeding and related behaviors in mice.
OBJECTIVE
The mesencephalic trigeminal sensory nucleus (Me5), which receives signals originating from oral proprioceptors and projects its fibers to the hypothalamus, regulates mastication and modulates satiation. Because the Me5 neurons display circadian rhythms in circadian mPer1 gene expression and bilateral Me5 lesions change feeding and exploratory behavior profiles, we speculated that Me5 may influence the daily timing of feeding. Therefore, we explored the effects of bilateral caudal Me5 lesions on the circadian profiles of feeding and its related behaviors.


METHODS
We measured the activities of feeding, drinking, and locomotion for 24h using an automated feeding behavior measurement apparatus and analyzed the mRNA expression levels of hypothalamic orexigenic and anorexigenic signaling molecules in both Me5-lesioned and sham-operated mice.


RESULTS
Food and water intake and locomotor activity decreased significantly in Me5-lesioned mice during the dark phase without affecting these total indexes when measured over the entire day. Analysis of the mRNA expression levels of hypothalamic orexigenic and anorexigenic signaling molecules showed that prepro-orexin (orexin) mRNA in the perifornical area was significantly decreased during the dark phase only in Me5-lesioned mice.


CONCLUSIONS
Bilateral caudal Me5 lesions alter the nocturnal properties of food and water intake and locomotor activity in mice and decrease the mRNA expression level of orexin in the perifornical area during the dark phase. These results suggest that Me5 activity may influence the nocturnal properties of feeding and its related behaviors by adjusting the activity of orexin neurons in the perifornical area.
Department of Basic Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan.
Sanae
S
Yokoyama
Ken-Ichi
K
Kinoshita
Yoshikage
Y
Muroi
Toshiaki
T
Ishii
D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D004435:Eating / Q000187:drug effects / Q000502:physiology*; D000431:Ethanol / Q000031:analogs & derivatives / Q000633:toxicity; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology*; D008124:Locomotion / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008636:Mesencephalon / Q000187:drug effects / Q000473:pathology*; D051379:Mice; D013238:Stereotaxic Techniques; D014278:Trigeminal Nuclei / Q000187:drug effects / Q000473:pathology*
C062527:tribromoethanol; D000431:Ethanol
Circadian rhythm; Feeding; Food intake; Hypothalamus; Locomotion; Me5 lesions; Nocturnal property