title: A daily palatable meal without food deprivation entrains the suprachiasmatic nucleus of rats.
abstract: Food is considered a potent Zeitgeber for peripheral oscillators but not for the suprachiasmatic nucleus (SCN), which is entrained principally by the light-dark cycle. However, when food attains relevant properties in quantity and quality, it can be a potent Zeitgeber even for the SCN. Here we evaluated the entrainment influence of a daily palatable meal, without regular food deprivation, on the circadian rhythm of locomotor activity and the c-Fos and PER-1 protein expression in the SCN. Rats fed ad libitum, in constant darkness, received a palatable meal for 6 weeks starting in the middle of the subjective day. Locomotor activity showed entrainment when the offset of activity coincided with the palatable meal-time. In the SCN, the peak expression of c-Fos was observed at palatable meal-time and PER-1 showed a peak during the onset of subjective night, as predicted according to the behavioural entrained pattern. In addition, c-Fos and PER-1 expression in the paraventricular thalamic nucleus (PVT) showed increased expression at palatable meal-time, while the intergeniculate leaflet did not, suggesting that the PVT may be involved as an input pathway of palatable food-entrainment to the SCN. These results demonstrate that daily access to a palatable meal can entrain the SCN; several stimuli can be implicated in this process, including motivation and arousal.
authors.affiliation: Departamento de Anatomía, Facultad de Medicina, Universidad Nacional Autónoma de México, México DF, 04510, México. jmendoza@neurochem.u-strasbg.fr
authors.forename: Jorge
authors.initials: J
authors.lastname: Mendoza
authors.forename: Manuel
authors.initials: M
authors.lastname: Angeles-Castellanos
authors.forename: Carolina
authors.initials: C
authors.lastname: Escobar
mesh_terms: D000818:Animals; D001143:Arousal / Q000502:physiology; D002452:Cell Count; D002940:Circadian Rhythm / Q000502:physiology*; D003624:Darkness; D004435:Eating / Q000502:physiology*; D005136:Eye Proteins / Q000502:physiology; D005508:Food Deprivation / Q000502:physiology; D005518:Food Preferences / Q000502:physiology*; D005829:Geniculate Bodies / Q000166:cytology / Q000502:physiology; D007150:Immunohistochemistry; D008297:Male; D020644:Midline Thalamic Nuclei / Q000166:cytology / Q000502:physiology; D009043:Motor Activity / Q000502:physiology; D056950:Period Circadian Proteins; D016760:Proto-Oncogene Proteins c-fos / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012201:Reward; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000378:metabolism / Q000502:physiology*
chemical_list: D005136:Eye Proteins; C539024:Per1 protein, rat; D056950:Period Circadian Proteins; D016760:Proto-Oncogene Proteins c-fos