title: Artificial feeding synchronizes behavioral, hormonal, metabolic and neural parameters in mother-deprived neonatal rabbit pups.
abstract: Nursing in the rabbit is under circadian control, and pups have a daily anticipatory behavioral arousal synchronized to this unique event, but it is not known which signal is the main entraining cue. In the present study, we hypothesized that food is the main entraining signal. Using mother-deprived pups, we tested the effects of artificial feeding on the synchronization of locomotor behavior, plasma glucose, corticosterone, c-Fos (FOS) and PERIOD1 (PER1) rhythms in suprachiasmatic, supraoptic, paraventricular and tuberomammillary nuclei. At postnatal day 1, an intragastric tube was placed by gastrostomy. The next day and for the rest of the experiment, pups were fed with a milk formula through the cannula at either 02:00 h or 10:00 h [feeding time = zeitgeber time (ZT)0]. At postnatal days 5-7, pups exhibited behavioral arousal, with a significant increase in locomotor behavior 60 min before feeding. Glucose levels increased after feeding, peaking at ZT4-ZT12 and then declining. Corticosterone levels were highest around the time of feeding, and then decreased to trough concentrations at ZT12-ZT16, increasing again in anticipation of the next feeding bout. In the brain, the suprachiasmatic nucleus had a rhythm of FOS and PER1 that was not significantly affected by the feeding schedule. Conversely, the supraoptic, paraventricular and tuberomammillary nuclei had rhythms of both FOS and PER1 induced by the time of scheduled feeding. We conclude that the nursing rabbit pup is a natural model of food entrainment, as food, in this case milk formula, is a strong synchronizing signal for behavioral, hormonal, metabolic and neural parameters.
authors.affiliation: Centro de Investigaciones Biomédicas, Universidad Veracruzana, Xalapa, Ver., México CIRA, CINVESTAV-UAT, Tlaxcala, Tlax., México.
authors.forename: Elvira
authors.initials: E
authors.lastname: Morgado
authors.forename: Claudia
authors.initials: C
authors.lastname: Juárez
authors.forename: Angel I
authors.initials: AI
authors.lastname: Melo
authors.forename: Belisario
authors.initials: B
authors.lastname: Domínguez
authors.forename: Michael N
authors.initials: MN
authors.lastname: Lehman
authors.forename: Carolina
authors.initials: C
authors.lastname: Escobar
authors.forename: Enrique
authors.initials: E
authors.lastname: Meza
authors.forename: Mario
authors.initials: M
authors.lastname: Caba
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology*; D001786:Blood Glucose / Q000378:metabolism; D002940:Circadian Rhythm / Q000502:physiology*; D003345:Corticosterone / Q000097:blood; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D007031:Hypothalamus / Q000033:anatomy & histology / Q000502:physiology; D007774:Lactation / Q000502:physiology*; D008426:Maternal Deprivation; D009043:Motor Activity / Q000502:physiology; D056950:Period Circadian Proteins / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D011817:Rabbits
chemical_list: D001786:Blood Glucose; D056950:Period Circadian Proteins; D016760:Proto-Oncogene Proteins c-fos; D003345:Corticosterone
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