In mammals these rhythms are under control of a master clock in the suprachiasmatic nucleus (SCN), in the brain. The results indicate that rabbit pups show food anticipatory activity, and that timing of nursing differentially affects PER1 expression in the SCN and DMH.Ĭircadian rhythms are fluctuations with a period around 24 hrs and the most remarkable in humans is the awake-sleep cycle.

Comparison of nursed and 48 h fasted pups indicates that the timing of PER1 expression was similar in the SCN and DMH, with fewer PER1-positive cells in the latter group. In contrast, DMH peak PER1 expression occurred 8 h after pups were fed, corresponding to the shift in timing of nursing. In the SCN, PER1 and FOS peaked during the night in both groups, with a longer duration of elevated protein expression in the night-fed group. All pups exhibited anticipatory locomotor activity before daily nursing. To explore the effect of the timing of feeding, pups were maintained in constant darkness, while females housed in a light-dark cycle were permitted to nurse their pups either during the night (night-fed group) or day (day-fed group). Nursing visits to the litters also occurs during the dark phase. Rabbit pups are born in the dark, with eyelids closed. The present study explored neural mechanisms mediating the timing of nursing in this natural model of food anticipatory activity, focussing on the suprachiasmatic nucleus (SCN), the locus of the master circadian clock and on the dorsomedial hypothalamic nucleus (DMH), a region implicated in timing of food-entrained behavior. In nature and under laboratory conditions, dams nurse rabbit pups once daily for a duration of fewer than 5 min. The mother offers the possibility of studying nursing as a non-photic synchronizer, also with minimal manipulation, as suckling stimulation from the litter occurs only once daily. In conclusion, the rabbit pup is an extraordinary model for studying the entraining by a single daily food pulse with minimal manipulations. These findings suggest that circadian activities are modulated, in the mothers, by suckling stimulation and, in the young, by the ingestion of milk and/or the perception of the mammary pheromone.

suprachiasmatic nucleus, paraventricular nucleus) in relation to providing or ingesting milk in mothers and young, respectively. Per1) are differentially expressed in specific brain regions (e.g. In the brain, clock genes and their proteins (e.g. Other metabolic and hormonal parameters follow an exogenous or endogenous rhythm which is affected by the time of nursing. In pups corticosterone has a circadian rhythm with highest levels at the time of nursing. Research is revealing that the circadian rhythm of locomotion shifts in parallel to the timing of nursing in both parties.

In this review we present behavioral, metabolic and hormonal correlates of this phenomenon in mother rabbits and their pups. Despite this limited contact mother rabbits and their pups are tuned to each other to ensure that the capacities of each party are used efficiently to ensure the weaning of a healthy litter. 3 min) and occur inside the maternal burrow. Mother rabbits nurse their young once a day with circadian periodicity. Moreover, in contrast to other altricial mammals, the circadian visual system, although not essential for entraining the rhythm during first two weeks of life, is present and functional in rabbit pups from birth. We conclude that in the SCN there is a 'gating' mechanism to FOS induction by light that develops several days after birth, as in other mammals, and in the rabbit is already present at PD12. Light-induced FOS was observed during day and night at PD1, but mainly during night at PD12, 19 and adults. We also explored the response of the SCN to a light pulse by assessing the induction of FOS protein, a marker of neuronal activation, at PD1, 12, 19 and in adults. The results revealed that the retinal projections were present at PD1 with a bilateral symmetry, and with a contralateral tendency at PD19 and adults. Using the anterograde tracer cholera toxin-B, we examined the retinal projections to the SCN at postnatal days (PD) 1, 9, 19 and in adult animals. The present study examined the retinal projections to the suprachiasmatic nucleus (SCN) and the functional responses of the SCN to light exposure. However, the photic entrainment of the circadian system in rabbit pups during this developmental stage is not well understood. Therefore, they are considered a natural model of food anticipatory activity. In rabbit pups, nursing by the mother is the prevailing entraining signal for their circadian rhythms during at least the first two weeks of life.

Que es el nucleo