Sincronização dos ritmos de atividade motora e temperatura central à disponibilidade de glicose em ratos

Food is essential for the survival of all animals. Its temporal availability is an important enviromental cue for the behavioral and physiological organization throughout the 24 hours of day in different species. Rats and mice, for example, show increased locomotion in the hours before food availability when it is presented in a recurrent manner, a behavior named foodanticipatory activity. Several lines of evidence indicate that this anticipation is mediated by a circadian oscillator. In this work, based on the hypothesis that pre- or post-ingestive humoral signals are involved in the entrainment process, we tested whether the daily intake of glucose is sufficient to induce anticipatory activity in rats. The rhythms of motor activity and central temperature were recorded in animals undergoing 10 days of temporal glucose (solution at 50%) or chow restriction in light-dark (LD) and constant darkness (DD). Animals under temporal glucose restriction increase motor activity and and central temperature in the hours preceding glucose availability and such aticipation is extremely similar to that observed in animals under temporal chow restriction. Glucose ingestion is, therefore, a sufficient temporal cue to induce anticipation in rats. It is possible that the increase in plasma glucose after food ingestion constitutes one of the signals involved in the behavioral entrainment process to food availability

Caracterização do ritmo circadiano de atividade e repouso em saguis idosos (Callithrix Jacchus)

Advanced age may become a limiting factor for the maintenance of rhythms in organisms, reducing the capacity of generation and synchronization of biological rhythms. In this study, the influence of aging on the expression of endogenous periodicity and synchronization (photic and social) of the circadian activity rhythm (CAR) was evaluated in a diurnal primate, the marmoset (Callithrix jacchus). This study had two approaches: one with longitudinal design, performed with a male marmoset in two different phases: adult (three years) and older (9 y.o.) (study 1) and the second, a transversal approach, with 6 old (♂: 9.7 ± 2.0 y.o.) and 11 adults animals (♂: 4.2 ± 0.8 y.o.) (study 2). The evaluation of the photic synchronization involved two conditions in LD (natural and artificial illuminations). In study 1, the animal was subjected to the following stages: LD (12:12 ~ 350: ~ 2 lx), LL (~ 350 lx) and LD resynchronization. In the second study, the animals were initially evaluated in natural LD, and then the same sequence stages of study 1. During the LL stage in study 2, the vocalizations of conspecifics kept in natural LD on the outside of the colony were considered temporal cue to the social synchronization. The record of the activity was performed automatically at intervals of five minutes through infrared sensor and actimeters, in studies 1 and 2, respectively. In general, the aged showed a more fragmented activity pattern (> IV < H and > PSD, ANOVA, p < 0.05), lower levels of activity (ANOVA, p < 0.05) and shorter duration of active phase (ANOVA, p < 0.05) in LD conditions, when compared to adults. In natural LD, the aged presented phase delay pronounced for onset and offset of active phase (ANOVA, p < 0.05), while the adults had the active phase more adjusted to light phase. Under artificial LD, there was phase advance and greater adjustment of onset and offset of activity in relation to the LD in the aged (ANOVA, p < 0.05). In LL, there was a positive correlation between age and the endogenous period () in the first 20 days (Spearman correlation, p < 0.05), with prolonged  held in two aged animals. In this condition, most adults showed free-running period of the circadian activity rhythm with  < 24 h for the first 30 days and later on relative coordination mediated by auditory cues. In study 2, the cross-correlation analysis between the activity profiles of the animals in LL with control animals kept under natural LD, found that there was less social synchronization in the aged. With the resubmission to the LD, the resynchronization rate was slower in the aged (t-test; p < 0.05) and in just one aged animal there was a loss of resynchronization capability. According to the data set, it is suggested that the aging in marmosets may be related to: 1) lower amplitude and greater fragmentation of the activity, accompanied to phase delay with extension of period, caused by changes in a photic input, in the generation and behavioral expression of the CAR; 2) lower capacity of the circadian activity rhythm to photic synchronization, that can become more robust in artificial lighting conditions, possibly due to the higher light intensities at the beginning of the active phase due to the abrupt transitions between the light and dark phases; and 3) smaller capacity of non-photic synchronization for auditory cues from conspecifics, possibly due to reducing sensory inputs and responsiveness of the circadian oscillators to auditory cues, what can make the aged marmoset most vulnerable, as these social cues may act as an important supporting factor for the photic synchronization.

Caracterização do ritmo circadiano de atividade e repouso em saguis idosos (Callithrix Jacchus)

Advanced age may become a limiting factor for the maintenance of rhythms in organisms, reducing the capacity of generation and synchronization of biological rhythms. In this study, the influence of aging on the expression of endogenous periodicity and synchronization (photic and social) of the circadian activity rhythm (CAR) was evaluated in a diurnal primate, the marmoset (Callithrix jacchus). This study had two approaches: one with longitudinal design, performed with a male marmoset in two different phases: adult (three years) and older (9 y.o.) (study 1) and the second, a transversal approach, with 6 old (♂: 9.7 ± 2.0 y.o.) and 11 adults animals (♂: 4.2 ± 0.8 y.o.) (study 2). The evaluation of the photic synchronization involved two conditions in LD (natural and artificial illuminations). In study 1, the animal was subjected to the following stages: LD (12:12 ~ 350: ~ 2 lx), LL (~ 350 lx) and LD resynchronization. In the second study, the animals were initially evaluated in natural LD, and then the same sequence stages of study 1. During the LL stage in study 2, the vocalizations of conspecifics kept in natural LD on the outside of the colony were considered temporal cue to the social synchronization. The record of the activity was performed automatically at intervals of five minutes through infrared sensor and actimeters, in studies 1 and 2, respectively. In general, the aged showed a more fragmented activity pattern (> IV < H and > PSD, ANOVA, p < 0.05), lower levels of activity (ANOVA, p < 0.05) and shorter duration of active phase (ANOVA, p < 0.05) in LD conditions, when compared to adults. In natural LD, the aged presented phase delay pronounced for onset and offset of active phase (ANOVA, p < 0.05), while the adults had the active phase more adjusted to light phase. Under artificial LD, there was phase advance and greater adjustment of onset and offset of activity in relation to the LD in the aged (ANOVA, p < 0.05). In LL, there was a positive correlation between age and the endogenous period () in the first 20 days (Spearman correlation, p < 0.05), with prolonged  held in two aged animals. In this condition, most adults showed free-running period of the circadian activity rhythm with  < 24 h for the first 30 days and later on relative coordination mediated by auditory cues. In study 2, the cross-correlation analysis between the activity profiles of the animals in LL with control animals kept under natural LD, found that there was less social synchronization in the aged. With the resubmission to the LD, the resynchronization rate was slower in the aged (t-test; p < 0.05) and in just one aged animal there was a loss of resynchronization capability. According to the data set, it is suggested that the aging in marmosets may be related to: 1) lower amplitude and greater fragmentation of the activity, accompanied to phase delay with extension of period, caused by changes in a photic input, in the generation and behavioral expression of the CAR; 2) lower capacity of the circadian activity rhythm to photic synchronization, that can become more robust in artificial lighting conditions, possibly due to the higher light intensities at the beginning of the active phase due to the abrupt transitions between the light and dark phases; and 3) smaller capacity of non-photic synchronization for auditory cues from conspecifics, possibly due to reducing sensory inputs and responsiveness of the circadian oscillators to auditory cues, what can make the aged marmoset most vulnerable, as these social cues may act as an important supporting factor for the photic synchronization.