Maternal Entrainment of the Developing Circadian System in the Siberian Hamster (Phodopus sungorus)

Abstract

The aim of these studies was to investigate maternal entrainment of developing circadian locomotor activity rhythms in the Siberian hamster. In Experiment 1, mothers were transferred from a 16:8 LD cycle into constant dim red light (DD) from the day of parturition, and wheel-running activity of the mother and pups was individually monitored from the time of weaning. The phases of the individual pups' rhythms were found to be synchronized both to the phase of the mother and to the phase of lights off (ZT 12) of the photo cycle that the mother was exposed to until the day of parturition. To investigate whether this synchrony might reflect direct effects of light acting upon the fetal circadian system in late gestation, the experiment was repeated but with mothers placed into DD early in pregnancy (≤ day 7 of gestation). The results were similar to the first study, suggesting that the mother rather than the photo cycle during the latter part of gestation entrains the developing circadian system. The third experiment investigated whether this entrainment occurred during the postnatal period. Breeding pairs were maintained on alternative light-dark cycles, LD and DL, that were 12 h out of phase. Litters born to mothers on one light-dark cycle were exchanged on the day of birth with foster mothers from the reversed light-dark cycle, then raised in DD. Control litters exchanged between mothers from the same light-dark cycle had similar litter synchrony as shown by nonfostered litters of Experiment 1. However, pups cross-fostered with mothers on reversed LD cycles showed a very different distribution of pup phases. Pups were not synchronized to their natural mother but to their foster mother. Moreover, pups were more scattered over the 24-h period and were found to be significantly synchronized to the phase of the reversed LD cycle. These results demonstrate the occurrence of postnatal entrainment in the Siberian hamster. The increased scatter produced by the cross-fostering paradigm results from some litters being completely entrained to the phase of the foster mother, some with an intermediate distribution between the phases of the natural and foster mothers, and a minority being associated with the phase of the natural mother. These results suggest that Siberian hamster pups are initially synchronized either prenatally or at birth but that the mother continues to provide entrainment signals during the postnatal period.

Conserved Expression of the Glutamate NMDA Receptor 1 Subunit Splice Variants during the Development of the Siberian Hamster Suprachiasmatic Nucleus

“…The N-methyl-D-aspartate (NMDA) type of glutamate receptor is of particular interest since it has been demonstrated to play a central role in the transduction of photic cues in the SCN [3], [6], and critical to normal development of visual pathways and associated with synaptogenesis and synaptic plasticity [4], [5], [7], [8]. Thus, it is possible that glutamate may play a role in the innervation of the SCN by the RHT, in synaptogenesis of the SCN during the postnatal period and in the functional switch between maternal to photic derived cues for entrainment of the circadian clock [9]–[13]. Moreover, these events in the SCN might be associated with changes in glutamate receptor subtype expression, with either a switch in expression being causal to a developmental event, or conversely, the switch being driven by a developmental event.…”

“…Also a photic response (light-induced immediate early gene c-Fos expression) first occurs in the SCN on PD3 [10]. During the late prenatal and early postnatal period the rodent circadian clock is entrained via signals derived from the mother [9], [12], [13], [33]–[37]. The photic response develops gradually during the first 2 weeks of postnatal life to eventually override the maternal entrainment mechanism [10]–[12], [33], [37], [38].…”

Social synchronization of circadian locomotor activity rhythm in the fruit fly Drosophila melanogaster

“…Several early studies in mammals showed that the clock of the mother can set time in the offspring, especially during early development (Viswanathan and Chandrashekaran, 1985;Reppert and Schwartz, 1986;Honma et al, 1987;Duffield and Ebling, 1998;Viswanathan, 1999). Social cues help in speeding up the rate of resynchronization to phaseshifted light-dark (LD) cycles.…”

The Development of a Circadian Pattern of Salivary Cortisol Secretion in the Neonatal Piglet

“…This may be due to the influence of the individual dam, perhaps through the secretion of glucocorticoids in milk, which have been shown to be present in various species [27]. Certainly, in the hamster, it has been shown that maternal entrainment of biological rhythms occurs [28]. This maternal entrainment most likely occurs in spite of the suppression of the activity of the HPA axis during lactation, as has been demonstrated in both the rat [29] an the pig [30].…”