Expression of Circadian Neuropeptides in the Hypothalamus of Adult Mice is Affected by Postnatal Light Experience

Abstract

The suprachiasmatic nuclei (SCN) of the hypothalamus are the principal pacemaker in mammals, controlling daily, circadian rhythms in physiology and behaviour. Environmental light during development has long-term effects on circadian behaviour, but it is still unclear what the relevant adaptations within the brain are. In the present study, we examined the manifestation of the circadian rhythm of locomotor activity, and the expression of arginine-vasopressin (AVP) and vasointestinal polypeptide (VIP) in the SCN of adult mice reared under different light environments during the suckling period, and synchronised to light/dark cycles after weaning. We found that animals reared under constant light had higher amplitude and more stable activity rhythms, together with lower levels of VIP- and AVP-immunostaining in the SCN, compared to mice reared under light/dark cycles or constant darkness. Differences in AVP expression were also found in the paraventricular nucleus and the supraoptic nucleus, two brain areas which receive SCN projections. These results indicate that the postnatal light experience may affect clock function and clock output, and suggest implications for the control of hormonal homeostasis and circadian behaviour.

Differential hypothalamic tyrosine hydroxylase distribution and activation by light in adult mice reared under different light conditions during the suckling period

“…These results suggest that PVN development may be programmed by postnatal light experience. This hypothesis is supported by our previous finding that AVP expression in the PVN is increased in DD-compared to LL-and LD-reared mice (Smith and Canal 2009).…”

“…cells are involved in the integration of photic inputs to the SCN. Interestingly, we have found VIP expression in the SCN to depend on postnatal light experience (Smith and Canal 2009). It is thus tempting to speculate that glutamate input to the SCN during development could initiate a cascade of events leading to altered neurotransmitter expression in VIP?…”

“…Immunoreactivity to TH (1:10,000; rabbit polyclonal, Sigma) and c-FOS (1:8,000, chicken polyclonal, Sigma) was detected using standard techniques as described by Smith and Canal (2009). Briefly, separate series of tissue sections were processed for TH, c-FOS or TH and c-FOS.…”

“…Moreover, the long-term differences in behaviour depended only on the light environment in which the pup had been reared, and not on the rhythmicity of its mother (Cambras et al 1997); and persisted after the animals had been enucleated (Canal-Corretger et al 2003). In addition, we have recently shown reduced expression of two critical circadian neuropeptides, arginine vasopressin (AVP) and vasointestinal polypeptide (VIP), in the SCN of adult mice reared under LL during the first three postnatal weeks, compared to those reared in LD or DD (Smith and Canal 2009). These results suggest that postnatal light experience may affect circadian clock function and clock output.…”

Influence of light exposure during early life on the age of onset of bipolar disorder

“…Between 1-3 months of age, the circadian system gradually matures and organizes physiological and behavioral activity in a 24-hour cycle, including rest/activity, temperature, and hormone secretion (Glotzbach et al, 1994;McGraw et al, 1999;Rivkees, 2007;Shimada et al,1999). Fourth, mammals raised under varying photoperiods (short versus long days) during the postnatal period exhibit changes to the circadian system that are persistent and associated with future circadian adaptation, animal behavior, retinal function and the immune response (Brooks et al, 2014;Canal et al, 2009;Ciarleglio et al, 2011;Jackson et al, 2014;Pyter and Nelson, 2006;Smith and Canal, 2009;Weil et al, 2006). For example, newborn mice raised in summer light conditions of long photoperiods had consistent physiologic and behavioral changes to future seasonal light-dark changes, whereas mice raised in winter light conditions of short photoperiods had unstable reactions to future seasonal light-dark changes (Ciarleglio et al, 2011).…”