Diurnal expression of period 2 and urocortin 1 in neurones of the non-preganglionic Edinger-Westphal nucleus in the rat

Abstract

Period 2 (Per2) is an important clock gene involved in the regulation of the major circadian clock in the mammalian central nervous system, the suprachiasmatic nucleus. In addition, Per2 is expressed in many other stress-sensitive brain structures. We have previously showed that the non-preganglionic Edinger-Westphal nucleus (npEW) is the main site of the corticotropin-releasing factor peptide family member urocortin 1 (Ucn1) and that this peptide undergoes conspicuous expression changes in response to various stressors. Here, we hypothesized that in the rat npEW both Per2 and Ucn1 would be produced in a diurnal, rhythmical fashion. This hypothesis was tested by following this expected rhythm on two days in rats killed at four time points each day (Zeitgeber times 0, 6, 12, and 18). We showed the co-existence of Per2 and Ucn1 in the npEW with double-label immunofluorescence and demonstrated with quantitative RT-PCR and semi-quantitative immunocytochemistry diurnal rhythms in Per2 mRNA expression and Per2 protein content, each on a single different day, with a minimum at lights-off and a maximum at lights-on. We furthermore revealed a diurnal rhythm in the number of Ucn1-immunopositive neurones and in their Ucn1 peptide content, with a minimum at night and at the beginning of the light period and a peak at lights-off, while the Ucn1 mRNA content paralleled the Per2 mRNA rhythm. The rhythms were accompanied by a diurnal rhythm in plasma corticosterone concentration. Our results are in line with the hypothesis that both Per2 and Ucn1 in the rat npEW are produced in a diurnal fashion, a phenomenon that may be relevant for the regulation of the diurnal rhythm in the stress response.

Chronic Stress Induces Sex-Specific Alterations in Methylation and Expression of Corticotropin-Releasing Factor Gene in the Rat

“…Determining the nature of this mechanism is beyond the scope of the present study, but it may be relevant to note that chronic mild stress is known to affect circadian rhythmicity of locomotion in rats [36]. Therefore, it would be interesting to study if the presently found sex- and brain center-specific effects of CVMS on neuronal activities, reflect, at least for a part, disturbed circadian activity of these centers, as such disturbances of brain activity have been presumed to mediate stressor-induced brain disorders like depression [38], [76].…”

“…Then, rats were transcardially perfused with 50 ml 0.1 M sodium phosphate-buffered saline (PBS; pH 7.4), for 10 min, followed by 250 ml 4% ice-cold paraformaldehyde in PBS, for 20 min, decapitated, and their brains dissected and postfixed in the paraformaldehyde fixative, for 16 h. For the other two experiments rats were immediately decapitated and their brains frozen till further processing. Since the central stress response in rodents is known to have a circadian nature [38], all decapitations were carried out between 9 and 11 am.…”

Research progress on the central mechanism underlying regulation of visceral biological rhythm by per2 (Review)

“…The CeA and BNST receive dopamine signals (30) and are enriched in CRF-ir neurons (31)(32)(33). Unilateral 6-hydroxydopamine injury of dopaminergic neurons in the medial forebrain bundle causes reduced PER2 expression in the ipsilateral BNST and CeA, and also decreased expression of CRF neurons (34,35). Following unilateral CRF gene silencing in the BNST and CeA, ipsilateral PER2 expression almost disappears.…”

About a snail, a toad, and rodents: animal models for adaptation research

“…In view of the assumed relation between the axis and the npEW, the presence of such rhythmicity and its possible underlying molecular mechanism (clock genes) were investigated in the Ucn1-neurons of the npEW. They reveal co-existence of diurnal rhythms in Period 2 mRNA expression and Period 2 protein content, with a minimum at lights-off, and a maximum at lights-on (Gaszner et al, 2009b). We furthermore found a diurnal rhythm in the number of Ucn1-immunopositive neurons and in their Ucn1 peptide content, with a minimum at night and at the beginning of the light period and a peak at lights-off, while the Ucn1 mRNA content paralleled the Period 2 mRNA rhythm.…”

“…These rhythms in the rat npEW are accompanied by a diurnal rhythm in plasma corticosterone concentration. Diurnal production of Period 2 and Ucn1 in the npEW may be relevant for the maintenance of the known diurnal rhythm in the stress response (Gaszner et al, 2009b). …”