CIRCADIAN CHARACTERISTICS OF CORTICOSTERONE SECRETION IN REDBACKED VOLES (CLETHRIONOMYS GAPPERI)

Abstract

To provide necessary background for study of stress response in red-backed voles (Clethrionomys gapperi), the circadian and ultradian rhythm in corticosterone release was characterized. Animals were maintained under a 16h light, 8h dark cycle. A total of 55 males and 46 females provided 101 independent blood samples over a 6-month span. Samples were obtained at 1h to 2h intervals during the light and at 2h intervals during the dark. Using edited data (5 values beyond the upper 95% limit were removed), a significant time effect was found by analysis of variance (ANOVA) for both sexes at P < .001. The composite single cosine best describing the circadian wave-form for each sex consisted of three components (24h, 12h, and 6h), each significant at P < .05 (overall model P < .001). The 24h mean (mesor) was about 60% higher in females than males (646 ng/mL vs. 412 ng/mL, P = .01), with amplitudes of 429 and 298 ng/mL being proportional (66% vs. 72%) to the respective mesor. The predictable range of change within a 24h span (determined by the double amplitude of a 24h + 12h + 6h cosine model) was large: It was more than 1600 ng/mL for females and more than 900 ng/ mL for males. Highest values were found during the dark phase, with the 24h acrophase located at 2h into the dark span for both sexes. With the caveat of fewer samples obtained during dark than during light, the actual peak values for females occurred at 2h and for males at 6h into the 8h dark span. These results provide baseline information about the circadian time structure for serum corticosterone in red-backed voles under normal light-dark, low-stress conditions.

Serum Cortisol Levels in Goats Exhibit Seasonal But Not Daily Rhythmicity

“…A daily glucocorticoid rhythm has also been described in other mammalian species, such as pigs (Andersson et al, 2000;Whipp et al, 1970), horses (Irvine and Alexander, 1994;James et al, 1970), monkeys , hamsters (de Souza and Meier, 1987), and voles (Kramer and Sothern, 2001). The lowest concentrations are found during rest and a rapid rise occurs just before the beginning of the active period both in day-active and nocturnal species.…”

Differential Effects of Photophase Irradiance on Metabolic and Urinary Stress Hormone Concentrations in Blind and Sighted Rodents

“…Generally, these complex responses involve the activation of stress systems, mainly the sympatho-adreno-medullaty (SAM) system and the hypothalamic-pituitary-adrenocortical (HPA) axis that release catecholamines and corticosteroids, respectively, to the general circulating system (Axelrod & Reisine, 1984;Gavrilović & Dronjak, 2006;Sapolsky, 2002). Daily and seasonal variations in stress responses of both the HPA axis and SAM system, which are entrained by the environmental light/dark cycles, have also been broadly documented in mammal species, including members of the Microtidea family, such as M. socialis (Haus, 2007;Krame & Sothern, 2001;Nelson & Martin, 2007;Zubidat et al, 2008). In wildtype rodents, integrated and timed metabolic and stress responses are of significant survival value in natural habitats, where individuals need to allocate energy resources to appropriate avenues.…”

Spectral and duration sensitivity to light-at-night in ‘blind’ and sighted rodent species

“…al., 1999) and voles (Krame and Sothern, 2001). Overall, the rhythmicity of these stress hormones responds strongly to phase shifting of the day-night cycle (Sudo and Miki, 1995), is promptly refurbished upon stress relief (Droste et al, 2009) and is likely regulated directly by the SCN (Oster et al, 2006).…”