Thermoregulatory and endocrine responses to light pulses in short-day acclimated social voles (Microtus socialis)

Abed Elsalam Zubidat, Rachel Ben-Shlomo, Abraham Haim

Research output: Contribution to journalArticlepeer-review

Abstract

In mammals, nocturnal light pulses (NLP) have been demonstrated to affect physiology and behavior. However, the impact of NLP as a stressor has been less broadly examined. The purpose of this study was to examine the effect of NLP (three 15 min 450 lux light pulses) during each scotophase on both thermoregulation and endocrine stress responses under short-day (SD; 8L:16D) acclimation. Voles were acclimated to either SD (SD voles) or SD+NLP (NLP voles). Resistance to cold was estimated by measurements of body temperature (Tb) during cold exposure (5°C). Daily rhythms of energy expenditure (calculated from oxygen consumption), urine production, and urinary adrenaline and serum cortisol levels were measured. Tb values of SD voles were generally unaffected by the cold stimulus, whereas in NLP voles, resistance to cold was markedly lowered. While SD- and NLP voles showed similar ultradian characteristics in energy expenditure with a period of 3.5 h, mean energy expenditure levels were lowest for voles exposed to NLP-treatment. In SD voles, but not in NLP voles, urine production rates showed clear time variations and were consistently highest for SD voles, with significant differences during the scotophase. Both mean total urinary adrenaline and serum cortisol levels were significantly elevated in NLP-treated voles compared with the control group. Taken together, the results suggest that NLP negatively affects winter acclimatization of thermoregulatory mechanisms of M. socialis, probably by mimicking summer acclimatization, and consequently the thermoregulatory mechanisms respond inappropriately to ambient conditions. One important finding of this study is that NLP may act as a stressor and correspondingly impose a major threat to the physiological homeostasis of M. socialis, such that over-winter survival might be compromised.

Original languageEnglish
Pages (from-to)269-288
Number of pages20
JournalChronobiology International
Volume24
Issue number2
DOIs
StatePublished - Mar 2007

Keywords

  • Catecholamine
  • Corticosteroids
  • Nocturnal light pulses
  • Stress response
  • Thermoregulation

ASJC Scopus subject areas

  • Physiology (medical)
  • Physiology

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