Yes / Seasonal or photoperiodically sensitive animals respond to altered day length with changes in
physiology (growth, food intake and reproductive status) and behaviour to adapt to predictable
yearly changes in the climate. Typically, different species of hamsters, voles and sheep are the
most studied animal models of photoperiodism. Although laboratory rats are generally considered
nonphotoperiodic, one rat strain, the inbred Fischer 344 (F344) rat, has been shown to be
sensitive to the length of daylight exposure by changing its physiological phenotype and reproductive
status according to the season. The present study aimed to better understand the nature
of the photoperiodic response in the F344 rat. We examined the effects of five different photoperiods
on the physiological and neuroendocrine responses. Young male F344 rats were held
under light schedules ranging from 8 h of light/day to 16 h of light/day, and then body weight,
including fat and lean mass, food intake, testes weights and hypothalamic gene expression were
compared. We found that rats held under photoperiods of ≥ 12 h of light/day showed increased
growth and food intake relative to rats held under photoperiods of ≤ 10 h of light/day. Magnetic
resonance imaging analysis confirmed that these changes were mainly the result of a
change in lean body mass. The same pattern was evident for reproductive status, with higher
paired testes weight in photoperiods of ≥ 12 h of light/day. Accompanying the changes in physiological
status were major changes in hypothalamic thyroid hormone (Dio2 and Dio3), retinoic
acid (Crabp1 and Stra6) and Wnt/b-Catenin signalling genes (sFrp2 and Mfrp). Our data demonstrate
that a photoperiod schedule of 12 h of light/day is interpreted as a stimulatory photoperiod
by the neuroendocrine system of young male F344 rats.
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/10842 |
| Date | 26 January 2015 |
| Creators | Tavolaro, F.M., Thomson, L.M., Ross, A.W., Morgan, P.J., Helfer, Gisela |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Article, Published version |
| Rights | © 2015 The Authors. Journal of Neuroendocrinology published by John Wiley & Sons Ltd on behalf of British Society for Neuroendocrinology. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited., CC-BY |
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