Changes in day length (photoperiod) can serve as an important signal for the coming breeding season for mammals inhabiting predictable ecosystems in temperate zones. In unpredictable desert ecosystems, photoperiod changes are not a sufficient signal to predict the optimal time of breeding. Therefore, integration of various environmental cues should determine which species will be adapted to breed at the right time and to survive in xeric environments. In regards we asked the following question: What are the environmental cues and their mechanism used by xeric adapted small mammals for reproduction timing? The driving force in desert ecosystems is water and the intervals between episodes of water input into the ecosystem vary and in some years there may be no input. It has been suggested that water availability can serve as a reliable cue for reproduction. Vasopressin (VP), a hormone involved in water balance and osmoregulation is produced by the hypothalamus and released by the neuro-pituitary. VP secretion levels increase in response to elevated plasma osmolarity, representing water shortage. VP receptors are found in the reproductive tract. The different effects of VP on metabolism and reproduction make it candidate for mediating the transmission of environmental signals to the reproductive system of desert adapted rodents. We tested the metabolic and reproductive response of males from a desert adapted population of A. cahirinus to VP treatment under three week acclimation to two different photoperiod regimes short (SD- 8L:16D) and long (LD- 16L:8D). The results of our study show that VP treatment per se, caused a significant (p<0.05) decrease of testosterone level in SD-acclimated males. VP treatment caused an increase in FFA release of SD-acclimated males but not in LD-males. In addition, response was assessed from changes in mRNA receptor gene expression of VP (AVP) and aldosterone (nr3c2) in testis and white adipose tissue (WAT) of treated groups, compared with their control. VP treatment resulted in a decrease of VP receptor gene expression, in LD-acclimated male testis. VP caused a significant decrease in aldosteron receptor mRNA expression in SD-acclimated males, in testis, but caused its elevation in WAT. These results support the idea that water availability in the habitat may affect breeding through effects of VP, directly, on the testis, or indirectly through effects on WAT. These findings also support previous knowledge that different physiological systems could be integrated by a single hormonal signal.
|Title of host publication||Vasopressin|
|Subtitle of host publication||Mechanisms of Action, Physiology and Side Effects|
|Publisher||Nova Science Publishers, Inc.|
|Number of pages||15|
|State||Published - Jan 2013|
Bibliographical noteFunding Information:
We thank the ISF (Israel Academy of Science and Humanities) for financial support through a grant to Abraham Haim and Fuad Fares. We also would like to thank Ms. Lilach Ashkenazi for her help and constructive comments. We thank Ms. Nina Dainov and the staff of the department of Biology at Oranim Campus for their assistance in maintaining the animals. Authors also thank three anonymous reviewers for their constructive comments on an earlier version of this paper.
ASJC Scopus subject areas
- Medicine (all)
- Neuroscience (all)