Long-day photoperiod interacts with vasopressin and food restriction to modulate reproductive status, and vasopressin receptor expression of male Golden spiny mice

Abstract

SUMMARYWe tested the effects of photoperiod, water and food availability on body mass, reproductive status and arginine vasopressin receptor 1A (Avpr1a) mRNA expression in males of desert-adapted golden spiny mice, Acomys russatus. In Experiment 1, males were acclimated to short-day (SD; 8h:16h light:dark) or long-day (LD; 16h:8h light:dark) photoperiods with either saline (control) or vasopressin treatment for 3weeks. The results of this experiment revealed that under control conditions, SD mice increased body mass by ~5% while LD mice decreased it by ~4%. SD photoperiod had no effect on reproductive status and leptin levels, whereas LD males increased testes mass and serum testosterone, but the photoperiod had no effect on leptin levels. Vasopressin administration decreased LD-induced reproductive enhancement. Because no consistent effect of SD treatment was found on reproductive status, Experiment 2 was carried out only on LD-acclimated males kept under 75% food restriction (decrease from ad libitum) with saline or leptin treatment. Body mass, testes mass, serum testosterone, leptin concentrations and Avpr1a mRNA expression were measured. Food restriction remarkably decreased body mass, with a more potent effect in leptin-treated males, showing enhanced reproductive status and a significant increase in serum leptin compared with controls. Avpr1a expression was significantly upregulated in LD, vasopressin-treated and food-restricted males, with higher levels in the hypothalamus compared with the testes. We conclude that in A. russatus, LD photoperiod interacts with water and food availability to advance reproductive responses. Avpr1a is suggested to integrate nutritional and osmotic signals to optimize reproduction by modulating reproductive and energetic neuroendocrine axes at the central level. The interaction between photoperiod and other environmental cues is of an adaptive value to desert-adapted small rodents for timing reproduction in unpredictable ecosystems such as extreme deserts.

Melatonin Regulates Daily Variations in Electric Behavior Arousal in Two Species of Weakly Electric Fish with Different Social Structures

“…In amphibians, melatonin production during the dark phase influences the number of AVTergic cells [Lutterschmidt and Wilczynski, 2012]. Changes in the photoperiod, internally signaled by changes in melatonin pulses, influence AVT as well as arginine vasopressin systems, inducing seasonal and daily changes in behavior and reproductive state in fish and mice [Rodrí-guez-Illamola et al, 2011;Ben-Zaken et al, 2013]. In mammals, AVTergic production itself has an endogenous circadian rhythm [Jansen et al, 2000].…”

Photoperiodic effects on the male gonads of the Namibian gerbil, Gerbilliscus cf. leucogaster from central Namibia

“…Photoperiod, rainfall and the sudden flush of green vegetation are important factors for the onset of reproduction in rodents inhabiting arid and semi-arid habitats. These cues do not act separately, but in concert with one another for the onset and maintenance of reproduction and maximizing reproductive success (Ben-Zaken et al 2013). Photoperiod plays a very important role as a proximate factor, triggering reproductive events in terrestrial organisms and in particular those occurring at higher latitudes (Nelson et al 1992;Rani and Kumar 2014).…”

“…Mammals that are responsive to long-day length cease to breed as the day length becomes shorter towards the end of summer and with the onset of autumn (Muteka et al 2006;Prendergast et al 2001). Effects of photoperiod on reproduction have been investigated in several mammalian species such as the golden spiny mouse, Acomys russatus (Ben-Zaken et al 2013), the California vole, Microtus californicus (Nelson et al 1983), the vole, Microtus agrestis (Spears and Clarke 1986), black rat, Rattus norvegicus (Heideman and Sylvester 1997;Heidemann et al 1998), the California vole, the four-striped field mouse, Rhabdomys pumilio (Jackson and Bernard 1999), and the white-footed mouse, Peromyscus leucopus (Young et al 2000). Increasing day length coincides with the beginning of spring and reproductive recrudescence in seasonally breeding animals begins during this period to maximize the survival of the offspring (Jameson 1988;Flowerdew 1987).…”