Odor-specific effects on reentrainment following phase advances in the diurnal rodent, Octodon degus

Abstract

trainment following phase shifts of the light-dark (LD) cycle is accelerated in Octodon degus in the presence of olfactory social cues (i.e., odors) produced by conspecifics. However, not all odors from conspecifics were effective in facilitating reentrainment after a phase advance. In the current experiments, we examined whether nonanimal odors, odors from another species, or conspecific odors, including those manipulated by steroid hormones, can cause the same increased reentrainment of wheel-running activity as odors from an intact, adult female degu. A variety of odors, each selected to probe a particular aspect of the reentrainment acceleration phenomenon, were presented to a group of phase-shifting female degus. The shifting females (test animals) responded to odors of intact, female degu donors with decreased reentrainment time, but odors of ovariectomized (OVX), OVX with a single hormone replacement capsule (estradiol or progesterone) or phase-shifting females had no effect. Multiple males were effective odor donors, whereas a single male was ineffective in earlier studies. Rats and cloves were not effective in accelerating reentrainment. Furthermore, odors from rats delayed reentrainment. We conclude that the odors that effectively accelerate degu reentrainment after a phase advance of the LD cycle are species specific. We also report that repeated phase shifts, followed by complete recovery of phase relationships, do not alter the rate of recovery from a phase shift over time. These data suggest that in O. degus, a social species, odors may reinforce and strengthen the salience of the photic zeitgeber and/or facilitate synchronization of rhythms between animals. circadian rhythm; degu; phase-shift; entrainment; nonphotic signals CIRCADIAN RHYTHMS SUCH AS sleep/wake cycles, temperature fluctuations, and hormonal changes are synchronized by time cues (i.e

Maternal Olfactory Cues Synchronize the Circadian System of Artificially Raised Newborn Rabbits

“…In adult rodents, these signals affected the expression of daily patterns of body temperature and wheel-running activity [47,48]. Olfactory cues can also modulate the photic and non-photic entrainment of activity in adult rats [49,50]. Recently, it has been reported that adult rodents exhibit circadian rhythmicity in olfactory sensitivity [51,52], which persists even when the SCN is eliminated.…”

On the Chronobiology of Cohabitation

“…Some studies have shown circadian effects in some individuals upon presentation of a putative social cue alone. Supplying female degus with an odor cue from entrained degus has been reported to "temporarily" entrain some of the animals and to accelerate reentrainment to a phase-advanced light/dark cycle (Governale and Lee 2001;Jechura et al 2006). Some bird species can entrain to playbacks of conspecific birdsong presented every 24 hours (Gwinner 1966;Menaker and Eskin 1966), but house sparrows (Passer domesticus) can also entrain to periodic noise (Reebs 1989), so it is not clear if entrainment to birdsong playback is truly a social phenomenon or the result of nonspecific arousal.…”

Social modulation of the daily activity rhythm in a solitary subterranean rodent, the tuco-tuco (Ctenomys sp)

“…Changes in rhythmic patterns intermediated by chemical cues have been shown, for instance, in social interactions between two rodent Acomys species [35] and among socially interacting Octogon degus individuals [36] . It has been reported that through close inspection of urine, feces or dirt, tuco-tucos can discriminate chemical cues and use them to assess the reproductive condition of conspecifics [37] , [38] .…”