Odor-facilitated reentrainment in male and female juvenile Octodon degus

The social, diurnal rodent, Octodon degus, exhibits faster reentrainment rates of circadian activity when exposed to olfactory social cues from females already entrained to the new light cycle (donors) during reentrainment after a phase shift of the light:dark (LD) cycle. However, adult degus display sex differences in the use of olfactory stimuli to accelerate reentrainment, with intact males requiring odors from at least two females for accelerated reentrainment, while odors from a single female are sufficient for faster recovery for females. In addition, adult gonadal hormones modulate responsiveness to the rate-enhancing olfactory stimuli. The present study examines responsiveness to reentrainment-accelerating odors in juvenile animals just prior to puberty. We report that the sex difference in sensitivity observed in adults is not evident in juveniles; both males and females, when exposed to odors from one unfamiliar adult, accelerated reentrainment of circadian activity after a 6-h phase-advance of the LD cycle. In conjunction with adult data, these results suggest that the sensitivity-reducing role of testosterone does not change across the life span, while the sensitivity-enhancing role of ovarian hormones in females occurs only post-pubertally.