Female meadow voles housed in long and short daylengths respond to exogenous estrogen with similar mating latencies.
After weaning, adult female meadow voles were maintained for 7 weeks in either long (LD, 14 h light/day) or short photoperiods (SD, 10 h light/day). They were then ovariectomized and implanted with 3-week, timed-release estrogen pellets (0.0, 0.001, 0.05, or 0.5 mg/pellet of 17-beta-estradiol). An additional group received a sham ovariectomy (intact) and a 0.0-mg/pellet control (no estrogen) pellet. One week after surgery, females were paired with an LD sexually experienced male. Each pair was videotaped continuously until the first intromission or for 2 weeks. LD sham animals mated significantly earlier than did SD sham animals (P=.05). However, there were no differences in mating latencies between LD and SD control groups or between any of the LD and SD groups receiving estrogen replacement (P>.05). In addition, no ovariectomized animals receiving either the control or the 0.001-mg/pellet estrogen dosage mated within the 2-week time period, while all shams and all animals receiving either the 0.05- or 0.5-mg/pellet doses mated. The results indicate that there is some minimal amount of estrogen that is necessary for meadow voles to enter behavioral estrus and that LD and SD females do not differ in their sensitivity to estrogen, since animals in both photoperiods mate with similar latencies as long as enough estrogen is present.
Meek
L R
LR
University of Minnesota, Morris, 109 Camden Hall, Morris, MN 56267, USA. meeklesr@mrs.umn.edu
Schrump
S E
SE
Smith
D A
DA
Schulz
K M
KM
Dittel
P L
PL
Merkle
C J
CJ
D000818:Animals; D003411:Arvicolinae / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004343:Drug Implants; D004958:Estradiol / Q000494:pharmacology; D004967:Estrogens / Q000502:physiology*; D005260:Female; D008029:Lighting; D008297:Male; D012726:Sexual Behavior, Animal / Q000187:drug effects / Q000502:physiology*
D004343:Drug Implants; D004967:Estrogens; D004958:Estradiol