Temperature regulation in the mouse,Peromyscus leucopus: Effects of various photoperiods,pinealectomy and melatonin administration

The white-footed mouse,Peromyscus leucopus, exhibits two responses to a decreasing series of photoperiods. The winter molt and reproductive regression occur in mice maintained on a photoperiods of 12 hours of light per day or less. Daily torpor and weight of lipid-free brown fat increase gradually between photoperiods of LD 13:11 — LD 12:12 and LD 10:14 — 9:15 LD. Pinealectomized mice maintained on a LD 9:15 photoperiod fail to exhibit the extent of daily torpor and increased nesting which are characteristic of sham-operated animals. Replacement therapy with chronically implanted beeswax pellets containing 3 mg of melatonin reverses the effects of pinealectomy.Presented at the Eighth International Congress of Biometeorology, 9–14 September 1979, Shefayin, Israel.