Effects of Photoperiod and Subcutaneous Melatonin Implants on the Reproductive Status of Adult White-footed Mice (Peromyscus leucopus)

¹ Department of Anatomy, University of Texas Health Science Center, San Antonio, Texas

The reproductive consequences of photoperiod and melatonin administration were compared in adult white-footed mice (Peromyscus leucopus). Animals were exposed either to a long photoperiod (16 hours of light:8 hours of dark) with and without subcutaneous melatoninbeeswax implants or to a short photoperiod (8 hours of light:16 hours of dark) for six weeks. Following treatment with either a short photoperiod or melatonin, testicular weights and volumes as well as plasma testosterone levels were significantly (P < 0.01) reduced relative to animals maintained under long daily photoperiods without melatonin Implants. Under the conditions of the present study, chronic melatonin administration is as repressive to the reproductive status as is a short photoperiod in adult white-footed mice.

     Key words: implant, melatonin, photoperiod, white-footed mouse, Peromyscus leucopus, testosterone, testes weight, testis volume

Submitted on September 16, 1980
Revised on October 13, 1980
Accepted on October 29, 1980