Present address: Deborah L. Drazen, Department of Psychiatry, University of Cincinnati Medical Center, PO Box 670559, Cincinnati, OH 45267-0559, USA
Exposure to short days, but not short-term melatonin, enhances humoral immunity of male Syrian hamsters (Mesocricetus auratus)
Article first published online: 2 AUG 2002
Journal of Pineal Research
Volume 33, Issue 2, pages 118–124, September 2002
How to Cite
Drazen, D. L., Jasnow, A. M., Nelson, R. J. and Demas, G. E. (2002), Exposure to short days, but not short-term melatonin, enhances humoral immunity of male Syrian hamsters (Mesocricetus auratus). Journal of Pineal Research, 33: 118–124. doi: 10.1034/j.1600-079X.2002.02915.x
- Issue published online: 2 AUG 2002
- Article first published online: 2 AUG 2002
- Received February 28, 2002; accepted May 15, 2002.
- day length;
Abstract: Many non-tropical rodent species rely on photoperiod as the primary cue to co-ordinate seasonally appropriate changes in physiology and behavior. Among these seasonal changes, several rodent species (e.g. deer mice, prairie voles, Siberian hamsters) adjust immune function in response to changes in ambient day lengths. The goals of the present study were to examine the effects of photoperiod on immune function of Syrian hamsters (Mesocricetus auratus), and to determine the role of melatonin in mediating photoperiodic changes in immunity. In Experiment 1, male Syrian hamsters were housed in long (LD 14:10) or short days (LD 10:14) for 10 wk. In Experiment 2, hamsters were housed in long days and half of the animals were given 10 consecutive days of i.p. melatonin injections (15 μg) in the early evening, while the remaining animals received injections of the vehicle alone. After the respective experimental manipulations, animals were injected with the antigen, keyhole limpet hemocyanin (KLH), blood samples were obtained and anti-KLH IgG antibody production was assessed. In Experiment 1, short-day hamsters underwent gonadal regression and reduced serum testosterone as well as displayed increased humoral immune function compared with long-day animals. In Experiment 2, short-term melatonin treatment did not affect gonadal mass, testosterone or humoral immune function. These results confirm previous findings of photoperiodic changes in immunity in rodents and suggest that changes in humoral immunity are not due to short-term changes in melatonin.