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701.
Timothy J. Greives Susannah S. French Devin A. Zysling Nicholas W. Garcia Gregory E. Demas 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(2):267-277
Seasonal variation in behavior and physiology, including changes in immune function, are common. This variability is elicited
by changes in photoperiod and often covaries with fluctuations in both energy reserves and reproductive state. It is unclear,
however, whether changes in either variable alone drive seasonal changes in immunity. We investigated the relative contributions
of reproduction and energy balance to changes in immune function. To accomplish this, we uncoupled seasonal changes in reproduction
from those related to energy balance via daily injections of N-methyl-d-aspartate (NMDA) in Siberian hamsters (Phodopus sungorus). NMDA is a glutamatergic agonist that blocks short day-induced gonadal regression, while leaving short-day declines in body
mass unaffected. In Experiment 1, we examined the effect of differing doses of NMDA on testosterone production as a proxy
for NMDA effects on reproduction; a dose-dependent rise in testosterone was observed. In Experiment 2, animals were maintained
on long or short days and received daily injections of NMDA. After 8 weeks, all animals underwent a humoral immune challenge.
Short-day animals receiving daily injections of NMDA maintained long day-like gonads; however, contrary to our predictions,
no trade-off between reproduction or energy balance and immune function was observed. Unexpectedly, NMDA treatment increased
immunoglobulin levels in all groups, suggesting that NMDA may provide an immunomodulatory signal, presumably through actions
on peripheral glutamate receptors. These results support a previous finding that NMDA blocks reproductive regression. In addition,
these findings demonstrate a general immunoenhancing effect of NMDA that appears independent of changes in reproductive or
energetic state of the animal. 相似文献
702.