Related Experiment Videos
Gonadal growth and hormone concentrations in photoregressed Siberian hamsters: pinealectomy versus photostimulation
K K Kelly1, B D Goldman, I Zucker
1Department of Psychology, University of California, Berkeley 94720.
Abstract:
In Siberian hamsters, long and short durations of nightly melatonin secretion are associated with testicular regression and development, respectively; surprisingly, the absence of a nightly melatonin signal induced by pinealectomy is less effective than a short (4-6 h) melatonin duration for promoting gonadal development. We compared the patterns of serum FSH and prolactin concentrations underlying pinealectomy-induced and photostimulated testicular growth in juvenile hamsters. Pinealectomy in photoinhibited hamsters on Day 18 produced significant gonadal development compared to that in short-day controls by Day 23. By Day 28, however, testes weights of pinealectomized hamsters were significantly lower than those of intact hamsters transferred to a long photoperiod. Pinealectomy was associated with significant elevations in serum FSH and prolactin concentrations over baseline by Day 21, but peak values were attenuated compared with those induced by exposure to long days. FSH titers of pinealectomized animals were significantly lower than those of photostimulated animals between Days 21 and 30 but were significantly greater on Days 35 and 40; prolactin values were comparable in pinealectomized and photostimulated hamsters between Days 21 and 25 but were significantly lower in the former group thereafter. Blunted elevation of FSH and prolactin secretion may underlie the slower rates of gonadal maturation observed in pinealectomized, juvenile hamsters. The neuroendocrine systems of pinealectomized hamsters appear to be in a state intermediate between those characteristic of hamsters kept in long and in short day lengths.
Insights
Pinealectomy in Siberian hamsters promotes testicular development but at a slower rate than long-day photostimulation. This suggests intermediate neuroendocrine states impacting gonadal maturation.
Area of Science:
- Reproductive biology
- Endocrinology
- Chronobiology
Background:
- Melatonin secretion duration influences Siberian hamster testicular function.
- Pinealectomy (absence of melatonin) is less effective than short melatonin durations for gonadal development.
Purpose of the Study:
- Compare FSH and prolactin patterns in pinealectomy-induced vs. photostimulated testicular growth.
- Investigate neuroendocrine mechanisms of gonadal maturation in juvenile hamsters.
Main Methods:
- Pinealectomy performed on photoinhibited juvenile Siberian hamsters.
- Serum FSH and prolactin concentrations measured over time.
- Testes weights compared between groups.
Main Results:
- Pinealectomy induced gonadal development, but testes weights were lower than long-day controls by Day 28.
- Pinealectomy elevated FSH and prolactin, but peaks were attenuated compared to long-day exposure.
- FSH and prolactin patterns in pinealectomized hamsters suggest an intermediate neuroendocrine state.
Conclusions:
- Blunted FSH and prolactin secretion may slow gonadal maturation in pinealectomized hamsters.
- Pinealectomy creates an intermediate neuroendocrine state between short and long day lengths.