This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Anchordoquy, H. C. Articles by Lynch, G. R. Search for Related Content PubMed PubMed Citation Articles by Anchordoquy, H. C. Articles by Lynch, G. R. Social Bookmarking                         What's this?

Timing of Testicular Recrudescence in Siberian Hamsters Is Unaffected by Pinealectomy or Long-Day Photoperiod after 9 Weeks in Short Days

G. Robert Lynch

Department of Environmental, Population, and Organismic Biology, University of Colorado at Boulder, Boulder, CO 80309-0334 USA

In this study, the authors asked whether pinealectomy or temporary exposure to a stimulatory photoperiod affects the timing of spontaneous testicular recrudescence in adult Siberian hamsters chronically exposed to short days (9:15 light:dark). In Experiment 1, hamsters were pinealectomized after 6, 9, or 12 weeks in short days. Pinealectomy after 9 or 12 weeks did not affect the timing of spontaneous gonadal growth (27.7 ± 1.9 and 25.4 ± 1.3 weeks, respectively) compared to sham-operated controls (28.6 ± 0.9 weeks). Enlarged testes occurred earlier in animals that were pinealectomized after 6 weeks in short days (21.8 ± 2.1 weeks). In Experiment 2, adult hamsters were exposed to short days for 9 weeks, transferred to long days (16:8 light:dark) for 4 weeks, and then returned to short days for 23 additional weeks. Although long-day interruption caused gonadal growth in 15 out of 19 hamsters, the temporary long-day exposure did not affect the timing of spontaneous gonadal growth following return to short days (28.2 ± 0.9 weeks) in 10 of the 15, relative to the timing observed in control hamsters continuously maintained in short days (28.2 ± 1.1 weeks). Four out of 19 hamsters did not show gonadal growth following long-day exposure. Spontaneous gonadal growth in these hamsters (28.0 ± 1.4 weeks) also occurred at the same time as controls. The remaining 5 hamsters exhibited enlarged testes following long-day exposure (12.0 ± 0.0 weeks) but were refractory to the second short-day exposure. All hamsters exhibited entrainment of wheel-running activity following the change in photoperiod. Afinal group of 13 animals were pinealectomized before long-day transfer. They exhibited gonadal growth (at 17.2 ± 0.8 weeks) but failed to regress a second time when returned to short days. The timing of gonadal growth in these animals was delayed relative to the sham-operated hamsters temporarily transferred to long days (Experiment 2) but accelerated relative to the hamsters pinealectomized at 9 weeks, which remained continuously in short days (Experiment 1). The results of both experiments suggest that a pineal-independent process mediates the timing of spontaneous gonadal growth in Siberian hamsters chronically exposed to a short-day photoperiod.

Key Words: reproductive cycle • photoperiodism • Siberian hamster • pinealectomy • recrudescence • Phodopus sungorus sungorus

Journal of Biological Rhythms, Vol. 15, No. 5, 406-416 (2000)
DOI: 10.1177/074873000129001495


CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				B. J. W. Teubner, C. D. Smith, and D. A. Freeman Multiple Melatonin Target Tissues Mediate Termination of Photorefractoriness by Long Day Lengths in Siberian Hamsters J Biol Rhythms, December 1, 2008; 23(6): 502 - 510. [Abstract] [PDF]

				J. H. Park, A. S. Kauffman, M. J. Paul, M. P. Butler, A. K. Beery, R. M. Costantini, and I. Zucker Interval Timer Control of Puberty in Photoinhibited Siberian Hamsters J Biol Rhythms, October 1, 2006; 21(5): 373 - 383. [Abstract] [PDF]

				A. S. Kauffman and I. Zucker Testicular Recrudescence in Intermediate Day Lengths Reflects Loss of Photoperiodic Memory in Siberian Hamsters J Biol Rhythms, August 1, 2002; 17(4): 345 - 352. [Abstract] [PDF]

				D. A. Freeman and I. Zucker Refractoriness to melatonin occurs independently at multiple brain sites in Siberian hamsters PNAS, May 22, 2001; 98(11): 6447 - 6452. [Abstract] [Full Text] [PDF]