Biology of Reproduction, Vol 20, 739-746, Copyright © 1979 by Society for the Study of Reproduction

Hypothalamic-Pituitary-Gonadal Interactions during Spontaneous Testicular Recrudescence in Golden Hamsters

¹ Physiology Section, School of Life and Health Sciences, University of Delaware, Newark, Delaware 19711

Golden hamsters exposed to short days (<12.5 h light/24 h) show a decrease in serum FSH and LH resulting, after 10-12 weeks, in testicular regression. This is followed by a spontaneous rise in serum FSH and LH (weeks 15-23) and a concomitant maturation of the reproductive system. In this study, we examined the interaction of negative feedback mechanisms and photoperiodic effects during the period of spontaneous recrudescence in hamsters exposed to continual short day treatment (LD 6 h:18 h). After 2 weeks, animals were divided into 4 groups. One group served as intact controls. Another group of intact males received 5 mm testosterone implants (in Silastic tubing). The others were castrated; half of these received testosterone implants. Five animals were sacrificed every 2 weeks in the control group and every week in the treatment groups. Spontaneous testicular recrudescence occurred between weeks 15-27 in control animals and weeks 20-29 in animals with testosterone implants. Analysis of serum gonadotropins in each treatment group revealed a temporal difference in the peak of FSH and LH that appears to correlate with circulating levels of testosterone. These data suggest that alternations in gonadotropin release during spontaneous testicular recrudescence may be controlled by a gradual change in the set point of the sensitivity of the hypothalamic-pituitary axis to testosterone.

Note:
ACKNOWLEDGMENTS We are grateful to Marcia Watson-Whitmyre and Gordon Grau for their assistance with the radioimmunoassays. These studies were supported by NSF Research Grant PCM-75-04039 to M.H.S.

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