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Temperature dependence of gonadal regression in Syrian hamsters exposed to short day lengths

2002; American Physiological Society; Volume: 282; Issue: 3 Linguagem: Inglês

10.1152/ajpregu.00299.2001

1522-1490

Jennie Larkin, Jennifer Jones, Irving Zucker,

Birth, Development, and Health

We sought to determine whether ambient temperature (T a ) affects gonadal function by altering the rate at which circadian rhythms entrain to short day lengths. Syrian hamsters were housed in cages where they received 14 h of light per day (“long days,” 14L) at 22°C. Hamsters were then transferred to cages to receive 10 h of light per day (“short days,” 10L) and kept at 5, 22, or 28°C or were maintained in 14L at 22°C. Body mass and estimated testis volume as well as duration of nocturnal locomotor activity (α), previously established as a reliable indicator of the duration of nocturnal melatonin secretion, were determined over the course of 24 wk. Testicular regression in short days was accelerated by 4 wk at 5°C and delayed by 3 wk at 28°C relative to 22°C. The interval between α-expansion and initiation of testicular regression was markedly affected by T a with delays of 0, 3, and 6 wk at 5, 22, and 28°C, respectively. All hamsters held at 5 and 22°C underwent testicular regression, but 25% of those maintained at 28°C failed to do so. We suggest that T a modulates testicular regression primarily by affecting responsiveness of neuroendocrine target tissues to long melatonin signals.