Food and Neonatal Androgen: DISCUSSION(5)

It is probably significant that the response to photoperiod is present to varying degrees in different strains of rats. The implication is that some of the wild ancestors of laboratory rats had the capacity to undergo both obligate and facultative inhibition of reproduction in SD, with longer reproductive delays in SD when food was scarce…

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Food and Neonatal Androgen: DISCUSSION(4)

Truly opportunistic breeders, such as the tropical cane mouse, show neither photoperiodic inhibition of reproduction nor interactions between photoperiod and neonatal androgen treatment or FR. In contrast, seasonal breeders such as the deer mouse (Peromyscus maniculatus) show strongly inhibited reproduction in SD, with greater inhibition when FR and SD are combined. Deer mice have both…

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Food and Neonatal Androgen: DISCUSSION(3)

The 2- to 4-wk added delay in reproductive maturation induced by the combination of SD and FR could be highly significant to young rats in the wild. However, the combined effect of SD and FR together was considerably weaker than the reproductive inhibition produced by SD alone in many obligately photoresponsive species. The level of…

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Food and Neonatal Androgen: DISCUSSION(2)

Interestingly, the effect of neonatal TP treatment was clearly restricted to reproductive responses to SD. Neonatal TP strongly inhibited testicular growth in SD but had no effect on body weight. This suggests that SD may act independently on the reproductive axis and body weight, such that neonatal TP can enhance one effect but not the…

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Food and Neonatal Androgen: DISCUSSION(1)

F344 rats possess both an obligate inhibition of testicular development in SD and a further facultative inhibition of testicular development in SD by FR or by neonatal TP (Figs. 2 and 4). Together, the obligate and facultative responses inhibit reproductive maturation in SD almost as strongly as observed in some highly photoresponsive rodents, but for…

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Food and Neonatal Androgen: RESULTS(2)

Experiment 2 Both SD and FR inhibited testicular growth (F = 153.9, p < 0.0001, and F = 56.1, p < 0.0001, respectively; Fig. 4). The effects of photoperiod and of food restriction were significant at Week 1, and both persisted through all 13 wk of the study (Fig. 4). There was a significant interaction…

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Food and Neonatal Androgen: RESULTS(1)

Experiment 1 Both SD and TP inhibited testicular growth (F = 220.6, p < 0.0001, and F = 122.3, p < 0.0001, respectively; Fig. 2). The effect of both photoperiod and TP were significant at Week 2 and persisted through Week 12 (Fig. 2), but by Week 21, the effects of both TP and photoperiod…

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