Reinitiation of Gonadotropin Release in Underfed Rats by Constant Light or Epinephrine1

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Abstract
The effects on reproductive function of 1/2 normal food intake alone, or with constant light or epinephrine, were evaluated in 180 adult female Sprague-Dawley rats. Underfeeding resulted in cessation of estrous cycles within 14 to 21 days, in decreased ovarian weight and in marked atrophy of interstitial and follicular tissues. Exposure of underfed rats to constant light for 10 days resulted in cornified vaginal smears in 100% of the rats, in greater than a 50% increase in ovarian weight, in marked stimulation of follicular growth, in almost a 2-fold increase in uterine weight and in mammary duct growth. Epinephrine injections (0.5 mg/ day) for 10 days produced a significant increment in ovarian weight, due almost entirely to an increase in number and size of corpora lutea, and also resulted in marked mammary lobuloalveolar growth. In the underfed rats, pituitary LH [luteinizing hormone] concentration was reduced to 1/3 and hypothalamic content of luteinizing hormone releasing factor (LRF) to about 1/4 of those of ad lib. fed controls. Neither constant illumination nor epinephrine altered pituitary FSH [follicle-stimulating hormone] or LH concentration or hypothalamic LRF activity in the underfed rats by the end of 10 days of treatment. These studies indicate that the depressing effects of underfeeding on FSH, LH and prolactin release can be partially or completely overcome by the stimulus of constant illumination or epinephrine injections.