Gonadal function in underfed rats: I. Effect of pineal gland and constant light on maturation and fecundity.

Abstract

Rats were underfed from birth to determine the effects of chronic food deprivation on gonadal function. Pups were allowed to nurse for 12 h out of 24 untilthey were weaned. Thereafter,they received 50 percent of the daily amount of food consumed by controls. Besides being underfed, animals were also pinealectomized and/or maintained in constant light. Although delayed, vaginal opening occurred in all underfed groups. Two or three extended estrous cyclesoccurred aftervaginalopening, then the animals became anestrus; however, cycling was restored when they were placed in constant light or with a male. Despite irregularestrous cycles in underfed females, they copulated, became pregnant and gave birth to littersof normal size and composition. Similarly, underfed males impregnated fed females. Continuous illumination or pinealectomy stimulated compensatory hypertrophy in the remaining ovary afterhemiovariectomy both in ratsunderfed from birth and in starved adults which had achieved normal growth prior to underfeeding; however, the lattertreatment was not as effectiveas the former. It did, however, increase ovarian weight prior to surgery. The adverse effects of underfeeding on reproductive function may be due to physiologic alteration resulting in a new pattern of control, rather than simply a reduced rate or lack of function due to less available energy, since the gonads may be stimulated to renewed activity by environmental or surgical manipulations.