Abstract
Summary
Lactating rats were killed after exposure to specific nursing intensities and suckling intervals to examine the effects of these factors on circulating leukocytes, plasma corticosterone, and mammary nucleic acids. Nursing durations of 0.25, 0.5, and 1 hr caused a 3-fold increase in plasma corticosterone when compared to nonnursed levels. In comparison, plasma corticosterone concentrations were similar to nonnursed control values after hours 2, 3, and 4 of nursing. In addition, exteroceptive stimuli associated with nursing provoked increases in plasma corticosterone that were comparable to values obtained from 0.25 or 0.5 hr of nursing. Circulating leukocytes decreased 24% during the first 0.5 hr of nursing with 10 pups; whereas mammary nucleic acid content increased 9%, suggesting an influx of leukocytes into mammary tissue. Histological examination of mammary glands revealed a striking increase in leukocytes within the alveolar lumina of glands within 0.5 hr after nursing. The results from this study indicate that nursing is a dynamic situation which is capable of provoking striking alterations in leukocytic and adrenocortical function.
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