Tactile and Nutritional Aspects of Maternal Care: Specific Regulators of Neuroendocrine Function and Cellular Development

Abstract

Development in mammals is influenced profoundly by many environmental stimuli, and those provided by the mother are the most critical for survival and growth. Disruption of the mother-infant relationship elicits marked behavioral and physiological responses in the offspring ranging from transient changes in body temperature, heart rate, and locomotor activity following short periods of separation, to marked retardation of growth and behavioral development following more long-term separation (1-4). A growing body of evidence demonstrates that extremely specific sensory cues from the mother regulate different physiological and behavioral responses in young animals. For example, nipple attachment in rats is promoted by specific organic substances on the ventral surface of the mother, and thermal input from the mother modulates locomotor activity in weanling-age rat pups, while compounds secreted by the mother's GI tract “orient” pups to the nest (5-8). Studies in this laboratory recently have shown that mother-pup interactions also have marked effects on biochemical processes in the developing pup. These biochemical processes, like behavior, respond to extremely specific environmental cues. The findings of our studies, which are described in the following review, have shown that mother-pup interactions seem to be important regulators of physiologic as well as behavioral function. We have found that sensory stimuli associated with the mother elicit coordinated physiological and biochemical responses which vary with the nature of the stimulus. While some environmental stimuli are important regulators of growth and development, others subserve quite different functions, like maintaining tissue sensitivity to specific hormones. The first group of studies we wish to discuss are those demonstrating that active tactile stimulation of preweanling pups by the mother provides specific sensory cues that maintain normal growth and development. The data that will be discussed demonstrate that restriction of active tactile interaction between mother and pup produces at least three different abnormalities in biochemical processes involved in growth and development.