The proposed studies provide new knowledge for understanding how events early in life shape physiology, behavior, and susceptibility to disease later in life. They focus on variation in nutrient availability in the perinatal period. The long-term health related objectives of the work are to improve early identification of individuals at risk for adult disease, to discover new prevention strategies, and to identify epigenetic alterations that account for the persistence of the effects of early experiences. Both animal models and human infants are studied. Assessments include measures of physiological, biochemical and behavioral characteristics of infants in both species in the first few days after birth. Indices derived from animal studies will be incorporated into human studies, and the underpinnings of correlative findings from human studies will be pursued in animal models. The presupposition for the work is that individuals, undergrown during gestation, express adaptations that can be seen as changes in autonomic nervous system (ANS) development, cardiovascular (CV) regulation, and feeding behavior. Aim 1. To determine if human infants with low birth weights express differences in CV and behavioral responses to feeding, differences in heart rate and blood pressure responses to postural challenge, and differences in physiologic and behavioral responses to changes in taste and/or formula composition. Aim 2. To determine, in rats, the effects of reduced food availability during gestation on physiologic and behavioral characteristics during the preweaning period. Key measurements will include assessments of Newborn feeding behaviors and food preferences and CV and responses to food and feeding. Aim 3. To determine, in rats, how variations in nutrient availability after birth alter the effects of gestational malnutrition. Does experimental manipulation of food intake during the postnatal period reprogram the effects of fetal undergrowth and, if so, is there a critical period for this intervention? Aim 4. To determine, in rats, if there are changes in patterns of DNA methylation in kidney, liver, hypothalamus, placenta, and blood samples obtained from animals reared under the conditions of Aims 2 and 3. If so, the DNA sequences with alterations in methylation will be identified and this information will guide methylation studies targeted to specific genes in the placenta and cord blood samples from humans.