DEVELOPMENT OF INGESTIVE BEHAVIOR

Swallowing represents a primary physiological function that provides f or the ingestion of food and fluid. In precocial species, swallowing a ctivity likely develops in utero to provide for a functional system du ring the neonatal period. The chronically instrumented ovine fetal pre paration has provided the opportunity for recent advances in understan ding the regulation of in utero swallowing activity. The near-term ovi ne fetus swallows fluid volumes (100-300 ml/kg) that are markedly grea ter, per body weight, than that of the adult (40-60 ml/kg). Spontaneou s in utero swallowing and ingestive behavior contribute importantly to the regulation of amniotic fluid volume and composition, the acquisit ion and potential recirculation of solutes from the fetal environment, and the maturation of the fetal gastrointestinal tract. Fetal swallow ing activity is influenced by fetal maturation, neurobehavioral state alterations, and the volume of amniotic fluid. Furthermore, intact dip sogenic mechanisms (osmolality, angiotensin II) have been demonstrated in the near-term ovine fetus. It remains unknown to what degree, if a ny, fetal swallowing may be influenced by nutrient appetite, salt appe tite, or taste. Nevertheless, the development of dipsogenic and additi onal regulatory mechanisms for ingestive behavior occurs during fetal life and may be susceptible to changes in the pregnancy environment. T his review describes what is currently known regarding the in utero de velopment of ingestive behavior and the importance of this activity fo r fetal and perhaps ultimately adult fluid homeostasis.