Progress in the Study of Maternal Behavior in the Rat: Hormonal, Nonhormonal, Sensory, and Developmental Aspects

This chapter discusses the progress that has been made in the study of maternal behavior in the rat with special focus on the research that has been carried out at the Institute of Animal Behavior. It describes how maternal behavior arises from the hormonal conditions that exist during pregnancy, particularly around parturition when maternal behavior normally begins. The chapter demonstrates that the maternal behavior cycle is a developmental product of hormonal events during pregnancy, especially at its termination, and of behavioral stimulation received during interactions between the mother and her young. Investigation of females whose pregnancies were terminated prematurely by hysterectomy and/or ovariectomy has shown that the rise in estrogen, primarily, is responsible for the onset of maternal behavior under these conditions. To be effective this rise must occur free of the inhibiting influence of high levels of progesterone and that the decline in progesterone in addition to its permissive action with respect to estrogen may itself facilitate a short-term increase in maternal responsiveness. The chapter further deals with postpartum stimulus factors, which regulate maternal behavior and are involved in its maintenance and eventual decline.