Hypothalamic Interaction with the Mesolimbic Dopamine System and the Regulation of Maternal Responsiveness

This chapter reviews research dealing with the neural basis of maternal behavior in rats. The major components of maternal behavior in this species are retrieval behavior, nest building, nursing behavior, and pup grooming. Retrieval behavior, which occurs when the postpartum female carries individual pups in her mouth, serves to transport the altricial pups from one location to another. This discussion classifies pup-seeking behaviors and retrieval behavior as voluntary proactive maternal responses, while nursing/crouching behavior is more of a reflexive maternal response that is closely tied to proximal pup stimulation. At parturition, the primiparous female rat shows the full complement of maternal behaviors on her first exposure to her own pups or to foster pups. In contrast, the naive virgin (nulliparous) estrous cycling female rat will not care for foster pups upon her initial exposure to them; she avoids such pups and may even attack them. This difference is very important because it shows that infant stimuli do not automatically elicit maternal responses in female rats. Important internal changes take place in the female who has just given birth, which increases maternal responsiveness or maternal motivation. Clearly, the brain circuits that are operative in the first-time mother must be different from those in the naive virgin female rat.