Maternal Motivation: Exploring the Roles of Prolactin and Pup Stimuli

Motherhood entails increased motivation for pups, which become strong reinforcers and guide maternal behaviours. This depends on steroids and lactogens acting on the brain of females during pregnancy and postpartum. Since virgin female mice exposed to pups are nearly spontaneously maternal, the specific roles of endocrine and pup-derived signals in the induction of maternal motivation remain unclear. This work investigates maternal motivation in dams and virgin female mice, using a novel variant of the pup retrieval paradigm, the Motivated Pup Retrieval Test. We also analyse the role of prolactin and of stimuli derived from a litter of pups and its mother, in the acquisition of maternal motivation. Experimental design included female mice in three conditions: lactating dams, comothers (virgins housed and sharing pup care with dams) and pup-na ïve virgins. Females underwent three motivated-pup-retrieval trials, with pups displaced behind a 10 cm high wire-mesh barrier. Dams retrieved with significantly lower latencies than comothers or virgins, indicating that full maternal motivation appears only after pregnancy. Although initially como thers and virgins showed no retrieval, comothers significantly improved throughout the experiment, suggesting an induced sensitisation process. Lengthening exposure of comothers to the dyad pups-dam (from 2 to 5 days at the beginning of testing) had no strong effects on maternal sensitisation. Prol actin responsiveness was analysed in these...
Source: Neuroendocrinology - Category: Endocrinology Source Type: research