Prolactin Action Is Necessary for Parental Behavior in Male Mice

Parental care is critical for successful reproduction in mammals. Recent work has implicated the hormone prolactin in regu-lating male parental behavior, similar to its established role in females. Male laboratory mice show a mating-induced suppres-sion of infanticide (normally observed in virgins) and onset of paternal behavior 2 weeks after mating. Using this model, we sought to investigate how prolactin acts in the forebrain to regulate paternal behavior. First, using c-fos immunoreactivity in prolactin receptor (Prlr) Prlr-IRES-Cre-tdtomato reporter mouse sires, we show that the circuitry activated during paternal interactions contains prolactin-responsive neurons in multiple sites, including the medial preoptic nucleus, bed nucleus of the stria terminalis, and medial amygdala. Next, we deleted Prlr from three prominent cell types found in these regions: glutama-tergic, GABAergic, and CaMKIIa. Prlr deletion from CaMKIIa, but not glutamatergic or GABAergic cells, had a profound effect on paternal behavior as none of these KO males completed the pup-retrieval task. Prolactin was increased during mat-ing, but not in response to pups, suggesting that the mating-induced secretion of prolactin is important for establishing the switch from infanticidal to paternal behavior. Pharmacological blockade of prolactin secretion at mating, however, had no effect on paternal behavior. In contrast, suppressing prolactin secretion at the time of pup exposure resulted in failure to retrieve pups, with exogenous prolactin administration rescuing this behavior. Together, our data show that paternal behavior in sires is dependent on basal levels of circulating prolactin acting at the time of interaction with pups, mediated through Prlr on CaMKIIa-expressing neurons.

Automated summary

Parental care is crucial for successful reproduction in mammals. Recent research has shown that the hormone prolactin plays a key role in regulating paternal behavior in male mice. The study found that two weeks after mating, male mice showed suppression of infanticide and the onset of paternal behavior. The researchers investigated the neural circuitry and found that prolactin-responsive neurons in multiple brain regions are activated during paternal interactions. Furthermore, they discovered that the presence of prolactin and the presence of Prlr on CaMKIIa-expressing neurons are important for paternal behavior.