Induction of Brain Prolactin Receptor Long-Form mRNA Expression and Maternal Behavior in Pup-Contacted Male Rats: Promotion by Prolactin Administration and Suppression by Female Contact

Abstract

Prolactin (PRL) is considered to induce maternal behavior toward foster young in female rats. In the present study, we studied the relationship between pup contact-induced maternal behavior and serum PRL concentrations and brain PRL receptor (PRL-R) mRNA expression in male rats. Both intact and castrated male rats exposed to foster pups gradually developed caretaking behavior such as crouching and licking, but their exhibitions of other maternal behavior components, retrieval/grouping and nest building, were incomplete. However, in the male rats displaying crouching and licking, the concomitant increases in serum PRL concentration and brain mRNA expression for long-form PRL-R were observed. The expression of short-form PRL-R mRNA in the brain was not stimulated by pup contact. Administration of PRL remarkably promoted the onset of those maternal responses in male rats. On the other hand, when an intact male rat was housed in a cage where a lactating female rat and her pups were living, his scores in maternal behavior tests toward pups were lowered. And, concomitantly, increases in serum PRL concentration and brain expression of long-form PRL-R mRNA were reduced. In castrated male rats, however, the ratings of maternal behavior toward foster young, serum PRL concentration increase, or brain long-form PRL-R mRNA expression were not reduced at all by cohabitation with a female and her pups. These findings indicated that maternal behavior was triggered and maintained in pup-contacted male rats through elevated serum PRL levels and induced brain long-form PRL-R.

Prolactin's mediative role in male parenting in parentally experienced marmosets (Callithrix jacchus)

“…The increase in prolactin due to infant contact appears to be the same in both sexes. Even non-paternal male rats will show the same induction of brain prolactin receptors of the long form mRNA expression as occurs in female rats (Sakaguchi et al, 1996). Exposure to estrogens increases the expression of prolactin receptors in the brain and elevates serum prolactin levels.…”

Prolactin Variants in Human Pituitaries and Pituitary Adenomas Identified With Two-Dimensional Gel Electrophoresis and Mass Spectrometry

“…PRL induces and maintains maternal behaviors in rabbit, rat, hamsters, and sheep (40). These maternal behaviors include cleaning, nesting, grouping, and nursing of the baby by the mother (41, 42). Aside from the effects of PRL on reproductive processes, PRL also plays a significant role to maintain homeostasis of the body's environment by development of blood vessels (angiogenesis), regulation of the immune systems, and osmotic balance (3).…”

Fathering in rodents: Neurobiological substrates and consequences for offspring

“…In males castrated as adults, treatment with high doses of estrogen, following priming with estrogen and progesterone, decreases the latency to the onset of paternal behavior during sensitization, whereas testosterone treatment increases the likelihood of infanticide (Lubin et al, 1972; Rosenberg, 1974; Rosenblatt et al, 1996). The onset of pup-induced paternal behavior can also be facilitated by treatment with prolactin (Sakaguchi et al, 1996). …”