The effects of bromocriptine treatment during early pregnancy on postpartum maternal behaviors in rats

Abstract

Prolactin, a hormone of the anterior pituitary, is involved in initiating maternal behavior, alleviating postpartum anxiety, and stimulating lactogenesis. Bromocriptine, a dopamine D2 receptor agonist, inhibits prolactin secretion. Bromocriptine administration represses postpartum maternal behaviors (pup retrieval) in mice, and causes elevated anxiety in the elevated plus maze [Larsen & Grattan (2010). Endocrinology 151(8): 3805-3814]. Whether similar effects exist in other species is unknown. The present study examined the possible involvement of prolactin during early gestation on maternal behavior and anxiety in rats. Bromocriptine given on days 2-4 of pregnancy resulted in impaired postpartum maternal behaviors in a novel environment during early lactation. However, compared to controls, bromocriptine-treated subjects did not exhibit increased postpartum anxiety in the elevated plus maze. These findings support work in mice that bromocriptine treatment during early gestation impedes postpartum maternal care, and indicate that early gestational hormonal status affects postpartum behavior more broadly in other mammals.

Keywords: anxiety; dopamine agonist; postpartum maternal behavior; rats.

FIGURE 1

The effect of bromocriptine treatment on total duration of pup retrieval (A), latency to nurse (B), duration of nursing (C), and time on nest (D). Values shown are means + SEM. (A) Combined groups of dams treated with bromocriptine (10 rats at a dose of .05 mg/kg, 8 rats at a dose of .2 mg/kg) took significantly longer to retrieve all eight of their pups in a novel cage compared to a home cage (t = 3.56, ^*p = .002). Rats treated with the vehicle did not differ in home and novel cage pup retrieval latencies. (B) Dams treated with bromocriptine took significantly longer to initiate nursing in a novel cage compared to a home cage (t = 2.11, ^*p < .001). Rats treated with the vehicle did not differ in latency of nursing between the home and novel cages. (C) Dams treated with bromocriptine spent a significantly shorter amount of time nursing their pups in a novel cage compared to a home cage (t = 2.86, ^*p = .01). Rats treated with the vehicle and tested in the home and novel cages did not differ in nursing duration. (D) Dams treated with bromocriptine spent a significantly shorter time on the nest in a novel cage compared to a home cage (t = 2.07, ^*p = .027). Rats treated with the vehicle did not differ in time spent on the nest in the home and novel cages.