Effect of progesterone on hypothalamic oxytocin messenger ribonucleic acid levels in the lactating rat.

Abstract

We recently reported that sequential administration of estrogen and progesterone and subsequent withdrawal of progesterone increased the level of hypothalamic oxytocin (OT) messenger RNA (mRNA) in the female rat. Both estrogen priming and progesterone withdrawal are critical components of this regimen. Rats experience this ovarian steroid pattern during certain lactational events such as on days 10-12 of lactation or with interruption of nursing for 48-72 h. In the present study, we used Northern blot and in situ hybridization to determine the association between the steroid exposure and the level of OT mRNA during these lactational conditions. Week 1 lactating rats that had pups removed for 24 and 48 h, but not 12 h, had significantly higher serum estradiol concentrations than animals continuously nursing their pups on a comparable day of lactation (F4, 15 = 6; P < 0.005). Serum progesterone levels declined significantly during the 48 h after litter removal (F4, 15 = 130.5; P < 0.0001). Significant increases in OT mRNA levels were found at 48 h, but not 12 or 24 h, after litter removal (F4, 15 = 4.3; P < 0.02). Implantation of progesterone-filled capsules to compensate for the spontaneous decline in progesterone that occurs with interruption of nursing attenuated this increase in OT mRNA levels. OT mRNA was significantly higher in the hypothalamic paraventricular nuclei (P < 0.0002) and supraoptic nuclei (P < 0.002) of nursing interrupted animals receiving empty vs. progesterone-filled implants. Implantation of day 12 lactating rats with progesterone capsules for 5 days before being killed blunted the increase in OT mRNA that normally occurs on this day of lactation. The data highlight the pivotal role of estrogen priming and progesterone withdrawal in the increased expression of the OT gene during select lactational events.

Hypothalamic Vasopressin Gene Expression Increases in Both Males and Females Postpartum in a Biparental Rodent

“…In rats, an increase in the hypothalamic oxytocin mRNA reached a peak even before parturition, suggesting that it is not the parturition per se but the hormonal changes associated with pregnancy that enhance oxytocin activity in the hypothalamus (12, 52, 53). The notion that steroid hormones regulate oxytocin expression is supported by the presence of an oestrogen response element (54) and a glucocorticoid response element (which can bind glucocorticoid and/or progesterone) (55) in the oxytocin gene.…”

Estradiol, Progesterone, and Prolactin Regulate Maternal Nest‐Building in Rabbits

“…Though the neuroactive agents that participate in controlling hair-pulling in doe rabbits are unknown, from the following evidence we may speculate that arginine-vasopressin (AVP) and/or oxytocin (OT) may participate in this process. Thus: a) hair-pulling may be viewed as an exaggerated form of grooming, a behavior stimulated by the icv infusion of AVP in rodents (16) and of OT in both rodents (17) and rabbits (18); b) in rodents testosterone stimulates the synthesis of AVP (19,20) and its receptor (21); c) both estradiol and P regulate OT synthesis (22)(23)(24) and OT receptors (25)(26)(27)(28) in rodents and sheep; d ) we have found in periparturient does (29) an increased number of AVP-immunoreactive (IR) neurons in the supraoptic nucleus (SON) and of OT-IR cells in the paraventricular nucleus (PVN) and lateral hypothalamic area (LHA). These females also show an increased size of AVP-and OT-IR cell bodies in the SON, PVN, and LHA, compared with intact, estrous females; e) we have recently determined that ovx does given EB/P (10 mg/day) as in this work, show similar changes in OT-IR neurons as those found in periparturient does (Caba, Beyer, and GonzalezMariscal; in preparation).…”

Connecting prosocial behavior to improved physical health: Contributions from the neurobiology of parenting

“…Typically, during pregnancy, it is the withdrawal of progesterone that increases oxytocin and stimulates the onset of labor and maternal behavior (Rosenblatt, Siegel, & Mayer, 1979). And, a progesterone antagonist, rU-486, has been shown to increase oxytocin, which suggests that progesterone can have an inhibitory effect on the oxytonergic system (Thomas, Crowley, & Amico, 1995). Consistent with this possibility, progesterone has been shown to be related to social behavior in ways that seem opposite from oxytocin, for example, progesterone can impair social recognition in animals (Bychowski & Auger, 2012).…”