Interfering with somatosensory stimulation from pups sensitizes experienced, postpartum rat mothers to oxytocin antagonist inhibition of maternal behavior.

Proximal separation (PS) refers to isolating pups in small cages so dams can hear, smell, and see pups but have very limited physical contact with them. Six days of PS diminished the number of discernible oxytocin (OT)- immunostaining perikarya in forebrain areas of rat dams compared with 6 days of total separation (TS) or no separation (NS) from pups. Dams exhibited a more rapid resurgence of maternal behavior after 4–6 days of PS than after 4–6 days of TS. Bilateral infusion of the OT antagonist (OTA; 1 μg/μl/side) into the ventral tegmental area blocked the resurgence of maternal behavior after 3–6 days of PS but not after 2 days of PS or 4–6 days of NS. The conclusion was that PS for 3 or more days reinstates OT as necessary and sufficient for the activation of maternal behavior in experienced rat mothers. These findings suggest that some aspects of somatosensory stimulation from pups regulate the role of OT in the control of maternal behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oxytocin activates the postpartum onset of rat maternal behavior in the ventral tegmental and medial preoptic areas.

Oxytocin binding (Bmax) was found to be higher in the ventral tegmental area (VTA) and the medial preoptic area (MPOA) at midparturition compared with Pregnancy Days 15–27 or Postpartum Days 5–7 in rat dams. Pup retrieval and assuming a nursing posture over pups were blocked in parturient dams by infusions of an oxytocin antagonist into the VTA or MPOA and by infusions of a vasopressin (V?) antagonist into the MPOA. These results implicate oxytocin in the VTA and MPOA and vasopressin in the MPOA, as well as a parturition-associated rise in oxytocin binding in these sites in the postpartum activation of maternal behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oxytocin mediates acquisition of maternally associated odor preferences in preweanling rat pups.

Three studies assessed the role of central oxytocin systems in maternal affiliation in preweanling rats. Fifteen-day-old rats were found to approach an odor faster and spend more time in contact with an odor when it had been paired with the mother on the previous day than when the odor was not paired with the mother, provided that the pairing occurred after either intracerebral administration of oxytocin (0.5 μg) or saline. However, if rats were administered an oxytocin antagonist (OTA) prior to odor-mother pairing, neither the decreased odor approach latency nor the increased odor preference was apparent in the odor-mother group. OTA treatment did not attenuate a single-trial odor aversion learning task, nor did it disrupt interaction with the anesthetized mother. Results are discussed in terms of a possible reward-satiety role for oxytocin in the infant-mother context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aggressive marital conflict, maternal harsh punishment, and child aggressive-disruptive behavior: Evidence for direct and mediated relations.

Direct associations between aggressive marital conflict and child aggressive-disruptive behavior at home and school were explored in this cross-sectional study of 360 kindergarten children. In addition, mediated pathways linking aggressive marital conflict to maternal harsh punishment to child aggressive-disruptive behavior were examined. Moderation analyses explored how the overall frequency of marital disagreement might buffer or exacerbate the impact of aggressive marital conflict on maternal harsh punishment and child aggressive-disruptive behavior. Hierarchical regressions revealed direct pathways linking aggressive marital conflict to child aggressive-disruptive behavior at home and school and a partially mediated pathway linking aggressive marital conflict to child aggressive-disruptive behavior at home. Further analyses revealed that rates of marital disagreement moderated the association between aggressive marital conflict and child aggressive-disruptive behavior at home, with an attenuated association at high rates of marital disagreement as compared with low rates of marital disagreement. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Oxytocin receptor activity in the ventrocaudal periaqueductal gray modulates anxiety-related behavior in postpartum rats.

Postpartum rats are less anxious than diestrous virgin females, a phenomenon requiring that mothers have recent contact with their infants. Oxytocin (OT) is one of many neurochemicals released intracerebrally while mothers interact with infants, and we investigated whether OT receptor activity in the ventrocaudal periaqueductal gray (cPAGv) contributes to mothers' reduced anxiety. Infusion of the highly specific OT receptor antagonist, desGly-NH?,d(CH?)?[D-Tyr2,Thr?]OVT, into the cPAGv reduced the percentage of time dams spent in the open arms of an elevated plus-maze, but had no effect on the open-arm behavior of diestrous virgins. Conversely, after separating dams from their litters for 4 hr to increase anxiety, a lower (2 ng) but not higher (5 ng) dose of OT infused into each hemisphere of the cPAGv doubled the percentage of time dams spent in open arms, but did not do so in virgins. OTergic manipulations inconsistently affected risk-assessment behaviors (stretch-attend postures, head dips) in both virgins and dams. Therefore, OT receptor activation in the cPAGv is an important consequence of contact with infants that reduces some anxiety-related behaviors in mother rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ability of oxytocin to induce short latency maternal behavior is dependent on peripheral anosmia.

Nulliparous female Sprague-Dawley rats, cannulated in the left lateral ventricle, were ovariectomized and estrogen primed, then either rendered anosmic via intranasal irrigation with zinc sulfate or left with intact olfaction. Forty-eight hr later, after a 2-hr habituation to the test cage, these animals were injected with either intracerebroventricular oxytocin (400 ng in 2 μl saline) or saline (2 μl). Only the group receiving both zinc sulfate and oxytocin became maternal. Additionally, approximately one third of the olfaction-intact rats and none of the anosmic rats cannibalized the rat pups. These results are discussed in regard to discrepancies in the literature regarding oxytocin's role in inducing maternal behavior, as well as the functional connection of the olfactory and oxytocin systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of chronic and acute cocaine treatment on the onset of maternal behavior and aggression in Sprague-Dawley rats.

Pregnant rats (N?=?17) were treated either throughout gestation (Gestational Day 1–20) with 30 mg/kg per day (chronic cocaine) or with 1 15-mg/kg dose immediately following parturition (acute cocaine). Chronic and acute cocaine treatment delayed or diminished the postpartum onset of some components of maternal behavior, and chronically treated dams were significantly more aggressive toward a male intruder than acute cocaine-treated or saline-treated dams. Cocaine increased the latency to crouch over pups and decreased crouch duration during a 30-min observation period that immediately followed parturition. Latencies to nest build were also longer in more chronic cocaine-treated dams than in saline controls. On Day 6 postpartum, 83% of chronic cocaine-treated dams pinned and attacked an intruder male 8 or more times during a 10-min observation period, whereas only 4% of acute cocaine-treated and none of the saline-treated dams exhibited this much aggression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Association between the amygdala and nucleus of the solitary tract in mu-opioid induced feeding in the rat

The central nucleus of the amygdala (CNA) and the nucleus of the solitary tract (NTS) are important in the regulation of ingestive behavior. We evaluated whether opioid-opioid signaling between the CNA and rostral NTS (rNTS) affect feeding behavior. To test this, rats were doubly cannulated with one cannula placed in the rNTS and one cannula in the CNA, allowing for co-administration of an opioid agonist into one site and an opioid antagonist into the other. Tyr-D-Ala-Gly-(me) Phe-Gly-ol (DAMGO) (2 nmol) injected into the CNA (CNA DAMGO) increased feeding more than two-fold compared to the vehicle-injected rats. This increase in food intake was blocked when doses of 26.5 and 79 nmol of naltrexone (NTX) were injected into the rNTs. In the reverse situation, rNTS DAMGO increased food intake above control levels, and CNA NTX blocked DAMGO-induced feeding when administrated in doses of 26.5 and 79 nmol. This suggests that a bi-directional opioid-opioid signaling pathway exists between the CNA and the rNTS which influences feeding via mu-opioid receptors.     

Cocaine treatment and prenatal environment interact to disrupt intergenerational maternal behavior in rats.

The link between impaired maternal behavior (MB) and cocaine treatment could result from drug-induced decreases in maternal reactivity to offspring, prenatal drug exposure (PDE) in offspring that could alter their ability to elicit MB, or the interaction of both, which could subsequently impair MB of the 1st-generation dams. Following chronic or intermittent cocaine or saline treatment during gestation, rat dams rearing natural or cross-fostered litters were compared along with untreated dams for MB. Untreated 1st-generation females with differentially treated rearing dams and PDE were tested for MB with their natural litters. The authors report disruptions in MB in dams and their 1st-generation offspring, attributable to main and interaction effects of maternal treatment, litter PDE, and rearing experience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental exposure to oxytocin facilitates partner preferences in male prairie voles (Microtus ochrogaster).

The authors investigated the effects of postnatal manipulations of oxytocin (OT) on the subsequent tendency to form a partner preference in male prairie voles (Microtus ochrogaster). Neonatally, males received either an injection of OT, an oxytocin antagonist (OTA), 0.9% saline vehicle, or handling without injection. As adults, males were tested for partner preference following 1 hr of cohabitation with a nonestrous female. In a 3-hr preference test, males neonatally exposed to exogenous OT exhibited a significant partner preference, not seen in males receiving OTA or saline. Both OT and OTA voles had significantly higher levels of social contact than saline controls. A single neonatal injection of OT increased both total and selective social behaviors in male prairie voles. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial preoptic area oxytocin and female sexual receptivity.

Intracerebroventricular (icv) administration of the nonapeptide oxytocin (OXT) increases sexual receptivity in female rats. The medial preoptic area (MPOA) appeared to be the most sensitive brain area to the facilitative effects of OXT. Bilateral infusions of 100 ng of OXT into the MPOA significantly elevated lordosis quotients in overiectomized (OVX), estrogen-treated rats. This dose of OXT was ineffective when infused icv or into the ventromedial hypothalamus, mesencephalic central gray, or ventral tegmental area. A 500-ng dose of OXT significantly elevated lordosis responding when infused icv, corresponding with our previous findings. Mounting by males significantly increased immunoreactive levels of OXT and decreased the number of OXT immunostaining cells in the MPOA of sexually receptive rats pretreated with estrogen and progesterone. The MPOA is a primary site of the OXT facilitation of sexual receptivity where OXT may be released during mating. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estrogen increases affinity of oxytocin receptors in the medial preoptic area-anterior hypothalamus

Analysis of binding data from saturation experiments using a radiolabeled oxytocin antagonist ([125I]OTA) demonstrated an increase in binding affinity after treatment with 5 micrograms estradiol benzoate (EB) for 3 days in membrane fractions from the medial preoptic area-anterior hypothalamus (MPOA-AH) of ovariectomized (OVX) rats. Analysis of data from competition experiments revealed high- and low-affinity [125I]OTA binding sites in the MPOA-AH, the medial basal hypothalamus (MBH), and hippocampus of OVX controls. Three days of EB treatment reduced low-affinity binding sites in the MPOA-AH and MBH, but not in the hippocampus. Treatment of membrane fractions from the MPOA-AH of oil-treated OVX rats in vitro with 100 nM OT or with estrogen or progesterone conjugated to bovine serum albumin (E-BSA and P-BSA) also reduced low-affinity [125I]OTA binding sites but BSA alone did not.     

Acute effects of intranasal oxytocin on subjective and behavioral responses to social rejection.

The hormone and neuropeptide oxytocin is believed to buffer against social stress and reduce social-threat perception. We employed a widely used ostracism paradigm, Cyberball, to investigate whether oxytocin ameliorated the acute behavioral and affective consequences of social rejection. In a double-blind, randomized, between-subjects design, 74 healthy male and female participants were administered intranasal oxytocin or placebo and subsequently ostracized or included during this virtual ball-tossing game. Ostracized participants reported negative affective and attachment-related reactions, as well as a significant motivational change in increased desire to be involved in the game; these effects were not influenced by oxytocin. Intranasal oxytocin did, however, increase included participants' desire to play again with the same participants, suggesting oxytocin enhanced desire for future social engagement following inclusion. These findings are argued to provide evidence that the effects of oxytocin in promoting social approach behavior may be context specific and sensitive to positive social cues. The results suggest that in an explicitly aversive context, oxytocin does not buffer against the immediate impact of blunt social rejection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Effects of chronic and acute cocaine treatment on the onset of maternal behavior and aggression in Sprague-Dawley rats": Correction.

Reports an error in the original article by J. M. Johns et al (Behavioral Neuroscience, 1994[Feb], Vol 108[1], 107–212). On page 108, in the Results, Maternal Behavior, the phrase in parentheses, "(8 min to crouch for 8 min or more of 30 min)' should read: "(6 min to crouch for 8 min or more of 30 min).' On page 109, the label on the upper right panel of Figure 1, "Percent That Crouch in 8 Minutes,' should read: "Percent That Crouch in 6 Minutes.' (The following abstract of this article originally appeared in record 1994-24731-001.) Pregnant rats (N?=?17) were treated either throughout gestation (Gestational Day 1–20) with 30 mg/kg per day (chronic cocaine) or with 1 15-mg/kg dose immediately following parturition (acute cocaine). Chronic and acute cocaine treatment delayed or diminished the postpartum onset of some components of maternal behavior, and chronically treated dams were significantly more aggressive toward a male intruder than acute cocaine-treated or saline-treated dams. Cocaine increased the latency to crouch over pups and decreased crouch duration during a 30-min observation period that immediately followed parturition. Latencies to nest build were also longer in more chronic cocaine-treated dams than in saline controls.… (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Toward a neurobiology of attachment.

Although much has been written about the psychological aspects of attachment, still relatively little is known about how the brain organizes this complex behavior or how attachment alters brain organization. Recent research has suggested that neuropeptides may be important as neural modulators for several complex behaviors. This review examines the research on one specific neuropeptide, oxytocin, to describe approaches to the neurobiology of attachment at several levels, including molecular, cellular, and whole animal studies. A key to understanding oxytocin's role in behavior is a careful analysis of the pattern of oxytocin receptors in the brain. The available data support the hypothesis that oxytocin is critical for maternal behavior and pair-bond formation in select nonhuman animals. Humans have oxytocin and brain oxytocin receptors, but the role of this neuropeptide system in human attachment remains highly speculative. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibitory effects of the 5-HT1A agonists, 5-hydroxy- and 5-methoxy-(3-di-n-propylamino)chroman, on female lordosis behavior

Sexually receptive, intact, proestrous rats were infused bilaterally into the ventromedial nucleus of the hypothalamus with one of several serotonin (5-HT) agonists and with the endogenous ligand, 5-HT. Serotonin (2000 ng) and the 5-HT1A agonists, 8-hydroxy-2-(di-n-propylamino)tetralin [8-OH-DPAT (200 ng)], 5-methoxy-3-(di-n-propylamino)chroman [5-MEO-DPAC (200-2000 ng)] and 5-hydroxy-3-(N-di-n-propylamino)chroman [5-OH-DPAC (200-2000 ng)] inhibited female lordosis behavior within 10 min of the infusion. The rank order of the effectiveness of these compounds was 8-OH-DPAT > 5-OH-DPAC > or = 5-MEO-DPAC > 5-HT. The nonselective 5-HT agonist, 1-(m-trifluoromethyl) piperazine [TFMPP (2000 ng)], did not reduce lordosis behavior. In addition to their reduction of lordosis behavior, the 5-HT1A agonists elicited resistive behavior toward the male's attempts to mount. There were minimal effects of the 5-HT1A agonists on either quality of the lordosis reflex or on proceptivity. However, rats pretreated with TFMPP and infused with 8-OH-DPAT 1 hr later, did show a transient suppression of lordosis quality. These results provide further evidence that the ventromedial nucleus of the hypothalamus contains 5-HT1A sites, the activation of which reduces lordosis behavior in regularly cycling, proestrous rats.     

Comparison of two positive reinforcing stimuli: Pups and cocaine throughout the postpartum period.

This set of experiments investigated the appetitive or motivational processes underlying the performance of maternal behavior. The place preference paradigm was adapted to simultaneously investigate the reinforcing properties of cocaine and pups for maternal, lactating dams. These modifications allowed the authors to assess which stimulus, either a 10 mg/kg sc injection of cocaine or 3 pups, had the strongest reinforcing value. At Postpartum Days 10 and 16, the dams preferred the cocaine cue-associated chamber, whereas the dams tested at Postpartum Day 8 preferred the pup cue-associated chamber. Overall, the data revealed an interaction between the postpartum period at testing and the exhibited preference for cocaine or pups. Further testing will investigate the neural circuitry underlying the appetitive processes of each stimulus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of pulsatile oxytocin administration to the pregnant ewe in the last third of gestation on fetal ACTH and cortisol response to acute hypoxemia

OBJECTIVE: The aim of this study was to examine the effect of increased myometrial contractility throughout the last third of pregnancy on the ovine fetal response to short-term hypoxemia. METHODS: Oxytocin (600 microU/kg/minute, n = 5) or saline (n = 7) was infused for 5 minutes every 20 minutes into the maternal jugular vein starting at 95-99 days of gestation and continuing throughout the last third of gestation. Fetuses were subjected to a hypoxemic challenge (1 hour) at 131 days of gestation while fetal plasma ACTH and cortisol levels and nuchal muscle electromyogram activity were monitored. RESULTS: The fetal plasma ACTH concentration before and during the hypoxemic challenge was similar in the control and oxytocin groups. The fetal plasma cortisol concentration in the oxytocin group was significantly lower before and during the hypoxemia than in the controls. During hypoxemia, fetal nuchal muscle activity was significantly reduced only in the control group. CONCLUSION: Increased myometrial contracture frequency throughout the last third of pregnancy alters both the neuroendocrine and behavioral responses of fetal sheep to short-term hypoxemia.     

Maternal adrenalectomy eliminates a surge of plasma dehydroepiandrosterone in the mother and attenuates the prenatal testosterone surge in the male fetus

Previous work has established a number of sex-related deficits in immune function, behavior, and endocrine responses to stress in the offspring of dams exposed to ethanol. To examine the potential role of maternal glucocorticoids as a mediator of these sexually dimorphic effects in the fetus, we examined the influence of prenatal alcohol exposure in the presence or absence of maternal glucocorticoids on fetal plasma corticosterone (CORT) production. An additional question to be addressed by these studies was whether maternal adrenalectomy could eliminate the known inhibition by ethanol of the prenatal surge of plasma testosterone in male fetuses. Pregnant dams were adrenalectomized (ADX) or sham-adrenalectomized on gestational day (G) 7 and placed on a liquid diet containing 35% ethanol-derived calories or pair-fed an isocaloric control diet throughout the experiment. On G18, G19, and G21, plasma levels of CORT, testosterone, and dehydroepiandrosterone (DHEA) were measured in male and female fetuses and their mothers. Ethanol administration consistently increased maternal plasma CORT levels but did not significantly alter CORT levels in the fetus. Maternal ADX resulted in compensatory increases in fetal CORT levels that were lower in fetuses of ADX dams on alcohol, suggesting a direct effect of ethanol on fetal pituitary-adrenal activity. There were no significant sex differences in fetal plasma CORT levels in response to any of these manipulations. A novel surge of maternal plasma DHEA was found on G19 that was absent in plasma from ADX dams. In spite of the absence of a surge on G19, plasma DHEA levels of ADX dams rose from very low levels at G18 to levels on G21 that were significantly higher than in Sham dams. A normal testosterone surge was observed in male fetuses on G18 and G19 from sham-adrenalectomized dams administered the pair-fed diet. However, this surge was greatly attenuated in males administered ethanol and also in male fetuses from ADX dams. These results reveal a direct inhibitory influence of ethanol on fetal CORT secretion as well as on the prenatal testosterone surge in males. Furthermore, these studies demonstrate the presence of a surge of DHEA in the pregnant rat. Overall, these data suggest that there is a critical adrenal factor in the rat that regulates the maternal surge of DHEA on G19 and the prenatal testosterone surge of male fetuses on G18-19.     

Transgenerational effects of social environment on variations in maternal care and behavioral response to novelty.

[Correction Notice: An erratum for this article was reported in Vol 122(2) of Behavioral Neuroscience (see record 2008-03769-025). Figure 1 on Page 1356 was incorrect. The correct figure is printed in this correction.] Cross-fostering studies in the rat have illustrated the importance of the postnatal environment in mediating the transmission of maternal licking/grooming (LG) from mother to offspring. The authors addressed the question of how postweaning social conditions can alter the patterns of maternal behavior. Juvenile female offspring of high LG and low LG mothers were placed in either standard, enriched, or impoverished postweaning environments for 50 consecutive days and then mated and observed with their own litters. Analysis of LG behavior indicated that the effect of postweaning environment was dependent on the level of postnatal mother-infant interaction. Postweaning isolation reduced exploratory behavior, maternal LG, and oxytocin receptor binding in the offspring of high LG mothers, whereas social enrichment enhanced exploration, LG behavior, and oxytocin receptor binding of low LG offspring. These effects were also transmitted to the next generation of offspring. Thus, maternal LG and the neural mechanisms that regulate this behavior exhibited a high degree of plasticity in response to changes in environment both within and beyond the postnatal period, with implications for the transmission of behavioral response to novelty and maternal care across generations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)