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Non-pulsatile oxytocin given during labour can negatively affect breastfeeding. The aim of this study was to assess whether intrapartum oxytocin administration has any effect on breastfeeding. Secondly, to assess whether some maternal or neonatal variables influence breastfeeding. A retrospective cohort study was done, comparing two groups: women exposed (n = 101) and not exposed to oxytocin (n = 100) during labour. Women with caesarean section, vacuum extraction/forceps, twin pregnancy, breech presentation, premature neonates and with an Apgar score <7 at 5 minutes were excluded. Duration of breastfeeding was evaluated by a phone call interview. A regression analysis was done, evaluating possible confounding factors. The use of oxytocin during labour was demonstrated to be a predictor of impaired first hour breastfeeding (OR =2.493, CI: 1.05-5.92; p = .038). At three months' postpartum, 26.7% women in the exposed group versus 14% in the non-exposed group were not breastfeeding (p = .035). This result was not statistically significant when adjusting for possible confounders. High pregestational body mass index was the best predictor of an impaired third month's postpartum breastfeeding (OR =0.901, CI: 0.835-0.972; p = .007). Intrapartum oxytocin administration could inhibit first hour breastfeeding. A novel association was detected, pregestational body mass index was a predictor of impaired breastfeeding at three months, possibly confounding the oxytocin effect. Additional prospective studies are needed to investigate potential associations between intrapartum oxytocin and breastfeeding. Impact statement What is already known on this subject? Oxytocin is a common medical intervention during labour. Some studies suggest a negative association between intrapartum oxytocin dose, newborn sucking and an increased risk of early breastfeeding discontinuation. However, some maternal variables were not considered in these studies and the impact synthetic oxytocin may have on breastfeeding has not been thoroughly researched. What do the results of this study add? In this study, intrapartum oxytocin administration seems to inhibit the first hour breastfeeding. However, a novel association was detected, high pregestational body mass index was a predictor of impaired breastfeeding at three months, possibly confounding oxytocin effects. What are the implications of these findings for clinical practice and/or further research? Additional prospective studies are needed to investigate potential associations between intrapartum oxytocin and breastfeeding. Therefore, health care professionals should help obese women, starting from conception, to maximise breastfeeding outcomes as much as possible.

Background: A mixture of eight fatty acids (lauric acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, elaidic acid, and linoleic acid) that are contained in human amniotic fluid, colostrum, and milk produces appetitive responses in newborns, suggesting the existence of a transition of sensorial cues that guide newborns to the maternal breast., Objective: To explore the ability of each of these eight fatty acids individually to produce appetitive responses in newborns., Methods: The study included 12 healthy human newborns<24h after birth. Using a longitudinal design, cotton swabs that were impregnated with each of the eight fatty acids and control substances (i.e., vehicle, saline, and vanilla) were placed approximately 1cm from the newborns' nostrils for 30s. Positive responses that were suggestive of acceptance included appetitive movements (i.e., suckling) and sniffing that were directed toward the cotton swab. Lateral movements of the head away from the swab were considered negative responses. Remaining stationary with no changes in facial expressions was considered indifference., Results: Compared with controls (i.e., vehicle, saline, and vanilla) and the other fatty acids tested, myristic acid produced the longest duration of positive facial responses (suckling and sniffing). No significant differences in negative facial responses were observed in response to the odoriferous stimuli. No reactions that were suggestive of disgust were observed., Conclusion: A complex combination of stimuli, including the odor of myristic acid, may integrate sensory cues that guide newborns to the maternal breast., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In the nasal olfactory epithelium, olfactory metabolic enzymes ensure odorant clearance from the olfactory receptor environment. This biotransformation of odorants into deactivated polar metabolites is critical to maintaining peripheral sensitivity and perception. Olfactory stimuli consist of complex mixtures of odorants, so binding interactions likely occur at the enzyme level and may impact odor processing. Here, we used the well-described model of mammary pheromone-induced sucking-related behavior in rabbit neonates. It allowed to demonstrate how the presence of different aldehydic odorants efficiently affects the olfactory metabolism of this pheromone (an aldehyde too: 2-methylbut-2-enal). Indeed, according to in vitro and ex vivo measures, this metabolic interaction enhances the pheromone availability in the epithelium. Furthermore, in vivo presentation of the mammary pheromone at subthreshold concentrations efficiently triggers behavioral responsiveness in neonates when the pheromone is in mixture with a metabolic challenger odorant. These findings reveal that the periphery of the olfactory system is the place of metabolic interaction between odorants that may lead, in the context of odor mixture processing, to pertinent signal detection and corresponding behavioral effect.

The brown planthopper (BPH), Nilaparvata lugens (Stål), is a migratory and destructive sucking insect pest of rice. Silicon (Si) amendment to plants can confer enhanced resistance to herbivores and is emerging as a novel approach for pest management. In the present study, we tested the effects of Si addition at 0.16 (low) and 0.32 (high) g Si/kg soil on sucking behaviors and population growth in BPH. Si amendment increased Si content in rice stems and extended non-probing event and phloem puncture followed by sustained phloem ingestion over that in the no-Si-addition control. High Si addition rate prolonged the stylet pathway and the time needed to reach the first phloem puncture, shortened durations of phloem puncture and phloem ingestion, and decreased the proportion of individuals that produced sustained phloem ingestion. BPH female feeding on and preference for plants with the high Si addition rate were also reduced. As a result, Si application significantly decreased BPH population growth rates while increased population doubling time. These results indicate that Si amendment, especially at the high rate, confers enhanced rice plant resistance to BPH through impairment of BPH feeding. Our results highlight the potential of Si amendment as an alternative for BPH management.

Aim: The consequences that intrapartum administration of hormones can have on breastfeeding are unclear. The aim of the study is to determine if synthetic intrapartum oxytocin, used routinely for induction/stimulation, has a relationship to initiation/duration of breastfeeding., Patients and Methods: We conducted a cohort study that was carried out in a tertiary university hospital distinguished by WHO-UNICEF as a BFHI (Baby-Friendly Hospital Initiative). A group of 53 mother and newborn dyads who had been exposed to intrapartum synthetic oxytocin were compared with 45 nonexposed dyads. A breastfeeding questionnaire was administered by a midwife blind to patient group through phone calls 3 and 6 months after delivery., Results: No statistically significant differences were observed between the two groups in the rates of mothers exclusively breastfeeding (EBF) or nonexclusively breastfeeding. The percentage of those who were EBF when discharged was 97.3% in the oxytocin-nonexposed group and 87.1% in the oxytocin-exposed group (p = 0.14). At 3 months, the group rates of exclusive breastfeeding were 72.5% in the nonoxytocin-exposed group versus 65.9% in the oxytocin-exposed group (p = 0.71). At 6 months, rates of breastfeeding were 31.4% versus 27.9% (p = 0.53) in the oxytocin-nonexposed and oxytocin-exposed groups, respectively., Conclusions: In this study, no statistically significant effect of intrapartum synthetic oxytocin administration was observed pertaining to the initiation or duration of breastfeeding.

Background and Objectives: Patients with Prader-Willi syndrome (PWS) display poor feeding and social skills as infants and fewer hypothalamic oxytocin (OXT)-producing neurons were documented in adults. Animal data demonstrated that early treatment with OXT restores sucking after birth. Our aim is to reproduce these data in infants with PWS., Methods: We conducted a phase 2 escalating dose study of a short course (7 days) of intranasal OXT administration. We enrolled 18 infants with PWS under 6 months old (6 infants in each step) who received 4 IU of OXT either every other day, daily, or twice daily. We investigated the tolerance and the effects on feeding and social skills and changes in circulating ghrelin and brain connectivity by functional MRI., Results: No adverse events were reported. No dose effect was observed. Sucking assessed by the Neonatal Oral-Motor Scale was abnormal in all infants at baseline and normalized in 88% after treatment. The scores of Neonatal Oral-Motor Scale and videofluoroscopy of swallowing significantly decreased from 16 to 9 (P < .001) and from 18 to 12.5 (P < .001), respectively. Significant improvements in Clinical Global Impression scale scores, social withdrawal behavior, and mother-infant interactions were observed. We documented a significant increase in acylated ghrelin and connectivity of the right superior orbitofrontal network that correlated with changes in sucking and behavior., Conclusions: OXT is well tolerated in infants with PWS and improves feeding and social skills. These results open perspectives for early treatment in neurodevelopment diseases with feeding problems., (Copyright © 2017 by the American Academy of Pediatrics.)

Background: Intrapartum drugs, including fentanyl administered via epidural and synthetic oxytocin, have been previously studied in relation to neonatal outcomes, especially breastfeeding, with conflicting results. We examined the normal neonatal behavior of suckling within the first hour after a vaginal birth while in skin-to-skin contact with mother in relation to these commonly used drugs. Suckling in the first hour after birth has been shown in other studies to increase desirable breastfeeding outcomes., Method: Prospective comparative design. Sixty-three low-risk mothers self-selected to labor with intrapartum analgesia/anesthesia or not. Video recordings of infants during the first hour after birth while being held skin-to-skin with their mother were coded and analyzed to ascertain whether or not they achieved Stage 8 (suckling) of Widström's 9 Stages of newborn behavior during the first hour after birth., Results: A strong inverse correlation was found between the amount and duration of exposure to epidural fentanyl and the amount of synthetic oxytocin against the likelihood of achieving suckling during the first hour after a vaginal birth., Conclusions: Results suggest that intrapartum exposure to the drugs fentanyl and synthetic oxytocin significantly decreased the likelihood of the baby suckling while skin-to-skin with its mother during the first hour after birth., (© 2015 The Authors. Birth published by Wiley Periodicals, Inc.)

Aim: Several synthetic peptide manipulations during the time surrounding birth can alter the specific neurohormonal status in the newborn brain. This study is aimed at assessing whether intrapartum oxytocin administration has any effect on primitive neonatal reflexes and determining whether such an effect is dose-dependent., Materials and Methods: A cohort prospective study was conducted at a tertiary hospital. Mother-infant dyads who received intrapartum oxytocin (n=53) were compared with mother-infant dyads who did not receive intrapartum oxytocin (n=45). Primitive neonatal reflexes (endogenous, antigravity, motor, and rhythmic reflexes) were quantified by analyzing videotaped breastfeeding sessions in a biological nurturing position. Two observers blind to the group assignment and the oxytocin dose analyzed the videotapes and assesed the newborn's state of consciousness according to the Brazelton scale., Results: The release of all rhythmic reflexes (p=0.01), the antigravity reflex (p=0.04), and total primitive neonatal reflexes (p=0.02) in the group exposed to oxytocin was lower than in the group not exposed to oxytocin. No correlations were observed between the dose of oxytocin administered and the percentage of primitive neonatal reflexes released (r=0.03; p=0.82)., Conclusions: Intrapartum oxytocin administration might inhibit the expression of several primitive neonatal reflexes associated with breastfeeding. This correlation does not seem to be dose-dependent.

Agonistic interactions are a powerful stressor. Conversely, positive social interactions can reduce the adverse effects of social stress. This possibly occurs through the action of oxytocin (OT), a neuropeptide able to reduce activation of the hypothalamo-pituitary-adrenal (HPA) axis. We hypothesized that repeated OT intranasal administration to neonatal pigs could provide long-lasting protective effects against social stress. In each of six litters, two pigs per litter received 0.5 mL of saline containing 24 IU (or 50 μg) of OT intranasally and two control littermates received 0.5 mL of saline as a control at 1, 2 and 3 days of age. Contrary to our predictions, when socially mixed after weaning at 17 days of age, neonatally OT-administered pigs received more aggressive interactions and performed more aggressive interactions in return, showed greater locomotion, spent less time in social contact, and had greater cortisol concentrations than control pigs. When this social mixing was repeated at 8 weeks of age, OT pigs still performed more aggressive interactions and had greater adrenocorticotropic hormone concentrations than control pigs. A dexamethasone suppression test and corticotropic releasing hormone administration challenge at 11 weeks of age revealed that OT pigs were less responsive to dexamethasone than control pigs, suggesting a deficient HPA axis' negative feedback control. Postnatal repeated OT administration altered social behavior and resulted in a long-term dysregulation of the HPA axis. These findings highlight the complex, fine-tuning of the neurobiological mechanisms regulating the development of social behavior and suggest caution in the application of neonatal peptide treatments during early development., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Suckling is a rhythmic jaw movement that is symmetrical on the left and right side and is highly coordinated with tongue movement. Thus, we investigated the neuronal mechanisms of the left/right and jaw/tongue coordinations during N-methyl-d-aspartate (NMDA)-induced fictive suckling using isolated brainstem-spinal cord preparations obtained from neonatal mice. We observed synchronous low-frequency rhythmic activity in the left/right trigeminal motor nerves, which differed from respiration, and high-frequency rhythmic trigeminal activity, which was side-independent. The low-frequency rhythmic trigeminal activity was also synchronized with the hypoglossal nerve activity. After a complete midline separation of the preparation or a partial midline transection of the brainstem from the anterior inferior cerebellar artery to the junction of the vertebral artery, the low-frequency rhythmic trigeminal activity disappeared, whereas the high-frequency rhythmic trigeminal activity and low-frequency rhythmic hypoglossal activity still remained. These results suggest that the neuronal network that generates low-frequency rhythmic activity likely contributes to the synchronized activity of the left/right jaw muscles and to the jaw/tongue muscles, where it sends its command to the trigeminal motoneurons mainly via the commissural pathway that crosses the transected midline region. Such a neuronal network may underlie the coordinated movements of the jaw and tongue during suckling., (Copyright © 2012 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.)

Aim: To investigate the effect intrapartum oxytocin administration can have on Primitive Neonatal Reflexes. The secondary objective was to observe the influence of intrapartum oxytocin may have on breastfeeding., Methods: Twenty healthy primiparae with a single gestation at term were included. To assess Primitive Neonatal Reflexes, video film was taken during an experimental situation designed to elicit Primitive Neonatal Reflexes. Three independent observers blinded to the oxytocin dose that had been administered coded the Primitive Neonatal Reflexes. Data regarding breastfeeding were collected by telephone at 3 months., Results: Medium oxytocin dose was 1931.9 ± 1754.4 mUI. A Kappa index >0.75 was obtained for four Primitive Neonatal Reflexes: swallow, jaw jerk, suck and gazing. A negative association was found between oxytocin dose and sucking (p = 0.03). At 3 months of life, women exclusively breastfeeding (63.1%) had received a significantly lower average dose of oxytocin than those not exclusively breastfeeding (36.8%) (p = 0.04)., Conclusion: In this pilot study, intrapartum exogenous oxytocin seems to disturb sucking and breastfeeding duration. Further studies are required to confirm these results and to ascertain whether there could be other effects of intrapartum oxytocin on newborn behaviour., (© 2012 The Author(s)/Acta Paediatrica © 2012 Foundation Acta Paediatrica.)

Mother-infant interactions are essential for proper neurobehavioral development of the offspring, and disruptions in those relationships may result in neuroendocrine, neurochemical and behavioral alterations at adulthood. The neural circuitries involved in mother-infant interactions have not been completely elucidated yet. The brain endocannabinoid system plays an essential role in prenatal and postnatal neurobehavioral development. Here, we will summarize and discuss the available findings about the role of endocannabinoids in three key aspects of mother-infant interactions in rodents: suckling, maternal behavior and separation-induced ultrasonic vocalizations (USVs). The studies reviewed here show that endocannabinoids are not only involved in suckling initiation and, therefore, in the feeding and growth of the offspring, but also regulate the emotional reactivity of rodent pups, as measured by the rate of isolation-induced USVs. Conversely, less information is available about endocannabinoid modulation of maternal behavior, and therefore more research in this direction is warranted. Indeed, since Cannabis sativa preparations are widely used by young people, including pregnant and lactating women, it is important to understand whether developmental exposure to cannabinoids interferes with mother-infant bond formation, potentially leading to neurodevelopmental alterations and increased vulnerability to psychopathology later in life.

Endogenous opioid peptides are involved in prolactin release during lactation, in part by decreasing tuberoinfundibular dopaminergic (TIDA) neuronal activity. Both mu (mu) and kappa (kappa) opioid receptors have a role in the suckling-induced prolactin rise after 4-5 h up deprivation. The aim of this study was to investigate effects of mu opioid receptor antagonist, beta-funaltrexamine (beta-FNA), and kappa opioid receptor antagonist, nor-binaltorphimine (nor-BNI), on prolactin secretion and TIDA neuronal activity in lactating rats after 18 h pup deprivation. After 4 h separation from pups, the suckling-induced prolactin rise was abolished by 16 microg nor-BNI and 5 microg beta-FNA, coincident with increased dihydroxyphenylacetic acid (DOPAC):dopamine ratio in the stalk-median eminence (SME). However, after 18 h pups separation, these same doses of nor-BNI and beta-FNA did not alter the prolactin surge or DOPAC:dopamine ratios in the SME. Higher doses of nor-BNI (32 microg) and beta-FNA (10 microg) were required to inhibit suckling-induced prolactin secretion. beta-FNA (10 microg) increased the DOPAC:dopamine ratio in the SME, whereas nor-BNI (32 microg) treatment had no effect. The mu and kappa opioid receptor mRNA levels in the mediobasal hypothalamus were similar to suckled control rats after 4 h pup deprivation, but increased 1.4-fold after 18 h pup deprivation. These data support involvement of endogenous opioidergic systems in the suckling-induced prolactin rise after a prolonged (18 h) period of pup deprivation, as well as the shorter (4 h) pup deprivation period previously reported. Suppression of TIDA neuronal activity likely played a part in mu opioid receptor input to the suckling-induced prolactin rise after both 4 h and 18 h separation, whereas non-dopaminergic input was implicated with kappa opioid receptors after 18 h pup deprivation. Increased mu and kappa opioid receptors gene expression in the mediobasal hypothalamus may contribute to reduced effectiveness of opioid receptor antagonists to block suckling-induced prolactin release after 18 h pup deprivation., (Copyright (c) 2010 IBRO. Published by Elsevier Ltd. All rights reserved.)

Objective: To explore relationships between maternal epidural analgesia and two measures of neurobehavioral organization in infants at the initial feeding 1 hour after birth., Design: Prospective comparative design., Setting: Inner-city community hospital, Chicago, Illinois., Participants: Convenience sample of 52 low-risk, mainly Black and Latino, mother/infant dyads., Methods: Mothers self-selected to labor with epidural or no labor pain medication. Neonatal neurobehavioral organization was measured in term infants at the initial feeding 1 hour after birth. A nutritive sucking apparatus generated data on total number of sucks and sucking pressure. Video recordings of infants (before and after the initial feeding) were coded for behavioral states, with analysis on frequency of alertness., Results: Total number of sucks and sucking pressure were not related to epidural exposure, although an epidural drug dosage effect on total number of sucks was evident when gender was a factor. Unmedicated girls demonstrated more sucks than girls in the high-dosage epidural group (p=.027). Overall, girls exhibited stronger sucking pressure than boys (p=.042). Frequency of alertness was not related to epidural exposure, although longer labor was related to greater alertness (p=.003), and Latino infants were more alert than Black infants (p=.002)., Conclusions: Results suggest attenuated neonatal nutritive sucking organization in girls after exposure to high maternal epidural dosages. In comparison to boys, girls may have enhanced neurobehavioral organization at birth. Race/ethnicity and alertness may have spurious associations in which hidden factors drive the relationship.

Suckling induces a GH surge simultaneously to that of prolactin, so we tested whether salsolinol, a dopamine derivative (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline), participates in the regulatory process of GH secretion in lactating sheep. A series of intracerebroventricular (i.c.v.) infusions of salsolinol, in two doses, was performed in nursing sheep, without suckling, during the fifth week of lactation. In other suckling sheep, we infused i.c.v. a structural analogue of salsolinol-1-methyl-3,4-dihydroisoqinoline (1-MeDIQ), which is able to antagonize salsolinol's action. Intracerebroventricular treatment of nursing sheep with a lower dose of salsolinol (total 50 ng) significantly increased plasma GH concentration, as compared with the concentrations noted before the infusion and in nursing controls. A higher dose of salsolinol (total 5 micrograms) did not affect GH release significantly. Intracerebroventricular treatment with 1-MeDIQ (total 300 micrograms) significantly reduced basal GH release, not affecting a pattern of GH surge in response to suckling. In conclusion, salsolinol may affect the regulatory process of GH secretion in lactating sheep, but its role seems not to be major.

During pregnancy and lactation, the enhanced intestinal Ca(2+) absorption serves to provide Ca(2+) for fetal development and lactogenesis; however, the responsible hormone and its mechanisms remain elusive. We elucidated herein that prolactin (PRL) markedly stimulated the transcellular and paracellular Ca(2+) transport in the duodenum of pregnant and lactating rats as well as in Caco-2 monolayer in a two-step manner. Specifically, a long-term exposure to PRL in pregnancy and lactation induced an adaptation in duodenal cells at genomic levels by upregulating the expression of genes related to transcellular transport, e.g., TRPV5/6 and calbindin-D(9k), and the paracellular transport, e.g., claudin-3, thereby raising Ca(2+) absorption rate to a new "baseline" (Step 1). During suckling, PRL surge further increased Ca(2+) absorption to a higher level (Step 2) in a nongenomic manner to match Ca(2+) loss in milk. PRL-enhanced apical Ca(2+) uptake was responsible for the increased transcellular transport, whereas PRL-enhanced paracellular transport required claudin-15, which regulated epithelial cation selectivity and paracellular Ca(2+) movement. Such nongenomic PRL actions were mediated by phosphoinositide 3-kinase, protein kinase C, and RhoA-associated coiled-coil-forming kinase pathways. In conclusion, two-step stimulation of intestinal Ca(2+) absorption resulted from long-term PRL exposure, which upregulated Ca(2+) transporter genes to elevate the transport baseline, and the suckling-induced transient PRL surge, which further increased Ca(2+) transport to the maximal capacity. The present findings also suggested that Ca(2+) supplementation at 15-30 min prior to breastfeeding may best benefit the lactating mother, since more Ca(2+) could be absorbed as a result of the suckling-induced PRL surge.

In female rats, estradiol (E(2)) and suckling induce prolactin (PRL) secretion. This involves inhibition of hypothalamic dopaminergic tone and stimulation by a PRL-releasing hormone, possibly oxytocin (OT). Infusing an OT antagonist (OTA) i.v., we evaluated the role of OT on suckling- and E(2)-induced PRL secretion. Three days after parturition at 0900 h, lactating dams were fitted with 24-h osmotic minipumps filled with saline or OTA. On d 5 of lactation, pups were separated from their dams for 6 h. Immediately or 20 min after the resumption of suckling, dam trunk blood was collected. Also, ovariectomized (OVX) rats were treated with E(2) (OVE) and OTA at 1000 h on d 1. Blood samples were obtained from 1300 to 2100 h on d 2 for PRL measurements. Additionally, OVX rats were evaluated on d 2 after receiving progesterone (P(4)). OTA blocked suckling and E(2)-induced release of PRL but not that induced by E(2)+P(4). Pups from treated dams failed to gain weight when allowed to nurse for 20 min on d 5 but gained more than 7 g when nursed on d 7 of lactation, indicating that the OTA was active 48 h later. Western blot analysis showed that E(2) treatment increased OT receptors in the anterior pituitary when compared with OVX animals. No further increase was observed in response to the P(4), suggesting that the enhancing effect of P(4) on E(2)-induced PRL release may act through mechanisms independent of OT. These data demonstrate the role of OT in the control of suckling and steroid-induced PRL secretion.

The influence of ghrelin on feeding behaviour during infancy is unknown. To determine whether ghrelin influences milk intake in rat pups, newborn rats received a single i.p. injection of either rat ghrelin (100 microg/kg) or rabbit anti-ghrelin immunoglobulin G (100 microg/kg) every 5 days from postpartum day 5 to day 30 (P5-P30). Milk intake was then assessed by body weight gain following a 2-h suckling period. Ghrelin significantly increased weight gain relative to vehicle-injected controls in P20, P25 and P30 pups, but not in younger animals. Similarly, after 8 h of milk restriction, anti-ghrelin injections significantly decreased weight gain in P25 and P30, but not in younger pups. Interestingly, however, ghrelin did increase independent feeding in P10 and P15 pups using a paradigm in which pups consumed milk from a milk-soaked paper towel. We therefore conclude that ghrelin stimulates milk intake at an early postnatal stage, primarily by affecting adult-type feeding behaviour.

Our understanding of prenatal behavior has been significantly advanced by techniques for direct observation and manipulation of unanesthetized, behaving rodent fetuses with intact umbilical connections to the mother. These techniques involve brief administration of an inhalant anesthesic, enabling spinal transection of the rat or mouse dam, after which procedures can continue with unanesthetized dams and fetuses. Because anesthetics administered to the mother can cross the placental barrier, it is possible that fetuses are anesthetized to varying degrees. We compared in perinatal rats the effects of prenatal maternal exposure to two inhalant anesthetics: ether and isoflurane. Fewer spontaneous fetal movements and first postpartum nipple attachments were observed following maternal exposure to ether as compared to isoflurane. Neonatal breathing frequencies and oxygenation did not account for group differences in nipple attachment. Our results provide evidence that the particular inhalant anesthetic employed in prenatal manipulation studies determines frequencies of perinatal behavior., (Copyright 2007 Wiley Periodicals, Inc.)

Recent evidence indicates that reactivation of consolidated memories returns them to a protein-synthesis-dependent state called reconsolidation. The hypothesis that memories reconsolidate has never been assessed in social memory. The authors tested whether sheep (Ovis aries) mothers' memory of their lambs undergoes reconsolidation upon reactivation. After 7 days of mother-young contact, ewes were separated from their lambs for 8 hr, after which the lambs were reintroduced to their mothers for a 10-min reactivation session. Before reactivation, mothers received a subcutaneous injection of either the protein-synthesis inhibitor cycloheximide (CY, 1 mg/kg) or vehicle. Mothers' lamb memory was tested 1 hr (short-term memory [STM]) or 16 hr (long-term memory [LTM]) after reactivation. Mothers treated with CY exhibited intact STM but deficient LTM. CY injection without reactivation or before presentation of an alien lamb induced no deficit in LTM. CY-induced LTM deficit was alleviated by (a) introducing a reminder just before the LTM test, (b) extending mother-young contact, and (c) preventing suckling by the familiar lamb during reactivation. Thus, reconsolidation can be shown to exist in social memory, and some of its boundary conditions are discussed., (Copyright (c) 2007 APA, all rights reserved.)

Rabbit pups display nipple-search behavior in response to maternal odor cues such as the Mammary Pheromone (MP). Here, we assessed in 3 steps whether the activity of the MP is influenced by prandial and/or rhythmic factors during early development. To address this point, the activity of the MP was tested in 690 pups varying in age (day 0, 2, 5 or 10), prandial state (sucked or un-nursed) and period of their 24-h cycle (-6 to +12 h after the daily sucking). In Experiment 1, the responsiveness of d0 pups was high and stable during the whole day, whether they are nursed or deprived of sucking. The MP activity was thus unaffected by colostrum ingestion. Experiment 2 revealed that some differences appear the next days: whereas the responsiveness of d2 pups was also very high during the 24-h cycle (>94%), it decreased in d5-d10 pups immediately after sucking (<48%), with a rapid recuperation in d5 pups. Experiment 3 showed that this postprandial drop in response to the MP disappeared in d5-d10 pups that missed the daily nursing, suggesting that it resulted from post-ingestive/post-absorptive events rather than from rhythm activity-related factors. Taken together, the results show a progressive change in the circadian dynamics of the MP-induced orocephalic response as a function of age modulated by prandial state. This indicates a transition from an automatic response to the MP to a response regulated by physiological factors associated with satiation.

The role of endogenous opioid system in learning (Pavlovian conditioning) and reinforcement was studied in newborn rats by pairing central injection of dynorphin A (1-13), an endogenous ligand with high affinity for kappa opioid receptors, with a surrogate nipple. For conditioning, the nipple served as the conditioned stimulus and dynorphin as the unconditioned stimulus. Dynorphin was found to elicit an immediate unconditioned, dose-dependent increase in the neonatal responsiveness to a surrogate nipple providing water, an effect apparently mediated through the kappa opioid receptors. This immediate effect of dynorphin was evident in the context of suckling behavior but not in the context of adult-like drinking when water was delivered through an intra-oral cannula. One hour after injection, the unconditioned stimulatory effect of dynorphin had dissipated and no longer affected responsiveness to the nipple. However, pairing of centrally injected dynorphin and suckling on a nipple delivering water substantially enhanced responsiveness to a nipple 1h later. This suggested conditioning, and hence reinforcement, by the centrally injected dynorphin. The conditioned sustained nipple attachment was mediated through both kappa and micro opioid receptors. These experiments confirm a central role for the brain opioid systems in reinforcement of neonatal behavior on the nipple.

Polychlorinated biphenyls (PCBs) are environmental contaminants known to cause multiple behavioral and developmental problems in humans and animals. In rats, gestational exposure to the PCB congener 3, 4, 3', 4'-tetrachlorobiphenyl (PCB 77) affects the brain and behavior of the offspring as well as the maternal behavior of the dams. Whether the behavior of dams is affected by direct effects of the contaminant or indirectly by actions of the PCB on the developing offspring is not known. We investigated this question using a cross-fostering paradigm in which pregnant rats were exposed to either oil vehicle or 2 mg/kg of PCB 77 on gestational days 6 through 18, and then raised pups that had been exposed to either oil or PCB 77 during gestation. Maternal behavior was observed on postnatal days 1, 2, 4 and 6. Some of the effects on maternal behavior, including an increase in the frequency of nursing bouts and in the amount of maternal autogrooming, can be ascribed to prenatal exposure of the litters to the PCB. Other behavioral effects, including an increase in time on the nest and in the amount of pup grooming as well as a reduction in high-crouch nursing, appear to be due to both direct effects of the PCB on the dams and effects mediated by changes in the offspring. Our results show that exposure to PCB 77 can have complex effects on the behavioral interactions between the dams and their litters with a potential impact on the development of the offspring.

Objective: To determine whether central nervous system functioning has an effect on the normal, term infant's ability to breastfeed in the first day following birth., Design: Breastfeeding behaviors and neurobehaviors were evaluated at birth and at 24 hrs of age in two groups of neonates. One group of neonates was born to mothers who received epidural analgesia during labor, and one group was born to mothers who received no pain medication. Breastfeeding behavior was evaluated using the Preterm Infant Breastfeeding Behavior Scale, and the infant's neurobehaviors were evaluated using the Neurologic and Adaptive Capacity Score., Participants: Fifty-six breastfeeding mother-newborn dyads. All mothers were healthy multiparae who gave birth vaginally to normal, full-term, healthy newborns., Main Outcome Measures: Newborns were observed for rooting, latch-on, sucking, swallowing, activity state, and neurobehavior., Result: Analysis of the data indicated that the higher the infant scored in relation to neurobehavioral functioning, the higher the infant scored on breast-feeding behaviors., Conclusion: When determining physiologically what is important for the infant to successfully latch on and feed, it appears that an intact and functioning central nervous system may be one of the crucial elements.

Polychlorinated biphenyls are environmental contaminants known to affect neurobehavioral development in many laboratory studies using different animal models. Because of their bioaccumulation and long half-life they are a serious concern for our own species. The dioxin-like PCB congener 3,4,3',4'-tetrachlorobiphenyl (PCB 77) has estrogenic and anti-estrogenic properties, and has been shown to affect brain chemistry and behavior of developing rats when administered during gestation. Since many developmental outcomes in mammals depend upon the type of maternal care provided by the dams, we investigated the effects of two doses of PCB 77 (2 and 4 mg/kg administered during gestational days 6-18) on the maternal behavior of the treated dams. Both doses of PCB 77 reduced the amount of nursing time in which the dams displayed the high-crouch posture over postnatal days 1-6. In addition, the high dose increased the amount of maternal licking and grooming of the litters and the amount of time the dams spent on the nest. The high dose also increased pup mortality, and both doses reduced the weight gain of the litters during the first 6 days of life. These results document effects of PCB 77 on maternal behavior and serve to raise questions about the importance of maternal contributions to the developmental effects of this and similar contaminants.

The effects of neonatal exposure to alcohol and/or cocaine on two measures of stress were studied in juvenile and young adult female rats. After implantation with an intragastric cannula, subjects were artificially reared from postnatal days 4-10. This "brain growth spurt" period is roughly equivalent to CNS development during the third trimester of human pregnancy. There were five treatment groups: alcohol (6 g/kg/day), cocaine (60 mg/kg/day), alcohol/cocaine (6 g/kg/day alcohol and 60 mg/kg/day cocaine), stock (an artificially reared control), and sham (a suckled control). Subjects were tested in open field and forced swim tests beginning at 21 or 60-70 days of age, respectively. Compared to controls, alcohol-exposed females displayed longer latencies to become immobile in the forced swim test as juveniles and cocaine-exposed females showed increased immobility as adults. Increased immobility can be interpreted as hyporesponsiveness to stress. In contrast, very few differences were observed in the open field. Furthermore, the group exposed to alcohol and cocaine in combination did not differ from controls in either paradigm. These findings suggest that the forced swim test may be more sensitive to neonatal drug effects than open field, although these effects may not be consistent across age.

In sheep, ewes at parturition are responsive to any newborn lamb, but within less than 1 h, mothers learn to recognize the odor of their lamb and restrict maternal care to their own offspring (maternal selectivity). In a first experiment, we investigated the long-term retention of maternal selectivity after various mother-young contact and separation durations. After 4 h of contact, 36 h of separation leads to a total loss of selectivity. Increasing contact duration to 7 days prior to this separation maintains selectivity. These data suggest that lamb memory after going through an initial labile state after parturition, is consolidated over time into a more stable long-term memory. Fos immunohistochemistry reveals that reintroduction of the lamb after 4 h of mother-young contact and 3 h of separation activates different maternal brain regions than reintroduction of the lamb after 7 days of mother-young contact and 3 h of separation. While the piriform cortex shows an enhanced activation at both times, a selective enhancement of activation is observed in the frontal medial and orbitofrontal cortices only after 7 days of mother-young contact. These data suggest that as consolidation occurs, the neurobiological networks sustaining lamb memory involve different structures.

Objective: To evaluate feeding difficulties and maternal behaviour during a feeding session with 1 month old infants prenatally exposed to cocaine and/or opiates., Methods: The study is part of the maternal lifestyle study, which recruited 11 811 subjects at four urban hospitals, then followed 1388 from 1 to 36 months of age. Exposure to cocaine and opiates was determined by maternal interview and meconium assay. At the 1 month clinic visit, biological mothers were videotaped while bottle feeding their infants. This sample included 364 exposed to cocaine, 45 exposed to opiates, 31 exposed to both drugs, and 588 matched comparison infants. Mothers were mostly black, high school educated, and on public assistance. Videotapes were coded without knowledge of exposure status for frequency, duration and quality of infant sucking, arousal, feeding problems, and maternal feeding activity and interaction., Results: No cocaine effects were found on infant feeding measures, but cocaine-using mothers were less flexible (6.29 v 6.50), less engaged (5.77 v 6.22), and had shorter feeding sessions (638 v 683 seconds). Opiate exposed infants showed prolonged sucking bursts (29 v 20 seconds), fewer pauses (1.6 v 2.2 per minute), more feeding problems (0.55 v 0.38), and increased arousal (2.59 v 2.39). Their mothers showed increased activity (30 v 22), independent of their infants' feeding problems., Conclusions: Previous concerns about feeding behaviour in cocaine exposed infants may reflect the quality of the feeding interaction rather than infant feeding problems related to prenatal exposure. However, opiate exposed infants and their mothers both contributed to increased arousal and heightened feeding behaviour.

Neonatal abstinence syndrome (NAS) is suffered by infants withdrawing from substances on which they have become physically dependent after in utero exposure. They may require prolonged treatment and spend weeks or even months in hospital. A wide range of drugs have been used to treat NAS. The efficacy of few, however, have been adequately investigated. Evidence suggests that opioids are the most appropriate, at least in infants exposed to diamorphine or methadone. In all "head to head" trials, diazepam has been shown to be ineffective. Morphine and methadone are currently the most commonly prescribed opioids to treat NAS, but randomised trials have not been undertaken to determine which is the more beneficial. Many infants with NAS have been exposed to multiple substances in utero. Further research is required into whether a single opiate or a multiple drug regimen is the best option for such patients.

The purpose of this study was to investigate whether a heme oxygenase substrate (hemin) or an inhibitor (chromium mesoporphyrin IX; CrMP) had any effect on the normal course of the estrous cycle, pregnancy, parturition or lactation in rats. The hypothesis was that these agents, acting on HO to increase or decrease endogenous production of carbon monoxide (CO) respectively, would disrupt these reproductive processes. The results showed that hemin administered s.c. at 30 micromoles/kg for 10 or 11 days, did not markedly influence the estrous cycle; whereas CrMP blocked the estrous cycle in a dose dependant fashion. At 2 and 4 micromoles/kg for 11 days CrMP significantly reduced the occurrence of estrus phase of the estrous cycle and the effect continued after the treatments were discontinued, while a dose of 1 micromole/kg produced no significant effects. CrMP, administered at 4 micromoles/kg during days 5-14 of pregnancy, led to massive fetal resorption with no live births from 14 successfully mated rats. Administration of hemin at 30 micromoles/kg for 10 days during lactation did not have any effect on milk production, whereas administration of CrMP at 4 micromoles/kg significantly decreased lactational performance which was attributed to milk production and not to suckling intensity of the pups. From these observations we conclude that heme oxygenase, and presumably endogenous CO, play positive roles in female reproductive processes and lactation in the rat.

Altering oxidation of fatty acids by administration of mercaptoacetate (MA) or methyl palmoxirate has been demonstrated to stimulate independent ingestion in rat pups by 12 to 15 days of age. However, in other work, neither agent has been demonstrated to affect intake in the context of suckling. In the present experiments, we tested the effects of MA on both suckling and independent ingestive behavior by examining changes in latency to initiate suckling or independent ingestion and by measuring intake in short-term (30 min) and longer term (4 hr) suckling and independent ingestion tests in pups aged 12 to 15 days of age. The results demonstrated that (a) MA does not affect suckling intake in short- or longer term tests; (b) MA does not affect latency to attach to a nipple, most likely due to floor effects on latency to attach in control pups; (c) MA stimulates independent ingestion in short-term, but not longer terms tests; and (d) MA reduces the latency to initiate independent ingestion. These results suggest that administration of MA preferentially stimulates the initiation of independent ingestion over suckling, and that this response develops at an age just prior to the time at which independent ingestion is typically first expressed by rat pups., (Copyright 2002 Wiley Periodicals, Inc. Dev Psychobiol 41: 103-111, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/dev.10056)

A fostering/crossfostering analysis of the effects of maternal ethanol exposure on lactation performance and offspring growth was performed. Wistar rats were kept under one of the three experimental nutritional treatments: alcohol-treated (EG), pair-fed-treated (PFG) (as a nutritional control of alcohol-associated malnutrition), and control or normal diet (CG). Rats from the EG group were accustomed to increased amounts of ethanol (5% during the first week to 20% in the fourth week). The 20% ethanol level was maintained throughout three additional weeks and during gestational and lactational period. Daily food intake, fluid consumption, body weight and gestational parameters were studied in control (CG), pair-fed (PFG) and ethanol dams (EG). At birth, half the litters were fostered to other dams of the same treatment (GLG) and half were cross-fostered to dams of the opposite treatment (GG, LG). No cross-fostering analyses were performed on the pair-fed group. Offspring body weight was controlled throughout lactation. Liver, kidney and spleen weights as well as milk consumption were also studied at the end of lactation period. In dams, a significant reduction of body weight was described throughout the suckling period. No ethanol detrimental effects were observed on body weight at birth, but in spite of a normal birth weight, alcohol during lactation was responsible for a growth deficit. Milk consumption was significantly reduced in offspring exposed to ethanol during gestation and/or lactation. Curiously, prenatal alcohol exposure affects adversely the suckling behaviour in pups at the time of weaning. In our study, alcohol treatment and malnutrition affects liver and spleen weights. However, malnutrition decreases spleen weights more than alcohol treatment. In the case of the kidney weights the alcohol decreases kidney weight more than malnutrition. Collectively, the data from the present study show similar effects following pre/postnatal and postnatal alcohol exposure. The findings suggest that chronic alcohol administration during gestation and/or lactation adversely affects pup growth at weaning as indicated by its effect on milk consumption, pup and organ weight.

The present study examined the role of endogenous activity at mu and kappa opioid receptors in attachment to and ingestion of milk from a surrogate nipple in cesarean-delivered newborn rats prior to regular suckling experience. Selective opioid antagonist drugs were injected into the cisterna magna (IC administration) or lateral ventricles (ICV administration). Blockade of endogenous activity at mu opioid receptors by IC administration of the selective antagonist CTOP reduced attachment time and markedly increased disengagements from the nipple. CTOP also increased the intensity of suckling measured as milk intake per min attached to the nipple, when milk was available from the nipple in a free-access regime, and enhanced intake when milk was infused through an intraoral cannula aside from the suckling context. The ICV administration of the selective kappa antagonist nor-BNI considerably increased latency to grasp the surrogate nipple, while time on the nipple and milk intake were decreased. The presented data suggest that populations of mu and kappa receptor-containing neurons, differentiable by the route of antagonist administration, play an important role in initiation and maintenance of suckling behavior in the newborn rat during its first encounter with the nipple and milk. The kappa opioid system is predominantly involved in the initiation of the newborn's behavior directed toward the nipple providing milk. The role of the mu opioid system seems more complicated: it transforms initial oral grasp responses into sustained attachment to the nipple and maintains the intake of milk at a certain physiological level., (Copyright 2000 John Wiley & Sons, Inc.)

Unlabelled: Obstetric analgesia in the form of pethidine (meperidine) to mothers during delivery has adverse effects on some aspects of the behaviour of their newborn infants. The non-nutritive sucking (NNS) pattern of nine healthy full-term infants exposed to pethidine in utero was compared to that of a control group of infants. The pattern was analysed and quantified using an automatic computer-based method. The results are discussed in the context of endogenous and exogenous opiates and their effect on brain-stem rhythm generators., Conclusions: The typical NNS pattern with alternating sucking activity (bursts) and pauses is preserved in the exposed infants. There is a significantly lower sucking frequency (md 1.74 vs 1.90 Hz, p = 0.030*) and a tendency to a less stable rhythm in pethidine-exposed infants.

The effect of stimulation (oral-gustatory with sucrose, tactile-bucal, and tactile-manual) on the frequency of hand contact with the oral (hand-mouth and hand sucking) and perioral (hands near the mouth) regions was compared in 24 full-term newborns. The 16-minute evaluation was divided into four equal periods, without intervals: (A) Baseline, no stimulation applied; (B) tactile-bucal, the newborn was allowed to suck the distal phalange of the researcher's little finger; (C) tactile-manual, the newborn was allowed to grasp the researcher's index finger; (D) 0.3 ml sucrose solution was administered orally to the newborns. After every three newborns were tested, the sequence of stimulation application was changed. The frequencies of the hand behaviors were calculated. It was observed that the sucrose significantly increased the frequency of hand sucking (p<0.05). Sucrose was, therefore, the most effective stimulus for eliciting the behavior of hand sucking., (Copyright 2000 John Wiley & Sons, Inc.)

Previous results from our laboratory have indicated that chronic (8 days) alcohol administration inhibits suckling-induced prolactin (PRL) release in response to 30 min of suckling. In addition, chronic alcohol administration to dams resulted in growth retardation of their litters. The present study was done to examine how an extended period of suckling (120 min) affected suckling-induced PRL release after chronic alcohol exposure. In addition, it was also examined whether the growth retardation observed during alcohol exposure persisted after alcohol infusions were discontinued. Dams were implanted with an atrial catheter on day 3 of lactation and saline or alcohol (1.0- or 2.0-g/kg BW) was administered daily for 8 days (lactation days 5 through 12). Following administration of the initial alcohol dose, the infusion was continued at rates required to maintain blood alcohol levels (BALs) for 4 h each day. Testing took place on day 12. As previously reported, suckling-induced PRL release was inhibited in dams receiving 2.0-g/kg alcohol after 30 min of suckling. However, after 120 min of suckling, PRL release in these dams was much higher than in either control or 1.0-g/kg alcohol dams. In addition, while the body weights of litters of dams administered 2.0-g/kg alcohol were reduced compared to litters of dams in the other two groups on days 8-16, their body weights rebounded and were not different from the other litters on days 18 or 20.

We examined the relationship of labor pain relief medications with neonatal suckling and breastfeeding duration in 129 mothers delivering vaginally. Suckling was measured using the Infant Breastfeeding Assessment Tool (IBFAT). Controlling for infant age, birthweight, and gender, infants of unmedicated mothers had higher IBFAT suckling scores than those of medicated mothers (x = 11.1 vs. x = 8.2 respectively, P = .001). IBFAT suckling scores for intravenous and epidural groups were similar (x = 8.5) while those who received a combination of both intravenous and epidural medications were lower (x = 6.4 +/- 2.96, P = .001). Mothers evaluated their breastfeeding similarly to nurse evaluators (Z = 9.39, P = .001). Breastfeeding duration did not differ between unmedicated and medicated groups; however, dyads with low IBFAT scores weaned earlier than those with medium or high scores. Labor pain relief medications diminish early suckling but are not associated with duration of breastfeeding through 6 weeks postpartum.

According to surveys from 1988, 1992 and 1996, Norwegian obstetric departments are still to a large extent using pethidine as birth analgesia. In this article we report recent knowledge of various pharmacological effects of pethidine in mothers and newborns. Pethidine has mainly a sedative effect, but very little analgesic effect in parturients. Pethidine has relatively long-acting behavioural and neurological effects in the newborn due to slow elimination. As a result, breastfeeding is delayed and the mother-infant interaction is disturbed according to recent studies. There is concern about the more or less routine administration of pethidine in many hospitals. We conclude that obstetric departments should reconsider their use of pethidine.

Localized injections of the mu antagonist CTOP into intracisternal (i.c.) or intracerebroventricular (i.c.v.) sites altered the behavior of 1-day-old rat pups during continuous exposure to an artificial nipple. Blockade of mu opioid receptors by i.c. injection decreased oral responsiveness to the nipple, while blockade of receptors by i.c.v. injection of CTOP increased oral responsiveness. The injection of CTOP into the i.c. site produced a transient reduction in body weight gain in pups suckling from their mother, while injection into the i.c.v. site had no effect. When cesarean-delivered pups were tested prior to suckling, injection of CTOP into the i.c. site increased latency of the first nipple attachment and decreased total time attached to a surrogate nipple providing milk. Injection of CTOP into the i.c.v. site decreased latency to the first nipple attachment. The results indicate that there is a caudal population of opioid receptors that is involved in the initiation of suckling behavior and a rostral population that plays a role in decreasing responsiveness at the nipple.

Endogenous activity at opioid receptors affects the appetitive behavior of Caesarean-delivered rat pups during presentation of a surrogate nipple that provides milk. Blockade of opioid receptors by peripheral injection of naloxone has no effect on responses evoked by the surrogate nipple. Similarly, blockade of caudal brain opioid receptors by injection of naloxone into the cisterna magna has no effect on the pup's behavior in response to the surrogate nipple. However, blockade of rostral opioid receptors by injection of naloxone into the cerebral ventricles increases the latency to the first oral grasp response, decreases total time on the nipple, and virtually eliminates ingestion of milk from the surrogate nipple (Experiment 1). Blockade of endogenous opioid activity does not affect responses to a nipple that provides distilled water (Experiment 2) or to an empty surrogate nipple (Experiment 3). These data indicate that during the initial suckling episode endogenous opioids in rostral brain regions affect the pup's behavioral responses to the nipple. The results are consistent with the hypothesis that milk engages opioid systems during the first suckling and that endogenous opioids play a role in early suckling.

This experiment was to test the hypothesis that suckling behavior in Bos taurus is related to milk ejection. Intra-gland milk transport was manipulated by applying four different treatments to four cow-calf pairs: T1, injection of oxytocin during the post-stimulation period; T2, injection of oxytocin before a meal; T3, injection of saline solution at the same times as oxytocin was applied (control) in T1 and T2; T4, injection of an oxytocin antagonist in a similar way as T1. Drugs were applied i.v. and by remote control in order to prevent the animals from noticing the injection. All non-control treatments resulted in significant changes in the time calves spent performing uninterrupted suckling at a specific teat.

This series of experiments examined whether gestational cocaine exposure alters later social behavior exhibited during competition for biologically relevant stimuli. Rat offspring were derived from dams that received subcutaneous injections of 40 mg/kg/3cc cocaine HCl daily on gestational Days 8-20, pair-fed dams injected with saline, or nontreated control dams. Offspring competed with peers for access to a nipple in infancy, and to water in adolescence or adulthood. Prenatal cocaine exposure resulted in a decreased ability of cocaine-exposed infant rats to compete successfully for a nipple. Although adolescent and adult cocaine-exposed rats were no less successful than controls when competing for water, they exhibited a notable increase in aggression toward competitors during testing. Data provide evidence of alterations in social behavior and social competition as a result of prenatal cocaine exposure.

The influence of exogenous oxytocin (OT) on maternal and infant behavior over 60 min of suckling, which followed 6 h of isolation, was investigated on Day 12 of lactation in rats. Mothers administered 1 IU of OT or saline through an indwelling atrial catheter and their litters indicated a similar nursing and suckling pattern, which was estimated by the crouching time of the mothers and the number of stretch reactions performed by the litters during a suckling period. To assess the alteration of the suckling intensity by OT administration, the plasma prolactin (PRL) level was determined by an Nb2 lymphoma cell bioassay. In the control group, the plasma PRL level increased and reached a peak at 45 min after the onset of suckling in 60% of the animals. The suckling-induced PRL release was completely inhibited and/or markedly delayed by OT administration. The difference in body weight of the litters before and after a suckling period was estimated as an index of the amount of milk suckled by the litters. There was no difference in the amount of milk between the control and OT-treated groups during a 60-min suckling period. However, it was significantly greater in the OT-treated group during the first 20 min of the suckling period. These results indicate that a dose of OT is a factor in the attenuation of the intensity of suckling done by the pups, whereas the nursing and suckling behavior is not influenced by OT administration.

The present study reported a new technique in which pups ingested fluids from a surrogate nipple. Cesarean-delivered pups tested before suckling experience showed oral grasp responses and ingested milk from the surrogate nipple. Pups ingested equal amounts of distilled water and milk and rejected saline. After ingesting milk from the surrogate nipple, pups remained attached to an empty surrogate nipple, while pups exposed to distilled water or saline did not show sustained attachment. Brief experience with milk from an oral cannula or from a surrogate nipple elicited sustained attachment to an empty nipple. Pups ingesting milk from a surrogate nipple showed increased intake of water and saline from the nipple when tested subsequently. The surrogate nipple provides a new technique for experimental study of early suckling behavior. The results suggest that initial experiences with milk may reinforce components of early suckling behavior.

This study was conducted to examine the effects of alcohol administered for 4 days during early lactational (days 5 to 8; experiment I) or midlactational (days 9 to 12; experiment II) stage in the rat on various lactational parameters. Litter size was adjusted to eight on day 2, and dams were implanted with an atrial catheter on day 3 (experiment I) or day 7 (experiment II). From days 5 to 8 in experiment I and days 9 to 12 in experiment II, dams were infused with saline (control rats) or alcohol in saline solutions (1.0 and 2.0 g/kg body weight; experimental groups). Blood alcohol levels (BALs) achieved after infusion of the initial doses were maintained for 4 hr daily by continuing infusion. To control for the reduced food intake in the high dose alcohol group, one control group and the group given 1.0 g/kg of body weight alcohol were pair-fed to the 2.0 g/kg body weight alcohol group. On day 8 (experiment I) or day 12 (experiment II), pups were separated from the dam at 0800 hr, and an extension was attached to the catheter. Alcohol or saline was infused, and the BALs achieved after infusion of initial doses were maintained for 4 hr. After removal of a baseline blood sample, pups were returned to dams, and additional blood samples were taken for prolactin measurement 10, 30, 60, and 120 min after suckling started. Suckling latency and milk consumed during the 120 min of suckling were measured. Litters were weighed every other day from days 2 to 21. In both studies, suckling-induced prolactin was inhibited by alcohol. Milk consumed by the pups during the 2-hr period was lower for alcohol groups, compared with control. The suckling latencies were comparable among groups. Litter weights showed no alcohol dose effect. In summary, based on the results from our previous and present studies, we conclude the following: alcohol administered for 1, 4, or 8 days inhibited suckling-induced prolactin release in lactating rats. During a 2-hr test period after alcohol administration, milk consumed by pups was not adversely affected after alcohol administration for 1 day. Whereas, 4 or 8 days of administration had a significant effect. The adverse effect of alcohol on litter growth, however, was evident only after 8 days of alcohol administration. Thus, the detrimental effects of alcohol on different lactational parameters seem to be correlated to the duration of alcohol administration to dams during lactation.

Contrary to medical folklore, previous research has demonstrated that alcohol consumption by lactating women diminished milk intake by their infants during breast feeding. To determine whether this decrease in milk consumption was due to the infants responding to the altered flavor of the milk that also resulted, we evaluated the infants' intake and sucking responses to alcohol-flavored human milk outside of the context of breast feeding, thereby separating the changes due to the infants response to the flavor from any other changes that could also result from acute maternal alcohol consumption such as alterations in milk ejection or the composition of milk. The testing procedure consisted of a two-bottle preference test that was composed of four, 60-sec trials in which the mother's milk flavored with alcohol was alternated with the mother's milk alone in an ABBA or BAAB design. Attached to the nipple of each bottle was a transducer that responded to pressure changes produced by the infants' suckling. There was no suppression of sucking or intake in response to the ethanol-flavored milk. Rather, the infants consumed significantly more and sucked more frequently when drinking the alcohol-flavored milk compared with the unaltered milk. That experience with the flavor of alcohol in mothers' milk modified the infants' responses to alcohol flavor is suggested by the relationship between the reported frequency of mothers' drinking during lactation and the infants' rhythm and frequency of sucking when feeding the alcohol-flavored milk. These findings indicate that infants can readily detect the flavor of alcohol in mother's milk but that the decrease in consumption at the breast after maternal alcohol consumption is apparently not due to the infants rejecting the flavor of alcohol in their mothers' milk.

Lithium carbonate is used for the treatment of bipolar disorder. Because of its widespread use, many women of childbearing age are taking lithium carbonate, which belongs to the US FDA Category D. Administration during pregnancy can result in fetal toxicity. A 17-y-old female with pre-eclampsia and a history of manic depression gave birth to an infant at 37-w gestational age. Several hours prior to delivery, the mother had a lithium level of 2.6 mEq/L. The infant's initial lithium level after birth was 2.1 mEq/L. A subsequent lithium level on the 3rd d of the child's life was 1.4 mEq/L; the half-life in the infant was > 24 h. During the first 4 d of life, the infant was lethargic and exhibited poor suck-swallow coordination that required supplemental enteral feeding. By the 7th d of life, the infant was alert and tolerating all oral feedings. Lithium carbonate readily crosses the placental barrier and can produce teratogenic effects and toxicity. Neonates exposed in utero should be carefully monitored for symptoms of toxicity. In this case only minor toxic effects occurred.

The use of methanol as a component of automobile fuel will increase perinatal exposures in the general population. Few studies have addressed questions concerning neurotoxicity stemming from such exposures. In the current study, four cohorts of pregnant Long-Evans rats, each cohort consisting of an exposure and a control group, were exposed to 4500 ppm methanol vapor in Rochester-type inhalation chambers for 6 hr daily beginning on Gestation Day 6. Exposure continued for both dams and pups through Postnatal Day 21 (PND 21) to model gestational and neonatal toxicity in humans. Several behavioral procedures were used to assess exposure effects in the offspring. Male-female littermates were studied whenever possible to examine sex differences, with one pair from a litter for each procedure. Exposure to methanol did not affect suckling latency and nipple attachment on PND 5 or performance on an aversive olfactory conditioning procedure on PND 10. Exposure to methanol did alter performances in a motor activity procedure. Methanol-exposed neonates were less active on PND 18, but more active on PND 25 than the equivalent control group pups. Two operant conditioning procedures, not used previously in this context, assayed other littermates as adults. A fixed ratio schedule required the rat to rotate a running wheel a specified number of revolutions to obtain food-pellet reinforcers. When the fixed ratio requirement changed, number of responses (revolutions) per 1-hr session displayed a complex interaction with treatment. Changes in performance over the course of training differed between males and females depending on exposure to methanol. Compared to initial baseline performances, methanol-exposed males showed decreases, and methanol-exposed females increases, in the rate of running. A stochastic spatial discrimination procedure permitted subjects to respond on any three levers, with the probabilities of food-pellet delivery determined by the location of the preceding response. A reinforcement matrix defined the response sequence required to maximize reinforcements. When the matrix was changed, the methanol-exposed subjects responded less efficiently at asymptotic levels of performance than controls. Across procedures, developmental exposure to 4500 ppm methanol vapor was associated with subtle behavioral changes in both neonates and adults.