Can adverse neonatal experiences alter brain development and subsequent behavior?

Developmentally supportive care in the newborn intensive care unit: early intervention in the community

The traditional focus of hospital nurses on the medical concerns of infants and toddlers is expanding to encompass the more global view that integrates the developmental level of each infant/toddler into the nursing care plan. Research on early brain development has supported the focus on developmentally supportive care in the NICU. Nursing support of the early relationship between infant and parent that will influence the infant's future development is part of this process. The integration of developmental care concepts including family-centered care that begins on admission to the NICU may continue into the process of discharge and transition to home. The nurse is in an excellent position to support the family in naming their concerns, their strengths, and the hopes and dreams they have for their infant. Nurses in the NICU, home care, community, and public health increasingly focus on a developmental perspective in their work but will be continually challenged to increase their knowledge and understanding of developmental milestones, neurodevelopmental assessment, and their role in collaborating with the wider world of early intervention. This collaboration includes the health care system, the educational system, and the social service system as equal players. For some nurses, this will be a new experience whereby the responsibility for the child is shared among members of an interdisciplinary team that includes the parents. Nurses are key to providing developmentally supportive care and working collaboratively on behalf of the infants and toddlers and their families.

Long-term sensitization of primary afferents in adult rats exposed to neonatal colon pain

We have previously shown that colon irritation (CI) in neonates results in chronic visceral hypersensitivity in adult rats, associated with central neuronal sensitization in the absence of identifiable peripheral pathology. The purpose of this study is to assess the relative contribution of peripheral mechanisms to chronic visceral hypersensitivity by examining the changes in responses of primary afferents at thoracolumbar (TL) and lumbosacral (LS) spinal segments to graded colorectal distension (CRD). Afferent discharges were recorded at the cut distal ends of spinal dorsal roots (DRs) in adult control and CI rats. We found that: (1). the average threshold of activation of LS afferents decreased significantly in CI rats; (2). the responses of TL and LS afferents to CRD in CI rats were significantly greater than those in control; (3). the spontaneous activity of LS afferents in CI rats was significantly stronger than that in control; (4). in CI rats, the average responses to graded CRD of LS DRs were significantly higher than those of TL DRs; and (5). the number of both LS DRs and TL DRs activated by CRD in CI rats was significantly larger than control. In summary, the results show that chronic visceral hypersensitivity is associated with peripheral sensitization, as well as central sensitization. TL visceral afferents projecting seem to be more involved in the processing of sensitized nociceptive input from the colon than acute nociceptive input. However, LS afferents seem to be equally important in both sensitized and acute pain states.

Emotion regulation and touch in infants: the role of cholecystokinin and opioids

Behavioral-pharmacological research in infant rats supports the role of cholecystokinin (CCK) and opioid peptides in mediating early learning of new associations with aspects of the nest and dam, such as maternal odor, milk, and contact. The current paper reviews research that examines the hypothesis that these neuropeptide systems are further involved in mediating emotion regulation in infants, thus playing a role in the emergence of stress-reactivity and other motivational systems. The beneficial effects of maternal proximity, handling, and touch on the development of emotion regulation have been demonstrated in both human and animal models. Interventions that promote tactile stimulation of the infant ("touch therapy") and infant-mother contact ("skin-to-skin contact" or "kangaroo care") have been shown to improve the infant's ability to self-regulate, and to moderate the effects of some risk factors. Theoretical perspectives and empirical findings regarding emotion regulation in infants are first discussed. This is followed by a review of work providing evidence in animal models (and suggestive evidence in humans) for the importance of CCK and opioid neuropeptides in affecting infant emotion regulation and the impact of touch-based interventions, in particular in the context of infant-mother attraction, contact, separation, and attachment.

Olfactory experience mediates response to pain in preterm newborns

We assessed the effects of a familiar odor during routine blood draws in healthy preterm newborns. Infants were observed as they were undergoing either a capillary puncture on the heel (heelstick) or a venous puncture on the hand. During the procedure, one third of the infants were presented with an odor they had been familiarized with prior to the procedure, one third of the infants were presented with an odor, they had not been previously exposed to, and one third were presented with no odor. Heelsticks elicited more behavioral distress than venipunctures. Infants who were presented with a familiar odor during venipuncture showed no significant increase in crying and grimacing during the procedure compared to baseline levels. By comparison, infants presented with an unfamiliar odor or with no odor either during the heelstick or the venipuncture had a significant increase in crying and grimacing. When the pain was milder, i.e., during a venipuncture, and a familiar odor was presented, infants showed little to no crying. These results are consistent with a body of evidence on early memory and olfactory competence in fetuses and newborns.

Major surgery within the first 3 months of life and subsequent biobehavioral pain responses to immunization at later age: a case comparison study

OBJECTIVES

Pain exposure during early infancy affects the pain perception beyond infancy into childhood. The objective of this study was to examine whether major surgery within the first 3 months of life in combination with preemptive analgesia alters pain responses to immunization at 14 or 45 months and to assess whether these alterations are greater in toddlers with a larger number of negative hospital experiences.

METHODS

Two groups of 50 toddlers each were compared: index group and control group. All index toddlers had participated within the first 3 months of their life in a randomized, clinical trial that evaluated the efficacy of preemptive morphine administration for postoperative analgesia. The controls were matched by type of immunization and community health care pediatrician. Pain reactions were recorded at routine immunization at either 14 (measles-mumps-rubella immunization) or 45 months (diphtheria-tetanus-trivalent polio immunization) of age. Outcome measures were facial reaction, coded by the Maximum Discriminative Facial Movement Coding System; heart rate (HR); and cortisol saliva concentration. Negative hospital experiences included number of operations requiring postoperative morphine administration, cumulative Therapeutic Intervention Scoring System scores, and length of stay in the intensive care unit or total hospitalization days.

RESULTS

No differences were found between the index and control groups in the facial display of pain, anger, or sadness or in physiologic parameters such as HR and cortisol concentrations. Intragroup analyses of the index group showed that after measles-mumps-rubella vaccination, the number of negative hospital experiences correlated positively with the facial responsiveness and negatively with HR responses. No effect was seen after diphtheria-tetanus-trivalent polio immunization.

CONCLUSIONS

Major surgery in combination with preemptive analgesia within the first months of life does not alter pain response to subsequent pain exposure in childhood. Greater exposure to early hospitalization influences the pain responses after prolonged time. These responses, however, diminish after a prolonged period of nonexposure.

Neonatal handling reduces the number of cells in the locus coeruleus of rats

Neonatal handling induces long-lasting effects on behaviors and stress responses. The objective of the present study was to analyze the effects of neonatal handling (from the 1st to the 10th day after delivery) on the number of cells and volume of locus coeruleus (LC) nucleus in male and female rats at 4 different ages: 11, 26, 35, and 90 days. Results showed significant reductions in the number of cells and the volume of the LC nucleus in neonatally handled males and females compared with nonhandled rats. Environmental stimulation early in life induced a stable structural change in a central noradrenergic nucleus, which could be one of the causal factors for the behavioral and hormonal alterations observed in adulthood.

Nitrous oxide exerts age-dependent antinociceptive effects in Fischer rats

Nitrous oxide (N(2)O) is an inhalational anesthetic/analgesic gas that has been used for clinical practice for more than a century. While its anesthetic mechanisms remain largely unknown, the underlying analgesic mechanisms are now being unraveled. It has been proposed that N(2)O induces opioid peptide release in the midbrain, leading to the activation of descending noradrenergic inhibitory neurons, which modulates pain processing within the spinal cord. Because descending noradrenergic inhibitory neurons are not functional at birth we posit that N(2)O only becomes an effective analgesic/antinociceptive agent in young patients when the descending noradrenergic inhibitory neurons become fully functional. In the present study, we have examined the age-dependence of N(2)O-induced antinociceptive effects on the formalin test. Fischer rats of various ages (7-, 15-, 19-, 23-, and 29-day-old, and adult) were injected 5% formalin into the hind paw during exposure to 75% N(2)O. Both their behavioral responses and changes in Fos-like immunoreactivity in the spinal cord were assessed as markers of N(2)O's antinociceptive effect. Adult-like antinociceptive responses to N(2)O, both behaviorally and immunohistochemically, were only present in rats older than 3 weeks (23- and 29-day-old). These findings support our hypothesis that N(2)O lacks antinociceptive effects in the very young animals.

The effects of analgesia in the vulnerable infant during the perinatal period

Although our knowledge of pain and its management in the perinatal period has increased, little is known about the first hours and days of life when major physiologic transition events occur. Prematurity and critical illnesses further complicate analgesic use during this time. Increased morbidity and mortality have been shown in infants receiving placebo infusions after surgery compared with infants with analgesia, highlighting the negative consequences of pain in infants. Opioids can help promote hemodynamic stability, promote respirator synchrony, and decrease the incidence of grade III & IV intraventricular hemorrhage in ventilated preterm neonates. Long-term follow-up studies suggest improved behavioral and cognitive outcomes in children given morphine infusions during NICU confinement. The necessity of fetal analgesia is dictated by the ability of the fetus to feel pain and by the adverse effects of noxious stimuli on future sensory development. Effects of drugs given to the pregnant woman on the (preterm) newborn might be influenced by decreased or absent transplacental transport, compression of the umbilical cord during delivery, or diminished blood flow in the placenta in pre-eclamptic women, resulting in higher serum concentrations. Pharmacokinetics and drug metabolism change in the last trimester, and pain sensitivity may be altered after 32 weeks of gestation. Consequently, dose and dose interval may vary considerably between neonates and within an individual during the first days of life. This subpopulation is not homogenous, and drug doses in a term neonate with a postnatal age of 2 weeks may be quite different from those at birth and are certainly different from those in a premature neonate. Size must be disentangled from age-related factors when examining developmental pharmacokinetic parameters. There are no longitudinal studies published investigating the pharmacokinetic properties of any analgesic more than once per infant. Polymorphisms of the genes encoding for the enzymes involved in the metabolism of analgesics or in genes involved in receptor expression may contribute to the large interindividual pharmacokinetic parameter variability. Polymorphism of the human mu opioid receptor has not yet satisfactorily explained pharmacodynamic variability.

Animal models of long-term consequences of early exposure to repetitive pain

Although animal models will never match the complexity of human systems, a number of basic mechanisms can be accessed only by using animal models. Results from studies using animal models of pain can give insight into basic mechanisms underlying long-term consequences of pain and provide sufficient data to generate hypotheses to be tested in human infants. Interaction between clinicians and basic scientists, with an understanding of the domain in which each group is working, is critical to the meshing of efforts from these domains. With collaboration between these groups, more relevant research can be conducted that can lead to the decrease in pain and its consequences in neonates.

Vulnerability of the developing brain. Neuronal mechanisms

Despite the improved survival of tiny preterm neonates, their neurodevelopmental outcomes remain a cause for grave concern. The authors propose two primary mechanisms leading to enhanced neuronal cell death in the immature brain: (1) NMDA-mediated excitotoxicity resulting from repetitive or prolonged pain, and (2) enhanced naturally occurring neuronal apoptosis during early development due to multiple metabolic stresses or lack of social stimulation. The pattern and magnitude of abnormalities will depend on genetic variability as well as the timing, intensity, and duration of adverse environmental experiences. Thus, cumulative brain damage during infancy will finally lead to reductions in brain volume, abnormal behavioral and neuroendocrine regulation, and poor cognitive outcomes during childhood and adolescence. The public health and economic importance of preventing or ameliorating the subtle brain damage caused by these mechanisms cannot be overestimated. This certainly justifies concerted efforts by neuroscientists and clinicians to investigate the mechanisms underlying early neuronal injury, to minimize the impact of adverse experiences and environmental factors in neonates, and to develop novel therapeutic strategies for improving the cognitive and behavioral outcomes of ex-preterm neonates.

Postnatally induced differences in adult pain sensitivity depend on genetics, gender and specific experiences: reversal of maternal deprivation effects by additional postnatal tactile stimulation or chronic imipramine treatment

Postnatal endotoxin exposure, handling or maternal deprivation produce long-lasting individual differences in various neuroendocrine and behavioural responses. However, the impact of postnatal experiences on adult pain sensitivity and its reversibility by postnatal additional tactile stimulation or antidepressants in adulthood is not well understood. Therefore, postnatal endotoxin application as a model for infection, maternal deprivation as a model for depression, and postnatal handling as a model for stimulation were compared with respect to the effects on pain sensitivity in adult Fischer 344 (F344) and Lewis (LEW) rats. Handling increased hot plate latencies in adult F344 and LEW rats, while maternal deprivation shortened hot plate latencies only in LEW rats. Prophylactic treatment strategies, such as tactile stimulation of the dorsal neck region of pups directly after maternal deprivation, or chronic treatment of adult maternally deprived rats using imipramine, successfully provide protection against the maternal deprivation-induced shortening of hot plate latencies. Thus, there is considerable specificity of certain postnatal experiences in modulating adult pain sensitivity and the maternal deprivation-induced hyperalgesia is reversible by different interventional regimes. These findings may explain some of the individual differences in pain sensitivity of humans and the differential efficacy of antidepressants in pain syndromes.

Apoptosis in the preterm and near term ovine fetal brain and the effect of intermittent umbilical cord occlusion

Programmed cell death or apoptosis plays a central role during the development of the brain, but can also be activated by hypoxic/ischemic insult. The purpose of the present study was to determine the regional distribution of apoptotic cells in the preterm and near term ovine fetal brain and thus in relation to the maturation of neurobehavioural activity, and the effect of intermittent umbilical cord occlusion (UCO), which might then contribute to adverse neurodevelopment. Fetal sheep (control and experimental groups at 0.75 and 0.90 of gestation) were studied over 4 days with UCOs performed in the experimental group animals by complete inflation of an occluder cuff for 90 s every 30 min for 3 to 5 h each day. Animals were then euthanized and the fetal brain perfusion-fixed and prepared for subsequent histology and apoptosis staining using the TUNEL assay method. The number of TUNEL positive cells for both the preterm and near term control group animals was low but with a significant regional hierarchy whereby values were higher in the cerebellar peduncle and cortex and lower in the cortical grey and white matter, hippocampus, and pons. While the apoptotic indices (expressed as TUNEL positive cells/1000 cells or high powered field) for most brain regions were not significantly changed between the preterm and near term control group animals, that for the hippocampus and pons were increased approximately 5- and 4-fold, respectively, (both P<0.05), in the near term animals. Intermittent UCO with severe but limited hypoxemia and no cumulative acidosis to ensure longer term survival, had no significant effect on apoptotic indices in the brains of either the preterm or near term animals, although hippocampal values for both occlusion groups were increased approximately 2-3-fold. Levels of apoptosis noted for the ovine fetal brain at 0.75 to 0.90 of gestation are thus low and likely approaching the basal levels of later life, but there are regional differences and changes over this period although little change in response to intermittent cord occlusion as studied, with implications for behavioural state activity and antenatal hypoxic insults in the brain's development.

Maternal smoking during pregnancy and severe antisocial behavior in offspring: a review

OBJECTIVES

Recent research suggests that in utero exposure to maternal smoking is a risk factor for conduct disorder and delinquency. We review evidence of causality, a controversial but important public health question.

METHODS

We analyzed studies of maternal prenatal smoking and offspring antisocial behavior within a causal framework.

RESULTS

The association is (1) independent of confounders, (2) present across diverse contexts, and (3) consistent with basic science. Methodological limitations of existing studies preclude causal conclusions.

CONCLUSIONS

Existing evidence provides consistent support for, but not proof of, an etiologic role for prenatal smoking in the onset of antisocial behavior. The possibility of identifying a preventable prenatal risk factor for a serious mental disorder makes further research on this topic important for public health.

Effect of multisensory stimulation on analgesia in term neonates: a randomized controlled trial

Many attempts have been made to obtain safe and effective analgesia in newborns. Oral glucose-water has been found to have analgesic properties in neonates. We investigated whether other sensory stimulation added to oral glucose provided more effective analgesia than oral glucose alone. In a randomized prospective double-blind trial, we studied 120 term newborns during heel prick. The babies were divided randomly into six groups of 20, and each group was treated with a different procedure during heel prick: A) control; B) 1 mL 33% oral glucose given 2 min before the heel prick; C) sucking; D) 1 mL 33% oral glucose plus sucking; E) multisensory stimulation including 1 mL 33% oral glucose (sensorial saturation); F) multisensory stimulation without oral glucose. Sensorial saturation consisted in massage, voice, eye contact, and perfume smelling during heel prick. Each heel prick was filmed and assigned a point score according to the Douleur Aiguë du Nouveau-né (DAN) neonatal acute pain scale. Camera recording began 30 s before the heel prick, so it was impossible for the scorers to distinguish procedure A (control) from B (glucose given 2 min before), C (sucking water) from D (sucking glucose), and E (multisensory stimulation and glucose) from F (multisensory stimulation and water) from the video. Procedure E (multisensory stimulation and glucose) was found to be the most effective procedure, and the analgesia was even more effective than that produced by procedure D (sucking glucose). We conclude that sensorial saturation is an effective analgesic technique that potentiates the analgesic effect of oral sugar. It can be used for minor painful procedures on newborns.

Postnatal maternal deprivation aggravates experimental autoimmune encephalomyelitis in adult Lewis rats: reversal by chronic imipramine treatment

Stressful experiences can modulate multiple sclerosis, but stress protection is currently not considered a treatment option. Here, we show that maternal deprivation, an adverse stress experience in infancy, increases emotionality in behavioral tests of adult female Lewis rats and concomitantly causes a more severe course of experimental autoimmune encephalomyelitis. Treatment of these effects in adulthood by chronic antidepressants (imipramine) reversed the behavioral symptoms and attenuated the course of the encephalomyelitis in deprived rats. Increased IL-4 plasma levels accompanied the protective-like effects of antidepressants. In contrast, attempts to prevent these effects in infancy by tactile stimulation aggravated the encephalomyelitis, possibly by decreasing corticosterone and increasing IFN-gamma levels during the disease. This indicates that antidepressants exert protective effects in an animal model of multiple sclerosis, and suggests that drugs modifying stress responsiveness may have a potential role as adjuvant treatment of the disease.

Skin-to-Skin contact (Kangaroo care) promotes self-regulation in premature infants: sleep-wake cyclicity, arousal modulation, and sustained exploration

The effect of mother-infant skin-to-skin contact (kangaroo care, or KC) on self-regulatory processes of premature infants was studied. Seventy-three infants who received KC were compared with 73 infants matched for birth weight, gestational age, medical risk, and family demographics. State organization was measured in 10-s epochs over 4 hr before KC and again at term. No differences between KC infants and controls were found before KC. At term, KC infants showed more mature state distribution and more organized sleep-wake cyclicity. At 3 months, KC infants had higher thresholds to negative emotionality and more efficient arousal modulation while attending to increasingly complex stimuli. At 6 months, longer duration of and shorter latencies to mother-infant shared attention and infant sustained exploration in a toy session were found for KC infants. The results underscore the importance of maternal body contact for infants' physiological, emotional, and cognitive regulatory capacities.

To die or not to die, does it change the function? Behavior of transgenic mice reveals a role for developmental cell death

In humans, perturbations in the developmental neuronal death leading to an excess of neurons could be associated with developmental neuropsychiatric disorders. Hu-bcl-2 transgenic mice appear to be a valuable tool to study the functional role of developmental programmed cell death. Indeed, the over-expression of the anti-apoptotic gene bcl-2 decreases developmental neuronal death and Hu-bcl-2 mice present supernumerary neurons in several brain regions. A detailed behavioral analysis of these mice revealed selective deficits. Hu-bcl-2 mice have normal vision, general activity and motor skills. Only the most complex behavior like anxiety and learning abilities are impaired in these mice.

Sensorial saturation: an effective analgesic tool for heel-prick in preterm infants: a prospective randomized trial

Pain is traumatic for preterm infants and can damage their CNS. We wanted to assess whether multisensorial stimulation can be analgesic and whether this effect is only due to oral glucose or sucking. We performed a randomized prospective study, using a validated acute pain rating scale to assess pain during heel-prick combined with five different procedures: (A) control, (B) 10% oral glucose plus sucking, (C) sensorial saturation (SS), (D) oral water, and (E) 10% oral glucose. SS is a multisensorial stimulation consisting of delicate tactile, vestibular, gustative, olfactory, auditory and visual stimuli. Controls did not receive any analgesia. We studied 85 heel-pricks (5 per baby) performed for routine blood samples in 17 preterm infants (28-35 weeks of gestational age). We applied in random order in each patient the five procedures described above and scored pain. SS and sucking plus oral glucose have the greater analgesic effect with respect to no intervention (p < 0.001). The effect of SS is statistically better than that of glucose plus sucking (p < 0.01). SS promotes interaction between nurse and infant and is a simple effective form of analgesia for the NICU.

Cerebral white matter damage in the preterm infant: pathophysiology and risk factors

Based on clinical, epidemiologic, and experimental studies, the aetiology of white matter damage, specifically periventricular leukomalacia (PVL), is multifactorial and involves pre- and perinatal factors possibly including genetic factors, hypoxic-ischaemic insults, infection, excess cytokines, free radical production, increased excitatory amino acid release, and trophic factor deficiencies. The article summarizes research findings about the aetiology of white matter damage and cerebral palsy in preterm infants. The information is organized according to specific antecedents, for which we present epidemiological and neurobiological data. The most important prenatal factor appears to be intrauterine infection. We discuss the evidence supporting the hypothesis that the foetal inflammatory response contributes to neonatal brain injury and later developmental disability. We recently established an animal model of excitotoxic lesions in the developing mouse brain. Brain damage was induced by intra-cortical injections of ibotenate, a glutamatergic agonist. When administered on post-natal day 5 ibotenate induced the formation of white matter cysts. Our animal model could be used to further explore the mechanisms involved in the formation of PVL. Potentially preventive strategies will be discussed.

Long-term effects of short-lasting early local inflammatory insult

We examined the long-term effects of a short-lasting (approximately 24 h) inflammatory insult generated by injections of 0.25% carrageenan (1 microl/g) into the hindpaws of newborn (P0) rat pups. At P60 animals which experienced this early inflammatory insult showed significant alterations in the withdrawal responses to noxious stimulation of the affected paws. Furthermore, in the absence of ongoing inflammation, the withdrawal latencies to heat stimulation and withdrawal thresholds to mechanical stimulation were increased by such experience. In the presence of ongoing CFA-induced inflammation, however, the same early experience decreased these parameters of response to noxious stimulation. These data suggest that early inflammatory insult may differentially affect the aspects of nociceptive circuitry involved in transient pain sensitivity and in inflammation-induced hyperalgesia.

The premature infant and painful procedures

Pain management for premature infants raises challenging questions for nurses. This group of infants is often physiologically fragile and they may undergo frequent painful procedures on a daily basis. Contrary to ideas from the past, premature infants are able to feel pain, and nervous system elements required for the transmission of painful stimuli are functional by 24 weeks gestation. Painful procedures are harmful to the infant's physiological stability and the ability to self-regulate, which includes maintenance of motor control and stable sleep/wake cycles. Assessment of pain in the premature infant is complex. Major indicators of pain include facial grimaces and physiological parameters such as heart rate and oxygen saturation. The Premature Infant Pain Profile (PIPP) is one tool designed specifically for preterm infants. Nonpharmacological nursing measures such as swaddling or nesting and offering a pacifier are useful strategies to help infants cope with painful procedures. The nurse may also maintain a therapeutic environment to assist the infant in self-regulation. Pharmacological agents such as morphine, fentanyl, and acetaminophen are effective in relieving procedural pain. The use of oral sucrose before and during painful procedures offers new possibilities for pain relief. Recent research shows that oral sucrose is a safe and effective analgesic for short-term procedures. Research studies to determine the most effective doses and modes of oral sucrose administration are ongoing. It is thought that the relief of pain is owing to the sweet taste of the sucrose that activates endogenous pain-modulating systems.