Effects of vaginal birth versus caesarean section birth with general anesthesia on blood gases and brain energy metabolism in neonatal rats

Brain Volumes in Mice are Smaller at Birth After Term or Preterm Cesarean Section Delivery

The rate of cesarean section (CS) delivery has steadily increased over the past decades despite epidemiological studies reporting higher risks of neonatal morbidity and neurodevelopmental disorders. Yet, little is known about the immediate impact of CS birth on the brain, hence the need of experimental studies to evaluate brain parameters following this mode of delivery. Using the solvent clearing method iDISCO and 3D imaging technique, we report that on the day of birth, whole-brain, hippocampus, and striatum volumes are reduced in CS-delivered as compared to vaginally-born mice, with a stronger effect observed in preterm CS pups. These results stress the impact of CS delivery, at term or preterm, during parturition and at birth. In contrast, cellular activity and apoptosis are reduced in mice born by CS preterm but not term, suggesting that these early-life processes are only impacted by the combination of preterm birth and CS delivery.

Exposure of Hyperandrogen During Pregnancy Causes Depression- and Anxiety-Like Behaviors, and Reduced Hippocampal Neurogenesis in Rat Offspring

The hippocampus is a region in which neurogenesis persists and retains substantial plasticity throughout lifespan. Accumulating evidences indicate an important role of androgens and androgenic signaling in the regulation of offspring hippocampal neurogenesis and the survival of mature or immature neurons and gliocyte. Hyperandrogenic disorders have been associated with depression and anxiety. Previous studies have found that pregnant hyperandrogenism may increase the susceptibility of the offspring to depression or anxiety and lead to abnormal hippocampal neurogenesis in rats. In this study, pregnant rats were given subcutaneous injection of aromatase inhibitor letrozole in order to establish a maternal hyperandrogenic environment for the fetal rats. The lithium chloride (LICl) was used as an intervention agent since a previous study has shown that lithium chloride could promote neurogenesis in the hippocampus. The results revealed that pregnant administration of letrozole resulted in depressive- and anxious-like behaviors in the adolescent period. A remarkable decrease in immature nerve cells marked by doublecortin and mature neurons co-expressed by Brdu and NeuN in adult years were detected in the hippocampal dentate gyrus of adolescent rats. Lithium chloride alleviated the effects on neurobehavioral and promoted the differentiation and proliferation of neural progenitor cells, while a hyperandrogenic intrauterine environment had no effects on astrocytes marked by GFAP in the dentate gyrus. Furthermore, the Wnt/β-catenin signaling pathway related to normal development of hippocampus was examined but there was no significant changes in Wnt signaling pathway members. Our study provides evidence that exposure of androgen during pregnancy leads to alterations in depressive, anxious and stereotypical behaviors and these phenotypes are possibly associated with changes in neurogenesis in the dentate gyrus.

Parturition and the perinatal period: can mode of delivery impact on the future health of the neonate?

Caesarean section and instrumental delivery rates are increasing in many parts of the world for a range of cultural and medical reasons, with limited consideration as to how 'mode of delivery' may impact on childhood and long-term health. However, babies born particularly by pre-labour caesarean section appear to have a subtly different physiology from those born by normal vaginal delivery, with both acute and chronic complications such as respiratory and cardio-metabolic morbidities being apparent. It has been hypothesized that inherent mechanisms within the process of labour and vaginal delivery, far from being a passive mechanical process by which the fetus and placenta are expelled from the birth canal, may trigger certain protective developmental processes permissive for normal immunological and physiological development of the fetus postnatally. Traditionally the primary candidate mechanism has been the hormonal surges or stress response associated with labour and vaginal delivery, but there is increasing awareness that transfer of the maternal microbiome to the infant during parturition. Transgenerational transmission of disease traits through epigenetics are also likely to be important. Interventions such as probiotics, neonatal gut seeding and different approaches to clinical care have potential to influence parturition physiology and improve outcomes for infants.

Perinatal Asphyxia in Rat Alters Expression of Novel Schizophrenia Risk Genes

Epidemiological studies suggest that obstetric complications, particularly those related to hypoxia during labor and delivery, are a risk factor for development of schizophrenia. The impact of perinatal asphyxia on postnatal life has been studied in a rodent model of global hypoxia, which is accompanied by cesarean section birth. This asphyxia model shows several behavioral, pharmacological, neurochemical, and neuroanatomical abnormalities in adulthood that have relevance to schizophrenia. Further, it is suggested that schizophrenia has a strong genetic component, and indeed novel candidate genes were recently identified by a genome-wide association study. Here, we examined alteration in the novel schizophrenia risk genes, CNNM2, CSMD1, and MMP16 in the brains of rats undergoing cesarean section with or without global hypoxia. The brain regions studied were the prefrontal cortex, striatum, and hippocampus, which are all relevant to schizophrenia. Risk gene expression was measured at three time periods: neonatal, adolescence, and adulthood. We also performed an in vitro analysis to determine involvement of these genes in CNS maturation during differentiation of human neuronal and glial cell lines. Cnnm2 expression was altered in the brains of asphyxia model rats. However, Csmd1 and Mmp16 showed altered expression by exposure to cesarean section only. These findings suggest that altered expression of these risk genes via asphyxia and cesarean section may be associated, albeit through distinct pathways, with the pathobiology of schizophrenia.

Developmental Sex Differences in the Metabolism of Cardiolipin in Mouse Cerebral Cortex Mitochondria

Cardiolipin (CL) is a mitochondrial-specific phospholipid. CL content and acyl chain composition are crucial for energy production. Given that estradiol induces CL synthesis in neurons, we aimed to assess CL metabolism in the cerebral cortex (CC) of male and female mice during early postnatal life, when sex steroids induce sex-dimorphic maturation of the brain. Despite the fact that total amount of CL was similar, its fatty acid composition differed between males and females at birth. In males, CL was more mature (lower saturation ratio) and the expression of the enzymes involved in synthetic and remodeling pathways was higher, compared to females. Importantly, the sex differences found in CL metabolism were due to the testosterone peak that male mice experience perinatally. These changes were associated with a higher expression of UCP-2 and its activators in the CC of males. Overall, our results suggest that the perinatal testosterone surge in male mice regulates CL biosynthesis and remodeling in the CC, inducing a sex-dimorphic fatty acid composition. In male's CC, CL is more susceptible to peroxidation, likely explaining the testosterone-dependent induction of neuroprotective molecules such as UCP-2. These differences may account for the sex-dependent mitochondrial susceptibility after perinatal hypoxia/ischemia.

Angiogenesis induced by prenatal ischemia predisposes to periventricular hemorrhage during postnatal mechanical ventilation

BACKGROUND

Three risk factors are associated with hemorrhagic forms of encephalopathy of prematurity (EP): (i) prematurity, (ii) in utero ischemia (IUI) or perinatal ischemia, and (iii) mechanical ventilation. We hypothesized that IUI would induce an angiogenic response marked by activation of vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9), the latter degrading vascular basement membrane and increasing vulnerability to raised intravenous pressure during positive pressure mechanical ventilation.

METHODS

We studied a rat model of hemorrhagic-EP characterized by periventricular hemorrhages in which a 20-min episode of IUI is induced at E19, pups are born naturally at E21-22, and on P0, are subjected to a 20-min episode of positive pressure mechanical ventilation. Tissues were studied by H&E staining, immunolabeling, immunoblot, and zymography.

RESULTS

Mechanical ventilation of rat pups 2-3 d after 20-min IUI caused widespread hemorrhages in periventricular tissues. IUI resulted in upregulation of VEGF and MMP-9. Zymography confirmed significantly elevated gelatinase activity. MMP-9 activation was accompanied by severe loss of MMP-9 substrates, collagen IV and laminin, in microvessels in periventricular areas.

CONCLUSION

Our findings are consistent with the hypothesis that positive pressure mechanical ventilation of the newborn in the context of recent prenatal ischemia/hypoxia can predispose to periventricular hemorrhages.

Prematurely delivered rats show improved motor coordination during sensory-evoked motor responses compared to age-matched controls

The amount of postnatal experience for perinatal rats was manipulated by delivering pups one day early (postconception day 21; PC21) by cesarean delivery and comparing their motor behavior to age-matched controls on PC22 (the typical day of birth). On PC22, pups were tested on multiple measures of motor coordination: leg extension response (LER), facial wiping, contact righting, and fore- and hindlimb stepping. The LER and facial wiping provided measures of synchronous hind- and forelimb coordination, respectively, and were sensory-evoked. Contact righting also was sensory-evoked and provided a measure of axial coordination. Stepping provided a measure of alternated forelimb and hindlimb coordination and was induced with the serotonin receptor agonist quipazine. Pups that were delivered prematurely and spent an additional day in the postnatal environment showed more bilateral limb coordination during expression of the LER and facial wiping, as well as a more mature righting strategy, compared to controls. These findings suggest that experience around the time of birth shapes motor coordination and the expression of species-typical behavior in the developing rat.

The health implications of birth by Caesarean section

Since the first mention of fetal programming of adult health and disease, a plethora of programming events in early life has been suggested. These have included intrauterine and postnatal events, but limited attention has been given to the potential contribution of the birth process to normal physiology and long-term health. Over the last 30 years a growing number of studies have demonstrated that babies born at term by vaginal delivery (VD) have significantly different physiology at birth to those born by Caesarean section (CS), particularly when there has been no exposure to labour, i.e. pre-labour CS (PLCS). This literature is reviewed here and the processes involved in VD that might programme post-natal development are discussed. Some of the effects of CS are short term, but longer term problems are also apparent. We suggest that VD initiates important physiological trajectories and the absence of this stimulus in CS has implications for adult health. There are a number of factors that might plausibly contribute to this programming, one of which is the hormonal surge or "stress response" of VD. Given the increasing incidence of elective PLCS, an understanding of the effects of VD on normal development is crucial.

Perinatal asphyxia reduces dentate granule cells and exacerbates methamphetamine-induced hyperlocomotion in adulthood

BACKGROUND

Obstetric complications have been regarded as a risk factor for schizophrenia later in life. One of the mechanisms underlying the association is postulated to be a hypoxic process in the brain in the offspring around the time of birth. Hippocampus is one of the brain regions implicated in the late-onset dopaminergic dysfunction associated with hypoxic obstetric complications.

METHODOLOGY/PRINCIPAL FINDINGS

We used an animal model of perinatal asphyxia, in which rat pups were exposed to 15 min of intrauterine anoxia during Cesarean section birth. At 6 and 12 weeks after birth, the behavior of the pups was assessed using a methamphetamine-induced locomotion test. In addition, the histopathology of the hippocampus was examined by means of stereology. At 6 weeks, there was no change in the methamphetamine-induced locomotion. However, at 12 weeks of age, we found an elevation in methamphetamine-induced locomotor activity, which was associated with an increase of dopamine release in the nucleus accumbens. At the same age, we also found a reduction of the dentate granule cells of the hippocampus.

CONCLUSIONS/SIGNIFICANCE

These results suggest that the dopaminergic dysregulation after perinatal asphyxia is associated with a reduction in hippocampal dentate granule cells, and this may partly contribute to the pathogenesis of schizophrenia.

Ontogeny of altered dendritic morphology in the rat prefrontal cortex, hippocampus, and nucleus accumbens following Cesarean delivery and birth anoxia

We used a delayed Cesarean birth model and the Golgi-Cox staining method to investigate the effects of perinatal anoxia on prefrontal cortex (PFC) and hippocampal (CA1) pyramidal neurons as well as nucleus accumbens (NAcc) medium spiny neurons. Dendritic morphology in these regions was studied on postnatal days (P) 2, 7, 14, 21, 35, and 70 in male Sprague-Dawley rats born either vaginally (VAG) or by Cesarean section either with (C + anoxia) or without (C-only) anoxia. The most striking birth group differences seen were at the level of dendritic spine densities on P35. During this postnatal period the dendritic spine density of PFC neurons was significantly lower in C + anoxia and C-only animals than in VAG controls; however, by P70 PFC spine densities in all birth groups were comparable. In contrast, hippocampal spine densities on P35 were comparably greater in C + anoxia animals than in VAG controls, whereas in C-only animals spine densities were lower than controls; here again, by P70 all groups had comparable hippocampal spine densities. In NAcc greater spine densities were seen on medium spiny neurons of C + anoxia animals on P35. These findings provide evidence that perinatal insult in the form of Cesarean birth with or without anoxia alters the dendritic development of PFC and hippocampal pyramidal neurons and to some extent also of NAcc medium spiny neurons. They also suggest that perinatal anoxia can alter the neuronal development of key structures thought to be affected in such late-onset dopamine-related disorders as schizophrenia and Attention Deficit Hyperactivity Disorder (ADHD).

Maternal care is similar for rat pups subjected to birth hypoxia and for controls

The rat model of global anoxia during cesarean section birth has been used extensively to investigate effects of birth hypoxia on central nervous system function. This study tested whether differential maternal care mediates central nervous system alterations in this model. Maternal care of mixed litters of pups born vaginally, by cesarean section or by cesarean section with anoxia, was assessed. Frequency and duration of licking and grooming by dams were similar for all birth groups. No group differences were observed in order of retrieval, when pups were displaced from the nest. The results indicate that altered central nervous system function in anoxic animals in this model are not due to differential maternal care, but may be mediated by other mechanisms such as direct hypoxic insult to neurons.

Birth insults involving hypoxia produce long-term increases in hippocampal [125I]insulin-like growth factor-I and -II receptor binding in the rat

Insulin-like growth factors-I and -II and insulin are structurally related mitogenic growth factors with multiple actions in the developing nervous system and adult CNS. Previous studies have demonstrated acute induction of insulin-like growth factors and their receptors, over a time course of several days, in response to hypoxic/ischemic insult to developing or adult brain. The current study tested whether birth insults involving hypoxia may produce long term changes in brain insulin-like growth factor or insulin receptor levels, lasting into adulthood. For this, rats were born vaginally (controls), by cesarean section, or by cesarean section with 15 min of added global anoxia (cesarean section+anoxia), and brain [125I]insulin-like growth factor-I, [125I]insulin-like growth factor-II and [125I]insulin receptor binding sites were assessed autoradiographically at adulthood. [125I]Insulin-like growth factor-I receptor binding sites were increased in all hippocampal subfields (CA1-CA3, dentate gyrus) in rats born either by cesarean section or by cesarean section+anoxia, compared with vaginal birth. [125I]Insulin-like growth factor-II binding was increased in all hippocampal subfields only in rats born by cesarean section+anoxia compared with either vaginal birth or cesarean section groups. [125I]Insulin-like growth factor-I and [125I]insulin-like growth factor-II binding in frontal cortex, striatum and cerebellum were unaffected by birth group, except for increased [125I]insulin-like growth factor-I binding in the cerebellar molecular layer of cesarean-sectioned animals. Birth group had no significant effect on [125I]insulin binding in any brain region. Affinity cross-linking experiments performed with hippocampal membranes from the three birth groups showed that i) [125I]insulin-like growth factor-I and [125I]insulin-like growth factor-II recognized bands of molecular weights characteristic of insulin-like growth factor-I and insulin-like growth factor-II receptors, respectively, and ii) [125I]insulin-like growth factor-I and [125I]insulin-like growth factor-II were displaced more potently by their respective unlabeled ligands than by related molecules. It is concluded that birth insults involving hypoxia can induce lasting increases in insulin-like growth factor-I and -II receptors in the CNS. There is specificity with respect to the subtype of insulin-like growth factor receptor affected by the particular birth insult and the brain region affected. It is suggested that enduring increases in levels of insulin-like growth factor receptors consequent to hypoxic birth insult may help to maintain hippocampal function at adulthood, and could modulate responsiveness to insulin-like growth factor administration.

Effects of birth insult and stress at adulthood on excitatory amino acid receptors in adult rat brain

Birth complications involving fetal hypoxia and stress at adulthood, which are risk factors for schizophrenia, can produce alterations in subcortical dopamine (DA) function in rat models. As adults, rats born either by cesarean section (C-section) or by C-section with added global anoxia show increased stress-induced DA release from nucleus accumbens and increased amphetamine-induced locomotion, compared to vaginally born controls. Moreover, stress at adulthood interacts with these birth insults to modulate DA receptor and transporter levels. Glutamatergic transmission at the level of the nucleus accumbens, prefrontal cortex, and hippocampus are known to modulate subcortical DA activity. Thus, altered excitatory amino acid (EAA) function might contribute to the dopaminergic changes observed in rats after birth insult and/or stress at adulthood. To test this possibility, rats born vaginally, by C-section, or by C-section with 15 min of anoxia, were either repeatedly stressed (15 min of tail pinch daily for 5 days) at adulthood or received no stress, and levels of EAA receptor binding were measured by ligand autoradiography in limbic brain regions. As adults, rats born by C-section showed increases in AMPA receptor binding in nucleus accumbens shell, NMDA receptor binding in cingulate cortex, and kainate receptor binding in the hippocampal CA1 region. Anoxic rats showed increases in CA1 kainate receptor and anterior olfactory NMDA receptor binding. Stress at adulthood increased AMPA receptor binding in several regions of prefrontal cortex and reduced NMDA receptor binding in infralimbic cortex and dentate gyrus, across all birth groups. Two instances of interactions between birth insult and stress at adulthood were observed. Stress reduced cingulate cortex NMDA receptor binding and increased olfactory tubercle kainate receptor binding only in C-sectioned animals, but not in controls. The possibility that the observed EAA receptor changes contribute to dopaminergic dysfunction in these animal models is discussed, in light of known glutamate-DA interactions.

Delivery modes and neonatal EEG: spatial pattern analysis

BACKGROUND

Animal studies indicate that postnatal adaptation and development of neonates could be different due to the birth method and that these effects may last throughout adulthood.

STUDY DESIGN

We applied a spatio-temporal analysis to EEG recordings of a group of neonates to investigate the influence of a cesarean section on maturation and extrauterine adaptation of the brain. EEG were recorded at 2 h and at 24 h after delivery.

SUBJECTS

A spectral analysis technique, the so-called Karhunen-Loeve (KL) method, was applied to EEG of 10 neonates from vaginal delivery and 17 from C-section to obtain the spatio-temporal eigenpatterns.

RESULTS

Spatio-temporal analysis showed noticeable pattern differences between the two groups. Compared to the C-section, the vaginal delivered neonate's EEG recordings showed a significant increase of amplitude at Fp1 in the pattern 24 h after the delivery, but not 2 h after delivery. Dynamics in this spectral analyses were not significantly different between both groups 2 h after delivery, but the regional differences increased during the next day between both groups.

CONCLUSIONS

This could come from the early insufficient complexity in C-section neonates. Global EEG complexity in C-section neonates fell short of that of vaginal delivered neonates 2 h after delivery. Many aspects of pattern change in C-section neonates followed the nature of vaginal delivered neonates. These could be considered as parts of a retarded transition of C-section neonates in the early adaptation, but some of the differences in global EEG pattern could not be explained in this way. Pattern analysis suggests that the neuronal activities of the neonatal brain are changing regionally concurrent with bi-hemispheric global dynamics. Moreover, the delivery modes could have an influence on the early postneonatal adaptation of the physiological activity in brain.

The Na,K-ATPase alpha 2 isoform is expressed in neurons, and its absence disrupts neuronal activity in newborn mice

Na,K-ATPase is an ion transporter that impacts neural and glial physiology by direct electrogenic activity and the modulation of ion gradients. Its three isoforms in brain have cell-type and development-specific expression patterns. Interestingly, our studies demonstrate that in late gestation, the alpha2 isoform is widely expressed in neurons, unlike in the adult brain, in which alpha2 has been shown to be expressed primarily in astrocytes. This unexpected distribution of alpha2 isoform expression in neurons is interesting in light of our examination of mice lacking the alpha2 isoform which fail to survive after birth. These animals showed no movement; however, defects in gross brain development, muscle contractility, neuromuscular transmission, and lung development were ruled out. Akinesia suggests a primary neuronal defect and electrophysiological recordings in the pre-Bötzinger complex, the brainstem breathing center, showed reduction of respiratory rhythm activity, with less regular and smaller population bursts. These data demonstrate that the Na,K-ATPase alpha2 isoform could be important in the modulation of neuronal activity in the neonate.

Birth insult interacts with stress at adulthood to alter dopaminergic function in animal models: possible implications for schizophrenia and other disorders

Altered subcortical dopaminergic activity is thought to be involved in the pathophysiology of several disorders including schizophrenia, substance abuse and attention deficit hyperactivity disorder. Epidemiological studies have implicated perinatal insults, particularly obstetric complications involving fetal or neonatal hypoxia, as etiological risk factors for schizophrenia. This suggests the possibility that perinatal hypoxia might have lasting effects on dopaminergic function. In animal models, dopaminergic systems appears to be particularly vulnerable to a wide range of perinatal insults, resulting in persistent alterations in function of mesolimbic and mesostriatal pathways. This review summarizes recent work characterizing long-term changes in dopaminergic function and biochemistry in models of Caesarean section (C-section) birth and of C-section birth with added global anoxia in the rat and guinea pig. C-section birth and C-section with anoxia appear to be two distinct hypoxic birth insults, with somewhat differing patterns of lasting effects on dopamine systems. In addition, birth insult alters the manner in which dopaminergic function is regulated by stress at adulthood. The possible relevance of these finding to effects of human birth procedures is discussed.

Dopamine D1 receptor changes due to caesarean section birth: effects of anesthesia, developmental time course, and functional consequences

There is an epidemiological association between increased obstetric complications and disorders involving CNS dopamine dysregulation, such as schizophrenia. In light of this, a rat model of global hypoxia during Caesarean section (C-section) birth has been used to directly test if birth complications can produce long-term dopaminergic dysregulation. Previous studies have shown that, compared to vaginal birth, C-section birth alone (without additional global hypoxia) is sufficient to increase D1-like receptor binding in rat brain at adulthood. The current study examined (1) the developmental time course of changes in D1-like or D2-like receptors following C-section birth; (2) whether C-section birth from isoflurane-anesthetized dams also results in altered D1-like receptor levels, as does C-section from decapitated dams; and (3) behavioral responses to D1 and D2 agonists in rats born vaginally compared to C-section. Increases in nucleus accumbens D1-like receptor binding due to C-section birth were observed only at adulthood (3 months) but not prepubertally (1 month or 2 weeks). D2-like receptor binding levels were unaffected by C-section birth across the three developmental time points. Compared to vaginal birth, D1-like receptors were increased following C-section birth from isoflurane-anesthetized dams, as well as from decapitated dams. Adult rats that had been born by C-section showed enhanced D1 potentiation of D2-induced locomotor behavior. These studies indicate that C-section birth, from either anesthetized or unanesthetized dams, results in postpubertal increases in D1-like receptor binding and enhanced functional responses to D1 receptor activation.

Genetic factors modulate effects of C-section birth on dopaminergic function in the rat

Genetic predisposition and environmental factors such as perinatal complications are believed to contribute to the etiology of schizophrenia, a disorder involving enhanced CNS dopaminergic activity. This study used a rat model to test whether genetic factors and a minor birth complication, i.e. Caesarean section (C-section) birth, interact in producing longterm effects on dopamine-mediated behavior. For this, we compared the effects of vaginal and C-section birth on amphetamine (AMPT)-induced locomotor activity in strains of rats differing in genetic composition. In Sprague-Dawley rats, C-section birth increased AMPT-induced locomotion compared with vaginal birth. By contrast in Lewis rats, C-section birth reduced AMPT-induced locomotion compared with vaginal birth. In Fischer rats, AMPT-induced locomotion was increased by C-section under maternal anesthesia but decreased by C-section after maternal decapitation, compared with vaginal birth. It is concluded that a minor birth complication like C-section can have differing long-term effects on dopaminergic function in the rat, depending on the genetic composition of the individual.