Perinatal distress leads to lateralized medial prefrontal cortical dopamine hypofunction in adult rats

Differential role of NMDA receptors in hippocampal-dependent spatial memory and plasticity in juvenile male and female rats

Early life, or juvenility, stands out as the most pivotal phase in neurodevelopment due to its profound impact over the long-term cognition. During this period, significant changes are made in the brain's connections both within and between different areas, particularly in tandem with the development of more intricate behaviors. The hippocampus is among the brain regions that undergo significant postnatal remodeling, including dendritic arborization, synaptogenesis, the formation of complex spines and neuron proliferation. Given the crucial role of the hippocampus in spatial memory processing, it has been observed that spatial memory abilities continue to develop as the hippocampus matures, particularly before puberty. The N-methyl-d-aspartate (NMDA) type of glutamate receptor channel is crucial for the induction of activity-dependent synaptic plasticity and spatial memory formation in both rodents and humans. Although extensive evidence shows the role of NMDA receptors (NMDAr) in spatial memory and synaptic plasticity, the studies addressing the role of NMDAr in spatial memory of juveniles are sparse and mostly limited to adult males. In the present study, we, therefore, aimed to investigate the effects of systemic NMDAr blockade by the MK-801 on spatial memory (novel object location memory, OLM) and hippocampal plasticity in the form of long-term potentiation (LTP) of both male and female juvenile rats. Our results show the sex-dimorphic role of NMDAr in spatial memory and plasticity during juvenility, as systemic NMDAr blockade impairs the OLM and LTP in juvenile males without an effect on juvenile females. Taken together, our results demonstrate that spatial memory and hippocampal plasticity are NMDAr-dependent in juvenile males and NMDAr-independent in juvenile females. These sex-specific differences in the mechanisms of spatial memory and plasticity may imply gender-specific treatment for spatial memory disorders even in children.

Association between 5-min Apgar score and attention deficit hyperactivity disorder: a Scotland-wide record linkage study of 758,423 school children

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) affects around 1 in 20 children and is associated with life-long sequelae. Previous studies of the association between Apgar score and ADHD have reported inconsistent findings.

METHODS

Record linkage of maternity, prescribing and school pupil census databases was used to conduct a population e-cohort study of singleton children born in Scotland and attending school in Scotland at any point between 2009 and 2013. Binary logistic regression analysis was used to investigate the association between 5-min Apgar score and treated ADHD adjusting for sociodemographic and maternity confounders.

RESULTS

Of the 758,423 children, 7,292 (0.96%) received ADHD medication. The results suggested a potential dose-response relationship between Apgar score and treated ADHD independent of confounders. Referent to an Apgar score of 10, risk of treated ADHD was higher for scores of 0-3 (adjusted OR 1.76, 95% CI 1.32-2.34), 4-6 (adjusted OR 1.50, 95% CI 1.21-1.86) and even 7-9 (adjusted OR 1.26, 95% CI 1.18-1.36) which are traditionally considered within the normal range.

CONCLUSIONS

In addition to reinforcing the need to maximise Apgar score through good obstetric practice, the findings suggest that Apgar score may be useful in predicting future risk of ADHD and therefore facilitating early diagnosis and treatment.

A Novel Rat Model of ADHD-like Hyperactivity/Impulsivity after Delayed Reward Has Selective Loss of Dopaminergic Neurons in the Right Ventral Tegmental Area

In attention deficit hyperactivity disorder (ADHD), hyperactivity and impulsivity occur in response to delayed reward. Herein we report a novel animal model in which male Sprague-Dawley rats exposed to repeated hypoxic brain injury during the equivalent of extreme prematurity were ADHD-like hyperactive/impulsive in response to delayed reward and attentive at 3 months of age. Thus, a unique animal model of one of the presentations/subtypes of ADHD was discovered. An additional finding is that the repeated hypoxia rats were not hyperactive in the widely used open field test, which is not ADHD specific. Hence, it is recommended that ADHD-like hyperactivity and ADHD-like impulsivity, specifically in response to delayed reward, be a primary component in the design of future experiments that characterize potential animal models of ADHD, replacing open field testing of hyperactivity. Unknown is whether death and/or activity of midbrain dopaminergic neurons contributed to the ADHD-like hyperactivity/impulsivity detected after delayed reward. Hence, we stereologically measured the absolute number of dopaminergic neurons in four midbrain subregions and the average somal/nuclear volume of those neurons. Repeated hypoxia rats had a significant specific loss of dopaminergic neurons in the right ventral tegmental area (VTA) at 2 weeks of age and 18 months of age, providing new evidence of a site of pathology. No dopaminergic neuronal loss occurred in three other midbrain regions. Fewer VTA dopaminergic neurons correlated with increased ADHD-like hyperactivity and impulsivity. Novel early intervention therapies to rescue VTA dopaminergic neurons and potentially prevent ADHD-like hyperactivity/impulsivity can now be investigated.

Effects of Tail Pinch on BDNF and trkB Expression in the Hippocampus of Roman Low- (RLA) and High-Avoidance (RHA) Rats

In this article, we describe the effects of tail pinch (TP), a mild acute stressor, on the levels of brain-derived neurotrophic factor (BDNF) and its tyrosine kinase receptor B (trkB) proteins in the hippocampus (HC) of the outbred Roman High- (RHA) and Low-Avoidance (RLA) rats, one of the most validated genetic models for the study of fear/anxiety- and stress-related behaviors. Using Western blot (WB) and immunohistochemistry assays, we show for the first time that TP induces distinct changes in the levels of BDNF and trkB proteins in the dorsal (dHC) and ventral (vHC) HC of RHA and RLA rats. The WB assays showed that TP increases BDNF and trkB levels in the dHC of both lines but induces opposite changes in the vHC, decreasing BDNF levels in RHA rats and trkB levels in RLA rats. These results suggest that TP may enhance plastic events in the dHC and hinder them in the vHC. Immunohistochemical assays, carried out in parallel to assess the location of changes revealed by the WB, showed that, in the dHC, TP increases BDNF-like immunoreactivity (LI) in the CA2 sector of the Ammon's horn of both Roman lines and in the CA3 sector of the Ammon's horn of RLA rats while, in the dentate gyrus (DG), TP increases trkB-LI in RHA rats. In contrast, in the vHC, TP elicits only a few changes, represented by decreases of BDNF- and trkB-LI in the CA1 sector of the Ammon's horn of RHA rats. These results support the view that the genotypic/phenotypic features of the experimental subjects influence the effects of an acute stressor, even as mild as TP, on the basal BDNF/trkB signaling, leading to different changes in the dorsal and ventral subdivisions of the HC.

Acoustic startle and prepulse inhibition deficits in adult monkeys with neonatal lesions of the hippocampus, amygdala and orbital frontal cortex

Sensory-motor gating, the process of filtering sensory stimuli to modulate motor responses, is impaired in many psychiatric diseases but especially schizophrenia. Sensory-motor gating assessed with the prepulse inhibition paradigm (PPI) measures startle in response to preceding acoustic stimuli. PPI studies in rodents have consistently found that neonatal hippocampal lesions impair sensory-motor gating in adult animals, but its applicability to primates has yet to be tested. The study examined acoustic startle responses and PPI in adult rhesus monkeys with neonatal lesions of the hippocampus (Neo-Hibo), amygdala (Neo-Aibo), and orbital frontal cortex areas 11 and 13 (Neo-Oasp) and with sham-operations (Neo-C). All monkeys were initially habituated to the startle apparatus and assayed for acoustic startle response curves. Subsequently, PPI was measured with the prepulse occurring at 60, 120, 240, 480, 1000 and 5000 msec prior to the pulse onset. No significant group differences in baseline startle were found. Compared to Neo-C monkeys, Neo-Hibo monkeys showed normal startle curves as well as normal PPI at short prepulse delays but prepulse facilitation (PPF) at longer prepulse intervals. Neo-Aibo monkeys displayed enhanced startle responses with only minor changes in PPI, whereas Neo-Oasp monkeys had severe dampening of startle responses and impaired PPI at shorter prepulse intervals. These results support prior evidence from rodent literature of the involvement of each of these areas in the development of the complex cortico-limbic circuit modulating sensory-motor gating and may shade light on the specific neural structures associated with deficits in PPI reported in neuropsychiatric disorders, such as schizophrenia, autism spectrum disorders, and post-traumatic disorders.

Animal Models for Assessing Impact of C-Section Delivery on Biological Systems

There has been a significant increase in Caesarean section (C-section) births worldwide over the past two decades and although it is can be a life-saving procedure, the enduring effects on host physiology are now undergoing further scrutiny. Indeed, epidemiological data have linked C-section birth with multiple immune, metabolic and neuropsychiatric diseases. Birth by C-section is known to alter the colonisation of the neonatal gut microbiota (with C-section delivered infants lacking vaginal microbiota associated with passing along the birth canal), which in turn can impact the development and maintenance of many important biological systems. Appropriate animal models are key to disentangling the role of missing microbes in brain health and disease in C-section births. In this review of preclinical studies, we interrogate the effects of C-section birth on the development (and maintenance) of several biological systems and we discuss the involvement of the gut microbiome on C-section-related alterations.

Paw preferences in mice and rats: Meta-analysis

Mice and rats are among the most common animal model species in both basic and clinical neuroscience. Despite their ubiquity as model species, many clinically relevant brain-behaviour relationships in rodents are not well understood. In particular, data on hemispheric asymmetries, an important organizational principle in the vertebrate brain, are conflicting as existing studies are often statistically underpowered due to small sample sizes. Paw preference is one of the most frequently investigated forms of hemispheric asymmetries on the behavioural level. Here, we used meta-analysis to statistically integrate findings on paw preferences in rats and mice. For both species, results indicate significant hemispheric asymmetries on the individual level. In mice, 81 % of animals showed a preference for either the left or the right paw, while 84 % of rats showed this preference. However, contrary to what has been reported in humans, population level asymmetries were not observed. These results are particularly significant as they point out that paying attention to potential individual hemispheric differences is important in both basic and clinical neuroscience.

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.

Inflammation and the neural diathesis-stress hypothesis of schizophrenia: a reconceptualization

An interaction between external stressors and intrinsic vulnerability is one of the longest standing pathoaetiological explanations for schizophrenia. However, novel lines of evidence from genetics, preclinical studies, epidemiology and imaging have shed new light on the mechanisms that may underlie this, implicating microglia as a key potential mediator. Microglia are the primary immune cells of the central nervous system. They have a central role in the inflammatory response, and are also involved in synaptic pruning and neuronal remodeling. In addition to immune and traumatic stimuli, microglial activation occurs in response to psychosocial stress. Activation of microglia perinatally may make them vulnerable to subsequent overactivation by stressors experienced in later life. Recent advances in genetics have shown that variations in the complement system are associated with schizophrenia, and this system has been shown to regulate microglial synaptic pruning. This suggests a mechanism via which genetic and environmental influences may act synergistically and lead to pathological microglial activation. Microglial overactivation may lead to excessive synaptic pruning and loss of cortical gray matter. Microglial mediated damage to stress-sensitive regions such as the prefrontal cortex and hippocampus may lead directly to cognitive and negative symptoms, and account for a number of the structural brain changes associated with the disorder. Loss of cortical control may also lead to disinhibition of subcortical dopamine-thereby leading to positive psychotic symptoms. We review the preclinical and in vivo evidence for this model and consider the implications this has for treatment, and future directions.

25 years of research on global asphyxia in the immature rat brain

Hypoxic-ischemic encephalopathy remains a common cause of brain damage in neonates. Preterm infants have additional complications, as prematurity by itself increases the risk of encephalopathy. Currently, therapy for this subset of asphyxiated infants is limited to supportive care. There is an urgent need for therapies in preterm infants - and for representative animal models for preclinical drug development. In 1991, a novel rodent model of global asphyxia in the preterm infant was developed in Sweden. This method was based on the induction of asphyxia during the birth processes itself by submerging pups, still in the uterine horns, in a water bath followed by C-section. This insult occurs at a time-point when the rodent brain maturity resembles the brain of a 22-32 week old human fetus. This model has developed over the past 25 years as an established model of perinatal global asphyxia in the early preterm brain. Here we summarize the knowledge gained on the short- and long-term neuropathological and behavioral effects of asphyxia on the immature central nervous system.

Enduring, Sexually Dimorphic Impact of In Utero Exposure to Elevated Levels of Glucocorticoids on Midbrain Dopaminergic Populations

Glucocorticoid hormones (GCs) released from the fetal/maternal glands during late gestation are required for normal development of mammalian organs and tissues. Accordingly, synthetic glucocorticoids have proven to be invaluable in perinatal medicine where they are widely used to accelerate fetal lung maturation when there is risk of pre-term birth and to promote infant survival. However, clinical and pre-clinical studies have demonstrated that inappropriate exposure of the developing brain to elevated levels of GCs, either as a result of clinical over-use or after stress-induced activation of the fetal/maternal adrenal cortex, is linked with significant effects on brain structure, neurological function and behaviour in later life. In order to understand the underlying neural processes, particular interest has focused on the midbrain dopaminergic systems, which are critical regulators of normal adaptive behaviours, cognitive and sensorimotor functions. Specifically, using a rodent model of GC exposure in late gestation (approximating human brain development at late second/early third trimester), we demonstrated enduring effects on the shape and volume of the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) (origins of the mesocorticolimbic and nigrostriatal dopaminergic pathways) on the topographical organisation and size of the dopaminergic neuronal populations and astrocytes within these nuclei and on target innervation density and neurochemical markers of dopaminergic transmission (receptors, transporters, basal and amphetamine-stimulated dopamine release at striatal and prefrontal cortical sites) that impact on the adult brain. The effects of antenatal GC treatment (AGT) were both profound and sexually-dimorphic, not only in terms of quantitative change but also qualitatively, with several parameters affected in the opposite direction in males and females. Although such substantial neurobiological changes might presage marked behavioural effects, in utero GC exposure had only a modest or no effect, depending on sex, on a range of conditioned and unconditioned behaviours known to depend on midbrain dopaminergic transmission. Collectively, these findings suggest that apparent behavioural normality in certain tests, but not others, arises from AGT-induced adaptations or compensatory mechanisms within the midbrain dopaminergic systems, which preserve some, but not all functions. Furthermore, the capacities for molecular adaptations to early environmental challenge are different, even opponent, in males and females, which may account for their differential resilience or failure to perform adequately in behavioural tests. Behavioural "normality" is thus achieved by the midbrain dopaminergic network operating outside its normal limits (in a state of allostasis), rendering it at greater risk to malfunction when challenged in later life. Sex-specific neurobiological programming of midbrain dopaminergic systems may, therefore, have psychopathological relevance for the sex bias commonly found in brain disorders associated with these systems, and which have a neurodevelopmental component, including schizophrenia, ADHD (attention/deficit hyperactivity disorders), autism, depression and substance abuse.

fMRI functional connectivity of the periaqueductal gray in PTSD and its dissociative subtype

BACKGROUND

Posttraumatic stress disorder (PTSD) is associated with hyperarousal and active fight or flight defensive responses. By contrast, the dissociative subtype of PTSD, characterized by depersonalization and derealization symptoms, is frequently accompanied by additional passive or submissive defensive responses associated with autonomic blunting. Here, the periaqueductal gray (PAG) plays a central role in defensive responses, where the dorsolateral (DL-PAG) and ventrolateral PAG (VL-PAG) are thought to mediate active and passive defensive responses, respectively.

METHODS

We examined PAG subregion (dorsolateral and ventrolateral) resting-state functional connectivity in three groups: PTSD patients without the dissociative subtype (n = 60); PTSD patients with the dissociative subtype (n = 37); and healthy controls (n = 40) using a seed-based approach via PickAtlas and SPM12.

RESULTS

All PTSD patients showed extensive DL- and VL-PAG functional connectivity at rest with areas associated with emotional reactivity and defensive action as compared to controls (n = 40). Although all PTSD patients demonstrated DL-PAG functional connectivity with areas associated with initiation of active coping strategies and hyperarousal (e.g., dorsal anterior cingulate; anterior insula), only dissociative PTSD patients exhibited greater VL-PAG functional connectivity with brain regions linked to passive coping strategies and increased levels of depersonalization (e.g., temporoparietal junction; rolandic operculum).

CONCLUSIONS

These findings suggest greater defensive posturing in PTSD patients even at rest and demonstrate that those with the dissociative subtype show unique patterns of PAG functional connectivity when compared to those without the subtype. Taken together, these findings represent an important first step toward identifying neural and behavioral targets for therapeutic interventions that address defensive strategies in trauma-related disorders.

Apgar Scores Are Associated with Attention-Deficit/Hyperactivity Disorder Symptom Severity

OBJECTIVE

Adverse events during pregnancy and delivery have been linked to attention-deficit/hyperactivity disorder (ADHD). Previous studies have investigated Apgar scores, which assess the physical condition of newborns, in relation to the risk of developing ADHD. We propose to go one step further and examine if Apgar scores are associated with ADHD symptom severity in children already diagnosed with ADHD.

METHOD

ADHD symptoms severity, while off medication, was compared in 2 groups of children with ADHD: those with low (≤6, n = 52) and those with higher (≥7, n = 400) Apgar scores sequentially recruited from the ADHD clinic.

RESULTS

Children with low Apgar at 1 minute after birth had more severe symptoms as assessed by the externalizing scale of the Child Behaviour Checklist, the Conners' Global Index for Parents, and the DSM-IV hyperactivity symptoms count (P = 0.02, <0.01, <0.01, respectively).

CONCLUSION

Low 1-minute Apgar scores are associated with a significant increase in ADHD symptom severity. These findings underline the importance of appropriate pregnancy and perinatal care.

Perinatal asphyxia results in altered expression of the hippocampal acylethanolamide/endocannabinoid signaling system associated to memory impairments in postweaned rats

Perinatal asphyxia (PA) is an obstetric complication that strongly affects the CNS. The endocannabinoid system (ECS) is a lipid transmitter system involved in several physiological processes including synaptic plasticity, neurogenesis, memory, and mood. Endocannabinoids, and other acylethanolamides (AEs) without endocannabinoid activity, have recently received growing attention due to their potential neuroprotective functions in neurological disorders, including cerebral ischemia. In the present study, we aimed to analyze the changes produced by PA in the major metabolic enzymes and receptors of the ECS/AEs in the hippocampus using a rodent model of PA. To induce PA, we removed uterine horns from ready-to-deliver rats and immersed them into a water bath during 19 min. Animals delivered spontaneously or by cesarean section were employed as controls. At 1 month of age, cognitive functions were assessed and immunohistochemical procedures were carried out to determine the expression of NeuN and glial fibrillary acidic protein, enzymes responsible for synthesis (DAGLα and NAPE-PLD) and degradation (FAAH) of ECS/AEs and their receptors (CB1 and PPARα) in the hippocampus. Postweaned asphyctic rats showed impaired recognition and spatial reference memory that were accompanied by hippocampal astrogliosis and changes in the expression of enzymes and receptors. The most remarkable findings in asphyctic rats were a decrease in the expression of NAPE-PLD and PPARα in both hippocampal areas CA1 and CA3. In addition, postweaned cesarean delivery rats showed an increase in the immunolabeling for FAAH in the hippocampal CA3 area. Since, NAPE-PLD and PPARα are proteins that participate in the biochemical process of AEs, specially the neuroprotective oleoylethanolamide, these results suggest that PA dysregulates this system. These data encourage conducting future studies using AEs as potential neuroprotective compounds in animal models of PA.

Mesocorticolimbic dopamine functioning in primary psychopathy: A source of within-group heterogeneity

Despite similar emotional deficiencies, primary psychopathic individuals can be situated on a continuum that spans from controlled to disinhibited. The constructs on which primary psychopaths are found to diverge, such as self-control, cognitive flexibility, and executive functioning, are crucially regulated by dopamine (DA). As such, the goal of this review is to examine which specific alterations in the meso-cortico-limbic DA system and corresponding genes (e.g., TH, DAT, COMT, DRD2, DRD4) might bias development towards a more controlled or disinhibited expression of primary psychopathy. Based on empirical data, it is argued that primary psychopathy is generally related to a higher tonic and population activity of striatal DA neurons and lower levels of D2-type DA receptors in meso-cortico-limbic projections, which may boost motivational drive towards incentive-laden goals, dampen punishment sensitivity, and increase future reward-expectancy. However, increasingly higher levels of DA activity in the striatum (moderate versus pathological elevations), lower levels of DA functionality in the prefrontal cortex, and higher D1-to-D2-type receptor ratios in meso-cortico-limbic projections may lead to increasingly disinhibited and impetuous phenotypes of primary psychopathy. Finally, in order to provide a more coherent view on etiological mechanisms, we discuss interactions between DA and serotonin that are relevant for primary psychopathy.

A comparison of presynaptic and postsynaptic dopaminergic agonists on inhibitory control performance in rats perinatally exposed to PCBs

Polychlorinated Biphenyls (PCBs) are very stable environmental contaminants whose exposure induces a number of health and cognitive concerns. Currently, it is well known that PCB exposure leads to poor performance on inhibitory control tasks. It is also well known that dopamine (DA) depletion within medial prefrontal cortex (mPFC) leads to poor performance on inhibitory control tasks. However, what is not well established is whether or not the inhibitory control problems found following PCB exposure are mediated by DA depletion in mPFC. This study was an investigation into the link between perinatal exposure to PCBs, the effect of this exposure on DA neurotransmission in the mPFC, and inhibitory-control problems during adulthood using a rodent model. The current study served to determine if microinjections of different DA agonists (the presynaptic DA transporter inhibitor and vesicular monoamine transporter agonist bupropion, the postsynaptic DA receptor 2 (DAD2) agonist quinpirole, and the postsynaptic DA receptor 1 (DAD1) agonist SKF81297) directly into the mPFC would differentially improve performance on an inhibitory control task in rats perinatally exposed to an environmentally relevant PCB mixture. Findings suggest several significant sex-based differences on differential reinforcement of low rates (DRL) 15 performance as well as some evidence of differential effectiveness of the DA agonists based on PCB exposure group.

Chronic stress alters the dendritic morphology of callosal neurons and the acute glutamate stress response in the rat medial prefrontal cortex

We have previously reported that interhemispheric regulation of medial prefrontal cortex (PFC)-mediated stress responses is subserved by glutamate (GLU)- containing callosal neurons. Evidence of chronic stress-induced dendritic and spine atrophy among PFC pyramidal neurons led us to examine how chronic restraint stress (CRS) might alter the apical dendritic morphology of callosal neurons and the acute GLU stress responses in the left versus right PFC. Morphometric analyses of retrogradely labeled, dye-filled PFC callosal neurons revealed hemisphere-specific CRS-induced dendritic retraction; whereas significant dendritic atrophy occurred primarily within the distal arbor of left PFC neurons, it was observed within both the proximal and distal arbor of right PFC neurons. Overall, CRS also significantly reduced spine densities in both hemispheres with the greatest loss occurring among left PFC neurons, mostly at the distal extent of the arbor. While much of the overall decrease in dendritic spine density was accounted by the loss of thin spines, the density of mushroom-shaped spines, despite being fewer in number, was halved. Using microdialysis we found that, compared to controls, basal PFC GLU levels were significantly reduced in both hemispheres of CRS animals and that their GLU response to 30 min of tail-pinch stress was significantly prolonged in the left, but not the right PFC. Together, these findings show that a history of chronic stress alters the dendritic morphology and spine density of PFC callosal neurons and suggest a mechanism by which this might disrupt the interhemispheric regulation of PFC-mediated responses to subsequent stressors.

Hormonal modulation of catecholaminergic neurotransmission in a prenatal stress model

Our laboratory has a long-standing interest in the effects of prenatal stress (PS) on various neurotransmitter pathways and the morphology of the developing brain as well as in behavioural aspects of the offspring. Employing a commonly used PS paradigm in which the dams were subjected to restraint stress during the last week of gestation, we observed that several of these pathways were altered in the offspring brain. In this chapter, we will summarize and discuss the results obtained with the main catecholaminergic pathways, namely dopamine (DA) and norepinephrine (NE). In our hands, PS produces an increase in dopamine D2-type receptors in limbic areas, a decreased DA release after amphetamine stimulation in prefrontal cortex (PFC) and an increase in NE release in the same area of the adult offspring brain. In addition, DA uptake is altered at prepubertal stages that persist through adulthood. However, the expression of the step-limiting enzyme of the DA synthesis, tyrosine hydroxylase (TH), is only impaired at early stages of development after PS in the neuronal bodies. At the nuclear regulation level, dopaminergic transcription factors Nurr1 and Ptx3 showed a high vulnerability to PS showing changes along the lifespan. It was striking to observe that many impairments observed in most of these pathways differed depending on whether they were tested before or after puberty indicating a particular sensitivity of the systems to variations in gonadal hormones peaks. In fact, we observed that PS induced long-term effects on the male offspring reproductive system and spermatogenesis development, particularly by inducing a long-term imbalance of circulating sexual hormone levels. Our findings suggest that PS exerts long-term effects on various neurotransmitter pathways altering the normal connectivity between brain areas. Since the developing forebrain was shown to be influenced by androgen exposure, and PS was shown to disrupt prenatal testosterone surges, our results suggest that prenatal insults might be affecting the organizational role of androgens during brain development and differentially modulating their activational role during pubertal brain maturation.

The motivational drive to natural rewards is modulated by prenatal glucocorticoid exposure

Exposure to elevated levels of glucocorticoids (GCs) during neurodevelopment has been identified as a triggering factor for the development of reward-associated disorders in adulthood. Disturbances in the neural networks responsible for the complex processes that assign value to rewards and associated stimuli are critical for disorders such as depression, obsessive–compulsive disorders, obesity and addiction. Essential in the understanding on how cues influence behavior is the Pavlovian–instrumental transfer (PIT), a phenomenon that refers to the capacity of a Pavlovian stimulus that predicts a reward to elicit instrumental responses for that same reward. Here, we demonstrate that in utero exposure to GCs (iuGC) impairs both general and selective versions of the PIT paradigm, suggestive of deficits in motivational drive. The iuGC animals presented impaired neuronal activation pattern upon PIT performance in cortical and limbic regions, as well as morphometric changes and reduced levels of dopamine in prefrontal and orbitofrontal cortices, key regions involved in the integration of Pavlovian and instrumental stimuli. Normalization of dopamine levels rescued this behavior, a process that relied on D2/D3, but not D1, dopamine receptor activation. In summary, iuGC exposure programs the mesocorticolimbic dopaminergic circuitry, leading to a reduction in the attribution of the incentive salience to cues, in a dopamine-D2/D3-dependent manner. Ultimately, these results are important to understand how GCs bias incentive processes, a fact that is particularly relevant for disorders where differential attribution of incentive salience is critical.

Pre-gestational stress alters stress-response of pubertal offspring rat in sexually dimorphic and hemispherically asymmetric manner

Background

There is increasing evidence that maternal stress may have long-term effects on brain development in the offspring. In this study, we examined whether pre-gestational stress might affect offspring rats on the medial prefrontal cortical (mPFC) dopaminergic activity in response to acute stress in puberty and if so, whether such effects exhibited hemispheric asymmetry or sexual dimorphism.

Results

We used behavioral tests to assess the model of chronic unpredictable stress (CUS). We found that the activity in the open field test and sucrose intake test were lower for maternal rats in the CUS group than those in the control group. Offspring rats in the CUS group floated more and swam or climbed less as compared to the offsprings in the control group in the forced swimming test. The floating time was longer and swimming or climbing time was shorter in the female offspring rats than those in the males. Serum corticosterone and corticotrophin-releasing hormone levels were significantly higher for CUS maternal rats and their offsprings than the respective controls. The ratio of dihydroxy-phenyl acetic acid (DOPAC) to dopamine (DA), DA transporter (DAT), norepinephrine transporter (NET) were lower in the mPFC of offspring rats in the CUS group than the control group. Levels of catechol-O-methyltransferase (COMT) in the left mPFC of female offspring rats and in the right mPFC of both female and male offspring rats were lower in the CUS group than those in the controls, but there was no difference in the left mPFC of male offspring between the CUS and control groups. DOPAC, the ratio of DOPAC to DA, NET and COMT were lower in the right mPFC than in the left mPFC of offspring rats in the CUS group. The ratio of DOPAC to DA in the right mPFC was lower in the female offspring rats than male offspring rats in the CUS group. The NET and COMT levels in both left and right mPFC were lower in the female offspring rats than those of the male offsprings in the CUS group.

Conclusion

Our data provide evidence that the effect of pre-gestational stress on the mPFC dopaminergic activity in response to acute stress exhibited hemispheric asymmetry and sexual dimorphism in the pubertal offspring rats.

Moderate and severe perinatal asphyxia induces differential effects on cocaine sensitization in adult rats

Perinatal asphyxia (PA) increases the likelihood of suffering from dopamine-related disorders, such as ADHD and schizophrenia. Since dopaminergic transmission plays a major role in cocaine sensitization, the purpose of this study was to determine whether PA could be associated with altered behavioral sensitization to cocaine. To this end, adult rats born vaginally (CTL), by caesarean section (C+), or by C+ with 15 min (PA15, moderate PA) or 19 min (PA19, severe PA) of global anoxia were repeatedly administered with cocaine (i.p., 15 mg/kg) and then challenged with cocaine (i.p., 15 mg/kg) after a 5-day withdrawal period. In addition, c-Fos, FosB/ΔFosB, DAT, and TH expression were assessed in dorsal (CPu) and ventral (NAcc) striatum. Results indicated that PA15 rats exhibited an increased locomotor sensitization to cocaine, while PA19 rats displayed an abnormal acquisition of locomotor sensitization and did not express a sensitized response to cocaine. c-Fos expression in NAcc, but not in CPu, was associated with these alterations in cocaine sensitization. FosB/ΔFosB expression was increased in all groups and regions after repeated cocaine administration, although it reached lower expression levels in PA19 rats. In CTL, C+, and PA15, but not in PA19 rats, the expression of TH in NAcc was reduced in groups repeatedly treated with cocaine, independently of the challenge test. Furthermore, this reduction was more pronounced in PA15 rats. DAT expression remained unaltered in all groups and regions studied. These results suggest that moderate PA may increase the vulnerability to drug abuse and in particular to cocaine addiction.

Postnatal aversive experience impairs sensitivity to natural rewards and increases susceptibility to negative events in adult life

Evidence shows that maternal care and postnatal traumatic events can exert powerful effects on brain circuitry development but little is known about the impact of early postnatal experiences on processing of rewarding and aversive stimuli related to the medial prefrontal cortex (mpFC) function in adult life. In this study, the unstable maternal environment induced by repeated cross-fostering (RCF) impaired palatable food conditioned place preference and disrupted the natural preference for sweetened fluids in the saccharin preference test. By contrast, RCF increased sensitivity to conditioned place aversion (CPA) and enhanced immobility in the forced swimming test. Intracerebral microdialysis data showed that the RCF prevents mpFC dopamine (DA) outflow regardless of exposure to rewarding or aversive stimuli, whereas it induces a strong and sustained prefrontal norepinephrine (NE) release in response to different aversive experiences. Moreover, the selective mpFC NE depletion abolished CPA, thus indicating that prefrontal NE is required for motivational salience attribution to aversion-related stimuli. These findings demonstrate that an unstable maternal environment impairs the natural propensity to seek pleasurable sources of reward, enhances sensitivity to negative events in adult life, blunts prefrontal DA outflow, and modulates NE release in the reverse manner depending on the exposure to rewarding or aversive stimuli.

Impact of prenatal ischemia on behavior, cognitive abilities and neuroanatomy in adult rats with white matter damage

Early brain damage, such as white matter damage (WMD), resulting from perinatal hypoxia-ischemia in preterm and low birth weight infants represents a high risk factor for mortality and chronic disabilities, including sensory, motor, behavioral and cognitive disorders. In previous studies, we developed a model of WMD based on prenatal ischemia (PI), induced by unilateral ligation of uterine artery at E17 in pregnant rats. We have shown that PI reproduced some of the main deficits observed in preterm infants, such as white and gray matter damage, myelination deficits, locomotor, sensorimotor, and short-term memory impairments, as well as related musculoskeletal and neuroanatomical histopathologies [1-3]. Here, we determined the deleterious impact of PI on several behavioral and cognitive abilities in adult rats, as well as on the neuroanatomical substratum in various related brain areas. Adult PI rats exhibited spontaneous exploratory and motor hyperactivity, deficits in information encoding, and deficits in short- and long-term object memory tasks, but no impairments in spatial learning or working memory in watermaze tasks. These results were in accordance with white matter injury and damage in the medial and lateral entorhinal cortices, as detected by axonal degeneration, astrogliosis and neuronal density. Although there was astrogliosis and axonal degeneration in the fornix, hippocampus and cingulate cortex, neuronal density in the hippocampus and cingulate cortex was not affected by PI. Levels of spontaneous hyperactivity, deficits in object memory tasks, neuronal density in the medial and lateral entorhinal cortices, and astrogliosis in the fornix correlated with birth weight in PI rats. Thus, this rodent model of WMD based on PI appears to recapitulate the main neurobehavioral and neuroanatomical human deficits often observed in preterm children with a perinatal history of ischemia.

Gestational restraint stress and the developing dopaminergic system: an overview

Prenatal stress exerts a strong impact on fetal brain development in rats impairing adaptation to stressful conditions, subsequent vulnerability to anxiety, altered sexual function, and enhanced propensity to self-administer drugs. Most of these alterations have been attributed to changes in the neurotransmitter dopamine (DA). In humans; dysfunction of dopaminergic system is associated with development of several neurological disorders, such as Parkinson disease, schizophrenia, attention-deficit hyperactivity disorder, and depression. Evidences provided by animal research, as well as retrospective studies in humans, pointed out that exposure to adverse events in early life can alter adult behaviors and neurochemical indicators of midbrain DA activity, suggesting that the development of the DA system is sensitive to disruption by exposure to early stressors. The purpose of this article is to provide a general overview of published studies and our own study related to the effect of prenatal insults on the development of DA metabolism and biology, focusing mainly in articles involving prenatal-restraint stress protocols in rats. We will also attempt to make a correlation between theses alterations and DA-related pathological processes in humans.

Perinatal Pitocin as an early ADHD biomarker: neurodevelopmental risk?

OBJECTIVE

To investigate a potential relationship between coincidental increases in perinatal Pitocin usage and subsequent childhood ADHD onset in an attempt to isolate a specific risk factor as an early biomarker of this neurodevelopmental disorder.

METHOD

Maternal labor/delivery and corresponding childbirth records of 172 regionally diverse, heterogeneous children, ages 3 to 25, were examined with respect to 21 potential predictors of later ADHD onset, including 17 selected obstetric complications, familial ADHD incidence, and gender. ADHD diagnosis and history of perinatal Pitocin exposure distinguished groups for comparison.

RESULTS

Results revealed a strong predictive relationship between perinatal Pitocin exposure and subsequent childhood ADHD onset (occurring in 67.1% of perinatal Pitocin cases vs. 35.6% in nonexposure cases, χ(2)=16.99, p<.001). Fetal exposure time, gestation length, and labor length also demonstrated predictive power, albeit significantly lower.

CONCLUSION

The findings warrant further investigation into the potential link between perinatal Pitocin exposure and subsequent ADHD diagnosis.

Effect of perinatal stress on the biogenic amine neurotransmitter level of the adult rat's brain

The amount of biogenic amines (dopamine and serotonin) and their metabolites (DOPAC, HVA, 5-HIAA, and 5-HTOL) in five regions of the brain (frontal cortex, hypothalamus, hippocampus, striatum, and brainstem) was studied in the male and female offspring of control and perinatally (48 h before birth or 48 h after birth) food and water deprived dams, when they were three months old, by using HPLC-EC determination. The increase of amine or metabolite level was dominant (19 values increased and 10 decreased related to control). Before-birth stress caused increase in 9 case and only 2 decreased, while in the case of after-birth stress 10 increased and 8 decreased. However, though there is no possibility to decide an exact tendency of direction, the after-birth stress (transmitted by milk) has more expressed effect. Striatum and brainstem were the most touched regions. There was a gender dependence with the dominance of males, except striatum. Blood plasma nociceptin level was also studied and there was a significant elevation in males after pre- and postnatal deprivation, while in females only after postnatal deprivation. The importance of the results in correlation with other stress effects is discussed.

Effects of early life stress on cognitive and affective function: an integrated review of human literature

RATIONALE

The investigation of putative effects of early life stress (ELS) in humans on later behavior and neurobiology is a fast developing field. While epidemiological and neurobiological studies paint a somber picture of negative outcomes, relatively little attention has been devoted to integrating the breadth of findings concerning possible cognitive and emotional deficits associated with ELS. Emerging findings from longitudinal studies examining developmental trajectories of the brain in healthy samples may provide a new framework to understand mechanisms underlying ELS sequelae.

OBJECTIVE

The goal of this review was twofold. The first was to summarize findings from longitudinal data on normative brain development. The second was to utilize this framework of normative brain development to interpret changes in developmental trajectories associated with deficits in cognitive and affective function following ELS.

RESULTS

Five principles of normative brain development were identified and used to discuss behavioral and neural sequelae of ELS. Early adversity was found to be associated with deficits in a range of cognitive (cognitive performance, memory, and executive functioning) and affective (reward processing, processing of social and affective stimuli, and emotion regulation) functions.

CONCLUSION

Three general conclusions emerge: (1) higher-order, complex cognitive and affective functions associated with brain regions undergoing protracted postnatal development are particularly vulnerable to the deleterious effects of ELS; (2) the amygdala is particularly sensitive to early ELS; and (3) several deficits, particularly those in the affective domain, appear to persist years after ELS has ceased and may increase risk for later psychopathology.

Potential programming of dopaminergic circuits by early life stress

Stress and high levels of glucocorticoids during pre- and early postnatal life seem to alter developmental programs that assure dopaminergic transmission in the mesolimbic, mesocortical, and nigrostriatal systems. The induced changes are likely to be determined by the ontogenetic state of development of these brain regions at the time of stress exposure and their stability is associated with increased lifetime susceptibility to psychiatric disorders, including drug addiction. This article is intended to serve as a starting point for future studies aimed at the attenuation or reversal of the effects of adverse early life events on dopamine-regulated behaviors.

The environment and susceptibility to schizophrenia

In the present article the putative role of environmental factors in schizophrenia is reviewed and synthesized. Accumulating evidence from recent studies suggests that environmental exposures may play a more significant role in the etiopathogenesis of this disorder than previously thought. This expanding knowledge base is largely a consequence of refinements in the methodology of epidemiologic studies, including birth cohort investigations, and in preclinical research that has been inspired by the evolving literature on animal models of environmental exposures. This paper is divided into four sections. In the first, the descriptive epidemiology of schizophrenia is reviewed. This includes general studies on incidence, prevalence, and differences in these measures by urban-rural, neighborhood, migrant, and season of birth status, as well as time trends. In the second section, we discuss the contribution of environmental risk factors acting during fetal and perinatal life; these include infections [e.g. rubella, influenza, Toxoplasma gondii (T. gondii), herpes simplex virus type 2 (HSV-2)], nutritional deficiencies (e.g., famine, folic acid, iron, vitamin D), paternal age, fetal/neonatal hypoxic and other obstetric insults and complications, maternal stress and other exposures [e.g. lead, rhesus (Rh) incompatibility, maternal stress]. Other putative neurodevelopmental determinants, including cannabis, socioeconomic status, trauma, and infections during childhood and adolescence are also covered. In the third section, these findings are synthesized and their implications for prevention and uncovering biological mechanisms, including oxidative stress, apoptosis, and inflammation, are discussed. Animal models, including maternal immune activation, have yielded evidence suggesting that these exposures cause brain and behavioral phenotypes that are analogous to findings observed in patients with schizophrenia. In the final section, future studies including new, larger, and more rigorous epidemiologic investigations, and research on translational and clinical neuroscience, gene-environment interactions, epigenetics, developmental trajectories and windows of vulnerability, are elaborated upon. These studies are aimed at confirming observed risk factors, identifying new environmental exposures, elucidating developmental mechanisms, and shedding further light on genes and exposures that may not be identified in the absence of these integrated approaches. The study of environmental factors in schizophrenia may have important implications for the identification of causes and prevention of this disorder, and offers the potential to complement, and refine, existing efforts on explanatory neurodevelopmental models.

Perinatal risk factors in the development of aggression and violence

Over the past several decades, the relative contribution of both environmental and genetic influences in the development of aggression and violence has been explored extensively. Only fairly recently, however, has it become increasingly evident that early perinatal life events may substantially increase the vulnerability toward the development of violent and aggressive behaviors in offspring across the lifespan. Early life risk factors, such as pregnancy and birth complications and intrauterine exposure to environmental toxins, appear to have a profound and enduring impact on the neuroregulatory systems mediating violence and aggression, yet the emergence of later adverse behavioral outcomes appears to be both complex and multidimensional. The present chapter reviews available experimental and clinical findings to provide a framework on perinatal risk factors that are associated with altered developmental trajectories leading to violence and aggression, and also highlights the genetic contributions in the expression of these behaviors.

The canary in the coalmine: the sensitivity of mesolimbic dopamine to environmental adversity during development

The hypothalamic-pituitary-adrenal axis has been the focus of extensive research with regard to the phenotypic plasticity this system shows in response to environmental influences on mammalian development. This review proposes that the mesolimbic dopamine system is similarly reactive to indicators of environmental adversity during development. Physical, physiological, and toxicological stressors encountered during perinatal development have been routinely demonstrated to affect dopamine neurophysiology, most likely through consequent exposure to maternal glucocorticoids or a reduction in oxygen supply. However, findings remain inconsistent with regard to the nature of impact these events have on the dopamine system. Both hyper- and hypo-dopaminergic changes have been noted. This review argues that the directionality of change is a function of chronicity and severity of the insult, and that both resultant phenotypes are adaptive developmental responses, despite their potential for conferring vulnerability for psychopathology in humans.

Lateralized and sex-dependent behavioral and morphological effects of unilateral neonatal cerebral hypoxia-ischemia in the rat

Neonatal cerebral hypoxia-ischemia (HI) is an important cause of neurological deficits. The Levine-Rice model of unilateral HI is a useful experimental tool, but the resulting brain damage is mainly restricted to one hemisphere. Since the rat presents morphological and biochemical asymmetries between brain hemispheres, behavioral outcome from this model is probably dependent on which hemisphere is damaged. We here investigated the effects of sex and lesioned hemisphere on the outcome of open field, plus maze, inhibitory avoidance and water maze tasks in adult rats previously submitted to neonatal unilateral HI. Females were more active than males in some of studied parameters and males presented better spatial learning. Hypoxia-ischemia caused spatial deficits independently of sex or damaged hemisphere. Right-HI increased locomotion only in males and caused working memory in females and on aversive learning in both males and females. Morphological analysis showed that right-HI animals presented greater reduction of ipsilateral striatum area, with females being more affected. Interestingly, males showed greater hippocampal volume. These results show that task performance and cerebral damage extension are lateralized and sex-dependent, and that the right hemisphere, irrespective of sex, is more vulnerable to neonatal cerebral hypoxia-ischemia.

Role of perinatal adversities on tic severity and symptoms of attention deficit/hyperactivity disorder in children and adolescents with a tic disorder

OBJECTIVE

To investigate the role of perinatal adversities with regard to tic severity and comorbid attention deficit/hyperactivity disorder (ADHD) symptoms in children with a tic disorder.

METHODS

In 75 children and adolescents with a tic disorder, we retrospectively assessed presence of pregnancy, delivery, and postnatal complications and of prenatal exposure to smoking and alcohol. Children with and without these perinatal adversities were compared regarding tic and ADHD symptom severity. Furthermore, through linear regressions, we investigated whether perinatal adversities would interact with presence in first-degree relatives of tic or any mental disorders with the tic or ADHD measure as outcome.

RESULTS

Presence of delivery complications was related to tic severity and prenatal smoking exposure to severity of comorbid ADHD symptoms. The relationship between smoking exposure in utero and ADHD symptom severity appeared to be more pronounced in children with a positive family history of mental disorders.

CONCLUSION

This study provides evidence of a role for perinatal adversities in the etiology of tic disorders. Children with perinatal adversities may be vulnerable to develop more severe tics or comorbid ADHD symptoms in the presence of a positive family history of mental disorders, suggesting a role for gene-environment interactions.

Models of neurodevelopmental abnormalities in schizophrenia

The neurodevelopmental hypothesis of schizophrenia asserts that the underlying pathology of schizophrenia has its roots in brain development and that these brain abnormalities do not manifest themselves until adolescence or early adulthood. Animal models based on developmental manipulations have provided insight into the vulnerability of the developing fetus and the importance of the early environment for normal maturation. These models have provided a wide range of validated approaches to answer questions regarding environmental influences on both neural and behavioral development. In an effort to better understand the developmental hypothesis of schizophrenia, animal models have been developed, which seek to model the etiology and/or the pathophysiology of schizophrenia or specific behaviors associated with the disease. Developmental models specific to schizophrenia have focused on epidemiological risk factors (e.g., prenatal viral insult, birth complications) or more heuristic models aimed at understanding the developmental neuropathology of the disease (e.g., ventral hippocampal lesions). The combined approach of behavioral and neuroanatomical evaluation of these models strengthens their utility in improving our understanding of the pathophysiology of schizophrenia and developing new treatment strategies.

The Association of Birth Complications and Externalizing Behavior in Early Adolescents: Direct and Mediating Effects

Prior studies have shown that birth complications interact with psychosocial risk factors in predisposing to increased externalizing behavior in childhood and criminal behavior in adulthood. However, little is known about the direct relationship between birth complications and externalizing behavior. Furthermore, the mechanism by which the birth complications predispose to externalizing behavior is not well explored. This study aims to assess whether birth complications predispose to early adolescent externalizing behavior and to test whether Intelligence Quotient (IQ) mediates relationships between predictor and outcome variables. We used data from a prospective, longitudinal birth cohort of 1,795 3-year-old boys and girls from Mauritius to test hypotheses. Birth complications were assessed from hospital record data, malnutrition from a pediatric exam at age 3 years, psychosocial adversity from parental interviews at age 3 years, and externalizing behavior problems from parental ratings at age 11 years. We found that babies with birth complications are more likely to develop externalizing behavior problems at age 11. Low IQ was associated with birth complications and was found to mediate the link between early predictors and later externalizing behavior. These prospective, longitudinal findings have potential clinical implications for the identification of early adolescent externalizing behavior and for public health attempts to prevent the occurrence of child externalizing behavior problems.

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).

Psychosis and autism as diametrical disorders of the social brain

Autistic-spectrum conditions and psychotic-spectrum conditions (mainly schizophrenia, bipolar disorder, and major depression) represent two major suites of disorders of human cognition, affect, and behavior that involve altered development and function of the social brain. We describe evidence that a large set of phenotypic traits exhibit diametrically opposite phenotypes in autistic-spectrum versus psychotic-spectrum conditions, with a focus on schizophrenia. This suite of traits is inter-correlated, in that autism involves a general pattern of constrained overgrowth, whereas schizophrenia involves undergrowth. These disorders also exhibit diametric patterns for traits related to social brain development, including aspects of gaze, agency, social cognition, local versus global processing, language, and behavior. Social cognition is thus underdeveloped in autistic-spectrum conditions and hyper-developed on the psychotic spectrum.;>We propose and evaluate a novel hypothesis that may help to explain these diametric phenotypes: that the development of these two sets of conditions is mediated in part by alterations of genomic imprinting. Evidence regarding the genetic, physiological, neurological, and psychological underpinnings of psychotic-spectrum conditions supports the hypothesis that the etiologies of these conditions involve biases towards increased relative effects from imprinted genes with maternal expression, which engender a general pattern of undergrowth. By contrast, autistic-spectrum conditions appear to involve increased relative bias towards effects of paternally expressed genes, which mediate overgrowth. This hypothesis provides a simple yet comprehensive theory, grounded in evolutionary biology and genetics, for understanding the causes and phenotypes of autistic-spectrum and psychotic-spectrum conditions.

Early life programming of hemispheric lateralization and synchronization in the adult medial prefrontal cortex

Neonatal maternal separation (MS) in the rat increases the vulnerability to stressors later in life. In contrast, brief handling (H) in early life confers resilience to stressors in adulthood. Early life programming of stress reactivity may involve the medial prefrontal cortex (mPFC), a region which modulates various stress responses. Moreover, hemispheric specialization in mPFC may mediate adaptive coping responses to stress. In the present study, neuronal activity was examined simultaneously in left and right mPFC in adult rats previously subjected to MS, H or animal facility rearing (AFR). In vivo electrophysiology, under isoflurane anesthesia, was used to conduct acute recordings of unit and local field potential (LFP) activity in response to systemic administration of N-methyl-beta-carboline-3-carboxamide (FG-7142), a benzodiazepine receptor partial inverse agonist which mimics various stress responses. MS decreased basal unit activity selectively in right mPFC. Basal LFP activity was reduced with MS in left and right mPFC, compared to AFR and H, respectively. Hemispheric synchronization of basal LFP activity was also attenuated by MS at lower frequencies. FG-7142 elicited lateralized effects on mPFC activity with different early rearing conditions. Activity in left mPFC was greater with AFR and MS (AFR>MS), whereas activity was predominantly greater with H in right mPFC. Finally, compared to AFR, MS reduced and H enhanced hemispheric synchronization of LFP activity with FG-7142 treatment in a dose-dependent manner. These results indicate that functionally-relevant alterations in mPFC GABA transmission are programmed by the early rearing environment in a hemisphere-dependent manner. These findings may model the hemispheric specialization of mPFC function thought to mediate adaptive coping responses to stressors. They also suggest the possibility that early environmental programming of hemispheric functional coupling in mPFC is involved in conferring vulnerability or resilience to stressors later in life.

Maternal high fat diet during the perinatal period alters mesocorticolimbic dopamine in the adult rat offspring: reduction in the behavioral responses to repeated amphetamine administration

RATIONALE

Early environment can shape the development and function of the mesocorticolimbic dopamine (DA) system and represents a possible risk factor for adult pathologies. One critical variable in the early environment is nutrition, and exposure to high fat (HF) in adulthood is known to change this DA system.

OBJECTIVES

We tested whether perinatal HF intake in rats could have long-term effects on DA function and behavior in adult offspring.

MATERIALS AND METHODS

Rat dams were fed either a control (5% fat, CD) or high fat (30% fat, HF) diet during the last week of gestation and lactation, and adult offspring were tested (PND 56-90) after weaning on CD. Locomotor responses to acute and repeated doses of D: -amphetamine (AMP, 0.75 mg/kg bw) were determined as were indices of DA function in the ventral tegmental area (VTA), nucleus accumbens (NAc), and the prefrontal cortex (PFC).

RESULTS

Adult HF offspring displayed increased tyrosine hydroxylase expression in the VTA and NAc and significant increases in DA and DOPAC content in the NAc, suggesting an elevated DA tone in this target field. In the NAc, there were no significant changes in D1, D2 receptors, or DA transporter (DAT) levels between diet groups. Perinatal HF feeding reduced AMP-induced locomotion and behavioral sensitization to AMP, suggesting that early diet might have caused long-lasting desensitization of postsynaptic receptor mechanisms in the NAc.

CONCLUSIONS

Our results demonstrate that both synthetic activity in VTA neurons and the responsiveness of accumbens DA neurons is altered by maternal nutrition. These effects subside long after termination of exposure to the HF diet.