Neurotransmission and the ontogeny of human brain

Prenatal exposure to oxcarbazepine increases hippocampal apoptosis in rat offspring

This study assessed apoptosis in the offspring of rats exposed to oxcarbazepine (OXC) from day 7 to 15 of gestation. Three groups of pregnant Wistar rats were used: 1) Control, treated with saline solution; 2) treated with 100 mg/kg OXC; 3) treated with 100 mg/kg of carbamazepine (CBZ, as a positive control for apoptosis); the route of administration was intragastric. Apoptosis was detected at three postnatal ages using the TUNEL technique in the CA1, and CA3 regions of the hippocampus and in the dentate gyrus (DG); neurogenesis was assessed in the DG using an antibody against doublecortin. The litter characteristics were recorded. OXC increased apoptosis in all regions (p < 0.01) at the three ages evaluated. Lamination disruption occurred in CA1 and CA3 due to the neuron absence and to ectopic neurons; there were also malformations in the dorsal lamina of the DG in 38% and 25% of the pups born from rats treated with OXC and CBZ respectively. CBZ also increased apoptosis. No clear effect on neurogenesis in the DG was observed. The size of the litter was smaller (p < 0.01) in the experimental groups. Nineteen-day OXC fetuses had low weight (p < 0.01), but 21 and 30 postnatal days old CBZ and OXC pups were overweight (p < 0.01). The results demonstrate that OXC administered during gestation is pro-apoptotic, alters the cytoarchitecture of the hippocampus, reduces litter size, and probably influences postnatal weight. We provide evidence of the proapoptotic effect of CBZ when administered early in gestation.

In utero exposure to atypical antipsychotic drug, risperidone: Effects on fetal neurotoxicity in hippocampal region and cognitive impairment in rat offspring

Clinical studies indicate that about one-third of pregnant women with psychotic symptoms are exposed to either typical or atypical antipsychotic drugs (APDs). Reports on prenatal subject/model are lacking hence, the present study was undertaken to investigate the effect of prenatal exposure to risperidone (RIS) on the fetal hippocampus, and their related functional changes in young rat offspring. In this study, pregnant Wistar rats were exposed to equivalent therapeutic doses of RIS at 0.8mg/kg, 1.0mg/kg, and 2.0mg/kg BW from gestation days (GD) 6 to 20. On GD 21, about half of the pregnant subjects of each group were euthanized, their fetuses were collected, fetal brains dissected, and processed for neurohistopathological evaluation. Remaining pregnant dams were allowed to deliver naturally and reared up to 8weeks of age for neurobehavioral study under selected paradigms of cognition. Our results indicate that there was a significant decrease in the thickness of fetal hippocampus with the disturbed cytoarchitectural pattern, and volume of striatum and choroid plexus was also reduced. Furthermore, RIS treated young rat offspring displayed memory impairment on different mazes of learning and memory. The current study concludes that maternal exposure to clinically relevant doses of RIS may induce neurostructural changes in developing hippocampus and striatum, and cognitive sequelae in young offspring, respectively. Therefore, caution must be taken before prescribing this drug to pregnant subjects, especially during the sensitive phase of brain development. Hence, clinical correlation of animal data is urgently warranted.

Neuropathological sequelae of developmental exposure to antiepileptic and anesthetic drugs

Glutamate (Glu) and γ-aminobutyric acid (GABA) are major neurotransmitters in the mammalian brain which regulate brain development at molecular, cellular, and systems level. Sedative, anesthetic, and antiepileptic drugs (AEDs) interact with glutamate and GABA receptors to produce their desired effects. The question is posed whether such interference with glutamatergic and GABAergic neurotransmission may exert undesired, and perhaps even detrimental effects on human brain development. Preclinical research in rodents and non-human primates has provided extensive evidence that sedative, anesthetic, and AEDs can trigger suicide of neurons and oligodendroglia, suppress neurogenesis, and inhibit normal synapse development and sculpting. Behavioral correlates in rodents and non-human primates consist of long-lasting cognitive impairment. Retrospective clinical studies in humans exposed to anesthetics or AEDs in utero, during infancy or early childhood have delivered conflicting but concerning results in terms of a correlation between drug exposure and impaired neurodevelopmental outcomes. Prospective studies are currently ongoing. This review provides a short overview of the current state of knowledge on this topic.

Cortisol levels in relation to maternal interaction and child internalizing behavior in preterm and full-term children at 18 months corrected age

Cortisol levels were compared in children born preterm at extremely low gestational age (ELGA; 24-28 weeks), very low gestational age (VGLA; 29-32 weeks), and full-term in response to cognitive assessment at 18 months corrected age (CA). Further, we investigated the relationship between maternal interactive behaviors and child internalizing behaviors (rated by the mother) in relation to child cortisol levels. EGLA children had higher "pretest" cortisol levels and a different pattern of cortisol response to cognitive assessment compared to VGLA and full-terms. Higher cortisol levels in ELGA, but not full-term, children were associated with less optimal mother interactive behavior. Moreover, the pattern of cortisol change was related to internalizing behaviors among ELGA, and to a lesser degree VLGA children. In conclusion, our findings suggest altered programming of the hypothalamic-pituitary-adrenal (HPA) axis in preterm children, as well as their greater sensitivity to environmental context such as maternal interactive behavior.

From benefit to damage. Glutamate and advanced glycation end products in Alzheimer brain

The glutamatergic system is the most widespread neurotransmitter system in the mammalian brain. It is connected to the acetylcholinergic neurotransmitter system to form the glutamatergic/aspartatergic-acetylcholinergic circuit, which is the morphobiochemical basis of learning, memory and cognition assisted by the glutamatergic N-methyl-D-aspartate receptor, which mediates long-term potentiation as the fundamental molecular mechanisms of these mental capacities. Glutamate and acetylcholine as ligands of the two neurotransmitter systems are products of the neuronal glucose metabolism as holds true also for advanced glycation end products (AGEs), which are markers of damaged and/or aged proteins. During normal aging, both the neurotransmitters glutamate and acetylcholine undergo strong functional variations. Their synthesis was found to be reduced as a common feature. In contrast, basal release of acetylcholine and receptor number decrease, whereas basal release of glutamate and receptor number increase. AGEs increase during aging obviously preferentially in glutamatergic pyramidal neurons in cerebral cortical layers prone to neurodegeneration. In sporadic Alzheimer disease (SAD), glutamate concentration was shown to fall since it may serve as a substitute for lacking glucose in the beginning of the disease. In contrast, glutamate receptor density was found to be much less involved indicating an excessive activation of the glutamatergic neurotransmitter system particularly via the NMDA receptor, mediating endogenous excitotoxicity. The morphological hallmarks of SAD neuritic plaques and neurofibrillary tangles have been demonstrated to crosslink with AGEs causing an increased rate of free radical production. First data from animal studies and investigations on human beings may indicate that the NMDA receptor antagonist memantine may have beneficial effects on the course of SAD and its clinical symptoms.

Brain aging phenomena in migrating sockeye salmon Oncorhynchus nerka nerka

Aging, a process occurring in all vertebrates, is closely related to a loss in physical and functional abilities. There is widespread interest in clarifying the relevance of environmental, metabolic, and genetic factors for vertebrate aging. In the Pacific salmon a dramatic example of aging is known. Looking for changes in the salmon brain, perhaps even in the role of initiating the aging processes, we investigated several biochemical parameters that should reflect brain functional activity and stress response such as the neurotransmitters dopamine, and serotonin, and two of their respective metabolites 3,4-dihydroxyphenylacetic acid, and 5-hydroxyindole acetic acid, as well as glutathione, glutathione disulfide, and the extent of terminal deoxynucleotidyltransferase-mediated dUTP nick end-labelling. The aging of migrating sockeye salmon (Oncorhynchus nerka nerka) is accompanied by gradual increase in dopamine and serotonin turnover and a gradual decrease of brain total protein and glutathione levels. There appears to be an increased need for detoxification of reactive biological intermediates since activities of superoxide dismutase and catalase increase with age. However, our data do not support a major increase in apoptotic cell death during late aging but rather implicate an age related downward regulation of protein and glutathione synthesis and proteolysis increasing the need for autophagocytosis or heterophagocytosis in the course of cell death.

Structural Effects and Neurofunctional Sequelae of Developmental Exposure to Psychotherapeutic Drugs: Experimental and Clinical Aspects

The advent of psychotherapeutic drugs has enabled management of mental illness and other neurological problems such as epilepsy in the general population, without requiring hospitalization. The success of these drugs in controlling symptoms has led to their widespread use in the vulnerable population of pregnant women as well, where the potential embryotoxicity of the drugs has to be weighed against the potential problems of the maternal neurological state. This review focuses on the developmental toxicity and neurotoxicity of five broad categories of widely available psychotherapeutic drugs: the neuroleptics, the antiepileptics, the antidepressants, the anxiolytics and mood stabilizers, and a newly emerging class of nonprescription drugs, the herbal remedies. A brief review of nervous system development during gestation and following parturition in mammals is provided, with a description of the development of neurochemical pathways that may be involved in the action of the psychotherapeutic agents. A thorough discussion of animal research and human clinical studies is used to determine the risk associated with the use of each drug category. The potential risks to the fetus, as demonstrated in well described neurotoxicity studies in animals, are contrasted with the often negative findings in the still limited human studies. The potential risk fo the human fetus in the continued use of these chemicals without more adequate research is also addressed. The direction of future research using psychotherapeutic drugs should more closely parallel the methodology developed in the animal laboratories, especially since these models have already been used extremely successfully in specific instances in the investigation of neurotoxic agents.

Developmental neuropathology of environmental agents

The developing central nervous system (CNS) is more vulnerable to injury than the adult one. Although a great deal of research has been devoted to subtle effects of developmental exposure, such as neurobehavioral changes, this review instead focuses on a number of chemicals that have been shown, in several experimental models as well as humans, to cause morphological changes in the developing nervous system. Chemicals that are discussed include methylmercury (MeHg), lead (Pb), antiepileptic drugs, and ethanol. Additionally, the issue of silent neurotoxicity, i.e., persistent morphological and/or biochemical injury that remains clinically unapparent until later in life, is discussed.

Is there a subtype of developmental Parkinson's disease?

Evidence accumulates suggesting that environmental factors including viral and risk factors associated with pregnancy and birth-giving, may increase the incidence of hypokinesia/parkinsonism in early life, or PD in later life. Such environmental pre-, peri- or postnatal stress may lead to disturbances in the developing brain and malformations in regions of particular interest and associated with PD. Genetic predisposition to hypoactivity plus environmental effects may lead to reorganization of brain circuitry including changes in monoaminergic and/or EAA systems, leading to a subtype of PD, i.e. genetic, drug induced, viral, developmental and other possible subtypes. The spectrum disorder of PD is going to be further substantiated into various etiopathologically verifyable subgroups.

Transplanted neuroblasts differentiate appropriately into projection neurons with correct neurotransmitter and receptor phenotype in neocortex undergoing targeted projection neuron degeneration

Reconstruction of complex neocortical and other CNS circuitry may be possible via transplantation of appropriate neural precursors, guided by cellular and molecular controls. Although cellular repopulation and complex circuitry repair may make possible new avenues of treatment for degenerative, developmental, or acquired CNS diseases, functional integration may depend critically on specificity of neuronal synaptic integration and appropriate neurotransmitter/receptor phenotype. The current study investigated neurotransmitter and receptor phenotypes of newly incorporated neurons after transplantation in regions of targeted neuronal degeneration of cortical callosal projection neurons (CPNs). Donor neuroblasts were compared to the population of normal endogenous CPNs in their expression of appropriate neurotransmitters (glutamate, aspartate, and GABA) and receptors (kainate-R, AMPA-R, NMDA-R. and GABA-R), and the time course over which this phenotype developed after transplantation. Transplanted immature neuroblasts from embryonic day 17 (E17) primary somatosensory (S1) cortex migrated to cortical layers undergoing degeneration, differentiated to a mature CPN phenotype, and received synaptic input from other neurons. In addition, 23.1 +/- 13.6% of the donor-derived neurons extended appropriate long-distance callosal projections to the contralateral S1 cortex. The percentage of donor-derived neurons expressing appropriate neurotransmitters and receptors showed a steady increase with time, reaching numbers equivalent to adult endogenous CPNs by 4-16 weeks after transplantation. These results suggest that previously demonstrated changes in gene expression induced by synchronous apoptotic degeneration of adult CPNs create a cellular and molecular environment that is both permissive and instructive for the specific and appropriate maturation of transplanted neuroblasts. These experiments demonstrate, for the first time, that newly repopulating neurons can undergo directed differentiation with high fidelity of their neurotransmitter and receptor phenotype, toward reconstruction of complex CNS circuitry.

An infant formula free of glycomacropeptide prevents hyperthreoninemia in formula-fed preterm infants

BACKGROUND

Hyperthreoninemia is a well-known phenomenon in infants fed a whey protein-predominant formula. Sweet whey is commonly used for the production of these whey-predominant infant milk formulas. Sweet whey contains not only whey proteins but also the threonine-rich glycomacropeptide (GMP). In the current study, an experimental formula based on acid whey without GMP and a formula based on sweet whey with GMP (threonine content 17.2% higher than in the experimental formula) but otherwise with identical composition were tested with particular respect to threonine metabolism.

METHODS

Fourteen preterm infants appropriate for gestational age were enrolled in this randomized cross-over study. After a feeding period of at least 7 days, the nutrition of each infant was switched to the other formula for the second feeding period. At the end of each feeding period, the concentrations of creatinine and amino acids in the plasma and in the urine were measured.

RESULTS

In the plasma, the threonine concentration was significantly lower in the group fed the experimental GMP-free formula than in the group fed the sweet whey formula (P < 0.001). Renal excretion of all essential amino acids was generally very low and less than 2% of the intake, indicating that the kidneys had no marked homeostatic function with respect to plasma amino acid. The plasma concentrations of the threonine metabolites glycine and serine, and that of urea were not influenced by diet.

CONCLUSION

Feeding a whey protein-predominant bovine milk produced from acid whey protein reduces significantly the hyperthreoninemia commonly found in formula-fed preterm infants. Thus, acid whey formulas should be recommended for feeding preterm infants.