Effect of prenatal protein deprivation on postnatal granule cell generation in the hippocampal dentate gyrus

Neurogenesis and pesticides: news of no new neurons

New hippocampal neurons are continuously generated in the adult human brain. Several studies have demonstrated that the proliferation of hippocampal cells is strongly influenced by a variety of stimuli, including pesticides exposure. These effects are particularly important because neurogenesis dysregulation could be associated with the decline of neuronal and cognitive functions and the possible development of neuropsychiatric disorders.

The enduring effect of prenatal protein malnutrition on brain anatomy, physiology and behavior

There is increasing evidence that the maternal environment exerts enduring influences on the fetal brain. In response to certain environmental stimuli such as reduced protein content, the fetus changes the course of its brain development, which leads to specific and programed changes in brain anatomy and physiology. These alterations produce a brain with a fundamentally altered organization, which then translates to alterations in adult cognitive function. The effects on brain and behavior may be linked, such that a prenatal stimulus relays a signal to alter brain development and encourage the selection and development of brain circuits and behaviors that would be beneficial for the environment in which the animal was anticipated to emerge. At the same time, the signal would deselect behaviors unlikely to be adaptive. We draw on evidence from rodent models to suggest that the brain that develops after a reduction in protein during the prenatal phase is not uniformly dysfunctional, but simply different. This perspective has implications for the role of prenatal factors in the production and expression of behavior, and may account for the elevation of risk factors for neurological and psychiatric illnesses.

Rotated nursing environment with underfeeding: A form of early-life adversity with sex- and age-dependent effects on coping behavior and hippocampal neurogenesis

We investigated how a unique form of early-life adversity (ELA), caused by rotated nursing environment to induce underfeeding, alters anxiety-like and stress-coping behaviors in male and female Sprague Dawley rats in adolescence and adulthood. Adult female rats underwent either thelectomy (thel; surgical removal of teats), sham surgery, or no surgery (control) before mating. Following parturition, litters were rotated between sham and thel rats every 12 h to generate a group of rats that experienced ELA (rotated housing, rotated mother, and 50% food restriction) from postnatal day 0 to 26. Control litters remained with their natal, nursing dams. Regardless of age and sex, ELA reduced activity in the periphery of the open field. ELA increased immobility in the forced swim test, particularly in adults. We used doublecortin immunohistochemistry to identify immature neurons in the hippocampus. ELA increased the number and density of immature neurons in the dentate gyrus of adolescent males (but not females) and reduced the density of immature neurons in adult males (but not females). This research indicates that a unique form of ELA alters stress-related passive coping and hippocampal neurogenesis in an age- and sex-dependent manner.

Role of astaxanthin in the modulation of brain-derived neurotrophic factor and spatial learning behavior in perinatally undernourished Wistar rats

Objective: Maternal health and nutrition during the perinatal period is the predominant factor influencing the functional development of the brain. Maternal malnutrition during the perinatal period causes retardation of brain development. The current study investigates the role of Astaxanthin (AsX) in spatial learning and memory and BDNF in perinatally undernourished Wistar rats.Methods: The albino wistar rats were perinatally undernourished and administered with different dosages of AsX. The spatial learning and memory performance and BDNF level were assessed. Data were collected and analysed.Results: The % Correct choice during the acquisition phase, performance at the end of the acquisition phase and the mean BDNF level at the Hippocampus, Cerebellum, and Cerebral cortex showed significant decline (P<0.001) in the PUN group and significantly high (P<0.001) in the PUNA2 group compared to the control. However, the mean RME and mean WME during different days of the acquisition phase were significantly high (P<0.001) in the PUN group and insignificant (P>0.05) in PUNA2 compared to the control.Discussion: The results showed that AsX effectively modulated the cognitive deficit that occurred in perinatally undernourished rats. This can be attributed to BDNF upregulation as evidenced by the significant increase of the BDNF level.

Hippocampal mechanisms in impaired spatial learning and memory in male offspring of rats fed a low-protein isocaloric diet in pregnancy and/or lactation

Maternal nutritional challenges during fetal and neonatal development result in developmental programming of multiple offspring organ systems including brain maturation and function. A maternal low-protein diet during pregnancy and lactation impairs associative learning and motivation. We evaluated effects of a maternal low-protein diet during gestation and/or lactation on male offspring spatial learning and hippocampal neural structure. Control mothers (C) ate 20% casein and restricted mothers (R) 10% casein, providing four groups: CC, RR, CR, and RC (first letter pregnancy, second lactation diet). We evaluated the behavior of young adult male offspring around postnatal day 110. Corticosterone and ACTH were measured. Males were tested for 2 days in the Morris water maze (MWM). Stratum lucidum mossy fiber (MF) area, total and spine type in basal dendrites of stratum oriens in the hippocampal CA3 field were measured. Corticosterone and ACTH were higher in RR vs. CC. In the MWM acquisition test CC offspring required two, RC three, and CR seven sessions to learn the maze. RR did not learn in eight trials. In a retention test 24 h later, RR, CR, and RC spent more time locating the platform and performed fewer target zone entries than CC. RR and RC offspring spent less time in the target zone than CC. MF area, total, and thin spines were lower in RR, CR, and RC than CC. Mushroom spines were lower in RR and RC than CC. Stubby spines were higher in RR, CR, and RC than CC. We conclude that maternal low-protein diet impairs spatial acquisition and memory retention in male offspring, and that alterations in hippocampal presynaptic (MF), postsynaptic (spines) elements and higher glucocorticoid levels are potential mechanisms to explain these learning and memory deficits.

Early malnutrition results in long-lasting impairments in pattern-separation for overlapping novel object and novel location memories and reduced hippocampal neurogenesis

Numerous epidemiological studies indicate that malnutrition during in utero development and/or childhood induces long-lasting learning disabilities and enhanced susceptibility to develop psychiatric disorders. However, animal studies aimed to address this question have yielded inconsistent results due to the use of learning tasks involving negative or positive reinforces that interfere with the enduring changes in emotional reactivity and motivation produced by in utero and neonatal malnutrition. Consequently, the mechanisms underlying the learning deficits associated with malnutrition in early life remain unknown. Here we implemented a behavioural paradigm based on the combination of the novel object recognition and the novel object location tasks to define the impact of early protein-restriction on the behavioural, cellular and molecular basis of memory processing. Adult rats born to dams fed a low-protein diet during pregnancy and lactation, exhibited impaired encoding and consolidation of memory resulting from impaired pattern separation. This learning deficit was associated with reduced production of newly born hippocampal neurons and down regulation of BDNF gene expression. These data sustain the existence of a causal relationship between early malnutrition and impaired learning in adulthood and show that decreased adult neurogenesis is associated to the cognitive deficits induced by childhood exposure to poor nutrition.

Mechanisms and correlates of a healthy brain: a commentary

In this monograph, the message is that early inactivity and obesity lead to later chronic disease, and, as such, physical inactivity should be recognized as a public health crisis. Sedentary behavior, to some extent, serves a purpose in our current culture (e.g., keeping children indoors keeps them safe), and, as such, may not be amenable to change. Thus, it is important that we understand the underpinnings of later-developing chronic disease as this complex public health issue may have roots that go deeper than sedentary behavior. In this commentary, I speculate on the mechanisms for physical activity exacting positive changes on cognitive abilities. Three potential mechanisms are discussed: glucose transport, postnatal neurogenesis, and vitamin synthesis, all of which are inextricably linked to nutrition. This discussion of mechanisms is followed by a discussion of tractable correlates of the progression to non-communicable disease in the adult.

Prenatal protein level impacts homing behavior in Long-Evans rat pups

OBJECTIVE

This study assessed the effect of varying prenatal protein levels on the development of homing behavior in rat pups.

METHODS

Long-Evans rats were fed one of the four isocaloric diets containing 6% (n = 7 litters), 12% (n = 9), 18% (n = 9), or 25% (n = 10) casein prior to mating and throughout pregnancy. At birth, litters were fostered to well-nourished control mothers fed a 25% casein diet during pregnancy, and an adequate protein diet (25% casein) was provided to weaning. On postnatal days 5, 7, 9, 11, and 13, homing behaviors, including activity levels, rate of successful returns to the nest quadrant and latencies to reach the nest over a 3-minute test period were recorded from two starting positions in the home cage. Adult body and brain weights were obtained at sacrifice (postnatal day 130 or 200).

RESULTS

Growth was impaired in pups whose mothers were fed a 6% or, to a lesser extent, a 12% casein diet relative to pups whose mothers were fed the 18 and 25% casein diets. The 6 and 12% prenatal protein levels resulted in lower activity levels, with the greatest reduction on postnatal day 13. However, only the 6% pups had reduced success and higher latencies in reaching the nest quadrant when compared with pups from the three other nutrition groups. Latency in reaching the nest quadrant was significantly and negatively associated with adult brain weight.

DISCUSSION

Home orientation is a sensitive measure of developmental deficits associated with variations in prenatal protein levels, including levels of protein deficiency that do not lead to overt growth failure.

Ecstasy exposure & gender: examining components of verbal memory functioning

OBJECTIVE

Studies have demonstrated verbal memory deficits associated with past year ecstasy use, although specific underlying components of these deficits are less understood. Further, prior research suggests potential gender differences in ecstasy-induced serotonergic changes. Therefore, the current study investigated whether gender moderated the relationship between ecstasy exposure and components of verbal memory after controlling for polydrug use and confounding variables.

METHOD

Data were collected from 65 polydrug users with a wide range of ecstasy exposure (ages 18-35; 48 ecstasy and 17 marijuana users; 0-2310 ecstasy tablets). Participants completed a verbal learning and memory task, psychological questionnaires, and a drug use interview.

RESULTS

Increased past year ecstasy exposure predicted poorer short and long delayed free and cued recalls, retention, and recall discrimination. Male ecstasy users were more susceptible to dose-dependent deficits in retention than female users.

CONCLUSION

Past year ecstasy consumption was associated with verbal memory retrieval, retention, and discrimination deficits in a dose-dependent manner in a sample of healthy young adult polydrug users. Male ecstasy users were at particular risk for deficits in retention following a long delay. Gender difference may be reflective of different patterns of polydrug use as well as increased hippocampal sensitivity. Future research examining neuronal correlates of verbal memory deficits in ecstasy users are needed.

Early undernutrition decreases the number of neurons in the locus coeruleus of rats

The effects of perinatal undernutrition on the number of neurons and apoptotic cells of the locus coeruleus (LC) of female and male rats at postpartum days 7, 12, 20, 30 and 60 were studied. Undernutrition reduces the number of neurons in both sexes without affecting cell death, as indicated by the ratio of apoptotic cells to neurons. The data suggest that in the undernourished groups lower rates of neurogenesis and proliferation (neurogenetic/proliferation rates) might avoid these animals achieving the number of LC neurons as in the control subjects. Although food restriction in both sexes apparently provokes the loss of cells, the effect does not appear to be equal in females and males, as shown by post weaning food rehabilitation. The results suggest that severe food deprivation may interfere with the ontogenetic processes underlying neuronal differentiation of the LC. Morphological damage in the LC due to undernutrition might alter the physiology of sexual and/or feeding behaviours in which this structure is implicated.

NADPH-diaphorase Histochemical Labeling Patterns in the Hippocampal Neuropil and Visual Cortical Neurons in Weaned Rats Reared during Lactation on Different Litter Sizes

Tissue distribution of nitric oxide-synthases was investigated in the rat hippocampus and visual cortex under nutritional changes induced by modification of the litter size. Young (30-45-days-old) rats, suckled in litters formed by 3,6 or 12 pups (called small, medium and large litters, respectively), were studied by using nicotine-adenine-dinucleotide phosphate-diaphorase histochemistry (shortly, diaphorase), a simple and robust procedure to characterize tissue distribution of nitric oxide-synthases. We assessed morphometric features of the diaphorase-positive cells in visual cortex, and the neuropil histochemical activity in hippocampal CA1 and dentate gyrus using densitometry analysis. In the large-litter group, the labeled-cell density in white matter of area 17 was higher, as compared to the small-litter group. There was a clear trend, in the large-litter group, to lower values of soma area, dendritic field and branches per neuron, but the differences were not significant. Densitometry analysis of hippocampus revealed a significant increase in the relative neuropil histochemical activity of the dentate gyrus molecular layer in the larger litters, which may be associated to increased compensatory blood flow in the hippocampus. The pathophysiological mechanisms of the observed changes remain to be investigated.

The role of nutrition in children's neurocognitive development, from pregnancy through childhood

This review examines the current evidence for a possible connection between nutritional intake (including micronutrients and whole diet) and neurocognitive development in childhood. Earlier studies which have investigated the association between nutrition and cognitive development have focused on individual micronutrients, including omega-3 fatty acids, vitamin B12, folic acid, choline, iron, iodine, and zinc, and single aspects of diet. The research evidence from observational studies suggests that micronutrients may play an important role in the cognitive development of children. However, the results of intervention trials utilizing single micronutrients are inconclusive. More generally, there is evidence that malnutrition can impair cognitive development, whilst breastfeeding appears to be beneficial for cognition. Eating breakfast is also beneficial for cognition. In contrast, there is currently inconclusive evidence regarding the association between obesity and cognition. Since individuals consume combinations of foods, more recently researchers have become interested in the cognitive impact of diet as a composite measure. Only a few studies to date have investigated the associations between dietary patterns and cognitive development. In future research, more well designed intervention trials are needed, with special consideration given to the interactive effects of nutrients.

Enhanced deficits in long-term potentiation in the adult dentate gyrus with 2nd trimester ethanol consumption

Ethanol exposure during pregnancy can cause structural and functional changes in the brain that can impair cognitive capacity. The hippocampal formation, an area of the brain strongly linked with learning and memory, is particularly vulnerable to the teratogenic effects of ethanol. In the present experiments we sought to determine if the functional effects of developmental ethanol exposure could be linked to ethanol exposure during any single trimester-equivalent. Ethanol exposure during the 1^st or 3^rd trimester-equivalent produced only minor changes in synaptic plasticity in adult offspring. In contrast, ethanol exposure during the 2^nd trimester equivalent resulted in a pronounced decrease in long-term potentiation, indicating that the timing of exposure influences the severity of the deficit. Together, the results from these experiments demonstrate long-lasting alterations in synaptic plasticity as the result of developmental ethanol exposure and dependent on the timing of exposure. Furthermore, these results allude to neural circuit malfunction within the hippocampal formation, perhaps relating to the learning and memory deficits observed in individuals with fetal alcohol spectrum disorders.

Malnutrition and brain development: an analysis of the effects of inadequate diet during different stages of life in rat

Protein malnutrition or undernutrition can result in abnormal development of the brain. Depending on type, age at onset and duration, different structural and functional deficits can be observed. In the present review, we discuss the neuroanatomical, behavioral, neurochemical and oxidative status changes associated with protein malnutrition or undernutrition at different ages during prenatal and immediately postnatal periods as well as in adult rat. Analysis of all data suggests that protein malnutrition as well as undernutrition induced impaired learning and retention when imposed during the immediately postnatal period and in adulthood, whereas hyperactivity including increased impulsiveness and greater reactivity to aversive stimuli occurred when malnutrition or undernutrition was imposed either pre or postnatally. This general state of hyperreactivity may be linked essentially to an alteration in dopaminergic system. Hence, the present review shows that in spite of the attention devoted in the literature to prenatal effects, cognitive deficits are more serious following malnutrition or undernutrition after birth. We thus clearly establish a special vulnerability to malnutrition after weaning in rats.

Effects of intra-uterine and early extra-uterine malnutrition on seizure threshold and hippocampal morphometry of pup rats

We evaluate the influence of different malnutrition paradigms (intra-uterine × extra-uterine) in body and brain weight, in seizure threshold and in hippocampus morphometry, in developing rats. Intra-uterine malnutrition model consisted in reduction by half of the ration offered to pregnant female; extra-uterine malnutrition consisted of progressive limitation of lactation, from P2 to P15. Seizure induction was accomplished by exposure to flurothyl, at P15. At the same day animals were sacrificed. Morphometric analysis was based on hippocampal pyramidal and granular cells estimate number, through volume calculation and cellular density. Extra-uterine malnutrition significantly reduced pups body and brain weight, seizure threshold and neuronal number in CA4 region only. Intra-uterine malnutrition reduced neuronal number in CA2, CA4 and DG regions regarding well-nourished and extra-uterine malnourished animals. In CA3, CA4 and dentate gyrus, a significant cell increase was observed in groups exposed to seizures, regarding similar control groups.

Nutrition and neurodevelopment: mechanisms of developmental dysfunction and disease in later life

Nutrition plays a central role in linking the fields of developmental neurobiology and cognitive neuroscience. It has a profound impact on the development of brain structure and function and malnutrition can result in developmental dysfunction and disease in later life. A number of diseases, including schizophrenia, may be related to neurodevelopmental insults such as malnutrition, hypoxia, viruses or in utero drug exposure. Some of the most significant findings on nutrition and neurodevelopment during the last three decades, and especially during the last few years, are discussed in this review. Attention is focused on the underlying cellular and molecular mechanisms by which diet exerts its effects. Randomized intervention studies have revealed important effects of early nutrition on later cognitive development, and recent epidemiological findings show that both genetics and environment are risk factors for schizophrenia. Particularly important is the effect of early nutrition on development of the hippocampus, a brain structure important in establishing learning and memory, and hence for cognitive performance. A major aim of future research should be to elucidate the molecular mechanisms underlying nutritionally-induced impairment of neurodevelopment and specifically to determine the mechanisms by which early nutritional experience affects later cognitive performance. Key research objectives should include: (1) increased understanding of mechanisms underlying the normal processes of ageing and neurodegenerative disorders; (2) assessment of the role of susceptibility genes in modulating the effects of early nutrition on neurodevelopment; and (3) development of nutritional and pharmaceutical strategies for preventing and/or ameliorating the adverse effects of early malnutrition on long-term programming.

Development of mitral cells and olfactory bulb layers in neonatally undernourished rats

Cell alterations in the central nervous system are consistent consequences of early undernourishment. Because little is known about the effects of neonatal udernourishment upon the main olfactory bulb (OB) in Golgi-Cox stained material, we evaluated the total OB cross-sectional area, the area of individual OB layers, and the area of type II mitral cells perikarya and their dendritic processes in undernourished Wistar rats of 7, 14, and 21 days of age. Data showed that neonatal undernourishment reduced both the OB and the individual layers areas; minimal perikarya effects and significant reductions in the number and extension of MC dendrites. Although macroneurons are formed prenatally, neonatal undernourishment at critical periods may have long-lasting effects that interfere with the functional maturity of the OB. These findings may have relevant consequences for early odor discrimination of the offspring, since olfaction is a fundamental sensorial avenue for newborn adaptive responses and maternal care.

Adult hippocampal neurogenesis and sudden unexpected death in epilepsy: reality or just an attractive history?

Neurogenesis persists throughout life in the adult mammalian dentate gyrus and is regulated by several environmental, physiological, and molecular factors. Seizure activity also influences dentate granule cell neurogenesis. In these lines, studies of neurogenesis have demonstrated the presence of hilar-ectopic dentate granule cells after status epilepticus induced experimentally and that these cells are migrate aberrantly, abnormally integrated and hyperexcitable, contributing with this to seizure generation and/or propagation. As we know, epilepsy is the most common serious neurological condition and sudden unexpected death in epilepsy (SUDEP) is the most important direct epilepsy-related cause of death. Information concerning risk factors for SUDEP is conflicting, but high seizure frequency is a potential risk factor. Additionally, potential pathomechanisms for SUDEP are unknown, but it is very probable that cardiac arrhythmias during and between seizures or transmission of epileptic activity to the heart via the autonomic nervous system potentially play a role. Based on these facts, in this paper we postulate that aberrant neurogenesis could influence negatively the cardiovascular system of the patient with epilepsy leading to cardiac abnormalities and hence SUDEP.

Exercise and food ad libitum reduce the impact of early in life nutritional inbalances on nitrergic activity of hippocampus and striatum

Nutritional imbalances were produced by varying litter size pups per dam: 3 (small), 6 (medium), and 12 (large). On the 21st day, 4 subjects of each litter, were sacrificed and the remaining were grouped, 2 per cage, with or without running wheels, with food and water ad libitum. Adult subjects were tested in water maze, their brains processed for NADPH-diaphorase histochemistry and quantified by densitometry. No differences were detected in water maze. At 21st day, S and L compared with M presented reduced NADPH-d in the stratum molecular of dentate gyrus (DG), stratum lacunosum of CA1 and in all CA3 layers but not in the striatum. On the 58th day, actvity remained low in S and L in CA3 and striatum and L in CA1 and DG. Voluntary exercise increased NADPH-d in DG, CA1, CA3, and striatum in S, and in the stratum lacunosum of CA1 and CA3 in L.

Protein malnutrition differentially alters the number of glutamic acid decarboxylase-67 interneurons in dentate gyrus and CA1–3 subfields of the dorsal hippocampus

In 30- and 90-day-old rats, using immunohistochemistry for glutamic acid decarboxylase 67 (GAD-67), we have tested whether malnutrition during different periods of hippocampal development produces deleterious effects on the population of GABA neurons in the dentate gyrus (DG) and cornu Ammonis (CA1-3) of the dorsal hippocampus. Animals were under one of four nutritional conditions: well-nourished controls (Con), prenatal protein malnourished (PreM), postnatal protein malnourished (PostM), and chronic protein malnourished (ChroM). We found that the number of GAD-67-positive (GAD-67+) interneurons was higher in the DG than in the CA1-3 areas of both Con and malnourished groups. Regarding the DG, the number of GAD-67+ interneurons was increased in PreM and PostM and decreased in ChroM at 30 days. At 90 days of age the number of GAD-67+ interneurons was increased in PostM and ChroM and remained unchanged in PreM. With respect to CA1-3, the number of labeled interneurons was decreased in PostM and ChroM at 30 days of age, but no change was found in PreM. At 90 days no changes in the number of these interneurons were found in any of the groups. These observations suggest that 1) the cell death program starting point is delayed in DG GAD-67+ interneurons, and 2) protein malnutrition differentially affects GAD-67+ interneuron development throughout the dorsal hippocampus. Thus, these changes in the number of GAD-67+ interneurons may partly explain the alterations in modulation of dentate granule cell excitability, as well as in the emotional, motivational, and memory disturbances commonly observed in malnourished rats.

Maternal nutrition and four-alternative choice

Two groups of 10 male rats were trained to nose poke for food pellets at four alternatives that provided differing rates of pellet delivery on aperiodic schedules. After a fixed number of pellets had been delivered, 5, 10 or 20 in different conditions of the experiment, a 10-s blackout occurred, and the locations of the differing rates of pellet delivery were randomized for the next component. Two groups of rats were used: The AD group consisted of 10 rats born to dams that had normal (ad libitum) nutrition during pregnancy, whereas the 10 rats in the UN group were from dams exposed to reduced food availability during pregnancy. All pups received normal nutrition after birth. Choice between the nose-poke alternatives quickly adapted when the rates of pellet delivery were changed in both groups, but there were no consistent differences in the speed of adaptation between the two groups. The generalized matching relation failed to describe the allocation of responses among alternatives, but the contingency-discriminability model provided a precise description of performance.

Global undernutrition during gestation influences learning during adult life

Intrauterine growth restriction can lead to significant long-term health consequences such as metabolic and cardiovascular disorders, but less is known about its effects on choice and behavioral adaptation in later life. Virgin Wistar rats were time mated and randomly assigned to receive either ad-libitum access to chow or 30% of that level of nutrition during pregnancy to generate growth-restricted offspring. At 60 days of age, 6 female offspring from each group were trained on concurrent variable-interval schedules. Sessions consisted of seven randomly arranged concurrent-schedule components, each with a different reinforcer ratio that varied from 27:1 to 1:27, and each component lasting for 10 reinforcer deliveries. Behavioral change across reinforcers in components, measured by sensitivity to reinforcement, was consistently lower for offspring of undernourished mothers, showing that their behavior was less adaptable to environmental change. These results provide direct experimental evidence for a link between prenatal environmental conditions and reduced behavioral adaptability--learning--in later life.

Organization of olfactory glomeruli in neonatally undernourished rats

Newborn rats maintain mother-litter bonds by using olfactory signals. At birth, units in the olfactory glomeruli (OG) are immature and vulnerable to noxious epigenetic factors like undernutrition. Because little is known about the effects of neonatal undernutrition upon the OG morphological organization, different OG parameters were studied in undernourished Wistar rats at 7, 14 and 21 days of age. The issue was addressed by analyzing the olfactory bulb (OB) cross sectional area, the total number and area of OGs in the OB coronal sections, and the distribution of OG area in dorsal and ventral quadrants. Reductions in the OB and OG cross sectional areas were detected at 7 and 14 days posnatally. OG area comparisons by OB quadrants were reduced along the study in quadrants, with larger effects in medial than in lateral OB quadrants. Current OG cytoarchitectonic modifications may affect the newborn capabilities for odour discrimination by disrupting early mother-litter interactions.

Alterations in cognitive function in prepubertal mice with protein malnutrition: Relationship to changes in choline acetyltransferase

We have found that protein malnutrition (PM) causes a significant impairment of memory-related behavior on the 15th and 20th day after the start of PM (5% casein) feeding in prepubertal mice but not in postpubertal mice, as measured by a passive-avoidance task. This impairment was almost completely reversed by merely switching to a standard protein (20% casein) diet on the 10th day after the start of PM. However, the reversal was not observed when the switching to a standard protein regimen was done on the 15th day of the PM diet. Interestingly, the impairment of memory-related behavior on the 20th day was improved by the chronic administration of physostigmine (0.1 mg/kg/day x last 10 days, i.p.), a cholinesterase inhibitor. To correlate brain cholinergic neuron function with the memory-related behavior impairment induced by PM, microphotometry was used to determine the histological distribution of the imunofluorescence intensity for choline acetyltransferase (ChAT), a functional marker of presynapse in cholinergic neurons. The change in the intensity of fluorescence indicated that ChAT protein was decreased in the hippocampus (CA1, CA3 and dentate gyrus) on the 20th day after PM feeding in comparison with controls. These results suggest the possibility that the memory-related behavior deficits observed in prepubertal mice with PM are caused by a dysfunction of the cholinergic neurons in the hippocampus.

Effects of postweaning undernutrition on exploratory behavior, memory and sensory reactivity in rats: implication of the dopaminergic system

The effects of early undernutrition on behavior and brain biochemistry were examined in rats. At weaning, rats were provided either an ad lib diet (control group) or maintained at 80% of the weight of their control littermates (undernourished group). Three weeks into the diet they were tested in an open field. After 6 weeks of diet, HPLC analyses were conducted on sample brains from each group to assess levels of dopamine and metabolites, respectively dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the striatum. At seven weeks of diet, remaining rats were trained in an 8-arm radial maze, and a retention test conducted 72 h after attaining the learning criterion. At fourteen weeks of diet, sensory reactivity was measured by tail-immersion in a water bath maintained at constant temperature 50 +/- 1 degrees C. Undernourished rats exhibited hyperactivity and increased exploratory behavior in the open field, as well as increased sensory reactivity in the tail flick test. In the radial maze, however, undernourished rats did not differ from controls in either learning or retention. Haloperidol (i. p. injection) impaired retention by control but not undernourished animals. HPLC analyses showed an increase in dopamine turnover in the striatum of undernourished rats. Our results suggest that, unlike its effects when induced immediately at birth or in adulthood, undernutrition at weaning does not appear to influence learning and retention but induced an hyperactivity and alterations in striatal DA turnover which was associated with a decrease in responsiveness to i. p. haloperidol injection.

Neurogênese e depressão: etiologia ou nova ilusão?

Novos neurônios continuam sendo gerados no cérebro adulto de diversas espécies animais. Muitos estudos têm demonstrado que diversos fatores ambientais, inclusive o estresse, influenciam a proliferação de células hipocampais. Nesse sentido, a diminuição da neurogênese induzida pelo estresse parece ser um importante fator na etiologia da depressão. Nessa revisão, a relação entre neurogênese e depressão é enfatizada.

Susceptibility to seizure-induced injury and acquired microencephaly following intraventricular injection of saporin-conjugated 192 IgG in developing rat brain

To study the role of neurotrophin-responsive neurons in brain growth and developmental resistance to seizure-induced injury, we infused saporin-conjugated 192-IgG (192 IgG-saporin), a monoclonal antibody directed at the P75 neurotrophin receptors (p75(NTR)), into the ventricles of postnatal day 8 (P8) rat pups. 7-10 days after immunotoxin treatment, loss of p75(NTR) immunoreactivity was associated with depletion of basal forebrain cholinergic projection to the neocortex and hippocampus. Kainic acid (KA)-induced seizures on P15 resulted in hippocampal neuronal injury in the majority of toxin-treated animals (13/16), but only rarely in saline-injected controls (2/25) (P < 0.001). In addition, widespread cerebral atrophy and a significant decrease in brain weight with preserved body weight were observed. Volumetric analysis of the hippocampal hilar region revealed a 2-fold reduction in perikaryal size and a 1.7-fold increase in cell packing density after 192 IgG-saporin injection. These observations indicate that neurotrophin-responsive neurons including basal forebrain magnocellular cholinergic neurons may be critical for normal brain growth and play a protective role in preventing excitotoxic neuronal injury during development.

The mossy fiber system of the hippocampal formation is decreased by chronic and postnatal but not by prenatal protein malnutrition in rats

We tested in 70-day-old Sprague-Dawley rats, whether malnutrition imposed during different periods of hippocampal development produced deleterious effects on the total reference volume of the mossy fiber system. Animals were treated under four nutritional conditions: (a) well nourished; (b) prenatal protein malnourished; (c) chronic protein malnourished and (d) postnatal protein malnourished. Timm's stained material was used in coronal hippocampal sections (40 microm) to estimate--using the Principle of Cavalieri--the total reference volume of the mossy fiber system in each experimental group. Our results show that chronic and postnatal protein malnourished, but not prenatal malnourished rats, decrease the mossy fiber system and the total reference volume of the mossy fiber system are selectively vulnerable to the type of dietary restriction. Thus, chronic and posnatal protein malnutrition produce deleterious effects, but only rats under prenatal protein malnutrition were able to reorganize synapses in this plexus. These findings raise the possibility that chronic malnutrition, as a long-term stressful factor, might be an important paradigm to test structural hippocampal changes that produce physiological and pathophysiological effects, or the possibility to recover its function for nutritional rehabilitation.

Gestational and postnatal malnutrition affects sensitivity of young rats to picrotoxin and quinolinic acid and uptake of GABA by cortical and hippocampal slices

It is widely known that a complex interaction between excitatory and inhibitory systems is required to support the adequate functioning of the brain and that significant alterations induced by early protein restriction are complex, involving many systems. Based on such assumptions, we investigated the effects of maternal protein restriction during pregnancy and lactation followed by offspring protein restriction on some GABAergic and glutamatergic parameters, which mediate inhibitory and excitatory transmission, respectively. The sensitivity of young malnourished rats to convulsant actions of the GABA(A) receptor antagonist picrotoxin (PCT; s.c.) and to N-methyl-d-aspartate (NMDA) receptor agonist quinolinic acid (QA; i.c.v) and also gamma-amino-n-butyric acid (GABA) and glutamate uptake by cortical and hippocampal slices were evaluated in P25 old rats. Early protein malnutrition induced higher sensitivity to picrotoxin, which could be associated with the observed higher GABA uptake by cortical, and hippocampal slices in malnourished rats. In contrast, we observed lower sensitivity to quinolinic acid in spite of unaltered glutamate uptake by the same cerebral structures. Picrotoxin enhanced GABA uptake in hippocampus in well- and malnourished rats; however, it did not affect cortical GABA uptake. Our data corroborate our previous report, showing that malnutrition depresses the glutamatergic activity, and point to altered modulation of GABAergic neurotransmission. Such findings allow us to speculate that malnutrition may affect the excitatory and inhibitory interaction.

Effect of food deprivation during early development on cognition and neurogenesis in the rat

Food deprivation has been recognized as having pronounced beneficial effects in adult animals, increasing longevity, reducing seizure susceptibility, and enhancing resistance to neurotoxins. It is not known whether food deprivation in developing animals is neuroprotective or harmful. To evaluate the effects of food deprivation on brain development, we evaluated visual-spatial learning and memory and neurogenesis in the dentate gyrus of the hippocampus in food-deprived (FD) and well-fed (WF) rats. To induce food deprivation, pups were removed from their dams for 12 hours per day from Postnatal Day (P) 2 to P19. FD and WF rat pups were then subjected to status epilepticus (SE) induced by lithium-pilocarpine at P20. After SE, neurogenesis was measured, while in another group of P38 rats, learning and memory were evaluated using the Morris water maze. Food deprivation was found to reduce neurogenesis when assessed after the period of food deprivation. Although SE reduced neurogenesis in the WF animals, it had little effect additional to food deprivation on neurogenesis in the FD rats. Compared with the WF group, FD rats had a mild impairment in memory in the water maze testing after SE. Our study demonstrates that food deprivation during the neonatal period in rats is associated with a decrease in neurogenesis and mild impairment of visual-spatial memory. Although SE decreased neurogenesis in the WF group, in FD animals, SE did not reduce neurogenesis more than what was seen with food deprivation alone. Our results suggest that although food deprivation during early development reduces dentate gyrus neurogenesis, the reduced neurogenesis is not a major factor in cognitive impairment after SE in FD rats.

Effects of prenatal protein malnutrition and acute postnatal stress on granule cell genesis in the fascia dentata of neonatal and juvenile rats

Although postnatal genesis of granule cells in the hippocampal fascia dentata is known to be influenced by prenatal protein deprivation or by stress, the combined effects of prenatal protein malnutrition and stress on these cells are unknown. This study was designed to examine this combined effect. Well-nourished and prenatally malnourished pups on postnatal day 7 (P7) were stressed by maternal separation and reduction of body temperature and on postnatal day 30 (P30) by immobilization with restraint. Bromodeoxyuridine (BrDU) was injected at the time of stress, and 2 h later, the numbers of immunolabeled cells were quantified by standard stereological techniques. In comparison to controls, prenatally malnourished rats showed a significantly lower number of cells tagged in the fascia dentata on P7 (p < or =0.05), and a significantly higher number of cells (p < or =0.05) on P30. In both age groups, control rats exposed to acute stress showed a significantly decreased number of cells tagged in the fascia dentata (p < or =0.05). In contrast, neurogenesis in malnourished rats was not significantly affected by acute stress at either age. Thus, the pattern of neurogenesis in the fascia dentata and its response to stress has been fundamentally altered by prenatal protein deprivation.

A paradigm of undernourishing and neonatal rehabilitation in the newborn rat

Perinatal undernutrition as a deficiency of nutrient availability, affects body and brain developmental processes and promotes recurrent health problems. Thus, altered mother-litter bonds and deficient environmental interactions may interfere with the brain pluripotential capabilities of the newborn. To gather information concerning the mechanisms underlying perinatal undernutrition we designed a paradigm of undernutrition and neonatal rehabilitation in the rat. An underfed group came from pregnant Wistar rats fed with 50% of the diet from G6 to G12 and with 60% from G13 until G21. After birth, pups were daily undernourished during 12 h daily by rotating a pair of lactating well-nourished dams which had one of their nipples subcutaneously ligated. The rehabilitated animals were undernourished pups neonatally fed by a pair of normally lactating dams. Controls received plenty of food during the pre- and neonatal periods. Pups were sacrificed at 12, 20 and 30 days of age. Perinatal underfeeding significantly reduced body and brain weights and neuronal morphometric parameters. Normal neonatal feeding in the newborn ameliorated the damages associated to food deprivation. The current undernourishing paradigm may be helpful to assess brain development alterations, as well as to study the compensatory mechanisms associated to salutary epigenetic influences.

Increased density of hippocampal kainate receptors but normal density of NMDA and AMPA receptors in a rat model of prenatal protein malnutrition

The postnatal development of excitatory amino acid receptor types including kainate, N-methyl-D-aspartate (NMDA), and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) was assessed in the hippocampus, entorhinal cortex, and adjacent neocortex in normal and prenatally protein malnourished rats ages 15, 30, 90, and 220 postnatal days by quantitative autoradiography. Tritiated ligands used to measure binding site density were (3)[H]kainate, (3)[H]MK-801, and (3)[H]AMPA, respectively. Kainate receptors showed statistically significant increases in binding density in stratum lucidum of CA3 (hippocampal mossy fiber zone) in 90- and 220-day-old malnourished rats compared with age- and sex-matched controls but not in 15- or 30-day-old malnourished rats. Compared with previous anatomic studies, these results are mostly in agreement with a significantly decreased hippocampal mossy fiber plexus in 15-, 90-, and 220-day-old rats but not in 30-day-old rats. These results suggested that the increased density of postsynaptic kainate receptors located mainly on proximal apical dendrites of CA3 pyramidal cells may be compensatory to decreased glutamate release due to the reduction in mossy fiber plexus. In contrast, the density of putative NMDA and AMPA receptors quantified in prenatally malnourished rats was comparable to the density quantified in age- and sex-matched control rats, as were all three receptor types in entorhinal cortex and adjacent neocortex. Thus, the selectivity of the compensation of (3)[H]kainate-labeled mossy fiber plexus in adult but not in early postnatal developing malnourished rats may help ensure continued breeding and survival of the species under otherwise adverse environmental conditions.

Birthdates and number of neurons in the serotonergic raphe nuclei in the rat with prenatal protein malnutrition

The effect of prenatal protein deprivation on timing of neurogenesis and on number of neurons generated in the serotonergic dorsal (DR) and median raphe (MR) nuclei of the rat was studied. These neurons are of interest because their neurogenesis occurs during the period of malnutrition and their axonal projections participate in the earliest stages of brain development. In this study, dams were maintained on a 25% casein diet or a 6% casein diet 5 weeks prior to mating and throughout pregnancy. At birth, all pups were cross-fostered to dams on a 25% casein diet. Bromodeoxyuridine, a thymidine analog that is incorporated into nuclear deoxyribonucleic acid during the cell cycle synthetic phase, was used as a marker of neurogenesis. Bromodeoxyuridine was administered on either embryonic day 11, 12, 13 or 14. On postnatal day 30, serial sections of raphe nuclei were processed with bromodeoxyuridine immunocytochemistry to determine the number of raphe cells generated on each day and with Nissl stain to determine the total number of cells generated. There were no significant differences between the two diet groups in timing of generation or in total number of cells generated, indicating that neurogenesis of these early generated neurons appears unaffected by concomitant protein deprivation.

Neonatal nutritional rehabilitation of morphological features in facial motoneurons altered by prenatally food deprivation in the rat

Undernutrition alters facial motoneurons development. Here, we evaluated the plastic characteristics of facial motoneurons in response to neonatal rehabilitation. Prenatally undernourished rat pups derived from pregnant rats fed with 50% of the diet from gestational days G6 to G12, and with 60% of food from G13 to G21 and rehabilitated after birth by a pair of control lactating foster dams. Morphological features of 640 Golgi-Cox impregnated motoneurons from 12, 20 and 30 days old pups were analyzed. Neonatal food rehabilitation increased the number and extension of the dendritic branches (main neuronal reception area) without altering significantly soma measurements (main neuronal firing area), suggesting that food and sensory maternal disponibility after birth ameliorates the damage due to prenatal deprivation. Findings showed that neonatal rehabilitation in addition to intense maternal polysensorial stimuli from the foster mothers partially diminished the morphological alterations associated to prenatal undernutrition, and provide evidence of plastic properties of facial motoneurons to the influence of environmental cues.

Seizure-induced damage in the developing human: relevance of experimental models

A considerable amount of money and effort is spent every year investigating the effects of seizure on the developing rodent brain. A critical question is the relevance of these studies to children. The goal of this chapter is to review the relationship between seizures during early development and cognitive impairment in children and rodents. While the majority of children with epilepsy have normal cognitive development, a small group of children with frequent, recurrent seizures show progressive cognitive impairment. Likewise, in rodent models recurrent seizures during early development are associated with cognitive impairment and histological changes including mossy fiber sprouting and reduced neurogenesis. Status epilepticus is associated with a lower morbidity and mortality rate in children than in adults. Status epilepticus in rodent models is associated with less cell loss and cognitive impairment than in adults. While rodent studies can offer a great deal of insight into mechanisms of seizure-induced brain damage, they also have significant limitations. No animal models have yet been developed that mimic human epileptic syndromes, such as infantile spasms, Lennox-Gastaut syndrome, or the severe myoclonic epilepsies. In addition, rodent studies supply only crude measures of learning and memory. Disturbances of language or higher cortical functions such as visual or auditory processing cannot be tested in animal models.

Effects of prenatal protein malnutrition and neonatal stress on CNS responsiveness

Maturation of the nervous system and consequent behavior depends in part on prenatal nutritional factors and postnatal environmental stimulation. In particular, the hypothalamus and the hippocampus are two important CNS areas that are vulnerable to such pre- and postnatal manipulations. Therefore, the present study was undertaken to explore the effects of both prenatal protein malnutrition and neonatal isolation stress on hypothalamic and hippocampal functioning in infant rats. Specifically, we assessed the levels of plasma corticosterone, as well as dopamine, serotonin and their metabolites in both the hypothalamus and hippocampus in rat pups that had been prenatally malnourished (6% casein diet) and isolated from nest, dam, and siblings for 1 h daily during postnatal days (PND) 2 through 8. We found that on PND 9 malnourished pups weighed less, had smaller hypothalami and a suppressed corticosterone response to acute and chronic isolation stress. However, their dopamine metabolism in the hypothalamus was increased following acute isolation on PND 9 as seen in isolated controls. Prenatal protein malnutrition also resulted in a significant elevation in serotonin in both brain areas, increased 5HIAA in the hypothalamus, and decreased dopamine in the hippocampus. Repeated isolation caused a reduction in 5HIAA in both brain parts, but only in control pups. These pre- and postnatal challenges may each cause a specific pattern of modifications in the CNS and, in combination, may be additive, particularly in the hypothalamic-pituitary-adrenal (HPA) stress response and the serotonergic functioning in both the hypothalamus and hippocampus, a finding with important clinical implications.

Reduced neurogenesis after neonatal seizures

Although neonatal seizures are quite common, there is controversy regarding their consequences. Despite considerable evidence that seizures may cause less cell loss in young animals compared with mature animals, there are nonetheless clear indications that seizures may have other potentially deleterious effects. Because it is known that seizures in the mature brain can increase neurogenesis in the hippocampus, we studied the extent of neurogenesis in the granule cell layer of the dentate gyrus over multiple time points after a series of 25 flurothyl-induced seizures administered between postnatal day 0 (P0) and P4. Rats with neonatal seizures had a significant reduction in the number of the thymidine analog 5-bromo-2'-deoxyuridine-5'-monophosphate- (BrdU) labeled cells in the dentate gyrus and hilus compared with the control groups when the animals were killed either 36 hr or 2 weeks after the BrdU injections. The reduction in BrdU-labeled cells continued for 6 d after the last seizure. BrdU-labeled cells primarily colocalized with the neuronal marker neuron-specific nuclear protein and rarely colocalized with the glial cell marker glial fibrillary acidic protein, providing evidence that a very large percentage of the newly formed cells were neurons. Immature rats subjected to a single seizure did not differ from controls in number of BrdU-labeled cells. In comparison, adult rats undergoing a series of 25 flurothyl-induced seizures had a significant increase in neurogenesis compared with controls. This study indicates that, after recurrent seizures in the neonatal rat, there is a reduction in newly born granule cells.

Brain development and generation of brain pathologies

The timing of brain development is genetically programmed and can be profoundly altered by a number of abnormal genes that control proliferation, differentiation, migration, synapse formation, and elimination of cells and synapses. With advances in genetic techniques both the gene and gene product responsible for brain malformation are being identified which will permit a better understanding of the pathophysiology of brain malformations. In addition to genetic abnormalities, brain development can be influenced by a variety of acquired disorders. The type of brain abnormality is highly dependent on the stage of brain development during which the insult occurs. While our understanding of experience- or activity-dependent processes on brain development is limited, it is now clear that this activity can significantly alter the timing of a number of maturational events including receptor maturation and neurogenesis. The future challenge will be both to understand the biological basis of these processes and to use this information to enhance brain development.

Behavioral effects of protein deprivation and rehabilitation in adult rats: relevance to morphological alterations in the hippocampal formation

In the present study we have analyzed the behavioral and neuroanatomical effects of protein deprivation in adult rats. Starting at 2 months of age, animals were maintained on 8%-casein diet either for 8 months (malnourished group), or for 6 months followed by a 2-month period of nutritional rehabilitation (17%-protein diet, rehabilitated group). Malnourished rats exhibited reduced emotional reactivity and impaired habituation in the open field. In a water maze, these animals did not differ from controls during training, but showed retention deficits on the probe trial. However, working memory, sensorimotor abilities and passive avoidance behavior were not significantly impaired in malnourished rats. The performance of rehabilitated group was similar to that of the control group throughout behavioral testing. Postmortem morphological analysis revealed that the total number of neurons in the granular layer of the dentate gyrus, and in CA3 and CA1 hippocampal fields was reduced in protein-deprived and rehabilitated rats relative to controls. In addition, it was found that protein deprivation caused a 30% loss of synapses established between mossy fibers and dendrites of CA3 pyramidal cells, whereas nutritional rehabilitation resulted in a reversal of this effect. These results show that prolonged malnutrition in adult rats produces marked loss of hippocampal neurons and synapses accompanied by substantial impairments of hippocampal-dependent behaviors. The fact that nutritional rehabilitation results in restoration of the total number of hippocampal synapses and parallel amelioration of the behavioral impairments suggests that the mature CNS possesses a remarkable potential for structural and functional recovery from the damage induced by this type of dietary insult.

Prenatal protein malnutrition results in increased frequency of miniature inhibitory synaptic currents in rat CA1 pyramidal cells

There is growing evidence for an effect of prenatal protein malnutrition on the GABAergic neurotransmitter system in the rat hippocampus and associated structures. In the present study, we examined the functional electrophysiological consequences of observed alterations in GABA(A) and benzodiazepine receptor systems. Whole-cell patch clamp recordings of spontaneous and of miniature inhibitory postsynaptic currents (mIPSCs) generated by CA1 pyramidal cells were performed in in vitro hippocampal slices prepared from control and prenatally protein malnourished adult male rats. The characteristics of spontaneous synaptic currents were unaltered by the prenatal insult, as were the amplitudes and kinetics of GABA(A) receptor-mediated mIPSCs. The frequency of mIPSCs, however, was significantly increased in CA1 pyramidal cells in slices prepared from prenatally malnourished vs. control rats. The effect of the benzodiazepine receptor agonist chlordiazepoxide on the characteristics of mIPSCs was also examined and found to be the same in cells from both nutritional groups. The increased frequency of mIPSCs together with the lack of a change in amplitude, kinetics, or modulation by benzodiazepines of mIPSCs in response to prenatal protein malnutrition indicate a presynaptic locus of effect of this insult.

Effects of prenatal protein malnutrition on mossy fibers of the hippocampal formation in rats of four age groups

The present study was undertaken to investigate the effect of prenatal protein deprivation on the postnatal development of the mossy fiber plexus of the hippocampal formation on postnatal (P) days 15, 30, 90, and 220. Although there is extensive information about the effects of malnutrition on cell body and dendrite morphology, little attention has been paid to axons or axon plexuses. The mossy fiber plexus represents the dentate gyrus granule cell axonal projection to areas CA4 and CA3 of the hippocampal formation and is readily demonstrated with Timm's heavy metal stain. With the use of this stain, the plexus was measured at 13 levels throughout the hippocampal complex. There was no effect of the diet on the anatomical distribution of the plexus. The current study, however, does show significant effects of prenatal protein malnutrition on postnatal development of the mossy fiber plexus that are age dependent. The prenatally malnourished rats show significant deficits in the total rostro-caudal extent and volume of the plexus on P15, P90, and P220, with the most marked dietary effect on P220. There was no significant diet effect on P30 in either extent or volume.