Gestational iron deficiency differentially alters the structure and function of white and gray matter brain regions of developing rats.

Gestational iron deficiency (ID) has been associated with a wide variety of central nervous system (CNS) impairments in developing offspring. However, a focus on singular regions has impeded an understanding of the CNS-wide effects of this micronutrient deficiency. Because the developing brain requires iron during specific phases of growth in a region-specific manner, we hypothesized that maternal iron deprivation would lead to region-specific impairments in the CNS of offspring. Female rats were fed an iron control (Fe+) or iron-deficient (Fe-) diet containing 240 or 6 µg/g iron during gestation and lactation. The corpus callosum (CC), hippocampus, and cortex of the offspring were analyzed at postnatal day 21 (P21) and/or P40 using structural and functional measures. In the CC at P40, ID was associated with reduced peak amplitudes of compound action potentials specific to myelinated axons, in which diameters were reduced by ∼20% compared with Fe+ controls. In the hippocampus, ID was associated with a 25% reduction in basal dendritic length of pyramidal neurons at P21, whereas branching complexity was unaffected. We also identified a shift toward increased proximal branching of apical dendrites in ID without an effect on overall length compared with Fe+ controls. ID also affected cortical neurons, but unlike the hippocampus, both apical and basal dendrites displayed a uniform decrease in branching complexity, with no significant effect on overall length. These deficits culminated in significantly poorer performance of P40 Fe- offspring in the novel object recognition task. Collectively, these results demonstrate that non-anemic gestational ID has a significant and region-specific impact on neuronal development and may provide a framework for understanding and recognizing the presentation of clinical symptoms of ID.

Ndfip1 is required for the development of pyramidal neuron dendrites and spines in the neocortex.

Ubiquitin ligases of the Nedd4 family are important for axon and dendrite development, but little is known about their adaptor, Nedd4 family-interacting protein 1 (Ndfip1), that is responsible for their enzymatic activation. To study the function of Ndfip1 in cortical development, we generated a conditional knock-out (conditional KO) in neurons. The Ndfip1 conditional KO mice were viable; however, cortical neurons in the adult brain exhibited atrophic characteristics, including stunted dendritic arbors, blebbing of dendrites, and fewer dendritic spines. In electron micrographs, these neurons appeared shrunken with compacted somata and involutions of the nuclear membrane. In culture, Ndfip1 KO neurons exhibited exuberant sprouting suggesting loss of developmental control. Biochemical analysis of postsynaptic density (PSD) fractions from Ndfip1 KO cortical and hippocampal neurons showed that the postsynaptic proteins (Arc and PSD-95) were reduced compared with wild-type controls. In addition, the PI3 kinase/Akt signaling pathway was altered. These results indicate that Ndfip1, through its Nedd4 effectors, is important for the development of dendrites and dendritic spines in the cortex.

Pregnancy or stress decrease complexity of CA3 pyramidal neurons in the hippocampus of adult female rats.

Pregnancy is a time of distinct neural, physiological and behavioral plasticity in the female. It is also a time when a growing number of women are vulnerable to stress and experience stress-related diseases, such as depression and anxiety. However, the impact of stress during gestation on the neurobiology of the mother has yet to be determined, particularly with regard to changes in the hippocampus; a brain area that plays an important role in stress-related diseases. Therefore, the aim of the present study was to understand how stress and reproductive state may alter dendritic morphology of CA1 and CA3 pyramidal neurons in the hippocampus. To do this, adult age-matched pregnant and virgin female Wistar rats were divided into two conditions: (1) control and (2) stress. Females in the stress condition were restrained for 1h/day for the last 2 weeks of gestation and at matched time-points in virgin females. Females were sacrificed the day after the last restraint session and brains were processed for Golgi impregnation. Dendritic length and number of branch points were quantified for apical and basal regions of CA1 and CA3 pyramidal neurons. Results show that regardless of reproductive state, stressed females had significantly shorter apical dendrites and fewer apical branch points in CA3 pyramidal cells. In addition, pregnant females, regardless of stress exposure, had less complex CA3 pyramidal neurons, as measured by Sholl analysis. No differences between conditions were seen in morphology of CA1 pyramidal neurons. This work shows that both repeated restraint stress and pregnancy affect dendritic morphology by decreasing complexity of CA3, but not CA1, neurons in the hippocampus.

[Effects of transcranial magnetic stimulation on recovery of neural functions and changes of synaptic interface and dendritic structure in the contralateral brain area after cerebral infarction: experiment with rats].

OBJECTIVE: To evaluate the effects of transcranial magnetic stimulation (TMS) on the brain plasticity and its role in functional outcome in cerebral infarction. METHODS: Twenty male SD rats underwent suture of the unilateral middle cerebral artery (MCA) so as to establish focal cerebral infarction models and then were randomly divided into 2 equal groups: model group, to be reared in the original living state, and TMS group, given in addition TMS treatment 1 day after infarction 2 times per day and 30 pulses per time for 4 weeks. Twenty-eight days after the rats were killed. Four rats from each group underwent microscopy of the brain to measure the dendritic structure of the pyramidal cells quantitatively. Other 4 rats from each group underwent electron microscopy of the brain to measure the parameters of synaptic interface in the sensorimotor cortex. Neural function scoring was conducted 24 hours after the establishment of model and before being killed. RESULTS: There was no significant difference in the neural function 24 h after the establishment of models, however, 28 days after the score of neural function of the TMA group was 0.58 +/- 0.49, significantly lower than that of the model group (0.92 +/- 0.28, P < 0.05). The total dendritic length, number of dendritic branching points, and dendritic density in layer V pyramidal cells within the undamaged motor cortex of the TMS group were 898 microm +/- 127 microm, 6.6 +/- 1.5, and 0.75/microm +/- 0.19/microm, all significantly higher than those of the model group (788 microm +/- 112 microm, 5.8 +/- 1.5, and 0.60/microm +/- 0.16/microm, P < 0.05 or < 0.01). Electron microscopy showed that the synaptic curvatures and post-synaptic density of the TMS group were 1.06 +/- 0.08 and 64 +/- 13 respectively, both significantly higher than those of the model group (1.02 +/- 0.06 and 54 +/- 12 nm respectively, P < 0.05 and P < 0.01), and the synapse cleft width of the TMS group was 19.5 +/- 2.1, significantly narrower than that of the model group (23.3 +/- 2.3, P < 0.01). CONCLUSION: TMS promotes the improvement of neural functions of the rats with cerebral ischemia by the potential mechanism that TMS strengthen the compensatory roles of the synaptic interface and dendritic structure in the undamaged sensorimotor cortex area and increase synaptic plasticity.

Increase in prefrontal cortex serotonin 2A receptors following estrogen treatment in postmenopausal women.

OBJECTIVE: This study investigated the effect of estrogen on brain serotonin 2A (5-HT(2A)) receptors in postmenopausal women and whether there was any correlation of receptor changes with cognition and mood. METHOD: Ten postmenopausal subjects underwent positron emission tomography measurements of 5-HT(2A) receptor binding with [(18)F]deuteroaltanserin before and after estrogen replacement therapy. RESULTS: 5-HT(2A) receptor binding was significantly increased after estrogen replacement therapy in the right prefrontal cortex (right precentral gyrus [Brodmann's area 9], inferior frontal gyrus [Brodmann's area 47], medial frontal gyrus [Brodmann's area 6, 10] and the anterior cingulate cortex [Brodmann's area 32]). In the inferior frontal gyrus [Brodmann's area 44]), receptor up-regulation was correlated with change in plasma estradiol. Verbal fluency and Trail Making Test performance, but not mood, were significantly improved by estrogen without correlation with receptor changes. CONCLUSIONS: Estrogen increases 5-HT(2A) receptor binding in human prefrontal regions.

Environmental enrichment: effects on stereotyped behavior and dendritic morphology.

We evaluated whether environmental enrichment-related effects on the development of stereotyped behavior in deer mice were associated with alterations in dendritic morphology. Deer mice were reared under enriched or standard housing conditions and then tested in automated photocell detectors and classified as stereotypic or nonstereotypic. Dendritic morphology was assessed in layer V pyramidal neurons of the motor cortex, medium spiny neurons of the dorsolateral striatum, and granule cells of the dentate gyrus using Golgi-Cox histochemistry. Enriched nonstereotypic mice exhibited significantly higher dendritic spine densities in the motor cortex and the striatum than enriched stereotypic or standard-cage mice. Significant increases in dendritic arborization following environmental enrichment also were observed. These results suggest that the enrichment-related prevention of stereotyped behavior is associated with increased dendritic spine density.

Brain serotonin 5-HT(1A) receptor binding in schizophrenia measured by positron emission tomography and [11C]WAY-100635.

BACKGROUND: Results of postmortem studies show an elevation in serotonin-1A (5-hydroxytryptamine-1A [5-HT(1A)]) receptor density in the prefrontal and temporal cortices of patients with schizophrenia. This study examined 5-HT(1A) receptors in vivo in patients with schizophrenia using positron emission tomography and [carbonyl-(11)C]-N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexane carboxamide ([(11)C]WAY-100635). METHODS: The 5-HT(1A) binding potential of 14 antipsychotic drug-naïve patients with a DSM-IV diagnosis of schizophrenia was compared with that of 14 age-matched healthy controls. Positron emission tomography data were analyzed using 9 cortical regions of interest, which were delineated on a coregistered magnetic resonance image and transferred to the positron emission tomographic image, with the cerebellum as the reference region for a simplified reference tissue model. We also performed a voxel-wise comparison using statistical parametric mapping. RESULTS: The region of interest-based analysis revealed a significant mean +/- SD cortical 5-HT(1A) receptor binding potential increase of 7.1% +/- 6.4% in patients with schizophrenia (F = 2.975; P =.02); local differences were +20% in the left medial temporal cortex (F = 9.339;P =.005) and +13% in the right medio temporal cortex (F = 4.453; P =.045). There were no significant differences in regional tracer delivery or cerebellar [(11)C]WAY-100635 uptake. The voxel-based analysis also confirmed a group difference in the left medial temporal cortex. CONCLUSIONS: The biological significance of elevated 5-HT(1A) receptor density in schizophrenia remains unclear. Given the location of 5-HT(1A) receptors on pyramidal cells, this elevation may reflect an abnormal glutamatergic network. Our finding needs to be viewed in light of preclinical evidence supporting a role for 5-HT(1A) receptors in mediating antipsychotic action and extrapyramidal adverse effects of drugs.

Functional recovery and dendritic hypertrophy after posterior and complete cingulate lesions on postnatal day 10.

Rats received lesions of the posterior cingulate cortex or both the anterior and posterior cingulate cortex (total cingulate), or sham procedures, on postnatal Day 10. As adults, animals were trained in the Morris water task. Both the cingulate lesion groups showed substantial functional recovery relative to our previous studies of adult operates or animals with perinatal cingulate lesions. A Golgi analyis of layer III pyramidal cells in parietal cortex showed an increase in dendritic length in the lesion animals relative to sham controls, which is similar to previous findings for rats with anterior cingulate but not motor or parietal lesions. In addition, there was a partial regeneration of the anterior tissue in the total cingulates, which in some cases extended into the posterior region. This is consistent with earlier findings that anterior cingulate lesions around Day 10 stimulate neurogenesis. It appears that there is something special about the reparative processes and subsequent functional recovery that follow midline neocortical lesions.

Neuroanatomy of cerebellum and olfactory bulb in a substrain of C57BL/6J inbred mice carrying a spontaneous mutation.

Mice of the inbred C57BL/6JNmg substrain carry a mutation decreasing the size of the zinc-rich hippocampal intra- and infrapyramidal mossy fibre (IIPMF) terminal fields. In the present experiment, it was investigated whether this neurological mutation has also effects on other characteristics of the brain. No morphological differences were found in two other laminated neural structures, the olfactory bulb, where the accessory granular layer is also rich in zinc terminals, and the cerebellum. However, the mutants had a somewhat inferior performance on a motor function task known to test cerebellar involvement. The present findings confirm that previously found effects of this mutation on different types of behaviour are most probably due to the IIPMF. These substrains provide a powerful tool to localise the gene involved and subsequently investigate the plausible pathways leading from gene to behaviour.

Gene expression in developing rat hippocampal pyramidal neurons appears independent of mossy fiber innervation.

In the rat, neonatal gamma-irradiation of the hippocampus induces a selective destruction of dentate granule cells and prevents the development of the mossy fiber-CA3 pyramidal cell connection. In the absence of mossy fiber input, the CA3 pyramidal neurons exhibit morphological alterations and rats deprived of dentate granule cells fail to develop kainate-induced epileptic activity in the CA3 pyramidal neurons. Neonatal elimination of the granule cells also impairs learning and memory tasks in adult rats. In the present work, we assessed by in situ hybridization and semi-quantitative RT-PCR, whether in the pyramidal layers, the absence of mossy fiber input alters the expression of a number of genes involved in activity-dependent signal transduction, in GABAergic neurotransmitter signaling and in neurite development via microtubule organization. Surprisingly, we show that the expression and the developmentally regulated alternative splicing of the genes we examined in the developing hippocampus are not altered in the pyramidal neurons, whether the dentate granule afferents are present or absent. Our results suggest that in the CA3 pyramidal layer, the developmental expression patterns of the mRNAs we studied are independent of extrinsic cues provided by mossy fiber input.

Correlation of hippocampal neuronal density and FDG-PET in mesial temporal lobe epilepsy.

PURPOSE: Interictal [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) reveals regional hypometabolism in 60-80% of patients with mesial temporal lobe epilepsy (MTLE). The extent of hypometabolism generally extends beyond the epileptogenic zone. The pathophysiology underlying this widespread change is unknown. This study evaluated the relation between hippocampal neuronal loss and hypometabolism in patients with MTLE. METHODS: Forty-three patients with MTLE after anterior temporal lobectomy were included. Pathology demonstrated mesial temporal sclerosis (n = 41) or endfolium sclerosis (n = 2). Interictal FDG-PET scans were graded by visual analysis on a scale ranging from normal (grade 1) to severe (grade 5) hypometabolism. Neuronal counting was performed in the subiculum, hippocampal subfields, and dentate granular cell layer (DG). Neuronal density of patients was compared with that of seven autopsy controls. Data were compared by using Student's t tests and Kruskal-Wallis one-way analysis of variance (ANOVA). RESULTS: Significant neuronal loss in CA1 through CA4 and DG was found in patients compared with controls. Neuronal density in the subiculum, CA1, CA4, and DG did not correlate with severity of hypometabolism. However, patients with abnormal FDG-PET had higher neuronal density in CA2 and CA3 versus patients with normal studies. CONCLUSIONS: This study supports a previous observation that degree of FDG-PET hypometabolism does not parallel severity of hippocampal neuronal loss in MTLE.