Effect of lithium in pyramidal neurons of Cornu Ammonis in an animal model

Bipolar disorder has been associated with a decrease in hippocampal size, and lithium appears to reverse this neuroanatomical abnormality. The objective of this work was to evaluate, at a cellular level, the size of both cell body and nucleus of pyramidal neurons located throughout the Cornu Ammonis (CA1 to CA4 regions). To perform this duty, we used 16 rats that were randomized into two groups: control and dietary lithium-treated. After one month, they were sacrificed and their brains removed for histopathological analysis. Serial photos of the entire Cornu Ammonis were taken and, after dividing them into 4 regions of interest, we measured the cell body and nucleus on each pyramidal neuron belonging to the first 5 photos of each region of interest. As a result of this histological analysis, cell body area and nuclear area were significantly larger in the experimental group in a specific area of the Cornu Ammonis that could correspond to CA2 or the transition between CA1 and CA2. These results suggest that the effect of lithium is not homogeneous throughout the hippocampus and allows directing future studies to a specific area of this structure.

Medial Temporal Lobe Anatomy

The medial temporal lobe (MTL) is a complex anatomic region encompassing the hippocampal formation, parahippocampal region, and amygdaloid complex. To enable the reader to understand the well-studied regional anatomic relationships and cytoarchitecture that form the basis of functional connectivity, the authors have created a detailed yet approachable anatomic reference for clinicians and scientists, with special attention to MR imaging. They have focused primarily on the hippocampal formation, discussing its gross structural features, anatomic relationships, and subfield anatomy and further discuss hippocampal terminology and development, hippocampal connectivity, normal anatomic variants, clinically relevant disease processes, and automated hippocampal segmentation software.

MRI volumetric changes in hippocampal subfields in psychosis: a protocol for a systematic review and meta-analysis

BACKGROUND

The hippocampus has for long been known for its ability to form new, declarative memory. However, emerging findings across conditions in the psychosis spectrum also implicate its role in emotional regulation. Systematic reviews have demonstrated consistent volume atrophic changes in the hippocampus. The aim of the systematic review and metanalysis which will follow from this protocol will be to investigate the volume-based neuroimaging findings across each of the subfields of the hippocampus in psychosis independent of diagnosis.

METHODS

Volume changes across subfields of the hippocampus in psychotic illnesses will be assessed by systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). MRI neuroimaging studies of patients with a definitive diagnosis of psychosis (including brief pre-diagnostic states) will be included. Studies lacking adequate controls, illicit drug use, medical psychosis, history of other significant psychiatric comorbidities, or emphasis on age groups above 65 or below 16 will be excluded. Subfields investigated will include the CA1, CA2/3, CA4, subiculum, presubiculum, parasubiculum, dentate gyrus, stratum, molecular layer, granular cell layer, entorhinal cortex, and fimbria. Two people will independently screen abstracts from the output of the search to select suitable studies. This will be followed by the two reviewers performing a full-text review of the studies which were selected based on suitable abstracts. One reviewer will independently perform all the data extraction, and another reviewer will then systemically check all the extracted information using the original articles to ensure accuracy. Statistical analysis will be performed using the metafor and meta-packages in R Studio with the application of the random-effects model.

DISCUSSION

This study will provide insight into the volumetric changes in psychosis of the subfields of the hippocampus, independent of diagnosis. This may shed light on the intricate neural pathology which encompasses psychosis and will open avenues for further exploration of the structures identified as potential drivers of volume change.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42020199558.

Volume deficits in hippocampal subfields in unaffected relatives of schizophrenia patients with high genetic loading but without any psychiatric symptoms

BACKGROUND

Hippocampal volume changes have been reported in schizophrenia patients and their relatives and are proposed to contribute to the pathophysiology of schizophrenia. However, volume changes in the total hippocampus have not been consistently reported in relatives. The hippocampus consists of multiple subregions, and based on previous inconsistent results, subtle changes in specific subregions may occur in relatives. Here, we examined the subregion volumes in unaffected, high-functioning relatives (URs) without any psychiatric symptoms with high genetic loading with at least one first-degree relative diagnosed with schizophrenia and at least one or more other affected first- to third-degree relatives.

METHODS

We acquired structural magnetic resonance imaging data from 50 URs, 101 first-episode psychosis (FEP) patients, and 101 healthy controls (HCs). The cornu ammonis (CA), dentate gyrus, and subiculum subfields were automatically segmented using FreeSurfer 7.1.0. Each subregion volume was compared across the groups.

RESULTS

Compared with the HCs, the URs had a significant volume reduction in the left anterior CA (p = 0.039, Cohen's d = 0.480). In addition, the URs had a significantly larger right posterior subiculum (p = 0.001, Cohen's d = 0.541) than the FEP.

CONCLUSIONS

The smaller left anterior CA in the URs may reflect their genetic vulnerability to schizophrenia and supports previous findings suggesting specific vulnerability in this region. The volume differences between the URs and FEP patients in the right posterior subiculum may suggest that a smaller volume in this region may reflect a risk for schizophrenia other than genetic vulnerability.

The DRD2 Taq1A polymorphism moderates the effect of PTSD symptom severity on the left hippocampal CA3 volume: a pilot study

RATIONALE AND OBJECTIVES

The hippocampus, especially the CA1, CA3, and dentate gyrus (DG) subfields, is reported to be associated with post-traumatic stress disorder (PTSD) after trauma. However, neuroimaging studies of the associations between PTSD and hippocampal subfield volumes have failed to yield consistent findings. The aim of this study is to examine whether the dopamine D2 receptor (DRD2) Taq1A polymorphism, which is associated with both hippocampal function and PTSD, moderated the association between PTSD severity and hippocampal CA1, CA3 and DG volumes.

METHODS

T1-weighted images were acquired from 142 trauma survivors from the 2008 Wenchuan earthquake using a 3.0-T magnetic resonance imaging system. Hippocampal subfield segmentations were performed with FreeSurfer v6.0. We used the simple moderation model from the PROCESS v3.4 tool for SPSS 23.0 to examine the association between the rs1800497 polymorphism, PTSD severity, and hippocampal CA3 and DG volumes.

RESULTS

A significant genotype × PTSD symptom severity interaction was found for the left CA3 volume (ΔF = 5.01, p = 0.008, ΔR² = 0.05). Post hoc, exploratory analyses deconstructing the interaction revealed that severe PTSD symptomatology were associated with reduced left CA3 volume among TC heterozygotes (t =  - 2.86, p = 0.005).

CONCLUSIONS

This study suggests that DRD2 Taq1A polymorphism moderates the association between PTSD symptomatology and left CA3 volume, which promotes an etiological understanding of the hippocampal atrophy at the subfield level. This highlights the complex effect of environmental stress, and provides possible mechanism for the relationship between the dopaminergic system and hippocampal function in PTSD.

Vascular Risk Factors of Hippocampal Subfield Volumes in Persons without Dementia: The Medea 7T Study

BACKGROUND

Vascular risk factors have been associated with risk of Alzheimer's disease (AD) and volume loss of the hippocampus, but the associations with subfields of the hippocampus are understudied. Knowing if vascular risk factors contribute to hippocampal subfield atrophy may improve our understanding of vascular contributions to neurodegenerative diseases.

OBJECTIVE

To investigate the associations between age, sex, and vascular risk factors with hippocampal subfields volumes on 7T MRI in older persons without dementia.

METHODS

From the Medea 7T study, 283 participants (67±9 years, 68% men) without dementia had 7T brain MRI and hippocampal subfield segmentation. Subfields were automatically segmented on the 3D T2-weighted 7T images with ASHS software. Using linear mixed models, we estimated adjusted associations of age, sex, and vascular risk factors with z-scores of volumes of the entorhinal cortex (ERC), subiculum (SUB), Cornu Ammonis (CA)1, CA2, CA3, CA4, and dentate gyrus (DG), and tail as multivariate correlated outcomes.

RESULTS

Increasing age was associated with smaller volumes in all subfields, except CA4/DG. Current smoking was associated with smaller ERC and SUB volumes; moderate alcohol use with smaller CA1 and CA4/DG, obesity with smaller volumes of ERC, SUB, CA2, CA3, and tail; and diabetes mellitus with smaller SUB volume. Sex, former smoking, and hypertension were not associated with subfield volumes. When formally tested, no risk factor affected the subfield volumes differentially.

CONCLUSION

Several vascular risk factors were associated with smaller volumes of specific hippocampal subfields. However, no statistical evidence was found that subfields were differentially affected by these risk factors.

Smaller volume of right hippocampal CA2/3 in patients with panic disorder

The hippocampus is thought to play an important role in conveying contextual information to the amygdala as the neural basis of panic disorder (PD). Previous studies have revealed functional abnormalities in the hippocampus in patients with PD compared with healthy control subjects (HC), but no study has reported volume abnormalities in the hippocampus or evaluated minute structural changes in the hippocampus in such patients. We thus investigated volume abnormalities in the subfields of the hippocampus to better understand the neurobiological basis of PD. The hippocampus was extracted from structural brain magnetic resonance images obtained from 38 patients with PD and 38 HC and then segmented into six subfields. The relative volume of each subfield was compared between the two groups. The severity of symptoms was assessed using the Panic Disorder Severity Scale (PDSS) and social functioning was assessed using the Global Assessment of Functioning (GAF) scale. Our results revealed that patients with PD had a significantly smaller volume of the right cornu ammonis (CA) 2/3 hippocampal subfield compared with HC. No significant associations were found between the volumes of the right CA 2/3 and the PDSS or GAF scores in correlation analyses. In conclusion, CA2/3 is thought to be related to contextual memory function, and our results suggest that this particular hippocampal subfield plays a role in the development of PD symptoms.

Gray matter increases within subregions of the hippocampal complex after pregnancy

Neuroimaging findings - although still relatively sparse in the realm of postpartum research - suggest significant tissue increases within the hippocampus or its vicinity after giving birth. Given that the hippocampus is not a homogenous structure, effects may manifest differently across the hippocampal complex. Thus, the goal of this study was to determine the presence, magnitude, and direction of postpartum gray matter changes within five hippocampal subregions, specifically the dentate gyrus, the subiculum, and the subfields of the cornu ammonis (CA1, CA2 and CA3). For this purpose, we analyzed brain images of 14 healthy women acquired at immediate postpartum (within 1-2 days of childbirth) and at late postpartum (at 4-6 weeks after childbirth). Changes in hippocampal gray matter between both time points were calculated for all subregions as well as the hippocampal complex as a whole by integrating imaging-based intensity information with microscopically defined cytoarchitectonic probabilities. Hippocampal gray matter increased significantly within the right subiculum, right CA2, and right CA3. These findings may suggest that brain tissue lost during pregnancy is being restored after giving birth, perhaps even expanded compared to before pregnancy. Possible events on the microanatomical level include dendritic branching as well as the generation of new synapses, glia cells, and blood vessels. Altogether, the outcomes of our study confirm that hippocampal gray matter increases in the female human brain after giving birth, with differential effects across the hippocampal complex.

Early Selective Vulnerability of the CA2 Hippocampal Subfield in Primary Age-Related Tauopathy

Primary age-related tauopathy (PART) is a neurodegenerative entity defined as Alzheimer-type neurofibrillary degeneration primarily affecting the medial temporal lobe with minimal to absent amyloid-β (Aβ) plaque deposition. The extent to which PART can be differentiated pathoanatomically from Alzheimer disease (AD) is unclear. Here, we examined the regional distribution of tau pathology in a large cohort of postmortem brains (n = 914). We found an early vulnerability of the CA2 subregion of the hippocampus to neurofibrillary degeneration in PART, and semiquantitative assessment of neurofibrillary degeneration in CA2 was significantly greater than in CA1 in PART. In contrast, subjects harboring intermediate-to-high AD neuropathologic change (ADNC) displayed relative sparing of CA2 until later stages of their disease course. In addition, the CA2/CA1 ratio of neurofibrillary degeneration in PART was significantly higher than in subjects with intermediate-to-high ADNC burden. Furthermore, the distribution of tau pathology in PART diverges from the Braak NFT staging system and Braak stage does not correlate with cognitive function in PART as it does in individuals with intermediate-to-high ADNC. These findings highlight the need for a better understanding of the contribution of PART to cognitive impairment and how neurofibrillary degeneration interacts with Aβ pathology in AD and PART.

Effect of caffeinated energy drinks on the structure of hippocampal cornu ammonis 1 and dentate gyrus of adult male albino rats

Energy drinks are available worldwide and frequently consumed to increase energy level and compensate lack of sleep. Energy drinks consumers aim to improve their cognitive functions. Red Bull is the most popular energy drink consumed in Egypt. However, the link between the impact of energy drinks on the structure of hippocampal cornu ammonis 1 (CA1) and dentate gyrus (DG), a highly vulnerable brain regions to various insults, has not yet documented. To study the effect of energy drinks on structure of hippocampal CA1 and DG of adult male albino rats. Twenty one adult male albino rats were divided into three groups; group I control group, groups II and III received Red Bull, with a dose of 3.75 ml/kg/day orally using gastric tube for four and eight consecutive weeks respectively. At the end of the experiment, brains were dissected and hippocampal specimens were processed for histopathological and immunohistochemical studies. Histopathological examination of hippocampal sections in group II revealed vacuoles, decrease thickness of pyramidal cell layer with irregular dark or ghost nuclei. However, changes were more severe in group III with cracks in pyramidal cell layer, massive vacuolation and signet ring cells. Moreover, star shaped astrocytes and glial fibrillary acidic protein immuno-reactivity were more abundant in group III than in group II. Caffeinated energy drinks produced neurodegenerative changes and reactive astrocytosis in hippocampal CA1 and DG of adult male albino rats. These changes were duration-dependent being more severe in longer duration of intake.

Abnormal resting-state functional connectivity of hippocampal subfields in patients with major depressive disorder

BACKGROUND

Many studies have found that the hippocampus plays a very important role in major depressive disorder (MDD). The hippocampus can be divided into three subfields: the cornu ammonis (CA), dentate gyrus (DG) and subiculum. Each subfield of the hippocampus has a unique function and are differentially associated with the pathological mechanisms of MDD. However, no research exists to describe the resting state functional connectivity of each hippocampal subfield in MDD.

METHODS

Fifty-five patients with MDD and 25 healthy controls (HCs) matched for gender, age and years of education were obtained. A seed-based method that imposed a template on the whole brain was used to assess the resting-state functional connectivity (rsFC) of each hippocampal subfield.

RESULTS

Patients with MDD demonstrated increased connectivity in the left premotor cortex (PMC) and reduced connectivity in the right insula with the CA seed region. Increased connectivity was reported in the left orbitofrontal cortex (OFC) and left ventrolateral prefrontal cortex (vlPFC) with the DG seed region. The subiculum seed region revealed increased connectivity with the left premotor cortex (PMC), the right middle frontal gyrus (MFG), the left ventrolateral prefrontal cortex (vlPFC) and reduced connectivity with the right insula. ROC curves confirmed that the differences between groups were statistically significant.

CONCLUSION

The results suggest that the CA, DG and subiculum have significant involvement with MDD. Specifically, the abnormal functional connectivity of the CA may be related to bias of coding and integration of information in patients with MDD. The abnormal functional connectivity of the DG may be related to the impairment of working memory in patients with MDD, and the abnormal functional connectivity of the subiculum may be related to cognitive impairment and negative emotions in patients with MDD.

When does conscious memory become dependent on the hippocampus? The role of memory load and the differential relevance of left hippocampal integrity for short- and long-term aspects of verbal memory performance

Supraspan list learning tests are sensitive measures used to assess temporal lobe dysfunction. Most frequently employed is the Rey Auditory Verbal Learning and Memory Test (RAVLT). The test's structure is determined by a short- and long-term memory component. During the first of five learning trials, the short-term memory component is the highest and steadily decreases over the following trials, while the long-term memory component concurrently increases and reaches its maximum at the delayed recall after a retention interval of 30 min. The study aimed to test the hypothesis that the functional relevance of left hippocampal integrity for conscious memory rises along with the increasing degree of the long-term memory component. Moreover, we investigated whether classical measures of short-term and working memory are also dependent on the hippocampus. The analysis was based on 37 adult patients who had undergone surgery for left mesial temporal lobe epilepsy. Neuronal cell densities of the resected left hippocampus were correlated with the presurgical memory performance across trials of the VLMT (the German RAVLT) and with digit span and working memory capacity (WMS-R). Whereas digit span and working memory capacity were not related to hippocampal cell counts, there was a significant correlation between left hippocampal integrity and VLMT memory performance, already regarding the first supraspan learning trial. Correlations steadily increased during the learning course. The highest correlation was seen regarding the delayed free recall. The results indicate an increasing correspondence between the integrity of the left hippocampus and verbal memory with an increasing long-term memory component. Immediate recall of verbal material became already dependent on left hippocampal integrity when the verbal memory load exceeded the memory span (supraspan list learning), while classical span measures that assess verbal short-term and working memory were not affected by left hippocampal pathology.

Hippocampal subfield volumes in major depressive disorder and bipolar disorder

BACKGROUND

The hippocampus is not a uniform structure, but rather consists of multiple, functionally specialized subfields. Few studies have explored hippocampal subfield volume difference in the same sample of major depressive disorder (MDD) and bipolar disorder (BD) cases. We aimed to investigate the difference of hippocampal subfield volume between patents with MDD and BD and healthy controls (HCs).

METHODS

A total of 102 MDD and 55 BD patients and 135 HCs were recruited and underwent T1-weighted image. Hippocampal subfield volume was calculated by automated segmentation and volumetric procedures developed by Iglesias et al. and implemented in FreeSurfer. Volume differences between the groups were analyzed using the analysis of covariance and controlling for age, sex, and total intracranial cavity volume.

RESULTS

Patients with MDD had significantly reduced volumes in the bilateral cornu ammonis 1 (CA1), CA4, the granule cell layer (GCL), molecular layer (ML), whole hippocampus, the left CA2/3, and right presubiclum and subiculum. Patients with BD had significantly reduced volumes in the right CA1, GCL, and the whole hippocampus as compared to HCs. No significant volume differences were observed between the MDD and BD groups. Illness duration was negatively correlated with volumes of the left CA1, CA4, ML, presubiculum, subiculum, and the whole hippocampus in patients with BD.

CONCLUSION

We observed hippocampal subfield volume reductions in both MDD and BD, a finding which more prominent in MDD. The inverse correlation between BD illness duration and hippocampal subfield volume may evidence the neuroprogressive nature of BD.

Neuroimaging hippocampal subfields in schizophrenia and bipolar disorder: A systematic review and meta-analysis

The hippocampus is a complex structure consisting of subregions with specialized cytoarchitecture and functions. Magnetic resonance imaging (MRI) studies in psychotic disorders show hippocampal subfield abnormalities, but affected regions differ between studies. We here present an overview of hippocampal anatomy and function relevant to psychosis, and the first systematic review and meta-analysis of MRI studies of hippocampal subfield morphology in schizophrenia and bipolar disorder. Twenty-one MRI studies assessing hippocampal subfield volumes or shape in schizophrenia or bipolar disorder were included (n 15-887 subjects). Nine volumetric group comparison studies (total n = 2593) were included in random effects meta-analyses of group differences. The review showed mixed results, with volume reductions reported in most subfields in schizophrenia and bipolar disorder. Volumetric studies using ex-vivo based image analysis templates corresponded best with the shape studies, with CA1 as the most affected region. The meta-analyses showed volume reductions in all subfields in schizophrenia and bipolar disorder compared to healthy controls (all p < .005; schizophrenia: d = 0.28-0.49, bipolar disorder: d = 0.20-0.35), and smaller left CA2/3 and right subiculum in schizophrenia than bipolar disorder. In conclusion, the hippocampal subfields appear to be differently affected in psychotic disorders. However, due to the lack of control for putative confounders such as medication, alcohol and illicit substance use, and illness stage, the results from the meta-analysis should be interpreted with caution. Methodological subfield segmentation weaknesses should be addressed in future studies.

High resolution in-vivo diffusion imaging of the human hippocampus

The human hippocampus is a key target of many imaging studies given its capacity for neurogenesis, role in long term potentiation and memory, and nearly ubiquitous involvement in neurological and psychiatric conditions. Diffusion tensor imaging (DTI) has detected microstructural abnormalities of the human hippocampus associated with various disorders, but acquisitions have typically been limited to low spatial resolution protocols designed for whole brain (e.g. > 2 mm isotropic, >8 mm³ voxels), limiting regional specificity and worsening partial volume effects. The purpose here was to develop a simple DTI protocol using readily available standard single-shot EPI at 3T, capable of yielding much higher spatial resolution images (1 x 1 x 1 mm³) of the human hippocampus in a 'clinically feasible' scan time of ~6 min. A thin slab of twenty 1 mm slices oriented along the long axis of the hippocampus enabled efficient coverage and a shorter repetition time, allowing more diffusion weighted images (DWIs) per slice per unit time. In combination with this strategy, a low b value of 500 s/mm² was chosen to help overcome the very low SNR of a 1 x 1 x 1 mm³ EPI acquisition. 1 mm isotropic mean DWIs (averaged over 120-128 DWIs) showed excellent detail of the hippocampal architecture (e.g. morphology and digitations, sub-regions, stratum lacunosum moleculare - SLM) that was not readily visible on 2 mm isotropic diffusion images. Diffusion parameters within the hippocampus were consistent across subjects and fairly homogenous across sub-regions of the hippocampus (with the exception of the SLM and tail). However, it is expected that DTI parameters will be sensitive to microstructural changes associated with a number of clinical disorders (e.g. epilepsy, dementia) and that this practical, translatable approach for high resolution acquisition will facilitate localized detection of hippocampal pathology.

Structural differences in hippocampal subfields among schizophrenia patients, major depressive disorder patients, and healthy subjects

Many MRI studies have reported a volume reduction of the hippocampus in psychiatric diseases. However, disease-related volume differences in hippocampus subfields remain unclear. Here we compared the volumes of hippocampus subfields in patients with schizophrenia, patients with major depressive disorder (MDD), and healthy subjects as controls. T2-weighted images were acquired in 20 patients with schizophrenia, 36 with MDD, and 35 healthy volunteers by 3-Tesla MRI. Hippocampal subfields were segmented using an automatic algorithm, Automatic Segmentation of Hippocampal Subfields (ASHS). Schizophrenia patients exhibited significant volume reductions in the cornu ammonis (CA)1 compared to the controls, and in the dentate gyrus compared to the controls and MDD patients without medication, whereas there was no significant difference between the MDD patients and controls. There was a nominal negative correlation between the perirhinal cortex volume and depression severity in the MDD patients without medication, whereas there were negative correlations between CA2 volume and both negative symptoms and the duration of illness in the schizophrenia patients. We identified differing volume reductions in hippocampal subfields and varying correlations between disease severity and subfield volumes depending on diagnosis, suggesting that volume differences in hippocampus subfields may provide important information regarding the pathophysiology of schizophrenia and MDD.

Effects of Long Term Exposure of 900-1800 MHz Radiation Emitted from 2G Mobile Phone on Mice Hippocampus- A Histomorphometric Study

INTRODUCTION

The advancement in the telecommunications technology with multi-functional added features in mobile phone, attracts more users of all age group. It is alarming to note that, the mobile phone use has increased amongst children and they are exposed to potentially harmful radiofrequency radiation in their lifetime.

AIM

To investigate the long term exposure of 900 to 1800 MHz radiations emitted from 2G mobile phone in mice hippocampus at histomorphometric level.

MATERIALS AND METHODS

With due approval from institutional animal ethics committee, 36 mice were exposed to 2G mobile phone radiation, 48 minutes per day for a period of 30-180 days. The control group was kept under similar conditions without 2G exposure. Mice were sacrificed and the brain was removed from the first month to six months period. Brain was removed from the cranial cavity and hippocampus region was dissected out carefully and processed for routine histological study. Random serial sections were analysed under microscope for histomorphometric changes. For statistical analysis, independent t-test was used for comparing control and 2G exposed groups.

RESULTS

The mean density of neurons in the hippocampus regions CA1, CA2 and DGDB from first to sixth month was significantly lower in the 2G exposed groups; however, in CA3 and DGVB, the 2G exposed mice showed significantly higher density of neurons. The mean nuclear diameter of neurons in the hippocampus region of CA1, CA2, CA3, DGDB and DGVB from first to sixth months showed lower nuclear diameter in 2G exposed mice.

CONCLUSION

The long term exposure to 900-1800 MHz frequency radiations emitted from 2G mobile phone could cause significantly reduced neuron density and decreased nuclear diameter in the hippocampus neurons of mice.

Hippocampal subfield analysis in medication-naïve female patients with major depressive disorder

BACKGROUND

Hippocampal volume loss is known as the best-replicated finding of structural brain imaging studies on major depressive disorder (MDD). Several evidences suggest localized mechanisms of hippocampal neuroplasticity lead the brain imaging studies on the hippocampus and MDD to perform analyses in the subfield level. The aim of this study was to investigate the differences in total and subfield hippocampal volumes, between medication-naïve female MDD patients and healthy controls, through automated segmentation and volumetric methods.

METHODS

Twenty medication-naïve female patients diagnosed with MDD and 21 age-matched healthy controls, underwent T1-weighted structural magnetic resonance scanning. Total volumes of both hippocampi and subfield regions were calculated by the automated procedure for volumetric measures implemented in FreeSurfer and automated segmentation method by Van Leemput et al.

RESULTS

We observed patients to have significantly smaller volumes of the left hippocampus, subiculum, cornu ammonis 2-3, cornu ammonis 4-dentate gyrus, and right subiculum compared to healthy controls. There were no significant predictors for these subfield region volumes among the illness burden-related parameters including duration of illness, number of depressive episodes, severity of depressive symptoms and memory performances.

LIMITATIONS

Our findings relied on the data of only female participants.

CONCLUSIONS

We found significant volume reductions in several hippocampal subfield regions in medication-naïve female MDD patients. Our results are consistent with neurobiological evidences on hippocampal neuroplasticity in MDD, and replicate previous findings that suggest morphologic changes of hippocampal subfields in MDD patients.

Dentate gyrus volume and memory performance in major depressive disorder

BACKGROUND

Magnetic resonance imaging (MRI) has shown lower hippocampal volume in major depressive disorder (MDD). Patients with MDD have consistently demonstrated worse performance than healthy controls a number of memory tests. Memory functions within the hippocampus in healthy younger subjects appear to be linked to cornu ammonis (CA1-3) and dentate gyrus (DG) subfields. Therefore, the main goal of the present study was to investigate whether memory deficits in MDD patients are related to reduction in hippocampal subfields volumes, particularly DG and CA 1-3.

METHODS

15 MDD patients meeting DSM-IV criteria for MDD with moderate or severe episodes were recruited, together with 15 healthy controls. We used T2-weighted 2D Fast Spin Echo (FSE) and T1-weighted 3D MPRAGE sequences at 4.7 T to compare hippocampal subfield volumes at 0.09 μl voxel volume. Participants were administered the Wechsler Memory Scale.

RESULTS

MDD patients underperformed in several episodic visual memory tasks, as well as in visual working memory, compared to healthy controls. Global hippocampal volumes were similar between groups; however, MDD patients showed significantly reduced DG volumes within the hippocampal body. Duration of depression correlated with MDD patients׳ total volumes in the hippocampal body and CA1-3 and DG subfields within it.

LIMITATIONS

Our study sample was relatively small and the majority of patients were on antidepressant treatment.

CONCLUSIONS

Our findings suggest that DG volumes in particular may be worthy of further study to further elucidate their precise role in MDD, both by itself as well as in relation to memory.

Stereological analysis of cornu ammonis in prenatally stressed rats: a heuristic neurodevelopmental model of schizophrenia

OBJECTIVE(S)

The hippocampus has been implicated in pathophysiology of schizophrenia. Prenatal stress is a contributing risk factor for a wide variety of neuropsychiatric diseases including schizophrenia. This study examined long-term effects of prenatal restraint stress on the stereological parameters in the Cornu Ammonis (CA) of adult male rats as an animal model of schizophrenia.

MATERIALS AND METHODS

Wistar pregnant dams in experimental group were stressed in a cylindrical Plexiglas restrainer daily for 1 hr during last week of gestation. Controls remained in the animal room and were exposed only to normal animal room conditions. At 2 months of age, the volume of the pyramidal cell layer of the CA, the numerical density and the somal volume of the respective neurons were assessed in the male offspring generated from stressed and control pregnancies. Cavalieri's principle, physical disector and nucleator were applied for stereological analyses.

RESULTS

This study showed that prenatal stress significantly decreased the volume of CA3 pyramidal cell layer and the individual somal volume of CA3 pyramidal neurons. However, there were no markedly differences in the numerical density, total number of CA3 pyramidal neurons and stereological parameters in CA1 of prenatally stressed and control animals.

CONCLUSION

These data indicate that prenatal stress exposure induced neuronal changes in the CA3 subfield of hippocampus which are similar to what is observed in schizophrenia.

Neuroprotective effects of Nigella sativa extract on cell death in hippocampal neurons following experimental global cerebral ischemia-reperfusion injury in rats

BACKGROUND

Global cerebral ischemia followed by reperfusion, leads to extensive neuronal damage, particularly the neurons in the hippocampal CA region. Recent studies have demonstrated that pharmacological agents, such as Nigella sativa L. (Ranunculaceae) that is an annual herbaceous flowering plant, given at the time of reperfusion afforded protection against ischemia, which is referred to as pharmacological post conditioning.

OBJECTIVES

The aim of this study was to evaluate the neuroprotective effects of Nigella sativa in the hippocampus neurons of rats exposed to global ischemia/reperfusion.

METHODS

In the present study 30 Wister rats (200-250 g) were divided into 5 groups namely sham (operated without treatment), control (operation with normal saline treatment), and 3 treatment groups with Nigella sativa 1mg/kg, 10mg/kg and 50mg/kg. Firstly, the animals were anesthetized by ketamin and xylazine, and then the right carotid artery was operated upon dissection of the soft tissues around it and ligation by a clamp for 20 min. The Nigella sativa extraction was used during surgery through IP route and after 72 h the animals were euthanized and their brain removed, fixed and prepared for histopathological examinations.

RESULTS

In treatment group (1mg/kg) the interstitial neuron frequency which contains cytoplasmic edema, along with CA, was 28 cells, whereas the edematous astrocyte number along with CA in this group was 115 cells. In the treatment group (10mg/kg) the interstitial neurons of cornua ammonis (CA) were 15 and the edematous astrocytes were 122 cells and in the treatment group (50mg/kg) the number of edematous interstitial neurons was 7 cells in distance of 2900 μ of CA. In such group the number of edematous interstitial neurons was less as well. In this group the appearance of CA cells was more similar to control group, not only the edema decreased in interstitial and astrocyte cells, but it dramatically decreased in pyramidal cells. Our study revealed that the Nigella sativa extraction could prevent intracellular edema of interneurons in 50mg/kg group significantly compared to sham group (91.6%) and the extraction (50mg/kg) decreased edematous astrocytes 67.1% dramatically compared to sham group. Furthermore there was no significant difference between control and two treatment groups (1 and 10mg/kg) (P>0.05), CONCLUSION: Our finding suggested that the N. sativa extraction could prevent the cerebral edema which the best result was obtained in 50mg/kg group; consequently such extraction is able to prevent ischemia/reperfusion in the hippocampus tissue of the brain.

Differential expression levels of synaptophysin through developmental stages in hippocampal region of mouse brain

The formation of neural synapses according to the development and growth of neurite were usually studied with various markers. Of these markers, synaptophysin is a kind of synaptic protein located in the synaptic vesicle of neuron or neuroendocrine cell known to be distributed consistently in all neural synapses. The purpose of this study was to investigate differential expression levels and patterns of synaptic marker (synaptophysin) in the mouse hippocampal region according to the developmental stages of embryonic, neonatal, and adulthood respectively. In the embryonic and neonatal groups, synaptophysin immunofluorescence was almost defined to cornu ammonis subfields (CA1 and CA3) of hippocampus and subiculum proper in the hippocampal region. However in dentate gyrus, synaptophysin immunoreactivities were insignificant or absent in all developmental stages. In embryonic and neonatal hippocampus, the intensities of immunofluorescence were significantly different between molecular and oriens layers. Furthermore, those intensities were decreased considerably in both layers of neonatal group compared to embryonic. The results from this study will contribute to characterizing synaptogenic activities in the central nervous system through developmental stages.