The Role of Adult Hippocampal Neurogenesis in Learning and Memory Function

Adult hippocampal neurogenesis is the lifelong production of new functional neurons from neural stem cells in the adult brain. Production of neurons in the adult brain is limited to two areas. One of these is the subgranular region in the hippocampus dentate gyrus (DG), the other is the subventricular zone of the lateral ventricles. New neurons produced in the hippocampus DG functionally integrate into mature circuits, and contribute to cognition and emotional control, learning and memory functions in particular. It is still unclear how that contribution occurs and a key issue that is being intensively investigated. Hippocampal neurogenesis declines both with age and in neurodegenerative diseases characterized by deterioration of memory. Understanding the contribution of hippocampal neurogenesis to memory function and investigating factors that affect neurogenesis have gained importance for protective or therapeutic approaches against these neurodegenerative diseases. It is suggested that new neurons produced in the DG contribute to spatial and episodic memory function by pattern separation (prevent overlapping of similar information by making separate presentations) through their electrophysiologic properties (being stimulated easier than mature neurons) in the maturation process. Hippocampal neurogenesis is important in episodic and spatial memory formation. In this review we will try to explain how hippocampal neurogenesis occurs, factors that affect the neurogenesis process, and the role of neurogenesis in memory function based on the present literature

Effects of erythropoietin pretreatment on single dose pentylentetrazole-induced seizures in rats

Although it is accepted that prolonged and repeated seizures can cause epileptogenesis, memory deficits and neuronal death, the precise relation between epileptic seizures and neuronal death remains unclear. Erythropoietin (EPO) exhibits neuroprotective and anti-epileptic effects. We investigated the effect of a single pentylentetrazole (PTZ) induced tonic-clonic seizure on the pyramidal neurons of the cornu ammonis 1 (CA1) and CA3 regions of hippocampus. We also investigated the effects of EPO on seizure, memory and on brain-derived neurotrophic factor (BDNF), tyrosine receptor kinase-B, sirtuin-1 (SIRT1), which are important for memory. Forty male rats were divided into four groups: control, saline treated, single 60 mg/kg dose PTZ treated, 3000 IU/kg EPO treated, and 3000 IU/kg EPO treated 24 h before PTZ administration. Seizure latency and severity were assessed following PTZ injection. A passive avoidance test was performed 24 h after seizure. BDNF, TrkB and SIRT1 levels were measured in serum, hippocampus and cortex. The hippocampus was examined histologically, and neuronal nuclear antigen (NeuN) was investigated using immunohistochemistry. EPO pretreatment decreased seizure severity and prolonged seizure latency. Single dose PTZ-induced seizures did not affect memory. Numbers of cells in the CA1 region did not change, although the number of dark stained neuron increased. Both total cell numbers and percentage of dark stained cells were elevated in the CA3 region following PTZ induced seizures. EPO pretreatment decreased the number of dark cells in both CA1 and CA3 regions and the number of cells in the CA3 region. NeuN labeling was unchanged in the CA1 and CA3 regions in the PTZ group; however, EPO pretreatment increased NeuN labeling in the CA3 region. Although EPO exhibited an anticonvulsive effect, single dose EPO pretreatment did not affect memory in either animals not exposed to PTZ or animals that had been subjected to PTZ-induced seizures. EPO pretreatment prolonged seizure latency and reduced seizure severity after PTZ-induced seizures. The anti-seizure and neuroprotective effects of EPO pretreatment may be due to the protection of CA1 and CA3 neurons, possibly owing to SIRT1 and BDNF activity

EFFECTS OF ERYTHROPOIETIN PRETREATMENT ON LIVER, KIDNEY, HEART TISSUE IN PENTYLENTETRAZOL-INDUCED SEIZURES ; EVALUATION IN TERMS OF OXIDATIVE MARKERS, PROLIDASE AND SIALIC ACID

Objective: The effects of erythropoietin (EPO) which has been frequently studied as an anti-epileptic agent, on peripheral tis-sues have not been investigated. This study investigated the ef-fects on malondialdehyde (MDA), advanced protein oxidation products (AOPP), superoxide dismutase (SOD), prolidase and sialic acid (SA) levels in the heart, kidney and liver tissues of EPO pretreatment in pentylenetetrazole (PTZ)-induced seizures

Long term consequences on spatial learning-memory of low-calorie diet during adolescence in female rats; hippocampal and prefrontal cortex BDNF level, expression of NeuN and cell proliferation in dentate gyrus.

Calorie restriction (CR) is argued to positively affect general health, longevity and normally occurring age-related reduction of cognition. Obesity during adolescence may adversely affect cognition in adulthood but, to date effects of CR have not been investigated. We hypothesized that feeding with as low as 15% low-calorie diet (LCD) during adolescence would increase hippocampal and prefrontal BDNF (Brain-derived neurotrophic factor) levels, proliferative cells and neuron numbers in dentate gyrus (DG), thus positively affecting spatial memory in adulthood. Spatial learning-memory function was improved in adult female Sprague Dawley rats fed with LCD during adolescence. PCNA (Proliferating cell nuclear antigen-cell proliferation marker) expressing cells and NeuN (Neuronal nuclear antigen-neuron marker) expressing cells in hippocampus DG which are critically involved in memory were increased. Hippocampus and prefrontal cortex BDNF levels were increased while serum glucose levels and level of lipid permddation indicator malondialdehyde in serum and hippocampus were reduced. Our unique results suggest that improved cognition in adult rats with LCD feeding during adolescence may result from the increase of neurogenesis and BDNF. These findings reveal the importance of nutrition in adolescence for cognitive function in adulthood. Our results may be useful for further studies aiming to treat age-related cognitive impairments. (C) 2015 Elsevier B.V. All rights reserved

The effects of 17 beta-estradiol on blood brain barrier integrity in the absence of the estrogen receptor alpha; an in-vitro model

The blood-brain barrier (BBB), which saves the brain from toxic substances, is formed by endothelial cells. It is mainly composed of tight junction (TJ) proteins existing between endothelial cells. Estrogen is an important regulatory hormone of BBB permeability. It protects the BBB before menopause, but may increase BBB permeability with aging. In addition, nitric oxide modulates BBB permeability. Alcohol impairs the integrity of the BBB with oxidants and inflammatory mediators such as iNOS. We investigated the effects of estrogen on BBB integrity in an in vitro BBB model created with ER alpha-free HUVEC (human umbilical vein endothelial-like cells) to mimics the menopausal period

An investigation of olfactory bulb and entorhinal cortex volumes in both patients with Alzheimers disease and healthy individuals, and a comparative analysis of neuropeptides

Alzheimers Disease (AD) is the most common neurodegenerative disease and is hard to diagnose at the early stages. The pathogenesis of AD is associated with the loss of a sense of smell. Reduction in the volumes of the Olfactory Bulb (OB) and Entorhinal Cortex (EC) is positively correlated with the decline of the smelling function where OB projects to EC. This study aims to detect the early changes in OB and EC volumes in AD patients by comparing them to healthy subjects. This study also aims to make a comparative analysis of plasma levels and the relationship between arginine-vasopressin (AVP) and Oxytocin (OT), which are neuropeptides associated with cognitive functions. The participants comprised 9 AD patients and 12 healthy individuals. We used volumetric methods such as MRICloud and IBASPM to measure the OB and EC volumes with the help of 3D MRI (Magnetic Resonance Imaging) images. We compared the left and right differentiation. Moreover, we investigated the neuropeptide levels in blood samples from the participants. We conducted a correlation analysis for all parameters. Bilateral OB atrophy was discovered in the AD patients in comparison to the control group (p=0.002 for right; p=0.015 for left). The right OB volume was measured to be larger than the left OB volume in the control group,but this asymmetry was not observed in the AD patients. The right and left EC's of the AD patients were atrophic in comparison to the control (p [Med-Science 2020; 9(4.000): 866-71