Hippocampal Neurons

In vitro neural cell culture systems (primary cell cultures and cell lines) are one of the most valuable research tools in areas like neuropathology, drug screening studies, gene-transfer technology, and three-dimensional (3D) cell culture models. Lonza primary cells and media have been used by different research groups for a better understanding of these applications. The hippocampus is crucial for normal brain function, especially for the encoding and retrieval of multimodal sensory information. Neuropsychiatric disorders such as temporal lobe epilepsy, amnesia, and the dementias are associated with structural and functional abnormalities of specific hippocampal neurons.

Lonza's portfolio also includes reliable neural media products that are optimized and tested specifically with our primary neural cells. Our serum-free neural media allows for the long-term maintenance and growth of neural cells in culture. Lonza guarantees the performance of its cells when cultured with the recommended medium and following the protocol.

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Hippocampal structure

Hippocampal neurons play a major role in the functioning of the human brain. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus belongs to the limbic system and plays an important role in the consolidation of information from short to long-term memory and enables navigation via spatial memory. The hippocampus can be seen as a ridge of gray matter tissue, elevating from the floor of each lateral ventricle in the region of the inferior or temporal horn. The cortex thins from six layers to the three or four layers that make up the hippocampus. The term hippocampal formation is used to refer to the hippocampus proper and its related parts. The neural layout and pathways within the hippocampal formation are very similar in all mammals.

It can be distinguished as an area where the cortex narrows into a single layer of densely packed pyramidal neurons, which curl into a tight U shape. One edge of the 'U,' – CA4, is embedded into the backward-facing, flexed dentate gyrus. The hippocampus is described as having an anterior and posterior part (in primates) or a ventral and dorsal part in other animals. Both parts are of similar composition but belong to different neural circuits. In rat, the two hippocampi resemble a pair of bananas, joined at the stems by the commissure of fornix (also called the hippocampal commissure). In primates, the part of the hippocampus at the bottom, near the base of the temporal lobe, is much broader than the part at the top. This means that in cross-section the hippocampus can show a number of different shapes, depending on the angle and location of the cut.

The Regions of the Hippocampus

Source: J. A. Kiernan modified from Edinger, 1899 (L. Edinger, The Anatomy of the Central Nervous System of Man and of Vertebrates in General, F.A. Davis, Philadelphia, Pa, USA, 5th edition, 1899, Edited by W. S. Hall assisted by P. L. Holland and E. P. Carlton.) Epilepsy Research and Treatment Vol 2012, Article ID 176157,12 pages doi:10.1155/2012/176157

Hippocampal function

Memory: Hippocampal neurons play a critical role in the formation of new memories and in the detection of new surroundings, occurrences and stimuli. It is involved in declarative memory; that is memories that can be stated verbally such as facts and figures. However, studies have shown that damage to the hippocampus does not affect a person's ability to learn a new skill such as playing a musical instrument or solving certain types of puzzles.

Spatial navigation and spatial memory: There are several navigational cell types within the brain that are either present in the hippocampus itself or strongly connected to it. One such example are speed cells present in the medial entorhinal cortex. Together these cells form a network that serves as spatial memory. When the hippocampus is dysfunctional, orientation is affected; people may have difficulty in remembering how they arrived at a location and how to proceed further. Studies with animals have shown that an intact hippocampus is required for initial learning and long-term retention of some spatial memory tasks, in particular ones that require finding the way to a hidden goal.

Behavioral inhibition: Damage to the hippocampus causes hyperactivity and affects the ability to inhibit previously learned responses.

Anxiety and depression: The involvement of the hippocampus in mood disorders is suggested by magnetic resonance imaging (MRI) studies demonstrating a small reduction in hippocampal volume in depressed patients.

Stress regulation: A less well-known function of the hippocampus is its role as a negative feedback regulator of the Hypothalamic Pituitary Axis (HPA). The high concentration of adrenal steroid receptors in the hippocampus and the hippocampal projections to the hypothalamus provide an indirect link between the hippocampus and regulation of the stress response.

Neuropathology of the hippocampus

Schizophrenia: Various studies have used neuronal cells and media from Lonza in order to understand the role of hippocampus in the pathophysiology of schizophrenia. In contrast to neurodegenerative disorders, total hippocampal cell number is not markedly decreased in schizophrenia. However, the expression of several genes, including those related to the GABAergic system, neurodevelopment, and synaptic function, is decreased in schizophrenia. Taken together, recent studies of hippocampal cell number, protein expression, and gene regulation point towards an abnormality of hippocampal architecture in schizophrenia.

Alzheimer’s disease: It is believed that in Alzheimer's disease (AD) some areas of the brain are particularly vulnerable to specific degenerative processes and that they could exhibit neuronal dysfunction in the earliest stage of the disease. The implications of the hippocampus in memory processes are very well known and it is likely that the hippocampus would be among the first areas of the brain affected by the pathogenic mechanisms occurring in AD. A study demonstrated and confirmed a significant neuronal loss of hippocampus in AD, as compared to an age-matched control group. Additionally, it seems that this decrease of hippocampal neuronal density was more prominent at the CA1 and CA3 hippocampal areas. This could have important implications in the design of therapeutic and investigative strategies of AD. Rat Hippocampal Neurons and Primary Neuron Growth Medium (PNGM^®) from Lonza have been used in order to study the significant degeneration of hippocampal neurons in AD.

Gene transfer technology - transfection

Efficient gene transfer is an important tool for studying the biology of neuronal function. The Nucleofector^® Technology, based on electroporation in a cell type–specific solution, enables direct delivery of DNA and/or RNA into the cell nucleus. This strategy results in reproducible, rapid, and efficient transfection of a broad range of cells, including primary neurons. Lonza has developed protocols for successful transfection of post-mitotic neurons. Primary hippocampal neurons were transfected with pmaxGFP^® Vector (Lonza), or double transfected with pSyn-GFP (eGFP under the control of the neuron-specific synapsin promoter, and pDsRed monomer-C1 RFP (CMV promoter, BD Pharmingen) with 30-50% efficiency and normal neural development.

Lonza Nucleofector^® Kits for Mouse and Rat Hippocampal cells have been used and reported by various other groups.

High Throughput Nucleofection^® of Primary Rat Hippocampal Neurons

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