Glossary

Astrocytes- These cells, a kind of glial cell, are  star-shapedand found in the central nervous system (CNS). Astrocytes are responsible for biochemical support of cells that form the blood-brain barrier, provide nutrients to neurons, and maintain extracellular ion balance.  They are produced by the same developmental pathway as neurons.

Antagonist- a compound that blocks or inhibits the action of a neurotransmitter on a synapse.

AMPA potentiator- AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors are the main contributors of excitatory (+) neurotransmission responsibly for desensitizing the excitation of numerous synapses. It is also responsible for the early response of a neuron to the glutamate neurotransmitter. AMPA receptor potentiators can be used as a means of enhancing neuroplasticity.

Apoptosis- natural process of programmed cell death.

BrdU- Bromodeoxyuridine (5-bromo-2-deoxyuridine) synthetic nucleoside that is an anologue of thymidine. Commonly used to label proliferating new cells during their  S phase cell cycle. During this stage the newly synthesized DNA replaces thymidine with BrdU. With the use of antibodies scientists are able to detect cells replicating their DNA.

Choline-precursor for the neurotransmitter Acetylcholine.

Confocal Microscopy- optical microscopy technique that allows reconstruction of three- dimensional structures that are obtained from still images.The confocal microscope utilizes point illumination and a pinhole to eliminate out-of-focus signal and only structures in the focal plane are visible. The achievable thickness is determined by the wavelength of    light used divided by the objective lens magnification.  The use of a laser is utilized to excite light to achieve high intensities. A detector is attached to a computer that constructs the image, one pixel at a time. Some advantages to confocal microscopy, include controllable depth of field, elimination of out of focus information, and ability to collect optical sections from thick specimens.

Dentate Gyrus- an area of the hippocampal formation that is thought to play a role in new memories. This region contains granule cells which send projections to  pyramidal cells and interneurons of the hippocampus. This region of the brain is accountable for a high rate of neurogenesis.

Endothelial cells- thin layer of cells that lines heart cavities and blood vessels.

GABAergic- term for neurons that contain the inhibitory neurotransmitter GABA.

Ganglia- are intermediate cells in the nervous system with different connections in the body that connect different nervous system parts, for example the peripheral nervous system to the central nervous system.

GFAP- (glial fibrillary acidic protein) is an intermidiate filament protein that is specific to astrocytes rather than neurons, also expressed in expressed in other astroglia in the central nervous system, in satellite cells in peripheral ganglia, and in non myelinating Schwann cells in peripheral nerves.

Glia- general term for support cells in the central nervous system.

Gliogenesis- proliferation of glia which are neuronal support cells (ex: astrocytes, microglia, etc)

Glutamate- an excitatory neurotransmitter released during the stress response.  An increase in glutamate causes a decrease in neurogenesis.

Granule cells-small neurons that are found within the dentate gyrus of the hippocampus, in the olfactory bulb, as well as in other brain regions. These cells are functionally and anatomically diverse.  In the olfactory bulb granule cells are GABAergic (inhibitory neurotransmitter) and axonless, while in the dentate gyrus they have glutamatergic (play key role in LTP plasticity) projection axons.Granule neurons are produced during neurogenesis in both regions.

Hippocampus- (greek for seahorse; cross sections of this forebrain region resembles a seahorse). Structure found in the medial temporal lobe, also part of the limbic system. This area includes the hippocampus proper, dentate gyrus, and subiculum. This brain region plays an important role in long-term memory and also spatial navigation.

Immature Neuron- undifferentiated young neurons that have not been incorporated into a neural network.

In vivo- Latin for “within the living”; experimentation using a whole, living organism.

Long-Term-Potentiation- (LTP) long-lasting increase in the excitability of a neuron in response to repetitive high-frequency synaptic input. This is an important process in synaptic plasticity and a cellular mechanism underlying learning and memory.

Mature Neuron- a neuron that has been incorporated and secretes specific neuronal factors such as NeuN

Microglia- type of non-neural cell in the central nervous system that regulates the extracellular environment by destroying foreign matter.

Morris Water Maze- (MWM) the Morris water navigation task is a commonly used behavioral task to test hippocampal spatial memory. The task consists of placing an animal in a small pool of water. The animal’s swimming patterns are recordeduntil it finds a hidden platform. Factors such as the time taken and total distance traveled are quantified for statistical analysis. Animals are expected to improve their performance in further trials since they have learned to locate platform according to visual cues.

Neocortex- mammalian brain region also referred to as the neopallium. This brain region is the outer layer of the cerebral hemispheres.  It is made of up of  a total of 6 distinct layers of neurons, the sixth layer is the inner most layer.  The neocortex is known to develop in an inside-out fashion. This region is involved in higher functions such as sensory perception, generation of motor commands, spatial reasoning, and even language.

NeuN- (neuronal nuclei) neuron-specific DNA-binding nuclear protein which functions as a marker for neurons. NeuN immunoreactivity is observed in post-mitotic neurons that are initiating cellular and morphological differentiation.

Neurogenesis- (birth of neurons) it is the process by which neurons proliferate, migrate, and integrate themselves in the brain. This process is significantly active during pre-natal development; however, adults continue to generate new neurons as well. Two main regions that undergo significant neurogenesis in adulthood are the subventricular zone (SVZ) and subgranular zone (SGZ).

Neuron- functional cells of the central nervous system. These cells are specialized to receive, conduct, and transmit electrochemical signals. Neurons are composed of a soma (cell body), dendrites, axon, and bouton.

Neuroplasticity- known as the malleability of the brain, its ability for neurons to strengthen or weaken their connectivity based on new experiences.  A fundamental principle of how neuroplasticity functions is related to the concept of synaptic pruning, where each individual neuronal connection is either refined or removed depending on usage specially in regards to learning and memory. In relation to neurogenesis, the plasticity of the brain also pertains to the birth of new neurons that will become integrated into different brain regions. Neuroplasticity also plays a role in the ability of the brain to recover after trauma.

Nigrostriatal pathway-neural pathway that connects the substantia nigra with the striatum.

Noradrenaline- A neurotransmitter which is released from the adrenal medulla during the fight or flight response.  It causes physiological arousal and increases heart rate and blood pressure.

Olfactory Bulb- protrusion at the end of the olfactory nerve which receives input from the olfactory receptors playing a role in the perception of odors.

Oligodendrocytes- neuronal support cells which insulate axons for more efficient synaptic transmission

Progenitor cells- these cells have the capacity to differentiate into specific cell types. However, these cells differ from stem cells because they are more specified and differentiate into particular target cells. Progenitor cells cannot divide indefinitely like stem cells but they have a limited number of divisions.

Rostral migratory stream-(RMS) is a pathway that originates in the SVZ of the brain by which neuronal precursors migrate to reach the olfactory bulb. Once they have reached the olfactory bulb they differentiate into interneurons. Since neurogenesis is known to occur in the SVZ this pathway is used for neurons to reach their final destination.

Schwann cells- cells located in the peripheral nervous system that support neurons (contained within nerves) and promote synaptic transmission.

Subependymal layer-cell layer lines the lateral ventricles in the brain.

Subgranular zone-(SGZ) This region lies in the dentate gyrus and it is where adult neurogenesis proliferation occurs. The SGZ lays within the hippocampal parenchyma in close proximity to the granule layer and the dentate gyrus. This site along with the subventricular zone are the main regions for adult neurogenesis.

Subventricular zone- (SVZ) This region lies in the lateral walls of the ventricles . The SVZ  is divided into four distinct layers with different cellular composition including neural stem cells. This region generates new neurons destined for the olfactory bulb including migrating neuroblasts, imaturature precursors, astrocytes, and ependymal cells. Along with the SGZ of the dentate gyrus, the SVZ are main regions for adult neurogenesis.

Sympathetic Nervous System- part of the automatic nervous system which regulates the bodies resources under stress and controls the  internal organs to activate the fight or flight response.

Synaptic transmission- chemical messengers that are the communicative language between neurons.

Tritiated thymidine- [H3] Thymidine contains the hydrogen radionuclide (H) tritium. It is used as a marker to detect neurogenesis since it measures the localized synthesis of DNA, where it becomes incorporated.

Ventricular zone-in this brain region which lies next to the ventricles is where cortical neurons are generated. It produces progenitor cells, which later on divide and produce glial and neuronal cells. In this zone is where radial glial cells are produced from progenitor cells they become enablers for the migration of other cells from the ventricular zone to form a laminar cortex.

Page by Natalia Ibanez