Chandelier Neuron
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The Chandelier neuron is a type of GABAergic cortical interneuron.
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Chandelier neuron
The Chandelier neuron is a cortical interneuron that is involved with the transport of a GABA membrane transporter, GAT-1. This regulates the reuptake of GABA. It is believed that the main function of the chandelier neuron is an inhibitory action on pyramidal neurons. Damage to a chandelier cell can lead to a hyperactive state in pyramidal neurons known as a hyperdopaminergic neurotransmission.
Chandelier cells function as long range messengers because one signal from a Chandelier cell activates a pyramidal neuron intead of hundreds of connections other neurons need to excite a pyramidal neuron. This lets the Chandelier cell activate many different pyramidal cells through the Chandelier cells long and intricate axon arbors. These important functions of Chandelier cells are one of the reasons Santiago Ramón y Cajal, described that they may be what makes us distinct from lower thinking species of animals because more complex brains usually contain more chandelier cells.
Neuronal Type: Cortical interneuron.
Anatomy
The cell body of the chandelier neruron is located in the center of a large networked structure of axon filaments. The axon arbors form an array that is called a cartridge. Each cartridge establishes large number of links with a pyrimidal neuron. The complexity of chandelier ells changes through different species with humans having one of the most intricate chandlier cell structure. The morphological differences between species could play a role in higher level brain function.
Molecular profile
- Unique Neurotransmitter: GAT-1 which is used as a signal for pyramidal neurons to reuptake GABA. GAT-1 helps the identify chandelier cells because the cells are immunoreactve to GAT-1 at the cartridge sites in their axon arbors.
Synaptic Connections
These chandelier cells act specifically on the axon initial segment of pyramidal cells. One connection from a chandelier cells is sufficient to activate a pyramidal neuron.
Synaptic Inputs
Chandelier cells usually contain an input from a nearby pyramidal cell.
Synaptic Outputs
Outputs from Chandelier cells connect to Basket cells and Pyramidal neurons through complex axon arbors labeled cartridges. The complexity of cartridges seems to increase in higher functioning mammals, especially in the frontal and pre-frontal cortex. Increased complexity of Chandelier cells might be directly correlated to increased intelligence in mammals.
Spiking properties
Chandelier cells are considered fast spiking neurons that react to the an excitation of a pyramidal neuron.
Behavior
Chandelier cells function to inhibit pyramidal neurons along with basket cells. Signals from the pyramidal neurons travel to the chandelier cell and in turn chandelier cells respond by sending an oppposing and inhibitory signal back to the pyramidal cells. Chandelier cells have also recently been found to propagate a signal sent by a specific pyramidal neuron. An activated chandelier cell can in turn activate multiple other cells like basket cells and other pyramidal neuron. This helps to send a long distance signal across the nervous system.
Loss of Function
When chandelier cells become degraded in the pre-frontal cortex of the brain, an association with schizophrenia is established. This may be due to a reduction in GABAergic inhibition of pyramidal neurons. It is unsure if an outside source causes the degradation of chandelier cells or it is spontaneous in itself but when their function is interrupted, pyramidal neurons do not properly receive an inhibitory signal which leads to a hyperactive state in the pyramidal neurons that can be attributed to the symptoms exhibited by those affected by the mental disorder.
References
- Woodruff A, Yuste R (September 2008). "Of Mice and Men, and Chandeliers". PLoS Biol. 6 (9): e243. PMID 18816168.
- Xiang Z, Huguenard JR, Prince DA. "Synaptic inhibition of pyramidal cells evoked by different interneuronal subtypes in layer v of rat visual cortex." J Neurophysiol. 2002;88:740–750.
- Yuste R, MacLean JN, Smith J, Lansner A. The cortex as a central pattern generator. Nat Rev Neurosci. 2005;6:477–483
- Ramon y Cajal S. Letter to Lorente. 1934. Courtesy of Dr Francisco Alvarez, translation by RY.
- Pierri JN, Chaudry AS, Woo T-UW, Lewis DA: Alterations in chandelier neuron axon terminals in the prefrontal cortex of schizophrenic subjects. Am J Psychiatry 1999; 156:1709–1719 PMID 10553733
