A neurite refers to the projection from the cell body of a neuron, which is either an axon or a dendrite.
An axon is the slender projection of a neuron that conducts electrical impulses away from the neuron’s cell body. The function of the axon is to transmit information to different neurons, muscles and glands.
Axons are insulated with myelin which is a fatty substance formed by two types of glial cells:
- Schwann cells – ensheathing peripheral neurons and
- Oligodendrocytes – insulating neurons of the central nervous system
Dendrites are the branched projections of a neuron that act to propagate the electrochemical stimulation received from other neural cells to the cell body, or soma. The electrochemical stimulation onto the dendrites are carried via the synapses located on the end of the dendrites.
A synapse is a structure that permits a neuron to pass the electrochemical stimulation signal to another neuron. At a synapse, the presynaptic neuron, via the presynaptic membrane, which is located on the axon, comes into close apposition with the postsynaptic neuron, via the postsynaptic membrane, which is located on a dendrite or soma.
Many neurodegenerative diseases and cognitive impairment are caused by: 1
- Neuritic atrophy
- Synaptic loss
The atrophy of neurites and synaptic loss has been observed in the following neurodegenerative diseases:
- Alzheimer’s disease
- Parkinson’s disease 5
- Huntington’s disease 6
- Creutzfeldt–Jakob disease 7
Scientists at the Uehara Memorial Foundation explored compounds that would facilitate the regeneration of neurites and the reconstruction of synapses, even in severely damaged neurons, and to show evidence of the effects in vivo as well as in vitro.
Their analysis and results were published in the British Journal of Pharmacology in April 2005. The article, entitled Neuritic regeneration and synaptic reconstruction induced by withanolide A, investigated the effects of withanolide A (WL-A), isolated from the Indian herbal compound Ashwagandha (root of Withania somnifera), on neuritic regeneration and synaptic reconstruction in cultured neurons damaged by Aβ(25–35) and cognitive-deficient mice by Aβ(25–35)-injection. 8
The authors hypothesized that reconstructing neuronal networks in the injured brain would be the most necessary step in the fundamental recovery of brain function. In order to reconstruct neuronal networks, neuritic regeneration and synaptic reconstruction must take place in the damaged brain. 9
Withania somnifera, known commonly as ashwagandha, is a plant in the Solanaceae or nightshade family. It is widely used as a medicinal herb in Ayurvedic medicine. The leaves contain the steroidal lactones withanolides.
Amyloid β and Aβ(25–35) is a major pathological cause of Alzheimer’s disease which forms deposits in the brain, and subsequently induces:
In the study, treatment with withanolide A (WL-A) (Ashwagandha) induced significant regeneration of both axons and dendrites, in addition to the reconstruction of pre- and postsynapses in the neurons. WL-A could also ameliorate the memory deficit in mice, and could generate neurites and synapses in the cerebral cortex and the hippocampus. 13
The authors concluded:
“WL-A is therefore an important candidate for the therapeutic treatment of neurodegenerative diseases, as it is able to reconstruct neuronal networks.” 14
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