Table I Dendrites in rat CA1 pyramidal cell
Dendritic |
Number of |
Proximal |
Branch |
Distal |
Dendrite |
Basal |
5 |
1μm |
30 |
0.5-1 μm |
130μm |
Stratum radiatum |
1 |
31 μm |
30 |
0.25-1 μm |
110μm |
Stratum |
15 |
0.25-1 μm |
500μm |
The cytoskeleton of dendrites is composed of microtubules, neurofilaments, and
actin filaments. Microtubules are long, thin structures, approximately 25 nm in
diameter, oriented to the longitudinal axis of the dendrite. In regions of the
dendrite free of large organelles, they are found in a regular array at a density of
50-150 μm-2. Microtubules are typically spaced 80-200 nm apart, except in
places where mitochondria or other organelles squeeze in between them.
Microtubules are the “railroad tracks” of the cell and they play an important role in
the transport of mitochondria and other organelles (Overly et al., 1996).
The cell body (soma) is the trophic center of the neuron and in CA1 neuron has
diameter ~ 21μm. The cell body (soma) contains the nucleus and the principal
protein synthetic machinery of the neuron. Axons have essentially no ability to
synthesize protein, since they do not contain ribosomes or significant amounts of
RNA. Thus, axons depend entirely on proteins produced in the cell body, which
are delivered into the axon by important transport processes. Dendrites do
contain small amounts of both mRNA and ribosomes, and this protein synthetic
machinery is thought to play an important role in dendritic function, but most of
the proteins that are present in dendrites are transported from the cell body.
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