Morphological and Biochemical Studies on
Early Development of Neurons in the
Cortex from Rat Brains.
Yen-Chung Chang
Dendritic
spine, immunocytochemistry, cell culture, rat cortical neuron, actin, tubulin
Abstract:
Dendritic spines
are tiny protrusions on dentrites of neurons where most excitatory synapses in
the brain are located. It has been shown that the plasticity of neurons and
neuronal signal transductions are affected by the location, quantity and
morphology of the dendritic spine. We examined the morphological and
biochemical changes of spines and associated these changes to the function of
neurons during the period of neuronal development. Cortex neurons from fetal
rat brains were cultured (at 105 cells/ml) and their development
within the first 3 weeks was monitored. The correlation between the
morphological alteration of cells and their electrophysiological properties
during the development was examined. The eEPSC frequency of a neuron was
recorded with the whole-cell patch-clamping technique and then labeled with
Lucifer yellow for morphological studies. Furthermore, changes in the structure
of cytoskeletons within the spine were studied by examining the distribution
actin and tubulin with the double-staining technique. Also, the association
between the formation of synapses and the type of spine was investigated by
observing the presence of actin and synaptophysin. Our observations showed
that, within 150 mm away from the soma, the density of spine was decreased as a
function of the developmental time; while the ratio of the amount of synapse
formed on the dendritic shafts to that on spines was increased. The tubulin
within spines was decreased during the developmental if observed randomly in
the neuron. The morphological character of spines was shifted from the headless
type to the headed type during the development; the latter type was mostly found
together with synapses. In addition, analysis of the location of synapses and
the excitatory electric signals from there showed that there was no correlation
between them. Therefore, the development of cortex neurons is clearly
correlated with the morphology and the amount of dendritic spines, together
with the biochemical compositons within.