Μελέτη της συναπτογενέσεως του ακουστικού φλοιού in vitro άνευ και κατόπιν ηλεκτρικού ερεθισμού ανάλογου προς τα ηλεκτρικά δυναμικά ενέργειας του κοχλιακού νεύρου

The synaptogenesis and the neuronal interactions of the rat's acoustic cortex were studied in explants cultured in vitro, exposed to a continuous sound of a certain frequency. The morphological findings were correlated morphologically with explants of the same area of the cortex from the same animals cultured in vitro under usual conditions, unexposed to any acoustic stimuli, used therefore as normal controls. All the explants which were exposed to continuous sound demonstrated: a) Increased synaptogenesis of all kinds of synaptic contacts. Large number of axodendritic, axosomatic, axoaxonic and dendrodendritic synapses was seen in all the specimens exposed to acoustic stimuli. b) Most of the synapses of the explants exposed to continuous sound demonstrated a marked polymorphism of the synaptic contacts between the presynaptic terminals and the postsynaptic dendritic spines. Very frequently, large number of presynaptic terminals developed synapses on the postsynaptic surfaces of the same spine or the same synaptic profile. It was a frequent finding also the presence of multiple spinules inside large presynaptic terminals. c) The explants exposed to a continuous sound demonstrated an increased myelinogenesis. Some atypical myelin sheath figures were also seen, such as common myelin sheath around two or three axons, myelination around cell bodies, abnormalities of the internal mesaxon, dilatation of the Smidt-Landermann incisures and increase of the distance between the interperiod lines. d) Large number of astrocytic sheaths around cell bodies, dendrites and the initial part of axons were seen in the explants which were exposed to acoustic stimuli. Most of the astrocytic sheaths were cellular processes of protoplasmic astrocytes which intervened in the neuronal circuits. e) The explants which were exposed to continuous sound showed large number of growth cones in all the types of neurons, especially in the large polyhedral ones. Most of the cones were surrounded by astrocytic sheath, though some of them were free in the neuropial space. f) The most impressive finding in the exposed explants to continuous sound was the tremendous number of the dendritic spines on the primary, secondary and tertiary dendritic branches of all the types of neurons some of the spines remained unattached embedded in the some of the astrocytes, showing the typical postsynaptic differentiation of the plasma membranes. In conclusion, the above described morphological findings support the hypothesis that the neuronal circuits of the specific senso-sensorial areas of the cerebral cortex are sensitive to the specific relevant exterior stimuli, having the preprogrammed tendency for developing new synaptic contacts under the influence of a continuous stimulus which normally had to be analyzed by a relevant sensorial organ. The extensive synaptogenesis in vitro in the explants exposed to a continuous stimulus emphasized also the plasticity of the neuronal circuits of the cerebral cortex and the multipotential character of the neuronal interactions.

Grantor dc:publisher

Aristotle University Of Thessaloniki (AUTH)

Year dc:date

1990

Authors dc:creator

• Manolidis, Spiros
• Μανωλίδης, Σπύρος

• Ιατρική και Επιστήμες Υγείας
• Επιστήμες Υγείας
• Medical and Health Sciences
• Health Sciences

Language dc:language

gre

Identifier

10.12681/eadd/1413

OAI identifier oai:identifier

oai:10442/1413