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Forschungsstelle
EU FRP
Projektnummer
96.0430-2
Projekttitel
Serotonin and abnormal development of the mouse sensory cortex in relation to the psychiatric syndrome of monoamine oxidase A deficiency
Projekttitel Englisch
Serotonin and abnormal development of the mouse sensory cortex in relation to the psychiatric syndrome of monoamine oxidase A deficiency

Texte zu diesem Projekt

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Abstract
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Erfasste Texte


KategorieText
Schlüsselwörter
(Englisch)
Neuroscience; brain development; serotonin
Alternative Projektnummern
(Englisch)
EU project number: BMH4CT972412
Forschungsprogramme
(Englisch)
EU-programme: 4. Frame Research Programme - 4.2 Agriculture and agroindustry
Kurzbeschreibung
(Englisch)
See abstract
Partner und Internationale Organisationen
(Englisch)
Coordinator: CNRS (F)
Abstract
(Englisch)
In the final period of this grant we completed the series of labelled thalamo-cortical axons and included earlier postnatal stages to have a final set of axons representing the following ages: PI, P4, P5, P7, P9, PIO and P12. For all these ages slices were prepared from normal and barrelless mice and axons were labelled by placement of small crystals of biocytin in the ventrobasal nucleus of the thalamus. Per strain of mice five axons were reconstructed for the following postnatal days: PI, P4, P8 and PIO/12. The morphometric analysis revealed:
-At PI, in both normal and barrelless mice the tangential extent in the cortical plate is larger than the size of the (tangential) area of a future barrel. The difference between the two strains is that the extent in barrelless is larger than that in normal mice;
-At PI, in comparison with observations in normal mice, the thalamo-cortical axons ofbarrelless mice have fewer branches but they are longer;
-At P4, thalamocortical axons in normal mice are restricted to a barrel, whereas in barrelless they remain occupying a larger tangential extent;
-No major differences in radial extent were observed. These results revealed that in development, thalamo-cortical axons in normal mice pass through a phase during which they 'explore' a larger cortical area than they occupy in adulthood. This phase lasts until the moment of the cytoarchitectonic formation of barrels. The thalamocortical axons in barrelless mice show differences with normal mice prior to the age at which barrels are formed. This indicates that the gene pertmbation affects general factors determining the outgrowth pattern of thalamocortical axons.
This anterograde tracing study was complemented with a retrograde tracing study in adult normal and barrelless mice. Biotinylated dextran was iontophoretically injected in a cortical column that, in a dimension tangential to the cortical surface, comprised a single barrel at the level of layer IV. Retrogradely labelled neurones were plotted in the thalamus of both strains of mice. The comparison revealed that in normal mice labelled cells form a dense cluster in the dorsal part of the ventrobasal nucleus of the thalamus. This cluster of cells has a characteristic, 'banana-like', shape in normal mice whereas in the barrelless mice, the group of labelled cells are more widely distributed and, as an ensemble, do not take shape. These differences in spatial distribution of the thalamic projection neurones complement the results of the anterograde tracing in adult mice. The following conclusion was formulated: in the barrelless mouse the thalamus relays information from a great number of whiskers to a single cortical column, whereas in the normal mice there is no similar anatomical substrate for such a convergent thalamic input.
A third part of our activities was directed to the final analysis of a DG-experiment reported upon earlier in which we induced cortical plasticity in normal and barrelless mice by denervation of a row of whisker follicles in adulthood. This type of peripheral intervention is followed by the regeneration of the interrupted nerve
fibres. At the level of the somatosensory cortex, the representation of the denervated follicles becomes reactivated by stimulation of (intact) follicles of the adjacent rows. This reactivation is progressive within a similar period of time in both strains. However, the detailed analysis carried out during this final period of the grant revealed that in barrelless the reactivation enters the deafferented zone from both sides, whereas in normal mice the reactivation is spread immediately throughout the deafferented area. This may difference correlates with the greater tangential extent of thalamocortical axons in barrelless mice that go well beyond the area occupied, functionally, by a single barrel domain.
Datenbankreferenzen
(Englisch)
Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. +41 31 322 74 82
Swiss Project-Number: 96.0430-2