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R Verley

Publications and source records attributed to R Verley.

At least 19 recordsLinked to original sources
PubMed1990

Plasticity of GABA- and glutamate-containing terminals in the mouse thalamic ventrobasal complex deprived of vibrissal afferents: an immunogold-electron microscopic study.

GABA and glutamate immunogold staining demonstrated that nerve cells of the thalamic ventrobasal complex (VB) of mice were positive exclusively for glutamate. None of the neuronal perikarya reacted the GABA antibody. By using alternate thin sections of the normal VB, it was also shown that large "specific" somatosensory and small corticothalamic terminals, both of which contained spherical synaptic vesicles, exhibited only glutamate-like immunoreactivity. A third axonal type, containing flat-ovoid synaptic vesicles, stained only for GABA. Seventy-five days after coagulation of the vibrissal follicles in newborn mice, a characteristic multiplication of GABA positive axon terminals was observed. In addition, it was demonstrated that, similarly to modified cortical endings (Hámori et al., J. Comp. Neurol. 254:166-183, '86), many GABA positive terminals appeared as specific afferent endings, replacing the missing "specific" vibrissal afferents. This finding shows a remarkable plasticity of inhibitory GABA axons during developmental synaptogenesis and provides further evidence that the size, location, and the type of attachment of presynaptic terminals are dependent on their postsynaptic target.

Afferent Pathways↗
PubMed1986

Morphological alterations in subcortical vibrissal relays following vibrissal follicle destruction at birth in the mouse.

Morphological modifications of two subcortical vibrissal relays were analyzed, following destruction of vibrissal follicles in newborn mice. The volume of the nucleus interpolaris (NI) of the trigeminal nuclear complex in the brainstem decreased by 33%, while the number of its neuronal perikarya decreased only moderately. Vibrissal deafferentation caused no shrinkage of the ventrobasal complex (VB). In the damaged medial vibrissal part of VB (VBm), however, neuronal density was higher than normal, indicating the prevention or retardation of physiologically programmed cell death in the afferentation deprived thalamic somatosensory relay station. It is suggested that the difference in neuron density produced by deafferentation is related to the states of maturation at birth of the two subcortical vibrissal relays. Following vibrissal deafferentation the basic organization of the synaptic neuropil appeared to be similar to the control. Quantitative electron microscopic (EM) analysis revealed, however, an increased number of axon terminals with ovoid synaptic vesicles in both deafferented relay stations. The increased density of gamma-aminobutyric acid (GABA)-immunostained boutons observed in the VBm following vibrissal deprivation suggested a compensatory increase most probably of the inhibitory axon endings. Quantitative EM analysis also provided evidence that many or most of the specific afferent terminals in the damaged VBm were not identical with but were substitutes for the original "vibrissal" specific afferents. Forty percent of all "specific" afferents were shown to be modified corticothalamic terminals. The modification and the resemblence of some cortical endings to specific afferents demonstrated the morphogenetic plasticity of synaptogenesis in these terminals during development as well as the importance and inductive potential of the postsynaptic target in the differentiation of presynaptic axon terminals.

Animals↗
PubMed1986

A morphometric study of mouse trigeminal roots after unilateral destruction of vibrissae follicles at birth.

Trigeminal sensory roots were studied in neonatal mice. On the deafferented side, the surface area of the cross-section through the sensory root is diminished by 31% and the number of myelinated fibers is reduced by 21%, but the proportion between myelinated and unmyelinated fibers remains unchanged. The distribution of axonal diameters, analysed in 7 dorso-ventral scanning bands through the sensory roots, indicates a loss or eventually an atrophy of large myelinated axons in the medial two thirds of the sensory root. In both control and deafferented sides the diameter of the myelinated fiber (outside the myelin sheath) is proportional to the axon diameter (inside the myelin sheath). Our results confirm the loss of most of the neurons innervating vibrissae and the lack of regeneration or sprouting in the deafferented root in the newborn mouse.

Animals↗
PubMed1986

[Organization of the nervous system after coagulation of the follicles of mystacial vibrissae in the newborn mouse: an example of neuronal plasticity].

In the mouse the vibrissae and the common fur of the head are a good model of the so called neural plasticity. The characteristics of this model are: the pattern of implantation of the vibrissae at the periphery and that of the arrangement of barrels in the contralateral cortical projection area of vibrissae as well as that of the "barreloïds" in the subcortical vibrissal relays (somato sensory thalamus and trigeminal nuclear complex) are homeomorphic with one another. Each barrel and "barreloïd" receives projections from one vibrissa. Moreover at the level of the cortex these projections are also in register with projections from ipsilateral vibrissae. Head fur hairs project to well defined but entirely distinct areas. Destruction of vibrissae follicles at birth beside preventing barrel and barreloïd formation in the CNS, leads to several morphological changes: degeneration of the primary sensory neurons innervating vibrissae in the trigeminal ganglion, thus degeneration of their central axons and the corresponding terminals in the trigeminal vibrissal relays changes in the distribution of the activity of succinate dehydrogenase in the IVth layer of the cortical vibrissal area and in the corresponding subcortical relays, from the normal discrete (barrel hollow) pattern--corresponding to the clustered vibrissal afferents--to a continuous band, keeping a normal level of activity, excepted in the trigeminal vibrissal relays and a remarkable preservation of cortical thickness but a notable atrophy in the trigeminal vibrissal projection areas. Beside upsetting the anatomy vibrissae follicle destruction causes marked functional changes an outstanding take-over of the deafferented cortical vibrissal area (still identifiable from projections of vibrissae ipsilateral to it) by the head fur hairs this take over exist also in the subcortical vibrissal relays a change in the thalamo-cortical connections. Modifications in the organization of connections are initiated by the loss of the primary sensory neurons innervating vibrissae, in the trigeminal ganglion and results only from early lesions. In mice lesioned when adults the loss of primary sensory neurons is less important and functional take over by the common fur is not observed.

Afferent Pathways↗
PubMed1985

[Histological changes in the somatosensory thalamus after unilateral coagulation of vibrissa follicles of the muzzle of the newborn mouse].

Light microscopic study of the thalamic ventro-basal complex (VB), after unilateral coagulation of vibrissae follicles in newborn mouse, revealed an excess of neuronal perikarya on the controlateral "deafferented" side as compared to the normal side. The higher density of nerve cells was confined to the vibrissal relay in the medial part of VB nucleus (VBm), whereas the cell number in the non vibrissal-lateral part of this nucleus (VB1) remained on the control level. Electron microscopic investigation of the thalamic vibrissal relay has shown signs of a modified synaptogenesis on the "deafferented" side: (a) the number of specific afferents has diminished and in contrast to the normal side, most of the specific sensory terminals contain small spheroid synaptic vesicles and (b) the number of axon terminals with ovoid pleomorphic vesicles has been doubled.

Afferent Pathways↗
PubMed1982

Reorganization of thalamo-cortical connections in mice dewhiskered since birth.

Localizations of thalamic relay neurons of vibrissae, common fur of the muzzle and head, as well as those projecting to the cortical vibrissal field in mice with vibrissae coagulated at birth, have been studied by retrograde transport of peroxydase. The tracer was injected in the corresponding cortical areas. In coagulated mice, labeled thalamic neurons were situated in the ventro-basal complex anterior to its vibrissa part, corresponding to the area labeled after intracortical injection of the muzzle and head fur area. These results indicate a reorganization in the origin of thalamo-cortical afferents in coagulated mice.

Animals↗
PubMed1981

A morphometric study of mouse trigeminal ganglion after unilateral destruction of vibrissae follicles at birth.

A morphometric study of the trigeminal ganglion after unilateral vibrissae follicles' coagulation in newborn mice has shown the following: (a) a 42.8% decrease of the total volume of the ganglion on the deafferented side with reference to the normal side; a 61.5% decrease of the ophthalmic-maxillary part of the ganglion where neurons whose axons innervate vibrissae follicles are located, and only a 24.1% decrease in the common part; (b) a 54.8% decrease of the neuronal cell body volume in the ophthalmic-maxillary part and practically no change in the common part, and (c) a 64.5% decrease of the volume occupied by the nerve fibers in the ophthalmic-maxillary part and only a 28.1% decrease in the common part. A comparison of the section areas in ganglion and of the bulk area of neuronal cell bodies at different levels has also been performed. Counting of the neuronal cell bodies in the ophthalmic-maxillary part of the ganglion indicated a mean neuronal loss of 36.5%. Peripheral reinnervation of the common fur by regenerated axons of neurons which previously innervated vibrissae, although unlikely, cannot be completely excluded.

Afferent Pathways↗
PubMed1979

Projections on the cortical somatic I barrel subfield from ipsilateral vibrissae in adult rodents.

In adult rats and mice, ipsilateral projections to SI posteromedial barrel subfield (PMBSF) are demonstrated for mystacial vibrissae (sinus hairs). Mechanical stimulation with angular deflections in the 2-5 degrees range, elicits potentials in limited areas of SI whose geometric centers coincide for two homologous (contra- and ipsilateral) vibrissae. The cortical domains for two adjacent vibrissae overlap one another slightly. Phase reversal of potentials and unit discharges are also present within the cortex. Ablation of the SI area contralateral to the SI area under study completely abolishes the ipsilaterally projected potentials. It is proposed that ipsilateral responses are mediated via the corpus callosum with an extra delay of 4-5 msec, thus giving each hemisphere the opportunity to compare vibrissal information originating from the two mystacial pads.

Animals↗
PubMed1979

Projections of the common fur of the muzzle upon the cortical area for mystacial vibrissae in rats dewhiskered since birth.

In normal adult rats, the mystacial vibrissae and the common fur of the snout project at different loci on the SI cortex. The surface area of the normal fur projection is 0.8 mm2, whereas the vibrissa field amounts to 3-4 mm2. In rats dewhiskered since birth, the vibrissa area can still be identified through the projections from ipsilateral vibrissae (undamaged side). It is shown that in the absence of the vibrissae since birth, the vibrissa area, and this alone, is invaded by projections from the contralateral fur (damaged side).

Animals↗
PubMed1977

[Organization in "barrels" of layer-IV cells of the S1 cortex in the mouse: effects of lesions or deprivation of the mystacial vibrissa].

In newborn mice the mystacial pads of the upper lips were submitted to different destructive or functionally reducing procedures. The effects on the barrels of the somato-sensory cortex were judged in mature animals and classified into 3 categories: 1. the barrels were present and normal; 2. the cortex was devoid of barrel structures; 3. the barrels were disorganized. Only procedures which involved peripheral lesions, and not those which reduced only the functional level, produced effects as deep as absence or disorganization of the barrels.

Animals↗
PubMed1977

[Comparative study of somatic and visual projections on the cerebral cortex of the normal adult rat, the rat enucleated at birth, and the young rat].

A comparative study of somatic and visual projections on the cerebral cortex of the adult of the normal rat or of the rat enucleated at birth, and of the young rat. This study was first designed to examine the developmental features of somate, sensory and visual projections to the rat cerebral cortex, together with their alteration as a consequence of early sensory deafferentation. We were led to a reevaluation of these projectins in the normal adult rat. This study specifically shows that topical projections exist, for both the somatic and the visual system. However, projections that are highly convergent in nature are present over most of the superolateral aspect of the cerebral cortex and we were unable to demonstrate any simple change resulting from early visual deafferentation.

Afferent Pathways↗