Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Vibrissae”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1984

Early development of changes in cortical representation of C3 vibrissa following neonatal denervation of surrounding vibrissa receptors: a 2-deoxyglucose study in the rat.

The development of changes in cortical representation of a C3 mystacial vibrissa in the rat was studied with [14C]2-deoxyglucose (2-DG) autoradiography after neonatal unilateral ablation of all but the C3 whisker follicle. The 2-DG-labeled column, which was produced by stroking the spared C3 vibrissa, was enlarged (35%) at postnatal day (p.d.) 5 and reached 140% by p.d. 12, as compared to the control C3 vibrissa column in the opposite hemisphere. The diameter of the C3 barrel itself on the involved side was about 40% larger than that of the control side at all ages. Based upon the above postoperative survival times, at least two stages in the altered development of the spared C3 vibrissa column are suggested.

Afferent Pathways↗
PubMed1992

Induction of follicle formation and hair growth by vibrissa dermal papillae implanted into rat ear wounds: vibrissa-type fibres are specified.

Adult vibrissa follicle dermal papillae have the capacity to induce hair growth and follicle formation when associated with epidermis from various sources. However, the range of conditions under which hair follicle induction will take place has not been established. The question of whether or not the adult papilla carries information to impose fibre-type specificity has also not been fully answered. This study describes how the implantation of isolated papillae into small incisional cuts on the rat ear pinna resulted in the subsequent emergence of abnormally large hair fibres from the wound sites. Many of these hairs were found to display vibrissa-type characteristics. Histological observations indicated that the papillae had interacted with the edges of the wound epidermis to produce new, and particularly large follicles, while immunohistochemical staining revealed that early follicle construction was accompanied by a profusion of the basement membrane constituents laminin and type IV collagen in the subjacent dermis. These findings show that adult rat papillae retain the capacity, as displayed by embryonic dermis, to determine vibrissa specificity in induced follicles.

Animals↗
PubMed1999

Vibrissae-evoked behavior and conditioning before functional ontogeny of the somatosensory vibrissae cortex.

The following experiments determined that the somatosensory whisker system is functional and capable of experience-dependent behavioral plasticity in the neonate before functional maturation of the somatosensory whisker cortex. First, unilateral whisker stimulation caused increased behavioral activity in both postnatal day (P) 3-4 and P8 pups, whereas stimulation-evoked cortical activity (14C 2-deoxyglucose autoradiography) was detectable only in P8 pups. Second, neonatal rat pups are capable of forming associations between whisker stimulation and a reinforcer. A classical conditioning paradigm (P3-P4) showed that the learning groups (paired whisker stimulation-shock or paired whisker stimulation-warm air stream) exhibited significantly higher behavioral responsiveness to whisker stimulation than controls. Finally, stimulus-evoked somatosensory cortical activity during testing [P8; using 14C 2-deoxyglucose (2-DG) autoradiography] was assessed after somatosensory conditioning from P1-P8. No learning-associated differences in stimulus-evoked cortical activity were detected between learning and nonlearning control groups. Together, these experiments demonstrate that the whisker system is functional in neonates and capable of experience-dependent behavioral plasticity. Furthermore, in contrast to adult somatosensory classical conditioning, these data suggest that the cortex is not required for associative somatosensory learning in neonates.

Animals↗
PubMed1998

Experience-dependent depression of vibrissae responses in adolescent rat barrel cortex.

A short period of vibrissae deprivation in an adolescent (approximately 1 month old) rat can lead to depression of the cortical response to stimulation of the regrown vibrissae. In a barrel column representing the deprived vibrissa, depression is greater for neurons located close to the barrel column representing the spared vibrissa. One possible explanation is that the spared vibrissa produces heterosynaptic depression of the principal vibrissa response (Glazewski & Fox, 1996). To test this idea further, we compared the effect of depriving all vibrissae (no heterosynaptic influence at all) with depriving a single vibrissa (maximal heterosynaptic influence expected). In addition we tested the origin of the depression by recording from subcortical structures. After 7 days' deprivation and 6-8 days' regrowth, we tested the responses of barrel cortex cells, thalamic VPm neurons and trigeminal ganglion cells to stimulation of the regrown vibrissae. We found that depression was greater in cortex if a single vibrissa had been deprived than if all vibrissae had been deprived. (Average principal vibrissae responses in single vibrissae deprived animals were 36% of those in all vibrissae deprived animals for layer II/III and 41% for layer IV.) This implicates the spared vibrissae in actively down-regulating responses to the deprived vibrissae. However, some depression could also be produced in animals deprived of all vibrissae (layers II/III were 39% and layer IV 74% of control levels). These results indicate that simple withdrawal of activation has a depressive effect on responses but that depression is far greater if some active inputs remain. Neither form of deprivation had an effect on responses to principal vibrissa stimulation in the thalamus or trigeminal ganglion however, suggesting that depression originates in the cortex. Within the cortex, intracortical connections seem most affected as the greatest depression was found in layers II/III and in layer IV among cells responding at intermediate latencies (9-14 ms).

Animals↗
PubMed1999

The effect of vibrissa deprivation pattern on the form of plasticity induced in rat barrel cortex.

Plasticity was induced in the barrel cortex of adolescent rats by depriving every second vibrissa on the contralateral vibrissa pad. This produced a chessboard pattern of barrels in the cortex where each barrel receiving its principal input from a spared vibrissa was surrounded by barrels for which the principal vibrissa had been deprived and conversely, each barrel receiving its principal input from a deprived vibrissa was surrounded by barrels for which the principal vibrissa had been spared. After 7 days' deprivation, responses to the regrown vibrissae were depressed in layers II/III (49% of control levels) and IV (60%). Depression was far greater than that seen with "all vibrissa" deprivation, suggesting that activity in the spared vibrissae accentuated the depression of the deprived vibrissae. Depression was not due to subcortical changes as thalamic Ventral Posterior Medial (VPM) responses to deprived vibrissa were unchanged. The short latency responses in layer IV (5-7 ms) were unaffected by deprivation, but the number of cells responding at intermediate latencies (8-13 ms) was markedly reduced (to 66% of control). Potentiation of the spared vibrissa response was substantial in the near side of the neighbouring barrel (2.2-fold increase in layers II/III, 2.9-fold in layer IV) but had not spread to the far side after 7 days' deprivation. Sparing multiple vibrissae may increase the rate of potentiation since 7 days is insufficient time for potentiation in single vibrissa spared animals. Potentiation was not due to subcortical changes as thalamic VPm responses to the spared vibrissa were normal. However, in the spared barrel the response latency decreased by 1-2 ms. Only the cells responding at short latency exhibited potentiated responses (39% increase) suggesting that some thalamocortical plasticity is still possible at P28-35. These results show that chessboard pattern deprivation is capable of inducing substantial plasticity over a wide area of barrel cortex. All the major forms of plasticity seen with other vibrissa deprivation patterns were present, although no other single deprivation pattern studied so far causes the complete repertoire seen with chessboard deprivation.

Algorithms↗
PubMed1986

Structure-function relationships in rat brainstem subnucleus interpolaris. I. Vibrissa primary afferents.

Intra-axonal recording and horseradish peroxidase labelling techniques were used to examine structure-function relationships for vibrissa-sensitive primary afferent fibers (N = 40) in rat trigeminal brainstem subnucleus interpolaris (SpVi). All responded at short (mean-0.42 ms) latencies to trigeminal ganglion shocks and to innocuous stimulation of an individual vibrissa in a slowly adapting type I, slowly adapting type IIa, slowly adapting type IIb, low-velocity-sensitive rapidly adapting, or high-velocity-sensitive rapidly adapting fashion. As in the medullary dorsal horn (Hayashi, '82; Jacquin et al., '86a), functionally distinct mystacial vibrissae-related fibers were morphologically indistinguishable. Each gave rise to up to ten collaterals that entered interpolaris perpendicular to the long axis of the nucleus and often overlapped to form a densely packed, highly circumscribed, and largely continuous column of terminal arbors. While some morphological variability was observed both within and between individual axons, variance within a given functional class was no greater than that between classes. Nonmystacial vibrissae afferent arbors also formed similar ovoid, dense circumscribed terminal plexuses. Presumably, these individual arbors collectively form a longitudinal tubelike vibrissae representation in this and other components of the trigeminal brainstem nuclear complex. The relative locations of each fiber's terminal field could be accurately predicted by the particular vibrissa innervated. Contrary to previous data obtained with similar methods (Hayashi, '82), but consistent with the findings of earlier transganglionic tracing (Arvidsson, '82) and histochemical (Belford and Killackey, '79) studies, the arbors of these fibers terminated throughout the mediolateral extent of SpVi. Axons innervating rostral vibrissae terminated medially, and those that supplied caudal vibrissae innervated the lateral SpVi. Dorsal vibrissae were represented in the ventral SpVi, while ventral vibrissae were represented more dorsally. This transverse topography extended largely throughout the rostrocaudal extent of interpolaris. In summary, the vibrissae primary afferent map in SpVi is inverted, faces medially, and is rostrocaudally consistent. In its most caudal aspect, as the displaced substantia gelatinosa swings laterally, the map is less orderly and incomplete. These generalizations also apply to the nonmystacial vibrissae afferents.

Adaptation, Physiological↗
PubMed1986

The sensory contribution of a single vibrissa's cortical barrel.

The sensory contribution of the cortex containing the cortical barrel of the C1 vibrissa was studied in rats using the ablation-behavior method. Three independent experiments were performed, each requiring stimulus transduction by the C1 vibrissa but varying in their perceptual demands. The first required detection of sinusoidal oscillations of the vibrissa generated by an oscillating airstream directed vertically onto the vibrissa tip. The second required detection of a change in rate of the oscillation. The third required the blinded rat to jump a gap in an elevated runway after palpating the far side with its vibrissa. Psychophysical determinations of the single vibrissa system's thresholds before and after ablation of the cortex containing its barrel show that normal sensitivity either for detecting an oscillation or for detecting a change in oscillation frequency are not dependent on either the contralateral or the ipsilateral cortical barrelfield. In contrast to the lack of effect of barrelfield ablation on the spatial and temporal acuity of the vibrissa, the third experiment shows that a rat's ability to collect situation-relevant information with the vibrissa is lost after ablation of the cortex containing its contralateral barrel but not after ablation of the cortex containing its homologous ipsilateral barrel. The results of repeated retesting of an individual rat's ability to make a jump-no jump decision on the basis of vibrissa-transduced information at each stage of a series of successive single-vibrissa removals and unilateral barrelfield ablations show that the loss of the cortex containing the vibrissa's contralateral barrel is tantamount to loss of the vibrissa itself.

Animals↗
PubMed1998

Spatio-temporal subthreshold receptive fields in the vibrissa representation of rat primary somatosensory cortex.

Spatio-temporal subthreshold receptive fields in the vibrissa representation of rat primary somatosensory cortex. J. Neurophysiol. 80: 2882-2892, 1998. Whole cell recordings of synaptic responses evoked by deflection of individual vibrissa were obtained from neurons within adult rat primary somatosensory cortex. To define the spatial and temporal properties of subthreshold receptive fields, the spread, amplitude, latency to onset, rise time to half peak amplitude, and the balance of excitation and inhibition of subthreshold input were quantified. The convergence of information onto single neurons was found to be extensive: inputs were consistently evoked by vibrissa one- and two-away from the vibrissa that evoked the largest response (the "primary vibrissa"). Latency to onset, rise time, and the incidence and strength of inhibitory postsynaptic potentials (IPSPs) varied as a function of position within the receptive field and the strength of evoked excitatory input. Nonprimary vibrissae evoked smaller amplitude subthreshold responses [primary vibrissa, 9.1 +/- 0.84 (SE) mV, n = 14; 1-away, 5. 1 +/- 0.5 mV, n = 38; 2-away, 3.7 +/- 0.59 mV, n = 22; 3-away, 1.3 +/- 0.70 mV, n = 8] with longer latencies (primary vibrissa, 10.8 +/- 0.80 ms; 1-away, 15.0 +/- 1.2 ms; 2-away, 15.7 +/- 2.0 ms). Rise times were significantly faster for inputs that could evoke action potential responses (suprathreshold, 4.1 +/- 1.3 ms, n = 8; subthreshold, 12.4 +/- 1.5 ms, n = 61). In a subset of cells, sensory evoked IPSPs were examined by deflecting vibrissa during injection of hyperpolarizing and depolarizing current. The strongest IPSPs were evoked by the primary vibrissa (n = 5/5), but smaller IPSPs also were evoked by nonprimary vibrissae (n = 8/13). Inhibition peaked by 10-20 ms after the onset of the fastest excitatory input to the cortex. This pattern of inhibitory activity led to a functional reversal of the center of the receptive field and to suppression of later-arriving and slower-rising nonprimary inputs. Together, these data demonstrate that subthreshold receptive fields are on average large, and the spatio-temporal dynamics of these receptive fields vary as a function of position within the receptive field and strength of excitatory input. These findings constrain models of suprathreshold receptive field generation, multivibrissa interactions, and cortical plasticity.

Animals↗
PubMed1985

Functional organization in cortical barrels of normal and vibrissae-damaged mice: a (3H) 2-deoxyglucose study.

The large mystacial vibrissae on the faces of rodents have punctate representations in all stations in the central trigeminal pathway, including layer IV of the somatosensory cortex (SmI). The cortical whisker correlates, multicellular units termed barrels, are not present at birth, and damage to the vibrissae during the first postnatal week results in altered adult cytoarchitectonics. The anatomical effects of vibrissae damage in the cortex have been well documented; here, we investigated the functional organization of altered SmI barrels with a high-resolution 2-deoxyglucose (2-DG) technique (Durham et al., '81, J. Neurosci. 1:519). The middle row of vibrissae was cauterized in 1-, 2-, 3-, 4-, or 5-day-old mice, and the animals were allowed to survive to sexual maturity. Various combinations of vibrissae were clipped acutely 24 hours prior to injection of 2-4 mCi of (3H)2-DG. Mice actively explored an empty cage for 60 minutes, stimulating the remaining vibrissae. The mice then were perfused and their brains prepared for paraffin histology and emulsion autoradiography. In tangential sections through layer IV, patterns of neuropil and cell body labeling were analyzed with respect to barrel cytoarchitecture in normal and vibrissae-damaged mice. In both control and experimental animals, patterns of neuropil and cell somata label corresponded exactly to barrel boundaries, whether normal or altered by vibrissae damage. Only those barrels for which vibrissae were intact had high levels of label, with anterior barrels more heavily labeled. Many neurons in the septa between these barrels and the adjacent barrels were labeled also. We found slightly higher neuropil label in the cortical zone corresponding to the damaged zone on the face in animals lesioned at any time. These data indicate that physiological somatotopy in vibrissae-damaged animals matches the anatomical cytoarchitecture.

Afferent Pathways↗
PubMed1986

Mystacial vibrissae representation within the trigeminal sensory nuclei of the cat.

Somatotopic arrangements of axon terminals of primary afferent fibers innervating follicles of the mystacial vibrissae were examined in the cat by the transganglionic horseradish peroxidase (HRP) method. Forty to 60 hours after injecting HRP into a single or a group of vibrissal follicles, transported HRP was visualized by the tetramethylbenzidine technique. HRP-labeled axon terminals were distributed in the ventral subnucleus of the principal sensory trigeminal nucleus (ventral Vp), in the oral and interpolar spinal trigeminal nuclei (Vo and Vi), and in the caudal spinal trigeminal nucleus (Vc) (layer I, deep part of layer II, layers III-V) with its spinal extension into the dorsal horn of the first cervical cord segment (rostral C1). In cross sections through the caudal parts of the ventral Vp, Vi, and layer IV of the Vc and rostral C1, a single mystacial vibrissa was represented in a one-to-one fashion by a patch of dense terminal arbors of primary afferent fibers. The more dorsally a horizontal row of the mystacial vibrissae was located, the more ventrally was it represented in the ventral Vp, the more ventrolaterally in the Vi, and the more ventrally in layer IV of the Vc and the rostral C1. In addition, the more anteriorly a vibrissa was located in a horizontal row of the mystacial vibrissae, the more medially was it represented in the ventral Vp, the more ventromedially in the Vi, and the more laterally in layer IV of the Vc and rostral C1; the most posteriorly located vibrissae in the horizontal rows of the mystacial vibrissae were represented along the lateral border of the ventral Vp and Vi, and most medially in layer IV of the Vc and rostral C1. Thus, the representation pattern in the ventral Vp was rotated clockwise at about 45 degrees angle in the Vi, and projected as a mirror image in layer IV of the Vc and rostral C1. It was also indicated that the anterior-posterior arrangement of the mystacial vibrissae was represented in a rostral-caudal organization within layer IV of the Vc and rostral C1. It was also indicated that the anterior-posterior arrangement of the mystacial vibrissae was represented in a rostral-caudal organization within layer IV of the Vc and rostral C1. Patchy patterns probably replicating the distribution of the vibrissae on the face of the cat were also revealed by the cytochrome oxidase histochemical staining in cross sections through the caudal parts of the ventral Vp, Vi, and layer IV of the Vc and rostral C1.

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

Multiple vibrissae sensory regions in rat cerebellum: a (14C) 2-deoxyglucose study.

Repetitive tactile sensory stimulation of the right mystacial vibrissae (whiskers) was performed in awake, adult rats. Regions of increased (14C) 2-deoxyglucose (2DG) uptake were mapped autoradiographically in cerebellum. Predominantly ipsilateral activation of multiple discrete granule cell regions occurred in paramedian lobule, crus 2, crus 1, lobulus simplex, and anterior lobe hemisphere. Bilateral and contralateral activation of cerebellum did occur. Multiple small patches, as well as large granule cell regions, were activated. Mossy fiber afferents from the spinal trigeminal nuclei (particularly interpolaris), principal trigeminal sensory nucleus, and superior colliculus could account for metabolic activation of the granular layer. The slight metabolic activation of the molecular layer could have occurred from climbing or parallel fibers. Comparisons of the paramedian lobule granule cell regions activated during repetitive sensory stimulation of the vibrissae (RSSV) to those activated during vibrissae motor cortex stimulation (VMIS) showed regions only activated by RSSV, regions only activated by VMIS, and regions activated by both RSSV and VMIS. The granule cell regions activated during RSSV and VMIS were usually adjacent to or overlapping each other. Regions only activated during RSSV or only during VMIS could represent technical problems in trying to compare vibrissae motor and sensory pathways in two different groups of animals. Alternatively, cerebellar regions activated only during RSSV could process vibrissae tactile inputs. Regions activated only during VMIS could process vibrissae motor and perhaps proprioceptive sensory input. Regions activated during both RSSV and VMIS might process vibrissae proprioceptive sensory input and/or might represent loci where vibrissae motor, proprioceptive sensory, and tactile sensory convergence occur. The results raise the possibility that vibrissae motor, proprioceptive sensory, and tactile sensory pathways could be processed in separate granule cell patches in parts of cerebellum and in the same granule cell patches in other parts of cerebellum.

Afferent Pathways↗
PubMed1992

Flow of excitation within rat barrel cortex on striking a single vibrissa.

1. Extracellular spike recordings were made from single cells in various layers of barrel cortex in adult rats anesthetized with urethan. Response magnitude and latency differences to brief 1.14 degrees deflections of mystacial vibrissae of center (principal) and surround receptive-field vibrissae were measured. Latency differences for pairs of cells in the same penetration to stimulation of the principal vibrissa were also collected. In separate experiments the domains of layer IV cells were mapped for their influence by a single vibrissa and their latencies to this vibrissa were recorded. In all experiments precise locations of layer IV cells in each penetration were identified using dye-lesioning and cytochrome oxidase staining of tangential sections. 2. The results suggest that principal vibrissa data are relayed radially in a column of neurons before parallel relay to adjacent columns. To the principal vibrissa, layers IV and Vb neurons discharged earliest, with layers II and III on average 2 and 3 ms later, respectively. Serial relay from layers IV to III to II was suggested to be the most common event. Although layer Va cells fired next, a single-column organization is not suggested for them because differences in latency or response magnitude to their principal and immediate surround vibrissae were not significant. Layer II, III and IV cells showed no statistical difference in latency to the nearest surround vibrissa but fired significantly later than to their principal input. 3. Because, from our previous studies, surround receptive fields of barrel cells in rat S1 cortex appear to be constructed intracortically, these data suggest a parallel column-column relay for their construction. Horizontal relay between barrels occurred first within the septae between barrels. Mean intracortical transmission velocities were calculated at approximately 0.05 m/s for column-column information transfer.

Animals↗
PubMed1994

Unilateral stimulation or removal of rat vibrissae: analysis of nerve growth factor and tyrosine hydroxylase mRNA in the brain.

Previous work has shown that unilateral manipulation of vibrissae in the rat can lead to behavioral asymmetries and to neuronal changes in the basal ganglia: in brief, vibrissae stimulation led to increases in neostriatal dopamine release, whereas unilateral removal of vibrissae led to asymmetries in striatal afferents and to bilateral changes in mesencephalic dopamine mechanisms which were related to the occurrence of behavioral asymmetries and the later recovery therefrom. In the present study, the analysis of neuronal mechanisms possibly affected by vibrissae manipulation was extended to the nerve growth factor and the expression of tyrosine hydroxylase mRNA. Unilateral stimulation or removal of the vibrissae did not lead to significant changes in tissue levels of nerve growth factor in the neostriatum, parietal cortex (including the barrel cortex) or the hippocampus. In contrast, tyrosine hydroxylase mRNA in the substantia nigra and ventral tegmental area was affected by vibrissae removal but not by stimulation, as a bilateral increase in labeling was observed on the level of individual neurons. This effect was only observed in animals tested 4 h after vibrissae removal but not after 10 days. The results are discussed with respect to the interaction of vibrissae function with the basal ganglia, the neurotransmitter dopamine and mechanism of functional recovery.

Afferent Pathways↗
PubMed1996

Mechanisms underlying experience-dependent potentiation and depression of vibrissae responses in barrel cortex.

Plasticity was studied in the barrel cortex of rats and mice. Vibrissae deprivation in adult and adolescent animals caused changes in the response properties of cortical neurons to stimulation of spared and deprived vibrissae. Plasticity involved both potentiation of spared vibrissae responses and depression of deprived vibrissae responses in layer II/III of the cortex. Vibrissae response potentiation was found to require alpha CaMKII in adult cortex. Vibrissae response depression was not found to occur in adult cortex but was found in adolescent animals for the principal vibrissa. Preliminary results suggested that vibrissae response depression exhibits both hetero- and homosynaptic components.

Animals↗
PubMed1994

Alterations in brainstem and cortical organization of rats sustaining prenatal vibrissa follicle lesions.

Vibrissa follicles were cauterized in late fetal or newborn rats to determine whether the relationships between brainstem and cortical changes observed after neonatal peripheral damage would also be obtained when vibrissa follicles were cauterized earlier in development. Vibrissa follicles were cauterized between embryonic day 15 (E-15) and the day of birth (P-0). The vibrissa-related representation in the brainstem was examined with cytochrome oxidase histochemistry, and that in the cortex was evaluated with either serotonin immunocytochemistry or anterograde labeling with Di-I when animals reached 6-8 days of age. There was a significant relationship between the ages at which lesions were carried out and the extent to which the representations of undamaged vibrissa follicles were altered in the brainstem and cortex. Peripheral lesions carried out between E-15 and E-18 resulted in significant increases in the cross-sectional areas of the patches corresponding to the undamaged vibrissa follicles in both the brainstem and cortex. Lesions at later ages resulted in significant increases only in the cortex. In some animals that sustained peripheral damage on E-20 and all of those that received lesions on P-0, there were aggregates of labeling in cortex that had no counterpart in the brainstem. Prenatal, but not postnatal, vibrissa follicle damage also reduced the overall dimensions of the cortical region devoted to the representation of these receptor organelles. Finally, there was a strong negative correlation between the magnitude of peripheral lesions (i.e., the number of vibrissa follicles ablated) and the extent of the reorganization in the brainstem and cortex.

Afferent Pathways↗
PubMed1998

Differential fasciculation of follicular nerves for transferring specifically localized cues of the vibrissa rudiments to the central trigeminal sensory system in mice, as exploited with DiI and DiA labeling.

Vibrissa connections play a decisive role in setting the somatotopic coordinates in the trigeminal sensory system. Although previous studies have examined the development of peripheral patterning, certain questions are still in dispute, for example, the way vibrissa connections are structured, and the relationship between periphery and central organization, and ganglion cell organization. In order to fill the blanks left by previous studies, the extension of ganglionic branches and the formation of vibrissa connections were reexamined by using fluorescent carbocyanin dyes, DiI and DiA, during embryonic days 10 to 14 in mouse. Whole-mount preparations satisfactorily demonstrated the ganglionic fiber system, which allowed detailed analysis at both macroscopic and microscopic levels. We show here that the differential fasciculation of follicular nerves is the critical process for organizing vibrissa connections which modulate the initially extending fiber pattern. Follicular nerves developed by fine fibers arising from initially ordered root fascicles, so as to connect with vibrissa rudiments that developed on the facial prominences. During differential fasciculation, ganglion cells were segregated into distinct groups by the vibrissa connections, whereas central fiber terminals did not yet develop specific structures in the nuclear region. In the primary order of the trigeminal sensory system, vibrissa connections in the periphery were organized before those of the central structure. These results indicate that trigeminal ganglion cells have a critical binomial function in order to transfer the somatotopic relations among vibrissa rudiments into the topographic coordinates of the central system.

Animals↗
PubMed1982

Somatotopic organization of vibrissae afferents in the trigeminal sensory nuclei of the rat studied by transganglionic transport of HRP.

Transganglionic transport of horseradish peroxidase (HRP) has been used to study the cell bodies and central projections of neurons innervating the vibrissae in the rat. These can be grouped into five horizontal rows and one posterior vertical row. Twenty-four to 48 hours after the nerves innervating different vibrissae were exposed to HRP, the trigeminal ganglia, brainstem, and upper cervical spinal cord were fixed by perfusion and serial sections were processed according to the tetramethylbenzidine technique. The results revealed a tendency for somatotopic organization in the trigeminal ganglion of cell bodies innervating the different vibrissae. Corresponding termination areas in the trigeminal sensory nuclei showed a detailed pattern of organization replicating the peripheral organization of the vibrissae. In all trigeminal sensory nuclei the horizontal rows are represented in an inverted fashion from dorsal to ventral, i.e., the most dorsal row is represented most ventrally. In addition, the more anterior a vibrissa is located, the deeper is it represented in the rostral nonlaminated nuclei. The situation is reversed in the laminated nucleus caudalis. The posterior vertical row is represented most superficially in the rostral nonlaminated nuclei, but most deeply in the laminated nucleus caudalis. In nucleus caudalis there are also rostrocaudal differences in the representation of different vibrissae. Thus, the posterior vibrissae in a horizontal row have their main representations more caudally than the anterior vibrissae. The posterior vertical row has its main representation most caudally, in the C1 segment.

Afferent Pathways↗