Biomedical subjects

R W Rhoades

Publications and source records attributed to R W Rhoades.

At least 145 records · Page 8Linked to original sources

PubMed1986

Structural and functional characteristics of commissural neurons in the superior colliculus of the hamster.

Intracellular recording and horseradish peroxidase (HRP) injection techniques were employed to delineate the structural and functional properties of superior collicular (SC) neurons in the hamster that were antidromically activated by electrical stimulation of the contralateral tectum. A total of 39 such cells were completely characterized, injected, and recovered. In ten of these, the axonal filling allowed us to reconstruct at least a portion of the terminal arborization in the SC contralateral to the labelled cell. Two of the recovered neurons were located in the stratum griseum superficiale (SGS), three were in the stratum opticum (SO), ten were in the stratum griseum intermediale (SGI), 11 were in the stratum album intermedium (SAI), 11 were in the stratum griseum profundum (SGP) and two were located in the stratum album profundum (SAP). The recovered cells were highly varied in both their morphological and their physiological characteristics. Somal areas ranged between 74 microns2 and 364 microns2, and the sample of recovered neurons included horizontal cells, narrow field vertical cells, and a variety of other multipolar neurons. Over one-third (38.5%) of the recovered cells were unresponsive, 2.6% were exclusively visual, 33.3% responded only to innocuous cutaneous stimuli, 10.2% were bimodal, 7.7% were specifically nociceptive, and 7.7% had complex (Rhoades, Mooney, and Jacquin: J. Neurosci. 3:1342-1354, '83) somatosensory receptive fields. We observed no clear-cut correlations between the structural and functional characteristics of these neurons. The conduction latencies of the commissural SC neurons ranged between 0.8 and 14.0 ms. The most rapidly conducting cells were located in the SGP and SAP. Conduction latency had a significant negative correlation with soma area. Labelled axons, in many cases, had at least one terminal arbor in a portion of the SC that was mirror symmetric with the location of the cell from which it originated. In several cases, however, commissural axons gave off a number of collaterals across the mediolateral extent of the tectum. commissural axonal terminations were visible only in the laminae ventral to the SO. Several commissural SC neurons also had extensive ipsilateral axon collaterals. Both the ipsilateral and commissural axon branches of these cells gave off en passant and terminal swellings.

Animals↗

PubMed1986

Superior collicular projection to intralaminar thalamus in rat.

The superior collicular (SC) cells which project to the intralaminar thalamus (IT; nuclei centralis lateralis, CL; paracentralis, PC; parafascicularis, Pf) in the rat were identified by means of retrograde transport of wheatgerm agglutinin conjugated horseradish peroxidase (WGA-HRP). SC-IT cells were located throughout the mediolateral and rostrocaudal extents of the tectum ipsilateral to the thalamic injection. In this SC, they had a primarily bilaminar distribution in the lower one-half of the stratum griseum intermediale (SGI) and upper portion of the stratum griseum profundum (SGP). In these laminae, SC-IT cells were arranged in clusters or patches similar to those which have been described for many inputs to the deep SC laminae. A small number of SC-IT cells were also observed in the deep laminae of the tectum contralateral to the thalamic injection. Double labelling experiments using True Blue (TB) and Diamidino Yellow (DY) demonstrated that less than 1% of the contralaterally projecting SC-IT cells also innervated ipsilateral IT. Anterograde tracing with [3H]leucine demonstrated further that SC projected heavily to CL, PC and Pf. This projection also extended into the medial portion of the posterior thalamus (PO).

Animals↗

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

Morphology, response properties, and collateral projections of trigeminothalamic neurons in brainstem subnucleus interpolaris of rat.

Intracellular recording, electrical stimulation and horseradish peroxidase (HRP) injection techniques were used to delineate the structural and functional characteristics of trigeminothalamic projection neurons in subnucleus interpolaris of the trigeminal brainstem nuclear complex in rat. Eleven such neurons were successfully characterized and recovered. All were medium to large multipolar neurons in the ventral part of interpolaris and all except one also projected to the superior colliculus. Six of these cells also sent axon collaterals to subnucleus principalis and the medullary parvicellular reticular formation and had local collaterals within interpolaris. None of these trigeminothalamic cells were antidromically activated from the cerebellum. All but one of the recovered cells were responsive to deflection of any one of a number (4-19) of vibrissae. The remaining cell was discharged by displacement of mystical guard hairs. Analysis of electrophysiological and anatomical data revealed significant correlations between receptive field size and dendritic area, thalamic conduction latency and axon diameter, and number of targets innervated and axon diameter.

Animals↗

PubMed1986

Topographic organization of peripheral trigeminal ganglionic projections in newborn rats.

Retrograde transport of fluorescent tracers (true blue and diamidino yellow) was employed to delineate the topography of the peripheral projections of trigeminal ganglion cells in newborn (less than 12 h of age) rats. Identical injections were made in adult animals for comparison. In neonates, both inter- and intradivisional topography of ganglionic projections were adult-like. Neurons which innervated mandibular fields were located posterolaterally while cells with ophthalmic or maxillary projections were restricted to the anteromedial and central parts of the ganglion, respectively. An adult-like topographic representation of the mystacial vibrissae follicles was also evident in the neonates.

Animals↗

PubMed1986

The structural and functional characteristics of striate cortical neurons that innervate the superior colliculus and lateral posterior nucleus in hamster.

Intracellular recording and horseradish peroxidase injection techniques were used to structurally and functionally characterize the striate cortical neurons in hamster that projected to the superior colliculus and/or lateral posterior nucleus of the thalamus. With two exceptions, the receptive field properties and morphological characteristics of the neurons antidromically activated from the colliculus and lateral posterior nucleus were quite similar. Striate corticotectal and striate cortico-lateral posterior neurons generally had non-oriented receptive fields which gave either "on-off' or no responses to flashed stimuli. Only a small number (less than 5%) were orientation selective, but about one-third were directionally selective. Most of the cells preferred movement with an upward component. Most striate corticotectal and cortico-lateral posterior cells responded to a wide range of stimulus velocities and exhibited little spatial summation. With the possible exception of two cells, all the projection neurons we recovered were large lamina V pyramidal cells whose apical dendrites extended to and branched extensively in layer I. All had extensive (in some cases over 1 mm) tangential axon collaterals, primarily in layers V and/or VI. The electrophysiological experiments also demonstrated that some (50% of a sample of 20 cells) corticotectal neurons also sent an axon collateral to the lateral posterior nucleus. Finally, our recordings showed that many (56% of a sample of 27 neurons) cells which could be antidromically activated from the lateral posterior nucleus, but not the superior colliculus had response latencies which exceeded those of almost all the cells which could be antidromically activated from the tectum. Retrograde transport of diamidino yellow and true blue confirmed the electrophysiological result that individual cortical neurons projected to both the superior colliculus and lateral posterior nucleus. These experiments showed that 20% of the striate cortical cells that projected into colliculus also sent an axon collateral to the lateral posterior nucleus.

Animals↗

PubMed1986

Structure-function relationships in rat medullary and cervical dorsal horns. I. Trigeminal primary afferents.

Intracellular recording and horseradish peroxidase (HRP) labeling were used to examine structure-function relationships in the medullary dorsal horn (MDH) and rostral cervical dorsal horn. In Nembutal-anesthetized rats, 78 trigeminal (V) primary afferent fibers were physiologically characterized and injected with HRP. Axons were sufficiently well stained to reconstruct all of their collaterals in the MDH. Many also extended into the cervical dorsal horn. Except for four axons, which responded best to noxious stimuli, all responded at short (mean = 0.50 ms) latencies to V ganglion shocks and to innocuous stimulation. Forty-five of our recovered fibers were associated with facial vibrissae and responded in either a rapidly adapting, slowly adapting type I, slowly adapting type IIa, or slowly adapting type IIb fashion. The adequate stimuli consisted of either slow deflection, high-velocity deflection, or a noxious pinch of the vibrissa follicle. The collaterals of all of the above-described mystacial vibrissa primary afferents proceeded directly to their region of arborization in a plane perpendicular to the lateral border of the medulla to collectively form a largely continuous, circumscribed terminal column. This longitudinally oriented column of terminal and en passant boutons angled from lamina V rostrally to lamina III caudally. In the magnocellular laminae of the MDH, all mystacial vibrissa primary afferents gave rise to similarly shaped arbors, regardless of their functional classification. While morphological variability was observed both within and between individual axons, variance between functional classes was no greater than that within a class. Moreover, number of collaterals, number of boutons, or bouton size did not distinguish functional classes. Nonmystacial vibrissa afferent arbors, with more caudal peripheral fields, had their primary arbor focus in C1 and C2 dorsal horn. These arbors had relatively little rostrocaudal overlap with mystacial vibrissa afferents, though they exhibited the same lamina V-to-III shift as they descended through the cervical cord. Unlike mystacial vibrissa afferents in the MDH, their collaterals followed a tortuous course and often occupied laminae II-V in one transverse section. The relative location of each vibrissa afferent's terminal field could be predicted by the particular vibrissa innervated. Dorsal vibrissae afferents had ventrolateral terminations and ventral vibrissae afferents terminated dorsomedially. Rostral vibrissae were represented in the rostral MDH, whereas caudal vibrissae were represented in the caudal MDH and rostral cervical dorsal horn.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1986

Structure-function relationships in rat medullary and cervical dorsal horns. II. Medullary dorsal horn cells.

In Nembutal-anesthetized rats, 31 physiologically identified medullary dorsal horn (MDH) cells were labeled with horseradish peroxidase (HRP). Ten responded only to deflection of one or more vibrissae. Six cells were activated by guard hair movement only, six by deflection of guard hairs or vibrissa(e), and seven by pinch of facial skin with serrated forceps. Different classes of low-threshold cells could not be distinguished on the basis of their somadendritic morphologies or laminar distribution. Neurons activated by multiple vibrissae were unique, however, in that one sent its axon into the medial lemniscus, and three projected into the trigeminal spinal tract. None of the guard hair-only or vibrissae-plus-guard hair neurons had such projections. Cells that responded best to noxious stimulation were located mainly in laminae I, II, and deep V, while neurons activated by vibrissa(e) and/or guard hair deflection were located in layers III, IV, and superficial V. Low-threshold neurons generally had fairly thick dendrites with few spines, whereas high-threshold cells tended to have thinner dendrites with numerous spines. Moreover, the dendritic arbors of low-threshold cells were, for the most part, denser than those of the noxious cells. Neurons with mandibular receptive fields were located in the dorsomedial portion of the MDH; cells with ophthalmic fields were found in the ventrolateral MDH, and maxillary cells were interposed. Cells sensitive to deflection of dorsal mystacial vibrissae and/or guard hairs were located ventral to those activated by more ventral hairs. Neurons with rostral receptive fields were found in the rostral MDH, while cells activated by hairs of the caudal mystacial pad, periauricular, and periorbital regions were located in the caudal MDH. Receptive-field types were encountered that have not been reported for trigeminal primary afferent neurons: multiple vibrissae; vibrissae plus guard hairs; and wide dynamic range. The latter two can be explained by the convergence of different primary afferent types onto individual neurons. Our failure to find a significant relationship between dendritic area (in the transverse plane) and the number of vibrissae suggests that primary afferent convergence may not be responsible for the synthesis of the multiple vibrissae receptive field. Excitatory connections between MDH neurons may, therefore, account for multiple vibrissae receptive fields in the MDH.

Animals↗

PubMed1986

Functional consequences of neonatal infraorbital nerve section in rat trigeminal ganglion.

Standard single-unit recording and stimulation techniques were used to assess the topographic organization, receptive field properties, and projections of cells (n = 297) in the ophthalmic-maxillary part of the trigeminal ganglion in 6 normal adult rats and 15 adults with unilateral infraorbital nerve section at birth (cells recorded ipsilateral to lesion: n = 641; cells recorded on the intact side: n = 223). Stimulating electrodes were placed on the central portion of the regenerate infraorbital nerve and in the trigeminal brain stem subnucleus caudalis in 6 nerve-damaged rats and at equivalent points in 5 normal animals. Data from the normal rats and the intact side of the nerve-damaged animals were identical and were considered together. Of these cells, 73.5% had infraorbital receptive fields. Of these, 77.2% were discharged by vibrissa stimulation (43.8% slow-adapt type I, 10.3% slow-adapt type II, 27.6% low-velocity sensitive rapid adapt, 16.8% high-velocity sensitive rapid adapt, and 1.5% noxious-biased), while the rest responded best to guard hair deflection (12.0%), gentle skin indentation (4.5%), or a strong pinch or deep pressure (6.3%). In stereotaxically matched penetrations in ganglia ipsilateral to the neonatal infraorbital nerve lesions, only 40.6% of the cells had infraorbital receptive fields. Of these, only 37.7% responded to vibrissa stimulation (29.8% slow-adapt type I, 1.2% slow-adapt type II, 2.2% low-velocity sensitive rapid adapt, 32.9% high-velocity sensitive rapid adapt, 33.9% noxious). Other infraorbital cells responded best to guard hair deflection (11.9%), gentle skin indentation (10.8%), or a strong pinch or deep pressure (39.6%). An additional 30 cells did not have a detectable receptive field and were identified only by infraorbital and brain-stem shocks. We also recorded cells with unusual infraorbital receptive fields: 9 units responded to more than 1 vibrissa, 4 were activated by both vibrissa and guard hair deflection, 10 had unusually large skin or deep receptive fields, 1 had a split receptive field, and 7 were discharged only by deep pressure to the region of the nerve section. Seven cells with infraorbital receptive fields were not driven by infraorbital shocks, and 2 were not activated by brain-stem shocks. In normal rats, all cells with infraorbital receptive fields were driven by both electrodes. The percentages of receptive field types for noninfraorbital cells were unchanged in ganglia ipsilateral to the damaged nerve.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1985

Effects of neonatal infraorbital lesions upon central trigeminal primary afferent projections in rat and hamster.

Transganglionic and anterograde horseradish peroxidase transport was used to evaluate the central projections of undamaged trigeminal (V) nerve branches in adult rats and hamsters subjected to transection of the infraorbital nerve and to cauterization of the vibrissae follicles at birth. In rats, deafferented regions of the V brainstem nuclear complex did not receive abnormal projections from undamaged mandibular sensory afferents. Undamaged ophthalmic-maxillary fibers also failed to terminate heavily in the region deafferented by the neonatal infraorbital lesions. In the hamster, on the other hand, neonatal infraorbital nerve lesions were associated with statistically significant increases in mandibular terminal fields in the principalis, subnucleus interpolaris, and subnucleus caudalis. Tracing experiments were also carried out in neonatal rats and hamsters to determine whether the above-described differences in the response to infraorbital nerve damage reflected a difference in the maturity of the V primary afferent projections to the brainstem at the time of our neonatal lesions. In neonatal rats, the infraorbital and mandibular projections to the V brainstem nuclear complex were quite adultlike, both in their pattern and in the extent of their overlap, which was minimal. Overlap between mandibular and infraorbital terminal fields was also minimal in the newborn hamsters.

Afferent Pathways↗

PubMed1985

Representation of whisker follicle intrinsic musculature in the facial motor nucleus of the rat.

Retrograde transport of wheatgerm-agglutinin horseradish peroxidase (WGA-HRP) and fluorescent tracers (true blue-TB, nuclear yellow-NY, and diamidino yellow-DY) from isolated whisker follicles was used to define the somatotopic organization of the facial (VII) motoneurons which innervate the intrinsic follicle muscles. Motoneurons supplying these muscles were restricted almost completely to the lateral (Martin and Lodge, '77) facial subnucleus and the motoneurons which innervated a given follicle were distributed over the entire length of this subnucleus. Cells projecting to dorsal (A-row) follicles were located in the most lateral part of the lateral subnucleus, while those supplying ventral (E-row) follicles were restricted to the medial part of the subnucleus. Injections of different tracers into rostral and caudal follicles within a given row revealed no somatotopic representation of the rostrocaudal axis of the whiskerpad. Additional control experiments demonstrated that some of the labelling obtained with WGA-HRP resulted from spread of this tracer to extrinsic muscles. This was not the case with the fluorescent tracers. The results of the control experiments suggested further that a significant percentage of the motoneurons in the lateral facial subnucleus innervate only intrinsic follicle muscles.

Animals↗

PubMed1985

Subcortical projections of area 17 in the anophthalmic mouse.

Anterograde and retrograde tracing methods were used to compare the subcortical projections of area 17 in ZRDCT-an, anophthalmic mice with those of sighted C57BL mice. In both groups, area 17 projected to the dorsocaudal striatum, the reticular, lateral and lateral posterior nuclei, the dorsal and vental lateral geniculate nuclei, the zona incerta, the anterior and posterior pretectal nuclei, the stratum griseum superficiale of the superior colliculus and the dorsolateral pons. Occasional labeled fibers in both groups were also seen in the ventrobasal nucleus, but it was not clear whether or not any axons terminated in this region. The projections to the superior colliculus and dorsal lateral geniculate nucleus were analyzed in greater detail. In both normals and blind mice the striate corticotectal projection arose from cells in layer V and that to the geniculate from neurons in lamina VI. The topographic organizations of these projections in the two groups were indistinguishable. The striate corticotectal projection to the colliculus in the anophthalmic mice did appear to terminate more dorsally in the stratum griseum superficiale than that in sighted animals. These data demonstrate that a signal from the retina is not required for either the restriction of 'visual' cortical axons to their normal subcortical targets or the achievement of normal topography within those target nuclei.

Animals↗

PubMed1985

Extensive recrossing of retinotectal axons after neonatal unilateral superior collicular lesions in hamster.

Anterograde transport methods were used to examine the ipsilateral retinocollicular projections of adult hamsters subjected to ablation of one superior colliculus (SC) on the day of birth. In many of these animals ipsilateral retino-SC axons were not limited to the medial part of the remaining tectum as previously reported but encompassed the entire rostrocaudal and mediolateral extents of this SC. A common pattern was the existence of a dense patch of label contiguous with the midline, a more lateral region of diffuse labeling, a second dense lateral patch and diffuse labeling which extended to the lateral boundary of the tectum. The dense patches of label were usually aligned into rostrocaudally oriented bands. Additional experiments in which one optic tract was sectioned a week prior to the eye injection showed that the reorganization was primarily due to axons which recrossed the midline at the level of the midbrain. However, the uncrossed retinotectal projection was also abnormally dense in the animals subjected to neonatal SC lesions. Dense patches of label in the caudal half of the tectum were only observed when recrossing fibers were labeled. In a final set of experiments, both the ipsilateral and contralateral projections were labeled with different tracers in individual hamsters. These experiments showed a clear tendency for fibers from the two eyes to segregate in the remaining SC. This segregation was, however, incomplete, even in regions where labeling from each eye was quite dense.

Animals↗

PubMed1985

Correlations between the structural and functional characteristics of neurons in the superficial laminae and the hamster's superior colliculus.

Intracellular recording, receptive field mapping, and horseradish peroxidase (HRP) injection techniques were used to determine the structural and functional characteristics of neurons in the superficial laminae (stratum griseum superficiale and stratum opticum) of the hamster's superior colliculus (SC). Fifty-nine neurons (from 38 different hamsters) were successfully characterized, injected with HRP, and recovered. Of these, 8 were marginal cells, 14 had stellate morphology, 10 had narrow, vertically oriented dendritic trees, 12 had wide, vertically oriented dendritic arbors, and 8 were horizontal cells. Seven neurons had somatodendritic morphologies which did not fall into any of these groups. Overall, the distribution of receptive field properties for these cells matched that obtained in previous extracellular recordings from the superficial SC laminae in this species (Chalupa, L.M., and R.W. Rhoades (1977) J. Physiol. (Lond.) 270: 595-626; Chalupa, L.M. and R.W. Rhoades (1978) J. Physiol. (Lond.) 274: 571-592). There were significant correlations between receptive field properties and morphology. Sixty-four percent of the stellate cells and 75% of the marginal cells were directionally selective. Only 17% of the other cell types exhibited this response property. In addition, only 36% of the stellate cells and 25% of the marginal neurons were discharged by stationary, flashed spots. Eighty-one percent of the other recovered cells gave reliable responses to such stimuli. Stellate and marginal cells could also be differentiated from the other cell types on the basis of speed selectivity. Only 29% of the stellate and 13% of the marginal cells responded to stimulus speeds in excess of 20 degrees/sec.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Dendrites of deep layer, somatosensory superior collicular neurons extend into the superficial laminae.

Intracellular recording and horseradish peroxidase (HRP) injection techniques were used to delineate the structural and functional properties of superior collicular (SC) neurons in hamsters. Of 34 cells recovered from the deep laminae (those ventral to the stratum opticum--SO), 26 were exclusively somatosensory and 10 of these extended dendrites into the superficial layers, the stratum griseum superficiale (SGS) and SO. In 2 instances, dendrites extended only to the SO, but in 8 others they reached the SGS. Three of the latter cells had dendrites which terminated just beneath the pial surface. These findings show that an anatomical substrate for communication from superficial to deep layer cells exists in the hamster SC, but that such communication may not necessarily be reflected in the response of deep layer neurons.

Animals↗

PubMed1984

A quantitative electron microscopic analysis of the infraorbital nerve in the newborn rat.

The infraorbital nerve (n = 3) was examined in newborn rats using electron microscopic techniques. Counts of the entire nerve revealed an average of 42,051 (S.D. = 2083) unmyelinated and 168 (S.D. = 47) myelinated fibers. The unmyelinated axons averaged 0.46 micron (S.D. = 0.16) in diameter while the myelinated fibers averaged 1.71 micron (S.D. = 0.17).

Animals↗

PubMed1984

Organization of the intercollicular pathway in rat.

The intercollicular pathway of the rat was studied using autoradiographic (ARG) and horseradish peroxidase (HRP) tracing techniques. The HRP experiments demonstrated that the cells of origin of the intertectal pathway were located primarily in the rostral stratum griseum intermediale ( SGI ), stratum album intermedium (SAI) and stratum griseum profundum (SGP). Intertectal neurons were in most cases multipolar and had average somal diameters which ranged between 8 and 33 micron. Only a small number of superficial layer neurons contributed axons to the intercollicular pathway. ARG tracing showed that the intertectal pathway terminated in the deep layers of the rostral one half of the colliculus. The primary terminal zone was SGP. In addition, labeled axons left this region and coursed dorsally to terminate in a series of patches in the lower SGI and upper SAI. A small number of labeled fibers also reached the stratum opticum (SO) and lower stratum griseum superficiale (SGS).

Animals↗

PubMed1984

Axon arbors of functionally distinct whisker afferents are similar in medullary dorsal horn.

Using the intra-axonal horseradish peroxidase (HRP) technique, we have found that the central axon arbors of functionally distinct mystacial whisker primary afferents in rat medullary dorsal horn were all similar with respect to their shape and density of terminal boutons. Arbors from slowly adapting, rapidly adapting, velocity or nociceptive biased whisker afferents all appeared to form a series of highly localized terminal aggregates within a specific rostrocaudal segment of the superficial or deep half of the lamina III-IV magnocellular region. Other trigeminal afferents adhered to previously described somatosensory structure-function relationships in the cat lumbosacral spinal cord. These findings suggest that topographic constraints, as well as functional considerations, are important in determining primary afferent terminal arbor patterns in the medullary dorsal horn.

Afferent Pathways↗