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P K Rose

Publications and source records attributed to P K Rose.

At least 19 recordsLinked to original sources
PubMed1992

Morphology of single vestibulospinal collaterals in the upper cervical spinal cord of the cat: I. Collaterals originating from axons in the ventromedial funiculus contralateral to their cells of origin.

Vestibulospinal neurons in the medial and descending vestibular nuclei have widespread bilateral terminations in the upper cervical spinal cord. These terminations arise from axons travelling in several funiculi, including the ventromedial, ventrolateral, lateral, and dorsolateral funiculi in addition to the dorsal columns. The purpose of the present study was to examine the morphology of single vestibulospinal collaterals which terminate in the upper cervical spinal cord and which originate from axons located in one of these funicular pathways, the ventromedial funiculus, contralateral (cVMF) to their cells of origin in the vestibular nuclei. The 32 collaterals described were selected from two separate sets of experiments which took advantage of different techniques. Nineteen of the collaterals were labelled following Phaseolus vulgaris leucoagglutinin (PHA-L) injections into the medial vestibular nucleus and medial regions of the descending vestibular nucleus. The remaining 13 collaterals originated from physiologically identified vestibulospinal axons that were stained after intra-axonal injections of horseradish peroxidase (HRP). The combined projection of all cVMF axon collaterals spread from laminae V to IX, and included the central cervical nucleus. There was a high degree of variability in the pattern of terminations of individual collaterals. This variability was more pronounced among PHA-L-labelled collaterals than HRP-labelled collaterals whose terminations were restricted to laminae VIII and IX. Some PHA-L-labelled collaterals had terminations which were focused within a single lamina, whereas others had termination zones spanning as many as four laminae. The differences between collaterals were compounded when the characteristics of branching patterns were considered. Some collaterals which occupied similar termination zones had different branching structures.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1992

Morphology of single vestibulospinal collaterals in the upper cervical spinal cord of the cat. II. Collaterals originating from axons outside the ventral funiculi.

Recent studies have shown that vestibulospinal axons reach the upper cervical spinal cord of the cat via several different funicular routes. The purpose of this study was to describe the projections of those axons travelling outside the well-recognized pathways in the ventral funiculi. These axons are located in the dorsal columns, dorsolateral funiculi, and lateral funiculi. Collaterals of these axons were stained following extracellular injections of Phaseolus vulgaris leucoagglutinin in the medial and descending vestibular nuclei. The trajectories of individual collaterals were reconstructed from serial histological sections. Collaterals arising from axons in the same funiculus usually had the same characteristic appearance. Axons in the lateral funiculi, ipsilateral or contralateral to their cells of origin, gave rise to collaterals that had a simple structure and usually followed a horizontal trajectory across laminae VII and VIII. The boutons of these collaterals were distributed throughout the mediolateral extent of laminae VI and VII and the dorsal half of lamina VIII. In contrast, axons in the dorsolateral funiculi, ipsilateral or contralateral to their cells of origin, terminated primarily in laminae IV and V. Many collaterals of these axons projected either rostrally or caudally and had a narrow mediolateral distribution. The combined distribution of boutons from collaterals originating from axons in the dorsal columns included the dorsal horn and intermediate zone. Although these collaterals were less common and formed a heterogeneous group, they were easily distinguished from collaterals originating from axons travelling in other funiculi. These results indicate that vestibulospinal axons travelling outside the ventral funiculi comprise several distinct systems. Each system travels by a different funicular route and is distinguished by differences in collateral morphology and termination zones.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1992

Connections from the lateral vestibular nucleus to the upper cervical spinal cord of the cat: a study with the anterograde tracer PHA-L.

The projections of neurons in the lateral vestibular nucleus (LVN) to the upper cervical spinal cord of the cat were investigated by means of the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L). At the junction of C1 and C2, axons were distributed bilaterally in the ventromedial funiculi, and ipsilaterally in the ventrolateral and lateral funiculi. The majority of boutons were found ipsilateral to the injection sites and most of these boutons were found at the base of the ventral horn and throughout the medial two-thirds of lamina VIII. A more modest termination zone was found along the ventral border of lamina VII and a small number of boutons were scattered in the dorsal horn. Contralateral termination zones were similar to the ipsilateral projections. There were significant changes in the distribution of vestibulospinal axons and density of boutons at the junction of C3 and C4. At this level, most vestibulospinal axons travelled ipsilaterally and were found along the medial border of the ventromedial funiculus and the ventral margin of the ventrolateral funiculus. The overall distribution of boutons near the border of C3 and C4 was similar to the pattern seen at the junction of C1 and C2. However, bouton density fell by a factor of three. Large zones of the grey matter were devoid of boutons in individual experiments. These results demonstrate that the projections of neurons in the LVN to the upper cervical spinal cord are densest in the regions containing motoneurons supplying suboccipital muscles. This result suggests that monosynaptic connections to those motoneurons may be an important part of the neural circuitry responsible for vestibulocollic reflexes. However, the large number of boutons found in regions dorsal to motoneuron nuclei in all upper cervical segments indicates that the primary path from vestibulospinal axons to neck motoneurons may be indirect and involve relays via spinal interneurons.

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PubMed1991

Projections of the tectospinal tract to the upper cervical spinal cord of the cat: a study with the anterograde tracer PHA-L.

The goal of the present experiments was to re-examine the spinal projections of neurons in the superior colliculus (SC) of the cat by taking advantage of the high sensitivity of the anterograde tracer, phaseolus vulgaris leucoagglutinin (PHA-L). In seven experiments, multiple injections of PHA-L into different regions of the SC labelled a total of 172 axons in the predorsal bundle; yet only 11 tectospinal tract (TST) axons were found in the upper cervical spinal cord. Collaterals emerging from these axons were rare and arose exclusively from TST axons with a diameter of less than 1 micron. Individual collaterals had different termination zones: some terminated in the lateral part of lamina V and VI after taking a dorsolateral course through lamina VII and VIII; others terminated in the medial part of lamina VII. One collateral terminated within lamina IX and the ventral part of lamina VIII. The combined termination of all collaterals was densest in lamina VII and dorsal lamina VIII. A small number of boutons were also found in the lateral parts of laminae V and VI, and in lamina IX and immediately adjacent regions in lamina VIII. Compared to axons belonging to other spinal descending systems, individual TST axons give rise to much simpler intraspinal collaterals with relatively few boutons. This feature, together with the relative paucity of TST axons, suggests that direct connections from the SC to neurons in the upper cervical spinal cord are sparse. Furthermore, our results are consistent with electrophysiological studies that show that few, if any, neck motoneurons receive monosynaptic connections from TST neurons. Projections to neck motoneurons must therefore involve a relay, either through other descending pathways, such as the reticulospinal system, or via local segmental interneurons.

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PubMed1991

Morphology and frequency of axon terminals on the somata, proximal dendrites, and distal dendrites of dorsal neck motoneurons in the cat.

The purpose of the present study was to compare the frequency of different classes of axon terminals on selected regions of the somatodendritic surface of dorsal neck motoneurons. Single motoneurons supplying neck extensor muscles were antidromically identified and intracellularly stained with horseradish peroxidase. By using light microscopic reconstructions as a guide, axon terminals on the somata, proximal dendrites (within 250 microns of the soma), and distal dendrites (more than 540 microns from the soma) were examined at the electron microscopic level. Axon terminals were divided into several classes based on the shape, density, and distribution of their synaptic vesicles. The proportion of axon terminals belonging to each axon terminal class was similar on the somata and proximal dendrites. However, there were major shifts in the relative frequency of most classes of axon terminals on the distal dendrites. The most common classes of axon terminals on the somata and proximal dendrites contained clumps of either spherical or pleomorphic vesicles. These types of axon terminals accounted for more than 60% of the axon terminals on these regions. In contrast, only 11% of the axon terminals found on distal dendrites belonged to these types of axon terminals. The most commonly encountered axon terminal on distal dendrites contained a dense collection of uniformly distributed spherical vesicles. These types of axon terminals accounted for 40% of all terminals on the distal dendrites, but only 5-7% of the axon terminals on the somata and proximal dendrites. Total synaptic density on each of the three regions examined was similar. However, the percentage of membrane in contract with axon terminals was approximately four times smaller on distal dendrites than somata or proximal dendrites. Axon terminals (regardless of type) were usually larger on somata and proximal dendrites than distal dendrites. These results indicate that there are major differences in the types and arrangement of axon terminals on the proximal and distal regions of dorsal neck motoneurons and suggest that afferents from different sources may preferentially contact proximal or distal regions of the dendritic trees of these cells.

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PubMed1990

Multiplicity of vestibulospinal projections to the upper cervical spinal cord of the cat: a study with the anterograde tracer Phaseolus vulgaris leucoagglutinin.

The distribution and frequency of vestibulospinal axons and boutons in the upper cervical spinal cord of the cat were investigated. The anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) was injected into discrete regions of the vestibular nuclei, including the medial and descending nuclei, as well as small regions of the lateral vestibular nucleus along its medial border with the medial vestibular nucleus. In contrast to previous reports, labelled vestibulospinal axons were not found to be restricted to the ventromedial and ventrolateral funiculi, but were also observed bilaterally in the lateral funiculi, the dorsolateral funiculi and the dorsal columns. The diameter of these axons ranged from 0.5 to 7.4 microns. Labelled boutons were found bilaterally from lamina IV to IX as well as in lamina X. Contralateral to the injection site, boutons were frequently found as far dorsal as lamina II. Ipsilaterally, boutons were found this far dorsal in only one experiment. There was a dense projection to the contralateral central cervical nucleus, while very few, if any, boutons were observed in the ipsilateral central cervical nucleus. In each experiment, the density of boutons was greater in the rostral cervical segments than in more caudal segments. The "new" vestibulospinal projections to the dorsal horn and central cervical nucleus were confirmed in separate experiments using retrograde transport of horseradish peroxidase. These results show that vestibulospinal axons project to the upper cervical spinal cord via multiple funicular paths. The rich terminations of these axons outside of the ventral horn, as well as in the neck motoneuron nuclei, indicate that vestibulospinal projections must play a wide variety of functions in addition to their well-documented role in the direct control of head movement.

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PubMed1988

Nonequivalent cylinder models of neurons: interpretation of voltage transients generated by somatic current injection.

1. Numerical methods were used to simulate the voltage responses to an intrasomatic current step of neuronal models that incorporated tapering dendrites, dendrites of unequal electrotonic length, nonlinear membrane properties, and regional differences in specific membrane resistivity (Rm). A "peeling" technique was used to estimate the time constants (tau 0 and tau 1) and coefficients (a0 and a1) of the first two exponential terms of the series of exponential terms whose sum represented the slope of the voltage response. 2. The electrotonic structure of models with a uniform Rm was calculated using equations derived by Rall or Johnston or Brown et al. The adequacy of these methods were tested using a wide variety of models that conformed to the equivalent cylinder approximation of Rall. Johnston's method provided the most reliable estimate of electrotonic length (L) and the ratio of the dendritic conductance to the somatic conductance (rho). However, if L exceeded 2 and rho was eight or larger, the equations derived by Johnston could frequently not be solved due to small errors in the peeled values of tau 0, tau 1, a0, and a1. Although the method suggested by Brown et al. could be applied to all models, this method invariably underestimated L and rho. These errors were particularly large for model neurons with L values of 1.5 or larger and rho values of four or larger. Estimates of L using Rall's method were only reliable if rho was large and L was two or less. 3. Changing the geometry of the dendritic tree (dendritic tapering or dendrites of unequal L) or the addition of a time- and voltage-dependent conductance designed to mimic a sag process commonly seen in spinal motoneurons caused systematic changes in tau 0, tau 1, a0, and a1. The sag process always led to an underestimate of tau 0 even after applying a correction procedure. On the other hand, the ratio, tau 0/tau 1, was not affected by the sag process or dendritic tapering.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1988

Differences in somatic and dendritic specific membrane resistivity of spinal motoneurons: an electrophysiological study of neck and shoulder motoneurons in the cat.

1. The voltage response to a hyperpolarizing current step was used to estimate the electrotonic structure of neck and shoulder motoneurons in anesthetized cats. The coefficients (a0 and a1) and time constants (tau 0 and tau 1) of the first two exponential terms of the series of exponential terms whose sum represented the slope of the voltage response were calculated using a standardized "peeling" technique. 2. Input resistance, membrane time constant, and electrotonic length were similar to values reported for other spinal motoneurons. The voltage response of most neck and shoulder motoneurons had a slow, nonlinear component, commonly known as sag, which is also a feature of other spinal motoneurons. Estimates of motoneuron surface area were up to two times larger than the surface area of hindlimb motoneurons. 3. It was possible to estimate electrotonic length and the ratio of the dendritic conductance to the somatic conductance using Johnston's technique for only 6 of 51 motoneurons examined. The responses of these motoneurons were identical to the responses of equivalent cylinder models that had an electrotonic structure derived from the application of Johnston's technique. 4. We were unable to use Johnston's technique for the remaining motoneurons because the ratio, a1/a0, exceeded 2.0. For these motoneurons it was usually impossible to find an equivalent cylinder model whose response matched the experimental data. The failure of equivalent cylinder models to accurately predict the responses of neck and shoulder motoneurons could not be attributed to the sag process or the dendritic geometry of these cells. 5. The electrotonic structure of a group of these motoneurons was further examined using the somatic shunt model developed by Durand and Kawato. After shifting the base line of the experimental records by 1-2 mV in the depolarizing direction, it was possible to find a somatic shunt model whose response was identical to the experimentally recorded voltage response.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1988

Compartmentalization of motor units in the cat neck muscle, biventer cervicis.

1. The neck muscle biventer cervicis is supplied by five separate nerve bundles that originate from segments C2-C5 and enter the muscle at different rostrocaudal levels. We have used the glycogen-depletion method to investigate the distribution of muscle fibers supplied by each nerve bundle and also the extent of motor-unit territories supplied by single motoneurons in the C3 segment. 2. Prolonged intermittent stimulation of each nerve bundle produced glycogen depletion in a compartment of muscle fibers that ran only a fraction of the whole-muscle length. The depleted compartment was separated by tendinous inscriptions from adjacent, serially arranged compartments that were supplied by different nerve bundles. Thus the muscle was divided into five in-series compartments, arranged in the same rostrocaudal sequence as the nerves by which they were supplied. 3. Six fast, glycolytic (FG) and five fast, oxidative-glycolytic (FOG) motor units were depleted by repetitive intracellular stimulation of their antidromically identified motoneurons in the C3 segment. The fibers of each motor unit were confined to a striplike subvolume whose cross-sectional area was only 20-40% of that for the whole compartment in which it was located. Single motor units contained an average of 408 extrafusal fibers (range: 262-582 fibers), and these were distributed with an average density of 20 fibers/mm2 in cross sections through their motor domains. No significant differences were found between the numbers or densities of fibers in FG and FOG motor units. 4. The specialized in-series organization of compartments has functional implications because the forces generated by one compartment of motor units must be transmitted through other in-series compartments of muscle fibers rather than directly onto skeletal attachments. The confined distribution of muscle fibers belonging to a single motor unit suggests that an additional level of organization may exist within individual compartments. The implications of these features for the physiological behavior and neural control of biventer cervicis are discussed.

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PubMed1988

Structure of the intraspinal projections of single, identified muscle spindle afferents from neck muscles of the cat.

The morphology and frequency of collaterals originating from single afferents supplying primary endings of muscle spindles in dorsal neck muscles have been examined using intra-axonal injections of HRP. Within the segment in which the afferent entered the spinal cord, one collateral was found for every 3.3 mm of stained axon. In contrast, afferents--one of more segments rostral to the segment in which they entered the spinal cord--had fewer collaterals: One collateral was found for every 6.3 mm of stained axon. The branching structure and terminal distribution of the collaterals were generally similar regardless of the muscle from which the afferent originated and the segment in which the collateral was found. Boutons were found in 2 zones: One of these was located in the intermediate zone, within and around the central cervical nucleus, and the other was found in laminae VIII and IX, including the motoneuron nuclei. The ventral termination zone of collaterals in the same segment as their parent axon entered the spinal cord was larger and had more boutons than the same projection of collaterals whose parent axon entered the spinal cord 1 or 2 segments caudal to the segment in which the collateral was found. These results indicate that afferents supplying primary endings of neck muscle spindles are more likely to contact neurons in the same segment in which the afferent enters the spinal cord than in more rostral segments. However, even within the same segment in which the afferent enters the spinal cord, the projection of neck muscle afferents to the ventral horn is less dense than the corresponding projection of hindlimb muscle spindle afferents in the lumbosacral spinal cord.

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PubMed1988

Monosynaptic projections of single muscle spindle afferents to neck motoneurons in the cat.

Monosynaptic connections to dorsal neck motoneurons of the cat from single afferents supplying primary endings of neck muscle spindles were studied using spike-triggered averaging techniques. Single-fiber EPSPs were detected in only 11 of the 112 afferent-motoneuron pairs examined. The average amplitude of single-fiber EPSPs recorded in motoneurons with a membrane potential of greater than -40 mV was 49 microV. Motoneurons receiving functional contacts from a single afferent were confined to a small rostrocaudal zone within the motor nucleus. The low frequency of single-fiber EPSPs in neck motoneurons could not be attributed to the absence of projections to the ventral horn or to damage to either the afferents or motoneurons. Our results suggest, therefore, that single afferents from neck muscle spindles make functional contacts with a small fraction of neck motoneurons, unlike the arrangement seen in more commonly studied hindlimb muscle systems (Henneman and Mendell, 1981).

Action Potentials↗
PubMed1986

Segmental projection from muscle spindles: a perspective from the upper cervical spinal cord.

The segmental connections of muscle spindle afferents originating from primary endings do not follow the same pattern at all levels of the spinal cord. This review is concerned with the characteristics of neck muscle spindle projections, which illustrate several differences between their segmental organization and the arrangement of hindlimb muscle spindle afferents in the lumbosacral spinal cord.

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PubMed1985

A quantitative analysis of the geometry of cat motoneurons innervating neck and shoulder muscles.

The geometry of the somata and dendritic trees of motoneurons innervating neck and shoulder muscles was investigated by using intracellular injections of HRP. In general, these motoneurons did not belong to a homogeneous population of motoneurons. Differences in average primary dendritic diameter, number of primary dendrites, and other measures of dendritic tree size were found between different neck and shoulder motoneuron groups. Several indices of proximal dendritic tree size (number of primary dendrites, sum of dendritic diameters, Rall's dendritic trunk parameter, and the sum of dendritic holes) were weakly correlated with the diameter or surface area of the soma. Some of these correlations depended on the muscle supplied by the motoneuron. The total combined dendritic length ranged from 66,660 to 95,390 microns. There was a weak, but positive, correlation between the diameter of primary dendrites and combined dendritic length. This relationship varied from motoneuron to motoneuron. The diameters of all dendrites of three trapezius motoneurons were examined in detail. The total dendritic surface area examined ranged from 415,000 to 488,100 microns 2 and represented approximately 99% of the total neuronal surface area. Last-order dendrites showed a high degree (39.9%) of taper. Dendritic tapering, by itself, was a major factor in the decrease of the (sum of dendritic diameters)3/2 measured at progressively distal sites from the soma. Although few parent and daughter dendrites obeyed the "three-halves law," the average exponent was 1.57. The diameters of primary dendrites and dendritic surface area were weakly correlated. The correlation between dendritic diameter and combined dendritic length or surface area improved if the weighted average of the diameter of second-order dendrites was used as a measure of dendrite size. Second-order dendrites, whose branches terminated in different regions of the spinal cord, showed different relationships between dendritic diameter and combined dendritic length or surface area. Comparisons between the motoneurons examined in the present study and motoneurons innervating other muscles indicate that, although all spinal motoneurons share several common features (e.g., long dendrites, dendritic tapering), each motoneuron group has a set of unique features (e.g., soma shape, relationship between primary dendrite diameter and dendritic surface area). Thus, the rules governing motoneuron dendritic geometry are not fixed but depend on the species of the motoneuron.

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PubMed1979

Neck muscle and trigeminal input to the upper cervical cord and lower medulla of the cat.

Experiments on chloralose-anaesthetized cats have shown that low-threshold neck muscle afferents project to laminae IV and V in the dorsal horn of the upper cervical cord, to lamina VI including the region which encompasses the central cervical nucleus, as well as to extensive regions of the ventral horn. At posterior medullary levels projections also exist to laminae IV, V, and VI of the spinal nucleus of V (although those to lamina IV are circumscribed), to the deep layers and lateral margin of the cuneate nucleus, and to the inferior olive. These projections are both from low- and high-threshold afferents. Evidence of a functional relationship between the trigeminal and neck muscle afferent system was found both in the upper cervical cord and lower medulla. About 40% of units in both regions receive a convergent input and when convergence could not be demonstrated, prior stimulation of one modality in some instances affected the responsiveness of the unit to the other modality. A motor role was found for some trigeminal afferent projections to the upper cervical cord. Trigeminal afferents consistently activated antidromically identified motoneurons of splenius, biventer cervicis, and complexus.

Action Potentials↗
PubMed1978

Morphology and organization of axon collaterals from afferent fibres of slowly adapting type I units in cat spinal cord.

1. The morphology of the collaterals of single axons innervating Type I slowly adapting receptors was studied by using the intra-axonal injection of the enzyme horseradish peroxidase in anaesthetized cats. The axons were impaled near their dorsal root entrance zone in the lumbosacral cord. The morphology was revealed by subsequent histochemistry. 2. Thirteen Type I axons were stained, nine with receptors in the hairy skin and four with receptors in the glabrous foot pad skin. Twelve axons could be traced back into their dorsal roots and 11 of these divided into rostral and caudal branches shortly after entering the spinal cord. 3. One hundred and twelve collaterals were given off the thirteen axons and all well filled collaterals had a similar morphology. In the dorsal horn they gave rise to wide elliptical areas of terminal arborization (in transverse sections of cord) that were limited to laminae III, IV and the dorsal part of lamina V. The terminal arborizations of collaterals from the same axon were in line in the saggittal plane, but only rarely did the terminal arborizations of adjacent collaterals overlap; usually there was a gap between adjacent terminal arborizations. 4. Synaptic boutons of Type I units from hairy skin were mainly of the "en passant" variety whereas those of Type I units from glabrous skin were generally "boutons terminaux" with very few boutons "de passage". 5. The morphology of axon collaterals of Type I units is compared with that of hair follicle units.

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PubMed1978

Tectospinal and tectoreticular cells: their distribution and afferent connections.

Experiments on chloralose-anaesthetized cats have shown that cells in the superior colliculus may be antidromically activated either from the pontomedullary reticular formation or the ventral cervical spinal cord, or from both sites. In tests on 111 units this has provided a basis for differentiating between cells of origin of the tectospinal tract and the tectoreticular system within the superior colliculus. Tectospinal cells may be activated both by spinal and pontine stimulation; tectoreticular cells cannot be activated by spinal stimulation. Both tectoreticular and tectospinal cells respond to visual and muscle afferent stimulation. The afferent connections may be strongly inhibitory as afferent input to the superior colliculus ofter prevented subsequent antidromic invasion. This was more commonly seen in tectospinal cells than tectoreticular cells. The distribution of the two cell populations within the superior colliculus was also found to be dissimilar. Evidence has also been obtained to suggest that the tectoreticular system, in part, consists of collaterals of the tectospinal tract.

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PubMed1977

Inhibition of spinocervical tract discharges from localized areas of the sensorimotor cortex in the cat.

1. Intracortical microstimualtion (ICMS) was applied within the sensorimotor cortex of cats anaesthetized with chloralose. 2. The effects of the ICMS were examined on the number of impulses in spinocervical tract (SCT) cells (recorded extracellularly in the contralateral lumbosacral spinal cord) evoked by peripheral stimulation. 3. Inhibition of SCT discharges was produced by ICMS in two distinct regions of the sensorimotor cortex. 4. One inhibitory regions was in part of cytoarchitectonic area 4 gamma in the upper bank of the cruciate sulcus. It sometimes extended caudally into area 4 delta, medially into area 3 alpha and/or rostrally into the part of area 4 gamma on the caudal lip of the cruciate sulcus. 5. The other inhibitory region was in the medial part of the posterior sigmoid gyrus and included parts of areas 3 alpha, 3 beta, 1, 5 alpha and 5 beta. 6. Most inhibitory sites were in cortical layers III, V and VI. 7. No regions were found in which ICMS consistently caused facilitation of SCT discharges.

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