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PubMed1994

Rubrospinal tract in the Formosan monkey: HRP and autoradiographic studies.

Neurons projecting from the red nucleus to the spinal cord in the Formosan monkey were identified with retrograde horseradish peroxidase and tritiated proline and fucose antegrade autoradiographic tracing methods. A topographic organization of projections from the red nucleus to the spinal cord was demonstrated. Medial and dorsal portions of the rostral red nucleus projected to the rostral half of the spinal cord. Neurons in the ventrolateral part of the red nucleus emitted fibers which terminated in the caudal half of the spinal cord. The spinal projections from the red nucleus are bilateral, but contralateral projection is dominant. These results indicated a well developed rubrospinal tract existence in the Formosan monkey.

Animals↗
PubMed1986

Anatomical observations on the afferent projections to the retractor bulbi motoneuronal cell group and other pathways possibly related to the blink reflex in the cat.

In the cat retractor bulbi (RB) muscle reflexively retracts the eye ball into the orbit. This reflex action is called the nictitating membrane response which, together with the reflex contraction of the orbicularis oculi muscle, constitutes the blink reflex. The retractor bulbi (RB) motoneuronal nucleus is a small cell group located in the lateral tegmentum of the caudal pons, just dorsal to the superior olivary complex. The nucleus is identical to the accessory abducens nucleus and sends its fibers through the abducens nerve. Autoradiographical tracing results indicate that the RB nucleus receives some fibers from the principal and rostral spinal trigeminal nuclei and from the dorsal red nucleus and dorsally adjoining tegmentum. The same areas project to the intermediate facial subnucleus, containing motoneurons innervating the orbicularis oculi muscle. It is suggested that the trigeminal projections take part in the anatomical framework for the R1 component of the blink reflex. Two other brainstem areas i.e.: a portion of the caudal pontine ventrolateral tegmental field and the medullary medial tegmentum at the level of the hypoglossal nucleus were also found to project to the RB motoneuronal cell group and to the intermediate facial subnucleus. These projections were much stronger than those derived from the trigeminal nuclei and red nucleus. Moreover, the medullary premotor area projects not only to the blink motoneuronal cell groups but also to the pontine premotor area. It is suggested that both areas are involved in the R2 blink reflex component. The medullary blink premotor area receives afferents especially from oculomotor control structures in the reticular formation of the brainstem while the pontine blink premotor area receives afferents from the olivary pretectal nucleus and/or the nucleus of the optic tract and from the dorsal red nucleus and its dorsally adjoining area. Because the oculomotor control structures in the reticular formation (by way of the superior colliculus) and the red nucleus receive afferents from trigeminal nuclei, they may play an important role in tactually induced reflex blinking, while the pretectum could take part in the neuronal framework of the visually induced blink reflex.

Afferent Pathways↗
PubMed1999

Survival of chronically-injured neurons can be prolonged by treatment with neurotrophic factors.

Axonal regeneration by chronically-injured supraspinal neurons can be enhanced by neurotrophic factor treatment at the site of injury, although the number of regenerating neurons decreases as the interval between spinal cord injury and treatment increases. This study investigated whether this decline in regenerative response could be due to continued loss of neurons during the post-injury period. Adult rats received a cervical hemisection lesion and axotomized neurons were labeled by retrograde transport of True Blue from the lesion site. Animals were killed one, four or eight weeks after injury and surviving neurons (True Blue-labeled) were counted in the red nucleus and lateral vestibular nucleus. The neuron number in the lateral vestibular nucleus was stable for eight weeks after spinal cord injury, while survival in the red nucleus decreased by 25% between four and eight weeks. To test how neurons respond to a second injury with or without trophic factor treatment, at four, eight, 14 or 22 weeks after injury the lesion cavity was enlarged by 0.5 mm in a rostral direction. Gel foam saturated with ciliary neurotrophic factor, brain-derived neurotrophic factor or basic fibroblast growth factor was placed into the cavity. Animals were killed four weeks later. Re-injury of the spinal cord caused a significant decrease in neuron survival in both the red nucleus and lateral vestibular nucleus, the effects of which were lessened by treatment with ciliary neurotrophic factor or brain-derived neurotrophic factor for the red nucleus and with ciliary neurotrophic factor for the lateral vestibular nucleus, when re-injured at four or eight weeks. Basic fibroblast growth factor did not affect neuron survival at any time post-injury. Ciliary neurotrophic factor was not effective with longer delays (14 or 22 weeks) between the initial injury and re-injury. These results indicate a delayed pattern of secondary neuronal cell loss after spinal cord injury that is exaggerated by re-injury, but which can be ameliorated by treatment with neurotrophic factors.

Animals↗
PubMed1987

[Synaptic processes in the rubrospinal neurons evoked by stimulation of the cerebellar nucleus interpositus in the cat].

Activity of red nucleus rubrospinal neurons to electrical stimulation of cerebellar nucleus interpositus was studied in nembutalized cats. Facilitation of cerebello-rubral transmission was shown to take place in the majority of neurons whose focal potentials and EPSPs to paired and frequency stimulation of cerebellar nucleus interpositus were analyzed. The mentioned facilitation was found not to be caused by changes in presynaptic volleys. Discussed modification of the transmission efficiency was supposed to be determined by peculiarities of functioning of cerebellar synapses on red nucleus neurons.

Animals↗
PubMed1997

Activation mapping in essential tremor with functional magnetic resonance imaging.

We used functional magnetic resonance imaging (FMRI) to study possible cerebral activation patterns associated with unilateral postural tremor in 12 patients with essential tremor (ET), with mimicked postural tremor in 15 control subjects, and with passive wrist oscillation in both groups. During essential tremor, patients showed mainly contralateral activation of the primary motor and primary sensory areas, the globus pallidus, and the thalamus, but bilateral activation of the nucleus dentatus, the cerebellar hemispheres, and the red nucleus. Only 2 patients presented with activity in the medulla close to the olivary nucleus. Unilateral passive wrist oscillation of ET patients resulted in only unilateral activation of the cerebellum, nuclei dentati, and red nuclei. In contrast to the involuntary tremor condition of ET patients, the mimicked tremor condition of the control subjects was not associated with bilateral activity in the cerebellum, nuclei dentati, or red nuclei. Involuntary tremor of ET patients was associated with a significantly larger extent of activation in the cerebellar hemispheres and the red nucleus (p < 0.003) compared with mimicked tremor in the control group. Our FMRI study indicates that ET is mainly associated with an additional contralateral cerebellar pathway activation and overactivity in the cerebellum, red nucleus, and globus pallidus without significant intrinsic olivary activation.

Aged↗
PubMed1996

In vivo and in vitro labelling of perineuronal nets in rat brain.

Previous lectin-histochemical and immunocytochemical investigations using fixed tissue revealed perineuronal nets as lattice-like accumulations of extracellular matrix proteoglycans at the surface of several types of neurons. In the present study, perineuronal nets in the rat brain were labelled for the first time in vivo by stereotaxic injections of biotinylated Wisteria floribunda agglutinin (Bio-WFA), as well as in vitro, by incubation of unfixed brain slices with the same lectin. Six days after Bio-WFA injections into the parietal cortex, medial septum, reticular thalamic nucleus and red nucleus, the lectin remaining bound to perineuronal nets was detected by streptavidin/biotinylated peroxidase complexes or red fluorescent Cy3-streptavidin, respectively. Double-fluorescence labelling showed that Bio-WFA applied in vivo reacted with the chondroitin sulphate proteoglycan immunoreactive perineuronal nets in the injection zone. Labelling of perineuronal nets in unfixed slices was obtained with either Cy3-tagged WFA or Bio-WFA and subsequent visualization by Cy3-streptavidin which confirmed the region-dependent distribution patterns and the structural characteristics of perineuronal nets known from histochemical studies. These results provide support for the role of extracellular matrix proteoglycans to maintain a considerable chemical and, probably, spatial heterogeneity of the extracellular space in vivo. The ability of in vivo and in vitro labelling may promote the functional characterization of the extracellular matrix in various brain structures including its species-dependent neuronal association patterns.

Animals↗
PubMed1995

Evidence for the involvement of histamine in the antidystonic effects of diphenhydramine.

Although diphenhydramine hydrochloride is known to eliminate or reduce the symptoms of dystonia in human patients with acute dystonic reactions and idiopathic torsion dystonia, its mechanism of action is still unclear. In the present study, we show that the antihistamine properties of diphenhydramine may contribute to its beneficial effects. Acute dystonic reactions were produced in rats with unilateral microinjection of haloperidol into the red nucleus as previously described. Similar to the pattern in humans, this effect could be attenuated by coadministration of diphenhydramine. Unilateral microinjection of histamine itself into the rat red nucleus produced dystonic postures (torticollis) in a dose-dependent manner, demonstrating that a histamine dysfunction could contribute to the pathophysiology of dystonia. The torticollis produced by histamine could be significantly attenuated with coadministration of the H1 antagonists diphenhydramine or pyrilamine or the H2 antagonist cimetidine. These effects are thought to be mediated through the red nucleus because significantly more torticollis was observed when histamine was injected into the red nucleus rather than surrounding mid-brain areas, the substantia nigra, or the lateral ventricle. The present data, taken together with studies in humans, suggest the involvement of histamine in some types of dystonia. Furthermore, the red nucleus and related motor pathways may have a more important role in dystonia than previously thought.

Animals↗
PubMed1981

Anatomical evidence for direct fiber projections from the cerebellar nucleus interpositus to rubrospinal neurons. A quantitative EM study in the rat combining anterograde and retrograde intra-axonal tracing methods.

A quantitative electron microscopic (EM) study combining the anterograde intra-axonal transport of radioactive amino acids and the retrograde intra-axonal transport of the enzyme horseradish peroxidase (HRP) was performed in the magnocellular red nucleus of the rat to obtain anatomical evidence as to whether there is a direct projection from the cerebellar nucleus interpositus to the cells in the red nucleus that give rise to the rubrospinal tract. Large asymmetrical synaptic terminals were radioactively labeled in the magnocellular red nucleus following injections of [3H]leucine into the cerebellar nucleus interpositus. In these same animals, the postsynaptic target neurons were labeled with HRP granules after injection of this substance in the rubrospinal tract. A quantitative analysis showed that more than 85% of the large and giant neurons in the magnocellular red nucleus were labeled with HRP granules and also received synaptic contacts from radioactively-labeled terminals. Thus, it can be concluded that in the rat, afferents from the cerebellar nucleus interpositus establish asymmetrical synaptic contacts with large and giant rubrospinal neurons, thus confirming and extending the previous physiological evidence of such direct monosynaptic connections.

Animals↗
PubMed1999

Rescue of axotomized rubrospinal neurons by brain-derived neurotrophic factor (BDNF) in the developing opossum, Didelphis virginiana.

Many rubrospinal neurons die in developing opossums when their axon is cut at thoracic levels of the spinal cord and in the present study we asked whether they can be rescued by brain-derived neurotrophic factor (BDNF). Bilateral injections of Fast Blue (FB) were made into the rostral lumbar cord to prelabel rubrospinal neurons and 5 days later the rubrospinal tract was cut unilaterally by hemisecting the thoracic cord. Immediately after hemisection, BDNF-soaked gelfoam was placed into the lesion cavity. Since pilot data indicated that one application of BDNF was not sufficient to produce a rescue effect, a second application was made 7 days later. Seven days after the second application the pups were killed by an overdose of anesthetic so that the red nucleus contralateral and ipsilateral to the lesion site could be examined for labeled neurons. The rubrospinal tract is almost entirely crossed, so the red nucleus contralateral to the lesion contained many axotomized neurons, whereas the red nucleus ipsilateral to it did not. Age-matched controls were subjected to the same procedures, but the gelfoam applied to the lesion site in the experimental animals was soaked only in the vehicle used to deliver BDNF. In all cases, labeled neurons were fewer in number in the red nucleus contralateral to the lesion than ipsilateral to it. It was of particular interest, however, that labeled neurons contralateral to the lesion were more numerous in the animals treated with BDNF than in the controls. We conclude that BDNF rescues at least some rubrospinal neurons from axotomy-induced cell death in developing opossums suggesting that loss of access to BDNF, and perhaps other neurotrophins, contributes to failure of rubrospinal neurons to survive axotomy.

Amidines↗
PubMed2002

A role for midbrain arcs in nucleogenesis.

Nuclei are fundamental units of vertebrate brain organization, but the mechanisms by which they are generated in development remain unclear. One possibility is that the early patterning of brain tissue into reiterated territories such as neuromeres and columns serves to allocate neurons to distinct nuclear fates. We tested this possibility in chick embryonic ventral midbrain, where a periodic pattern of molecularly distinct stripes (midbrain arcs) precedes the appearance of midbrain nuclei. We found that midbrain arc patterning has a direct relationship to the formation of nuclei. Both differential homeobox gene expression and diagnostic axon tracing studies established that the most medial arc contains primordia for two major midbrain nuclei: the oculomotor complex and the red nucleus. We tested the relationship of the medial arc to oculomotor complex and red nucleus development by perturbing arc pattern formation in Sonic Hedgehog and FGF8 misexpression experiments. We found that Sonic Hedgehog manipulations that induce ectopic arcs or expand the normal arc pattern elicit precisely parallel inductions or expansions of the red nucleus and oculomotor complex primordia. We further found that FGF8 manipulations that push the medial arc rostrally coordinately move both the red nucleus and oculomotor complex anlagen. Taken together, these findings suggest that arcs represent a patterning mechanism by which midbrain progenitor cells are allocated to specific nuclear fates.

Animals↗
PubMed1980

Topographical organization of ascending cerebellar projections from the dentate and interposed nuclei in Macaca mulatta: an anterograde degeneration study.

Discrete electrolytic lesions were placed in the dentate and interpositus cerebellar nuclei in th monkey Macaca mulatta and anterograde degeneration was traced in the ascending limb of the brachium conjunctivum using the Wiitanen technique. The dentate and interpositus anterior (IA) nuclei project topographically onto the two somatotopically organized divisions of the red nucleus and the ventrolateral-ventral intermediate nuclei of the thalamus (VL-Vim). Caudal parts of the dentate project to face areas in medial parts of the parvocellular red nucleus (RNpc) and VL-Vim, rostrolateral parts to central arm areas in these nuclei. There is a small projection from the rostroventral dentate to lateral hindlimb areas in RNpc and VL. Dorsal parts of the dentate project to ventral parts of RNpc and VLc-Vim (distal limb musculature area) exclusively, whereas ventral parts of the dentate project to dorsal parts of RNpc with some overlap ventrally dorsomedial VLc (proximal limb musculature and premotor areas). Caudal parts of IA project to medial forelimb and rostral parts to lateral hindlimb areas in the magnocellular red nucleus (RNmc) and VL-Vim. Projections from IA are greatest to distal musculature areas in VL-Vim. No projections from the interpositus posterior nucleus (IP) to the red nucleus could be identified positively, but projections to VL-Vim are to proximal hindlimb musculature and premotor areas.

Afferent Pathways↗
PubMed1979

The parieto-rubro-olivary pathway in the cat.

Stimulation of the parietal association cortex as well as the frontal motor cortex elicited clearly extracellular unitary activities or field potentials in the ipsilateral inferior olive in the cat. The parietal-induced responses came out generally at a longer and more variable latency than the frontal-induced ones. This suggested the existence of an indirect pathway from the parietal association cortex to the inferior olive. The recording sites for the parietal-induced responses were located not only in the dorsal lamella but also in the ventral lamella of the principal olive and in the medial accessory olive. Such olivary sites were exclusively in the rostral half of the inferior olive, and these areas in the olive were considered to give projection fibres predominantly to the hemispherical parts of the cerebe-lar cortex (neocerebellum). Small neuronal cells were labelled with horseradish peroxidase (HRP) homolaterally in the midbrain tegmentum, after HRP was injected through recording glass microelectrodes into the inferior olive where only the parietal-induced responses were evidently recorded. These small cells were distributed in the rostral one-third of the red nucleus and/or around the adjacent midbrain reticular formation close to the lateral border of the red nucleus. In referring to recent anatomical and physiological data, such small neurones labelled with HRP could be identified as the parvocellular red nucleus neurones. The present results indicate the existence of the parieto-rubro-olivary pathway system in the cat and suggest, in association with our previous studies, that the parvocellular red nucleus neurones participate in control of highly co-ordinated posture and movement predominantly through the neocerebellum.

Animals↗
PubMed1987

Sporadic case resembling autosomal-dominant motor system degeneration (Azorean disease complex).

We describe a case of an adult-onset progressive dystonia with external ophthalmoplegia, occurring in a black man without a family history of neurologic disorders. Neuropathologic examination demonstrated neuronal loss and gliosis in the anterior horn and Clarke's column in the spinal cord, nuclei of cranial nerves III, VI, X, and XII, vestibular complex, lateral cuneate nucleus, lower pontine tegmentum, red nucleus, substantia nigra, and dentate nucleus. The cerebral cortex, corpus striatum, basis pontis, inferior olives, and cerebellum were spared. The clinical and pathologic findings closely resemble autosomal-dominant motor system degeneration or "Azorean disease," without, however, demonstrable familial transmission. In addition to the absence of a family history, unique features of the case include the presence of Alzheimer type II glial cells in the red nucleus and an unexplained persistent elevated concentration of serum amylase.

Adult↗
PubMed1984

Olivary projections from the mesodiencephalic structures in the cat studied by means of axonal transport of horseradish peroxidase and tritiated amino acids.

By means of horseradish peroxidase (HRP) and autoradiographic methods, olivary projections from mesodiencephalic structures were studied in the cat. Following HRP injections in various parts of the inferior olive, many cells were labeled ipsilaterally in the nucleus of Darkschewitsch, the nucleus accessorius medialis of Bechterew, the nucleus of the fields of Forel, and the subnucleus dorsomedialis and ventrolateralis of the parvocellular red nucleus. Some labeled cells also occurred ipsilaterally in the suprarubral reticular formation and a few labeled cells in the interstitial nucleus of Cajal. After injection of tritiated amino acids in different parts of the mesodiencephalic region mentioned above, labeled fibers were found in different parts of the inferior olive, presenting a high degree of the topographic correlation within the mesodiencephalo-olivary projection, which was exclusively ipsilateral. That is, the nucleus of Darkschewitsch was found to project to the rostral half of the medial accessory olive and the dorsomedial cell column. There was mediolateral topographic relation in this projection. The nucleus accessorius medialis of Bechterew was found to project to the ventral lamella and the lateral part of the dorsal lamella as well as to small rostromedial part of the caudal half of the medial accessory olive. The subnucleus dorsomedialis and ventrolateralis of the parvocellular red nucleus projected to the rostral and caudal halves, respectively, of the medial part of the dorsal lamella. The subnucleus ventrolateralis of the parvocellular red nucleus also sent fibers to the lateral part of the ventrolateral outgrowth. The nucleus of the fields of Forel, suprarubral reticular formation, and interstitial nucleus of Cajal appeared to project to the caudal half of the medial accessory olive, the medial part of the ventrolateral outgrowth, the rostral part of the dorsal cap, and the caudal part of the dorsal accessory olive.

Animals↗
PubMed1999

Immunohistochemical localization of kininogen in rat spinal cord and brain.

Kininogen localization has been determined by immunocytochemistry in rat spinal cord and brain using a kinin-directed kininogen monoclonal antibody. In the spinal cord, there were immunostained neurons and fibers in laminae I, II, VII, and IX, intensely stained fibers in the superficial layers of the dorsal horn, and immunoreactive glial and endothelial cells. Small neurons, satellite cells, and Schwann cells immunostained distinctly in the dorsal root ganglion. In the brain stem, there were immunoreactive neurons and fibers in the tractus solitarius and nucleus, trigeminal spinal tract and nuclei, periaqueductal gray matter, vestibular nuclei, cochlear nuclei, trapezoid body, medial geniculate nucleus, and red nucleus. Immunostained neurons and fibers were also found in cerebellum (dentate nucleus), cerebral cortex (layers III and V), hippocampus (pyramidal cell layer), and corpus callosum. Glia and endothelial cells stained in all brain regions. The widespread location of kininogen in neurons and their processes, as well as in glial and endothelial cells, indicates more than one functional role, including those proposed as a mediator, a calpain inhibitor, and a kinin precursor, in a variety of neural activities and responses.

Animals↗
PubMed1997

The projections to the spinal cord of the rat during development: a timetable of descent.

In order to establish a timetable for the developmental descent of supraspinal descending projections in the rat, a retrograde neuronal tracer was injected into the spinal cord of rat fetuses and neonates both at different gestational ages and at different levels of the spinal cord. From the results of these experiments a position interval could be deduced for the leading descending fibers of each spinal-projecting nucleus at each age studied. The chronological series of position intervals of each supraspinal descending projection (the descent pattern) depicts the descent of its fiber front during development and allows for easy comparison between the various projections. According to these descent patterns the descent sequences of the various spinal-projecting nuclei were established. At E17 fibers from the lateral vestibular nucleus, the raphe magnus nucleus and the gigantocellular reticular nucleus were present in the lumbosacral spinal cord; their descent along the spinal cord thus occurs before this stage. At E18 fibers from the parafascicular prerubral nucleus, the interstitial nucleus of Cajal, the mesencephalic reticular nucleus, the caudal pontine reticular nucleus, the laterodorsal tegmental nucleus, the subcoerulean nucleus, the spinal vestibular nucleus, the interpolar spinal trigeminal nucleus, the raphe obscurus nucleus and the ventral medullary reticular nucleus arrived in the lumbosacral cord. At the same stage fibers from the oral and caudal spinal trigeminal nucleus reached their caudalmost extent in the spinal cord, respectively, the lower and upper thoracic cord. At E19 fibers from the oral pontine reticular nucleus, the parvocellular reticular nucleus, the ventral gigantocellular reticular nucleus and the ambiguous nucleus first appeared in the lumbosacral cord. At E20 fibers from Darkschewitsch's nucleus, the paralemniscal and parabrachial nuclei, cell group A5, the locus coeruleus, the gigantocellular reticular nucleus-alpha, the raphe pallidus nucleus, the paramedian reticular nucleus, and from the dorsal medullary reticular nucleus arrived in the lumbosacral cord. Last to arrive in the lumbar cord during the prenatal period, at E21, were fibers from the posterior commissural nucleus, the red nucleus, the Edinger-Westphal nucleus, the paragigantocellular reticular nucleus, the medial vestibular nucleus, Roller's nucleus, and the solitary nucleus. Fibers from the paraventricular hypothalamic nucleus and from the lateral hypothalamic area only arrived in the lumbosacral cord at P1, followed by fibers from the incertal nucleus at P4. A transient spinal projection from an unknown group of neurons located immediately lateral to and partly intermingled with the mesencephalic trigeminal nucleus arrived in the lumbosacral spinal cord at E18 and had disappeared at P1. This cell group, called Gr?, closely resembled the mesencephalic trigeminal nucleus (Me5). Both were teardrop shaped; an oblong mass of neurons at the caudal end with a long and thin trailing edge. The trailing edge of Gr?, however, curved dorsad towards the dorsal midline raphe of the caudal mesencephalon, while the trailing edge of Me5 curved rostrad, parallel to the sulcus limitans of the sylvian aquaduct. The neurons of Gr? are mainly round, but in the caudal part of the nucleus some horizontally oriented fusiform neurons were observed. All neurons of Gr? were tiny. These results confirm that the generation sequence of the source nuclei is not a prime determinant of descent sequence along the spinal cord. The distance between the source nucleus and the entrance to the target seems of influence only in the most extreme cases (diencephalic source nuclei and the cerebral cortex). Descent velocity of the fiber fronts is not equal between different sources, nor is the descent velocity of specific fiber fronts constant over time. (ABSTRACT TRUNCATED)

Animals↗
PubMed1999

Activity-dependent development of cortical axon terminations in the spinal cord and brain stem.

Corticospinal (CS) axon terminations in several species are widespread early in development but are subsequently refined into a spatially more restricted distribution. We studied the role of neural activity in sensorimotor cortex in shaping postnatal development of CS terminations in cats. We continuously infused muscimol unilaterally into sensorimotor cortex to silence neurons during the postnatal CS refinement period (weeks 3-7). Using anterograde transport of WGA-HRP, we examined the laterality of terminations from the muscimol-infused (i.e., silenced) and active sides in the spinal cord, as well as in the cuneate nucleus and red nucleus. We found that CS terminations from the muscimol-infused cortex were very sparse and limited to the contralateral side, while those from the active cortex maintained an immature bilateral topography. Controls (saline infusion, noninfusion) had dense, predominantly contralateral, CS terminations. There was a substantial decrease in the spinal gray matter area occupied by terminations from the side receiving the blockade and a concomitant increase in the area occupied by ipsilateral terminations from the active cortex. Optical density measurements of HRP reaction product from the active cortex in muscimol-infused animals showed substantial increases over controls in the ratio of ipsilateral to contralateral CS terminations for all laminae examined (IV-V, VI, VII). Our findings suggest that ipsilateral dorsal horn terminations reflect new axon growth during the refinement period because they are not present there earlier in development. Those in the ventral horn are present earlier in development and thus could reflect maintenance of transient terminations. Increased ipsilateral terminations from active cortex were due to recrossing of CS axons in lamina X and not to an increase in labeled CS axons in the ipsilateral white matter. Examination of brain stem terminations suggested that, between postnatal weeks 3 and 7, development of corticocuneate terminations also is activity-dependent but that development of corticorubral terminations is not. Activity-dependent CS development is a plausible mechanism by which early motor experiences could shape the anatomical and functional organization of the motor systems during a critical postnatal period.

Aging↗
PubMed1983

Brainstem projections to the facial nucleus of the opossum. A study using axonal transport techniques.

The horseradish peroxidase and autoradiographic techniques have been used to determine the origin and intranuclear termination of brainstem axons projecting to the facial nucleus of the opossum and to define networks which could be utilized in some oral-facial behaviors. Two regions of the midbrain have dense projections to the facial nucleus. One region is the ventral periaqueductal gray and adjacent interstitial nucleus of the medial longitudinal fasciculus which project bilaterally to those areas of the facial nucleus supplying auricular and cervical musculature. A second is the paralemniscal zone of the caudolateral midbrain which innervates the same areas of the contralateral facial nucleus. The red nucleus and/or the adjacent tegmentum send a less dense projection to those regions of the contralateral facial nucleus which innervate buccolabial and zygomatic muscles. The dorsolateral pons (the parabrachial complex, the nucleus locus coeruleus, pars alpha, and the nucleus sensorius n. trigemini, pars dorsalis) projects densely to those areas of the ipsilateral facial nucleus which innervate buccolabial and zygomatic musculature. In contrast, the nucleus reticularis pontis, pars ventralis, projects bilaterally to parts of the facial nucleus supplying auricular and cervical muscles. There was evidence of some rostral to caudal organization in the latter projection. Neurons in medial parts of the lateral reticular formation project bilaterally to the facial nucleus. Those within the nucleus reticularis parvocellularis and the rostral nucleus reticularis medullae oblongatae ventralis innervate areas supplying buccolabial and zygomatic muscles. Neurons in the nucleus reticularis medullae oblongatae ventralis located caudal to the obex favor regions of the facial nuclei which supply auricular and cervical muscles. Neurons in the nucleus reticularis medullae oblongatae dorsalis and lamina V of the medullary and spinal dorsal horns project ipsilaterally to the facial nucleus in a manner suggesting that information from specific cutaneous areas reaches neurons supplying the muscles deep to them. The brainstem-facial connections are discussed in relation to the functionally diverse roles served by the facial nucleus in oral-facial behavior.

Animals↗