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PubMed1975

A cytoarchitectonic and Golgi study of the red nucleus in the rat.

The cytology of rubral neurons was investigated using both paraffin and 1 mu thick Epon sections. The neurons were divided into four size categories which form a continuum with regard to cellular characteristics. Giant neurons (greater than 40 mu) and large neurons (26-40 mu) predominate in the caudal one-third of the nucleus. Large neurons extend up the ventral, medial and lateral borders of the nucleus into its middle one-third. The caudal one-third of the nucleus together with this extension of large cells is designated as the magnocellular part of the nucleus. The more rostral part of the nucleus contains predominantly small (less than 20 mu) and medium size (20-25 mu) neurons, and this constitutes the parvocellular part of the nucleus. The characteristics of each cell type are described. Camera lucida drawings of the rubral neurons were made in three different planes of section, and the extent of the magnocellular and parvocellular portions of the nucleus was determined. Dorsomedial and ventrolateral subgroups of the magnocellular part of the nucleus are found 300-400 mu from the caudal pole. A lateral horn of small and medium size neurons with the addition of a few large neurons extends from the lateral part of the nucleus 500-700 mu from the caudal pole. Golgi preparations of the red nucleus were examined in three planes of section. Giant and large neurons display short spines on the soma and also, along the entire length of the dendrites. Inaddition, more elongate spinous processes are seen on these dendrites and are frequently aggregated into tufts at loci on the dendrites or at their terminations. The dendrites of these neurons radiate in all directions from the soma but remain within the confines of the nucleus. Medium size neurons demonstrate radially arranged dendrites. Sparsely positioned spines are seen along the length of the dendrites but are absent on the soma. A number of such neurons demonstrate tufts of elongate spines on their dendrites. The dendrites of small neurons branch infrequently and remain within the confines of the nucleus. A few dendritic but no somatic spines are seen in association with these neurons.

Animals↗
PubMedDate not supplied

Projections from the red nucleus and surrounding areas to the brainstem and spinal cord in the cat. An HRP and autoradiographical tracing study.

HRP injections at the C2, T1 and S1 spinal levels and in the medullary lateral tegmental field revealed that the contralaterally projecting rubro-bulbospinal neurons are located not only in the caudal but also to a certain extent in the rostral red nucleus (RN). These RN projections are somatotopically organized. Neurons projecting to the sacral cord are located in the ventrolateral RN, those projecting to the upper part of the spinal cord lie in the dorsomedial RN and those projecting to the medullary lateral tegmentum were found in the dorsal portions of the RN. These last neurons are smaller than many of the other RN neurons. The HRP results also revealed that the RN does not project to the caudal raphe nuclei. The autoradiographical results confirmed the HRP findings. They further indicated that the contralateral RN projections to the caudal brainstem precerebellar nuclei (nucleus corporis pontobulbaris, lateral reticular nucleus, lateral cuneate nucleus) and the dorsal column nuclei are also somatotopically organized. This was also true for the RN projections to the dorsomedial and intermediate facial subnuclei and the caudal pontine and medullary lateral tegmental field. These areas receive afferents from mainly the dorsal portions of the RN. Regarding the RN projections to the spinal cord, the autoradiographical tracing results revealed somatotopically organized contralateral RN projections to laminae V, VI and VII. Moreover, a small but distinct RN projection to a dorsolaterally located group of motoneurons at the C8-T1 level was demonstrated. Ipsilaterally a minor projection to the cervical and upper thoracic lateral intermediate zone was observed. Finally, strong ipsilateral projections from the rostral mesencephalon to the inferior olive were seen. These projections were derived from various rostral mesencephalic areas, including the nucleus of Darkschewitsch, the nucleus accessorius medialis of Bechterew, the interstitial nucleus of Cajal and the area of the rostral interstitial nucleus of the medial longitudinal fasciculus. In the cat it was difficult to define which of the mesencephalic areas projecting to the inferior olive represented the parvocellular RN. A new subdivision of the RN is proposed based on its projections and not on the size of its cells. In this concept the first group is formed by the RN neurons projecting contralaterally to the caudal brainstem and spinal cord. The second group consists of RN neurons projecting to the inferior olive.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Synaptic responses of red nucleus neurons in the alert cat to cortical and cerebellar inputs.

Postsynaptic potentials of neurons of the red nucleus (RN), evoked to stimulation of the sensorimotor region of the cerebral cortex and cerebellar nucleus interpositus, were studied in chronic experiments on alert cats by means of an intracellular recording technique. Movements of the animals were restricted by rigid fixation (through a special device previously attached to the head) of the animal's head on the frame of the stereotaxic apparatus. Rubrospinal neurons were identified according to their antidromic activation in response to stimulation of the rubrospinal tract at the decussation level. A decrease in the critical level of depolarization necessary for spike generation was shown to be a characteristic peculiarity for mono- and polysynaptic reaction of the RN neurons in the alert animals. A rare possibility of recording separate EPSPs, the presence of burst discharges of rubrospinal neurons as well as a higher activity of RN interneurons was observed.

Animals↗
PubMed1992

Electrophysiological relations between the superior colliculus and the red nucleus in the cat.

The electrical activity of single units located in the parvicellular part of the red nucleus (pRP) was recorded extracellularly in nitrous oxide anesthetized and C1-transected adult cats. In this area, neurons were found to respond to electrical stimulation applied to intermediate and deep layers of the right superior colliculus (SC). Forty neurons located in the pRN of both sides were studied. Three neurons out of 18 (16.6%) located in the contralateral pRN and six neurons out of 22 (27.3%) located in the ipsilateral pRN were driven by the right SC stimulation. The pRN neurons were separated into four groups according to the latency response to the SC stimulation: 1) 0.6-1.9 ms, 2) 2-4 ms, 3) 4-6 ms, 4) variable latency responses. Each of these four groups of neurons showed a particular pattern of discharge, even though their discharge frequency showed a strong consistency. Four pRN neurons, which responded to SC stimulation, showed a significant correlation with spontaneous horizontal eye movements of saccadic type. It is known that the SC represents one of the main outputs of the striato-nigral motor system. The relation between the SC and the pRN described in the present study suggest that connections exist between the cortico-rubral and the striato-nigral systems, since both have the SC as a common output structure. It is likely, therefore, that the cortico-rubral-SC system is involved in the control of oculomotor functions, and that the SC may serve to establish interactions between systems concerned with eye movements.

Animals↗
PubMed1991

Task-related coding of stimulus and response in cat red nucleus.

In the present study we recorded the activity of single neurons in the forelimb area of red nucleus (RN) during performance of three step-tracking tasks designed to dissociate the coding of stimulus and response variables in the discharge of recorded neurons. In two of these tasks, the standard and stimulus-reversal arm tasks, elbow flexion and extension were elicited by different stimuli enabling us to distinguish activity correlated with the forelimb response from the stimulus eliciting it. The third task (neck task) allowed us to determine whether neuronal modulation was related to an unconditioned orienting response that occurred concurrently with the forelimb response. We have previously reported that these three tasks separate neurons in MCx whose modulation precedes the response (lead cells) into three distinct classes in which task-related activity either is correlated with the direction of the forelimb response, correlated with the stimulus, or not correlated with either (Martin and Ghez 1985). All lead cells, however, remained timed to the stimulus rather than to the response. The present results show that RN lead cells can be subdivided into the same three classes as those in MCx and their discharge was also contingent on the subsequent production of a behavioral response. (1) Force-direction neurons (35%; n = 16) showed changes in activity correlated with the production of forearm force in a particular direction suggesting that they could participate in selecting the appropriate forelimb response. The onset of task-related modulation of activity was better timed to the response, in contrast to force-direction neurons in MCx, which were better timed to the stimulus. (2) Stimulus-direction neurons (18%; n = 8) modulated their activity in relation to a particular stimulus evoking either flexor or extensor responses and during neck task performance. These neurons could be involved in processing stimulus information or in the production of neck torque. The task-related discharge of these lead cells was better timed to the stimulus than to either the forelimb or the neck response. (3) Nondirectional neurons (47%; n = 21) modulated their activity during all tasks examined. Their discharge did not correlate with any specific feature of the stimulus or response, and as a group, was better timed to the stimulus than to the response. Nondirectional neurons may participate in some aspect of motor preparation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Analysis of potentials induced in red nucleus neurones from the somaesthetic pathway stimulated at the bulbar level.

A somaesthetic pathway to the magnocellular red nucleus (RNm) via relays other than cortico- or cerebello-rubral relays was previously found to exist in the cat. At the brainstem level, the ascending spinorubral fibres follow the medial lemniscus (LM). The present paper aims at describing in detail and evaluating the quantitative importance of the short-latency responses in RNm cells after microstimulation performed in the LM through a monopolar electrode. The RNm cells, tested intracellularly in cats anaesthetized with alpha-choralose and placed in a stereotaxic device, were identified by their antidromic activation to stimulation of the rubrospinal tract in the cervical cord. It was established that single-shock stimulation below 100 miroA current delivered to the LM induced short-lantency postsynaptic potentials (PSPs) in 87% of all the rubrospinal cells tested. The responses were indeed due to activation of LM fibres, as demonstrated by different tests: the location of the electrode tip in the LM was verified by recording, with the same electrode, the potentials evoked by stimulating the dorsal columns of the cord. The site was later confirmed histologically. The absence of stimulus spread from the LM to the underlying pyramidal tract was systematically checked by simultaneously recording the responses evoked in RNm cells and in the motor cortex. Monosynaptic excitatory responses (EPSPs) were evoked in RNm cells with a minimum stimulating current of less than 20 microA in the LM and a mean threshold of 42 microA. Disynaptic inhibitory potentials (IPSPs) were evoked in 23% of these cells with single-pulse stimulation. These latter responses showed a temporal facilitation with short trains of three pulses, which indicated that they were transmitted through inhibitory interneurones. Recordings were also performed from presumed LM fibre terminals running inside the RNm. The results therefore confirm the existence of strong lemniscal projections to RNm and demonstrate that they transmit both excitatory and inhibitory messages to rubrospinal cells. As the somaesthetic pathway to the RNm was previously found to come from the spinal cord, where it is located in the ventral portion, the present results also confirm that the LM is composed of fibres originating not only from neurones in the dorsal column nuclei, but also from cells placed at the segmental levels of the cord. The presumed sensorimotor function of this ascending pathway is discussed.

Animals↗
PubMed1989

Red nucleus of Macaca fascicularis: an electron microscopic study of its synaptic organization.

The parvicellular and magnocellular divisions of the red nucleus of the old world monkey, Macaca fascicularis, were analyzed at an electron microscopic level to examine the morphology of the synaptic profiles terminating on rubral neurons and to categorize them by their individual characteristics. The parvicellular division, or anterior two-thirds of the nucleus, is composed of small (10-15 microns) and medium-size (20-30 microns) cells, which are uniformly distributed with high packing density throughout this portion of the nucleus. These cells have invaginated nuclei and are often indented by blood vessels and glial cell somata (satellite cells) that lie in close proximity. The magnocellular portion, occupying the caudal one-third of the nucleus, is composed of an additional population of large cells, ranging from 50-90 microns in diameter, which often contain prominent lipofuscin granules and are frequently indented by blood vessels. Satellite glial cells are not a prominent feature in the magnocellularis portion of the nucleus. The large cells are separated one from the other by fields of myelinated axons either coursing through the nucleus or projecting to and from the nucleus itself. Although the divisions of the nucleus in the Macaca fascicularis are spatially distinct, each possesses a morphological similarity in regard to the categories of synaptic profiles seen at the electron microscopic level. These synaptic profiles are classified as follows: large terminals containing numerous, predominantly rounded vesicles (LR), which can often be seen to form the central profile in a synaptic glomerular arrangement; terminals of similar size with predominantly rounded vesicles but with a pale axoplasmic matrix (LRP); small profiles with rounded vesicles (SR); profiles containing granular dense-cored vesicles (DCV); profiles with numerous flattened vesicles (F); profiles containing pleomorphic vesicles (PL), some of which can be interpreted as presynaptic dendrites (PSD) because they are seen to be postsynaptic and contain ribosomes; and profiles with rounded synaptic vesicles, which are associated with subsynaptic Taxi bodies (T). Most of the various synaptic profile types were found to have similar distributions on the dendritic arbors of rubral neurons in both divisions of the nucleus. However, the LRP-type terminal predominates on the cell bodies and proximal dendrites of the large neurons in magnocellularis. Unlike other regions in the nervous system, F type terminals are rarely seen to contact neuronal somata. This study provides a basis for future experimental studies of afferents to the nucleus in this species.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

GABA neurons in the cat red nucleus: a biochemical and immunohistochemical demonstration.

Following unilateral kainic acid lesioning of neuronal cell bodies in the cat red nucleus (RN), a large decrease in glutamic acid decarboxylase (GAD) activity was detected in the injected RN, compared to the RN from control, non-injected animals. Using GAD immunohistochemistry, reactive perikarya were visualized dorsolaterally to the rostral part of the nucleus as well as within the RN proper. Taken together, these results point to the existence of an intrinsic GABAergic innervation in the RN area of the cat. The GABAergic neurons characterized here might thus correspond to the inhibitory interneurons previously detected electrophysiologically as a putative source of GABA for large-sized neurons of the RN.

Animals↗
PubMed1999

[Role of red nucleus in inhibiting nociceptive responses of rat spindle afferent].

Using extracellular recording techniques, the effect of excitation of red nucleus (RN) on C-responses of wide dynamic range (WDR) neurons and the roles of RN in the inhibitory effect of spindle afferent activated by succinycholine (SCH) on C-responses of WDR neurons were studied. Stimulation of RN caused a significant reduction of nociceptive responses of WDR neurons, which was significantly attenuated by intravenous cyproheptadine and contralateral lesion of RN. These results suggest that the inhibitory effect on nociceptive responses of WDR neurons caused by RN stimulation was partly mediated by 5-HT and RN plays an important role in analgesia induced by the muscle spindle afferent activity.

Afferent Pathways↗
PubMedDate not supplied

Putative neurotransmitters in the red nucleus and their involvement in postlesion adaptive mechanisms.

A variety of putative neurotransmitters has been described in the red nucleus (RN). Measurement of neurotransmitter biochemical markers and study of their specific localizations using morphological techniques in lesion and deafferentation of the RN indicate the participation of glutamate (Glu) in corticorubral transmission and the presence of GABA in RN intrinsic neurones. The cerebellorubral projection may contain at least two populations of fibres, the one using acetylcholine and the other Glu as neurotransmitter. The presence of a serotoninergic input was also demonstrated. Selective deafferentations of the RN, particularly from its cerebellar input, result in biochemical and immunohistochemical responses indicative of increased corticorubral glutamatergic and local GABAergic transmission. These adaptive changes of neuronal transmission as well as the previously described sprouting of corticorubral nerve terminals may contribute to functional recovery after cerebellectomy in adult animals.

Animals↗
PubMed1987

Red nucleus lesions delay the evolution of amygdala kindling in cats.

There are some papers which claim that the red nucleus (RN) is related to epileptic manifestations. Though the lesion or electrographic recording of the RN include many paths which assemble into it, the possibility that its cells are implicated in epilepsy is deduced. This paper compares the evolution of amygdaloid kindling in cats with bilateral RN lesions, with the epileptic disturbances provoked by lesion or stimulation of approach cells. Due to the intrinsic error of the stereotaxic method, only 7 of 13 cats show lesions in the RN with a diameter extending down to 150 micron. Only these show a shortening of the afterdischarge duration, a delay in the appearance of the consecutive clinical stages, and a lengthening in the appearance of generalized tonic-clonic seizures. In comparison, the 6 other cats show lesions mainly in the adjacent central tegmental field, and their kindling evolution was similar to that of a control group with intact mesencephalon. We conclude that the RN lesions interfere with the kindling generation, presumably by lesioning the cerebello-cerebral paths which produce a depression of cortical activity, during the consolidation of clinical and electrographic manifestations.

Amygdala↗
PubMed1986

A Nissl, Golgi-Kopsch and ultrastructural study of the Gallotia galloti red nucleus.

The object of this study was to understand the different types of morphological neurons of the Gallotia galloti red nucleus using quantitative and qualitative analysis, under the aspects of optical (Nissl and Golgi-Kopsch) and electronic microscopy. The results from this study and considering the size, the distribution of NISSL bodies and the dendritic arborization, we have identified three neuronal types: ellipsoidal or ovoid (15 microns), triangular (15-35 microns) and polygonal (20-50 microns). In general the polygonal neurons contain a cytoplasm with abundant organelles, well developed Nissl bodies, perinuclear Golgi complex, numerous mitochondria, an ovoid nucleus and multiple dendrites. The triangular neurons have a similar structure, although the dendritic model is less ramified than that of the polygonal and the ellipsoidal neurons contain a smaller cytoplasm with less dendritic ramification. The contact with spines is not very frequent but can be observed in somas and dendrites. The neuronal population is heterogeneous and therefore neither the magnocellular part nor the other parvicellular were observed separately, but a mixture of both.

Animals↗
PubMed1992

Cortically evoked excitatory synaptic transmission in the cat red nucleus is antagonised by D-AP5 but not by D-AP7.

Extracellular recordings were made from magnocellular red nucleus neurons (mRN) in alpha-chloralose (50 mg/kg, iv.) anaesthetised cats. Iontophoretically applied N-methyl-D-aspartate (NMDA) excited the neuronal firing which was antagonised by 4 selective NMDA receptor antagonists: 2-amino-5-phosphonopentanoate (AP5), 2-amino-7-phosphonoheptanoate (AP7), RS-4-(phosphonomethyl) piperazine-2-carboxylic acid (PMPC) and R-4-(3-phosphonopropyl) piperazine-2-carboxylic acid (CPP), whereas AMPA responses were uneffected. Monosynaptic excitatory responses were produced by stimulation of the sensorimotor cortex. These responses were reduced and often abolished by AP5 and PMPC but not by AP7 or CPP. It is postulated that two NMDA receptor subtypes exist on mRN neurones.

2-Amino-5-phosphonovalerate↗
PubMed1978

Red nucleus cell activity in awake cats during a placing reaction.

It is known that the discharges of the posterior red nucleus (RN) cells are modulated during locomation (Orlovsky, 1972). The aims of the present investigation were to look for a possible relationship between the unitary activity of RN cells and movements as well as postural reactions of the forelimbs. In the experimental arrangement used, the cat stood on four transducers which recorded to forces on each limb. The animal was restrained by a hammock supporting a part of the total body weight. A horizontally moving plate touched one forepaw and pushed it backwards until a placing mavement was induced. During the first part of the sequence, the mechanically stimulated limb was actively unloaded just prior to the placing movement, while the contralateral forelimb simultaneously presented a loading postural reaction. The results can be summarized and interpreted in the following way: 1. The RN cells exhibit large variations of discharge frequencies during phasic muscular activities linked to movement and to postural adjustments, but no correlations can be established between tonic cell activity and static postural forces exerted by the limb. 2. During the swing phase, the neuronal activity of some RN cells is maximal during flexion, while for others the maximum is during extension. 3. When there is a modification in frequency at the onset of the placing reaction relative to activity during the unloading reaction, the beginning of this change occurs after the onset of the movement as recorded by a potentiometer placed at the elbow joint. 4. The increases of frequency are higher during reciprocal muscle activation (during the movement) than during coactivation of antagonistic muscles (during the postural loading reaction). 5. During the loading reaction (with mostly extensor activation) the frequency of firing of those neurones discharging during the flexion phase. Thus the data may indicate that the RN is included in a feed-back loop which is linked not to muscle activities but rather to phasic spinal reflexes.

Action Potentials↗
PubMed1965

SEQUENTIAL BEHAVIOR INDUCED REPEATEDLY BY STIMULATION OF THE RED NUCLEUS IN FREE MONKEYS.

Rhesus monkeys in a colony were stimulated by means of intracerebral electrodes controlled by radio, for 5 seconds every minute, day and night, for periods up to 14 days. Stimulations of the red nucleus evoked a reliable sequence of behavior including bipedal locomotion, climbing, vocalization, and social interactions. During periods of spontaneous sleep, stimulations produced only a small head movement, but the whole behavioral sequence reappeared as soon as the animal awoke. In monkeys injected with chlorpromazine, the evoked behavior was inhibited in the same way as during spontaneous sleep, while the administration of atropine, Regitine, and Indurol which blocked both sympathetic and parasympathetic systems, produced only minor modifications of the sequential response.

Animals↗
PubMed1975

Stimulants and lesions of the substantia nigra and red nucleus.

The interaction of altered activity levels by stimulants and brainstem lesions was examined. Lesions of the substantia nigra and red nucleus significantly increased activity over control levels in albino rats. The stimulant action of d-amphetamine and methylphenidate was additive with lesion effects. In addition, stimulants disrupted the normal light-dark relationship with activity while the lesions did not. It is suggested that there are two functionally separate systems regulating locomotor activity.

Animals↗
PubMedDate not supplied

Influences of cerebral cortex and cerebellum on the red nucleus of the rat.

The aim of the present work was to investigate the unitary responses of neurons belonging to the magnocellular and parvocellular division of the red nucleus (RN) to stimulation of efferents from motor cortex and cerebellum. In anesthetized rats spontaneous discharges of rubro-olivary (RO) and rubrospinal (RS) neurons were tested for stimulation of motor cortex (CX), pyramidal tract (PT), interpositus (IN) and dentate (DN) cerebellar nuclei. It has been observed that the majority of RO and RS neurons were influenced by stimulation of both IN and DN as well as by activation of CX and PT. These results indicate that (1) a segregation of cerebral and cerebellar afferents to RN of rat does not exist and (2) convergent responses from the same cerebral and cerebellar structures have been observed in a high number of both RS and RO neurons.

Animals↗
PubMed1983

Cat red nucleus changes of activity during the motor initiation in a reaction time task.

Unit recordings were made in the posterior red nucleus of 4 freely moving cats, performing a conditioned forelimb flexion in response to a sound, in a simple reaction time (RT) paradigm. More than 50% of the recorded neurons (154) were found to be task-related, with marked changes of firing (mostly increases) time-locked with the go-signal (mean latency: 40.8 ms +/- 12 ms SD) and frequency-correlated with the duration of the RT. These RT-correlated changes of firing disappeared or were markedly decreased when the movement was not triggered. Most of the task-related neurons also displayed late changes of firing during the force change, time-locked with the movement. Furthermore, a clear relation was observed between the rubral firing before and after the go-signal and the sensorimotor field of the recorded neuron: the neurons preferentially related to limb or trunk movements discharged with the highest frequency throughout the conditioned sequence and exhibited the best RT-correlated increases of firing during the movement initiation. In contrast, rubral neurons apparently related to head-movements generally discharged with low frequency and commonly exhibited decreases of firing in the initiation period. The changes of rubral firing prior to the motor activity, correlated to the RTs, suggest a command function for the RN, in the triggering of the conditioned motor response.

Animals↗