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PubMed2003

The neuronal structure of the red nucleus in newborn guinea pigs.

The preparations, stained according to the Nissl and Klüver-Barrera methods, were used to describe the topography and morphology of the red nucleus (RN) as well as the structure of the rubral perikarya in newborn (P0) guinea pigs. The Golgi impregnated preparations were used to distinguish types of neurons. RN is a uniform cell group and has the length from 740 to 860 microm. The Nissl stained perikarya were classified into three categories: big, medium-sized and small (A, B, C, respectively). The big perikarya, which contain a lot of tigroidal substance, were mainly observed at the caudal and ventral portions of RN. The small perikarya often have multiple nucleoli. The impregnated neurons were classified into 5 types: 1--large, aspiny, rich-arborised multipolar cells, 2--large and medium sized, spiny, rich-arborised fusiform or pear-shaped cells, 3--medium-sized, spiny, rich-arborised rounded cells, 4--medium-sized, spiny, rich-arborised bipolar cells, 5--small and single medium-sized cells. The 5th type constitutes a heterogeneous population and also has neurons in different developmental stages. Intraspecies variations concerning both the length of RN and a number of the triangular perikarya of the red nucleus were observed in the examined guinea pigs.

Animals↗
PubMed1986

Differential effects of stimulation of the cat's red nucleus on lumbar alpha motoneurones and their Renshaw cells.

The red nucleus region was stereotaxically stimulated with short trains of high-frequency alternating current pulses in anaesthetized cats. The effects were studied, in contralateral lumbar segments, on the responses of microrecorded individual Renshaw cells (RCs) to antidromic or orthodromic test shocks of ventral root or muscle nerve fibres. Monosynaptic reflexes (MRs) of their motoneurone pools were recorded from one of the cut lumbar ventral roots. Averages of 10-20 replicate test responses of the RC (converted into instantaneous frequency curves, IFCs) and of the MR shapes were computed and graphically displayed. 2. Orthodromic (afferent) test shocks induced simultaneously MRs as well as responses of a RC belonging to the same motor pool. From their paired records at systematically varied shock strengths, whole "linkage characteristics" of the relation between the two events could be obtained, representing the functional linkage from the motoraxon collaterals to the RC under study. The overall result of rubral conditioning was a change in the course of the characteristic, which indicated a reduction of this linkage (= relative inhibition of the RC against its recurrent input). 3. Sequential trials with test shocks of constant, submaximal strength were performed with 45 individual RCs. The clearest results were obtained with RC responses to antidromic ventral root shocks: 65% of the RCs were partially inhibited by rubral conditioning. Interposed minor facilitory subcomponents could be seen in the course of inhibited IFCs. Mixed sequences of manifest inhibitory/facilitory effects were observed in 11%; reversed sequences (facilitory/inhibitory) did not occur. A pure but weak facilitation was found in only one case, paralleled by an increase of the MR. RCs belonging to either extensor or flexor motor pools were affected about equally. A little over 20% of the tested RCs remained uninfluenced by rubral stimulation. 4. The MRs, induced by constant, submaximal, orthodromic test shocks, were usually enhanced with only few exceptions, by rubral stimulation. The effects on the orthodromic RC responses were mainly inhibitory, but could be more or less masked by the concurrent increase of the MR, providing a stronger recurrent input to the RC. Such inhibition could be uncovered, however, by observing the above described linkage change. 5. Variation of several parameters of rubral conditioning (train duration, timing of train with respect to test shock, strength of train) modified the inhibitory effects on antidromic RC responses to a certain extent without changing their principal character.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Functional and anatomic differentiation between parvicellular and magnocellular regions of red nucleus in the monkey.

Single unit recording in awake monkeys was used to search for functional differences between the two divisions of the red nucleus, and anatomical tracing of WGA-HRP was used to investigate inputs to the two divisions. We studied a total of 323 units in 4 red nuclei of two monkeys. Recording sites were identified in histological sections by the locations of lesions and the reconstruction of electrode tracks. Of the units in the RNm 98.5% discharged in high frequency bursts during movement. Only 52% showed reliable responses to somatosensory stimulation, and the responses observed were weaker than the movement-related discharge. None of the units recorded in the RNp showed strong movement-related discharge, and 51% were completely unresponsive during both motor and sensory tests. A dorsolateral group of medium-sized cells that overlaps the rostral half of the main RNm and the caudal pole of RNp appears to represent an extension of the magnocellular region. Retrograde transport of WGA-HRP indicated that some of these cells are rubrospinal neurons. Furthermore, the discharge properties of dorsolateral neurons are like the main RNm neurons, except for lower discharge rates and smaller spike amplitudes. Mouth movements are strongly represented in the dorsolateral region. Anterograde transport of WGA-HRP from the motor cortex demonstrated dense terminal label in RNp as contrasted with light label in RNm. Retrograde transport of WGA-HRP from RNm labeled many more cells in the cerebellar interpositus nucleus than in motor cortex. We concluded that input to RNm from the cerebellum is the likely source of the strong movement-related activity recorded from cells in the RNm. The absence of appreciable movement-related activity in parvicellular red nucleus provides a clear functional distinction between this division and the magnocellular division of the red nucleus.

Animals↗
PubMed1986

Red nucleus inputs to retractor bulbi motoneurones in the cat.

Rubral projections to retractor bulbi motoneurones were investigated by intracellular recording in the accessory abducens nucleus in the cat. Their post-synaptic effects were compared with those of trigeminal afferent pathways. Post-synaptic potentials evoked by stimulation of the contralateral red nucleus were predominantly excitatory, with latencies in the monosynaptic range. Post-synaptic potentials evoked by stimulation of the ipsilateral red nucleus, at threshold, were predominantly inhibitory with latencies indicating a di- or trisynaptic pathway. At above threshold intensity, an earlier excitatory post-synaptic potential (e.p.s.p.) preceded the inhibitory post-synaptic potential (i.p.s.p.) in about half the recorded neurones. Convergence of rubral and trigeminal inputs was also observed in other neurones, not identified as retractor bulbi motoneurones, but situated within the accessory abducens nucleus.

Abducens Nerve↗
PubMed1986

Lesions of the amygdala, but not of the cerebellum or red nucleus, block conditioned fear as measured with the potentiated startle paradigm.

Rats were given 10 light-shock pairings on 2 successive days. At 24-48 hr following training, groups of rats received bilateral transection of the cerebellar peduncles, bilateral lesions of the red nucleus (which receives most of the cerebellar efferents), or bilateral lesions of the central nucleus of the amygdala. Control rats were sham operated. At 3-4 days after surgery, the rats were tested for potentiated startle (increased acoustic startle in the presence of the light previously paired with shock). Potentiated startle was blocked by lesions of the central nucleus of the amygdala. Transection of the cerebellar peduncles or lesions of the red nucleus did not block potentiated startle. A second experiment in which a visual prepulse test was used indicated that the blockade of potentiated startle observed in the animals with amygdala lesions could not be attributed to optic tract damage. A third experiment demonstrated that the absence of potentiation in the animals with amygdala lesions was not simply due to a lowered startle level ceiling, because these animals could show increased startle with increased stimulus intensity and with administration of strychnine, a drug that increases startle. Taken together, the results are consistent with the hypothesis that the amygdala is involved in fear conditioning, because potentiated startle is a measure of conditioned fear.

Amygdala↗
PubMed1991

[Electrophysiologic properties of red nucleus neurons in the rat brain slices].

Intracellular recordings from the red nucleus (RN) neurons were made in experiments on the rat brain slices. Passive membrane properties (input resistance and membrane time constant) of the RN neurons were evaluated. Phenomena of potential-dependent rebound depolarization and time-dependent inward rectification were revealed by means of passing hyperpolarizing current pulses through the recorded cells. Injections of depolarizing currents caused repetitive firing of neurons with frequencies directly depending on the intensity of injected currents. Repetitive firing was also characterized by a fast frequency adaptation during injections of currents of different intensities. Stimulation of a region of slices presumably corresponding to the decussation of brachium conjunctivum evoked mainly monosynaptic EPSPs with a "fast"-rise time in the RN neurons, which suggests activation of the synaptic input from the cerebellar nucleus interpositus. Stimulation of the same region sometimes evoked EPSP-IPSP mixtures or pure IPSPs in the RN neurons.

Animals↗
PubMed1988

Afferents to the rat red nucleus studied by means of D-[3H]aspartate, [3H]choline and non-selective tracers.

Following injection of horseradish peroxidase-labeled wheat germ agglutinin or of rhodamine-labeled microspheres as non-selective tracers into the rat red nucleus, the origins of the corticorubral and cerebellorubral pathways, as well as a considerable number of other brain structures including dorsal raphé nucleus, zona incerta and several hypothalamic nuclei showed retrogradely labeled perikarya. Labeling patterns obtained with horseradish peroxidase-labeled wheat germ agglutinin compared well with those observed following application of rhodamine-labeled microspheres which produced injection sites restricted to the small nucleus. In these latter cases, counterstaining with phosphine allowed a better definition of anatomical structures. After D-[3H]aspartate application, retrogradely labeled perikarya were observed in cerebral cortex (layer V), zona incerta, dorsal raphé nucleus and in several other structures also labeled by non-selective tracers. Following application of [3H]choline and using an improved autoradiographic method, perikaryal labeling was massive within nucleus interpositus, while it was absent in dorsal raphé nucleus, cerebral cortex and zona incerta. Retrograde tracing experiments with D-[3H]aspartate and [3H]choline revealed that these transmitter related compounds are selective markers for two subsets of afferents to the red nucleus. The transmitter specificity of the selective labeling with [3H]choline in the cerebellorubral pathway is supported only in part by the results obtained with other methods. The selective labeling with D-[3H]aspartate in the corticorubral pathway, on the other hand, is consistent with its transmitter specificity.

Animals↗
PubMed1975

Electrical constants of neurons of the red nucleus.

Membrane electrical constants have been studied in neurons of the red nucleus (RN) of the cat which were identified antidromically from the spinal cord. For each cell, the input resistance was determined from the membrane potential changes to current steps and was found to be 2.5+/-0.9 Momega in twenty five RN cells studied. In addition, linear summation of the membrane responses induced by two current pulses was demonstrated. 2. From the membrane voltage transients to current steps, the first membrane time constant, tau0, and second time constant, tau1, were determined as 5.6+/-1.0 msec and 0.6+/-0.2 msec, respectively. The ratio of the amplitudes of two exponential functions, E1/E0, was 0.18+/-0.05. A linear relation was found between the ratio of these amplitudes of exponential functions and that of the two time constants. 3. The cable parameter (electrotonic length, L) of the combined soma and dendrites of the RN neutrons was estimated as 1.1 from membrane transient data using the relation developed by Rall (1969). 4. By using this parameter, an attempt was made to estimate the location of the two excitatory inputs on the soma-dendritic membrane of RN cells.

Animals↗
PubMedDate not supplied

Formation of new cortico-rubral synapses as a possible mechanism for classical conditioning mediated by the red nucleus in cat.

1.) By extracellular and intracellular recordings of the red nucleus (RN) cell activity, we investigated enhancement of signaling effectiveness at the cortico-rubral synapses underlying the establishment of classical conditioning mediated by RN in the cat. The classical conditioning of forelimb flexion was produced by pairing the conditioned stimulus (CS) to the cerebral peduncle (CP) with the unconditioned stimulus (US) to the forelimb skin at an interval of 100 msec for about a week. 2.) The increased responsiveness of RN cells to the CS was correlated with acquisition of the conditioned forelimb flexion, i.e. RN cells responded to the CS with higher firing probability in the animals which received the paired conditioning than those in the animals which received the CS alone or pairing of the CS and the US at random intervals or those in the naive animals which did not receive any training. 3.) Monosynaptic excitation of RN cells in response to the single pulse to CP was most enhanced in the animals which received the paired conditioning. By contrast, response of RN cells, as well as the behavioral response, induced by stimulation of the cerebellar interpositus nucleus (IP) was not enhanced after the paired conditioning. The difference between the responses to the stimulation of CP and IP suggested that the primary site of neuronal change is the cortico-rubral synapses. 4.) In the animals that received the paired conditioning, the excitatory postsynaptic potentials (EPSPs) induced by stimulation of CP had fast-rising components superimposed on the normal slow-rising EPSPs. On the other hand, most of the CP-EPSPs recorded in the naive animals showed a slow time course. The slow time course of the CP-EPSPs has been attributed to the peripheral localization of the cortico-rubral synapses on the dendrites of RN cells. 5.) The electrotonic length of RN cells in the animals which received the paired conditioning was not shorter than that in the naive animals. Therefore, it was suggested that the appearance of the fast-rising component in the CP-EPSPs is cause by formation of the new cortico-rubral synapses on proximal portions of the soma-dendritic membrane of RN cells. 6.) Since it has been established that new synapses formed by collateral sprouting are retained for more than several months, the formation of new synaptic connections could underlie long-lasting behavioral modification.

Animals↗
PubMed2000

Effects of noxious skin heating on spontaneous cell activity in the magnocellular red nucleus of the cat.

Neurones were extracellularly recorded in the magnocellular red nucleus (RNm) of decerebrated cats and identified by their monosynaptic responses to stimulation of the contralateral brachium conjunctivum (BC), and by their antidromic responses after stimulation of the rubrospinal tract in the cord. After each cell was isolated, noxious stimulation was applied to the skin, by touch-free radiant heat. The large majority of the cells (91.5%) responded to noxious stimulation of the skin, even after the RNm was deprived of cerebellar input by sectioning the contralateral BC. About half of this cell group was activated by noxious stimulation and the other half was inhibited. To obtain responses in RNm cells, the stimulus had to be above the thermal pain threshold, and the stimulation area had to be inside the somatic receptive field of the cell for low-threshold afferents. Thus, the receptive fields for nociceptive and low-threshold afferents are similarly organized somatotopically. Noxious stimulation sometimes induced a rhythmic pattern of spike bursts in RNm cells, which could be a reflection of the locomotor-like activity generated in the spinal cord. The results indicate that nociceptive information participates in sensorimotor control via the spinorubrospinal loop, which may also transmit low-threshold cutaneous input and corollary discharge of the activity in spinal motor centres to the RNm.

Action Potentials↗
PubMed1975

An ultrastructural study of the red nucleus in the rat.

The red nuclei of 14 adult male rats of the Wistar strain were prepared for electron microscopic study following perfusion with a mixture of aldehydes, Neurons of four size categories were identified in 1 mu Epon sections and their ultrastructural characteristics were studied in adjacent thin sections. Giant (greater than 40 mu) and large (26-40 mu) neurons are distinguished primarily by size and possess similar ultrastructural features: extensive areas of rough endoplasmic reticulum (RER), a prominent perinuclear Golgi complex, numerous mitochondria and pigment granules and a large, ovoid nucleus which occasionally contains intranuclear rodlets. Medium size neurons (20-25 mu) have less extensive, poorly organized RER and randomly distributed Golgi complexes. The nuclear envelopes of these cells frequently show multiple invaginations and continuity with the RER cisternae. In small neurons (less than 20 mu) the RER occurs as single or anastomosing strands whi le golgi complexes and pigment granules are few. In both medium size and small neurons, aggregates of condensed chromatin are adherent to the inner nuclear membrane. Three main types of synaptic terminals may be distinguished in the red nucleus: (1) small terminals with flattened vesicles and symmetrical densities (F terminals), (2) small terminals with rounded vesicles and asymmetrical densities (RS terminals), and (3) large (10-15 mu) asymmetrical, rounded vesicle terminals which form multiple contacts along their length (RL terminals). The small neurons receive both F and RS terminals on their dendrites and infrequently on their cell somas. The large and giant neurons receive F, RS and RL terminals on their somas and proximal dendrites and F and RS terminals on their distal dendrites. The somas and dendrites of medium size neurons receive both F and RS terminals but RL terminals do not lie in relation to them. Spine contacts are common throughout the nucleus and occur on both somas and dendrites.

Animals↗
PubMed1993

An ascending spinal pathway transmitting a central rhythmic pattern to the magnocellular red nucleus in the cat.

The activity of cells in the magnocellular red nucleus (RNm) was recorded extra- and intracellularly in the curarized thalamic cat performing fictive locomotion. The locomotor episodes were detected from the rhythmic activity recorded in the motor nerves of the contralateral hindlimb. It was confirmed that, during fictive locomotion, a large proportion of the rubrospinal cells (56% in our sample) exhibit a rhythmic pattern of activity which is synchronized with the efferent spinal motor nerve activity. On the basis of the intracellular recordings it was established that phases of intense synaptic activity with mixed excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) are involved in this rhythmicity. After eliminating the cerebellar input to the RNm, it was observed that the cells still received intense excitatory and inhibitory inputs, resulting in a continuous modulation of their membrane potential, due to the occurrence of EPSPs and IPSPs. During fictive locomotor-like activity and after elimination of the cerebellar afferents to the RNm, it was observed that the spontaneous PSPs in RNm cells (in the case of 45% of the cells) were organized in repetitive subthreshold bursts occurring in phase relationships with the activity recorded in the motor nerves. Some extracellularly recorded cells (12%) showed a rhythmic firing pattern. It is generally recognized that, in the thalamic cat preparation, the locomotor pattern observed in efferent nerves originates from the central pattern generator (CPG) of the spinal cord. It therefore seems likely that the rhythmicity observed here in the RNm may originate from the spinal CPG and be transmitted through the spino-rubral pathway ascending in the ventral part of the cord. It is concluded that the spino-rubral pathway may transmit both somatosensory information and corollary discharges relating to the activity of the spinal CPG for locomotion.

Animals↗
PubMed2002

Contribution of primate magnocellular red nucleus to timing of hand preshaping during reaching to grasp.

Magnocellular red nucleus (RNm) is involved in controlling goal-directed limb movements such as reaching to grasp. We tested two hypotheses related to RNm's role in controlling reach-to-grasp movements. One hypothesis is that forelimb RNm neurons are grasp specific, and the other is that they specify the timing of metacarpi-phalangeal (MCP) extension to preshape the hand during the appropriate phase of the reach. We recorded single-unit discharge while monkeys performed two behavioral tasks that elicited similar reaches but differed in grasp. One task consisted of a reach with a precision grasp that elicited independent use of thumb and forefinger; the other included a whole-hand grasp that elicited concerted use of the four fingers. Most RNm neurons tested were engaged strongly during both the whole-hand and precision tasks, and the magnitude of discharge modulation did not differ between tasks. Thus most RNm neurons are not grasp specific but, instead, may contribute to behavioral features common to the two tasks. Two methods were used to investigate relations between single-unit discharge and kinematic data from the same individual trials of the whole-hand and precision tasks for a subset of forelimb RNm neurons. One method focused on correlations between parameters of RNm discharge and the duration, amplitude, and velocity of rotation of forelimb joints for each of the tasks. The second method compared between-task differences in times of peak neuronal discharge to between-task differences in times of rotations of forelimb joints. Parameters of reach-related RNm discharge were more frequently correlated with parameters of MCP extension than with parameters of rotation of wrist, elbow, and shoulder joints. Analyses of temporal relations between discharge and kinematic data during both the whole-hand and precision tasks indicate that discharge was time locked most frequently to MCP extension and, to a lesser extent, elbow extension during both tasks. We conclude that RNm may command muscle synergies that provide a basic preshape of the hand at the appropriate phase of limb transport. In addition, the timing of RNm's contribution to hand preshaping varies with the behavioral requirements of the task.

Animals↗
PubMed1981

Quantitative differences in collateralization of the descending spinal pathways from red nucleus and other brain stem cell groups in rat as demonstrated with the multiple fluorescent retrograde tracer technique.

In 8 rats 'True Blue' was injected into dorsal half of C5-C8 spinal grey, 5 days later 'Nuclear Yellow' was injected in midthoracic, upper lumbar, lumbosacral and sacral cord respectively. The animals were sacrificed about 43 hours after NY injections. The distribution of retrogradely labeled neurons was studied in Red Nucleus, in Ventrolateral Pontine Tegmentum and in Nucleus Raphe Magnus, all of which project to spinal dorsal grey. In Red Nucleus large populations of single TB-labeled neurons and single NY-labeled ones occurred in the dorsomedial and ventrolateral part, respectively. In addition, about 8% of the neurons labeled with TB from C5-C8 were double labeled with NY from L5-S1, and 35% from T7-8, which percentages resemble those of electrophysiological studies. However, in ipsilateral Nucleus Raphe Magnus about 40% of the TB-labeled neurons were double labeled from L5-S1. This percentage resembles the 66% obtained in electrophysiological studies of reticulospinal collaterals. These findings in rat support electrophysiological findings in cat and show, that rubrospinal neurons distribute their fibers primarily to the grey matter of specific groups of spinal segments, while many of the raphe spinal neurons distribute fibers throughout the spinal cord.

Animals↗
PubMed1983

Red nucleus lesions disrupt the classically conditioned nictitating membrane response in rabbits.

Sixteen rabbits received classical conditioning of the right nictitating membrane response using a tone CS and electrostimulation of the right eye as the US. Single electrocoagulating RF lesions of the medial portion of the left magnocellular red nucleus eliminated or severely reduced the previously acquired conditioned response. This finding is consistent with the idea that an essential anatomical substrate of the conditioned response includes a circuit from the cerebellum to the contralateral red nucleus which projects contralaterally in turn to pontine motoneurons mediating the defensive nictitating membrane response.

Animals↗
PubMed1982

Formation of functional synapses in the adult cat red nucleus from the cerebrum following cross-innervating of forelimb flexor and extensor nerves. I. Appearance of new synaptic potentials.

We investigated the effects of cross-innervating the peripheral forelimb flexor and extensor nerves of adult cats on the time course of corticorubral EPSPs. Red nucleus neurons were identified by antidromic invasion from C1 or L1 spinal segments as innervating the upper spinal segments (C-cells) or sending axons to the lumbosacral cord (L-cells). In C-cells, a fast-rising component, superimposed on the slow-rising corticorubral EPSPs induced by the cerebral sensorimotor cortex or the cerebral peduncle (CP) stimulation, was noted. The mean time-to-peak of this component in cross-innervated cats operated more than two months earlier was 1.9 +/- 0.9 ms (n = 160), shorter than in normal cats (3.6 +/- 1.4 ms, n = 100). The same value in cats cross-innervated less than two months before was 2.7 +/- 1.0 ms (n = 53). The mean time-to-peak of CP-EPSPs from L-cells was 2.9 +/- 0.9 ms (n = 115). The fast-rising component had a latency of 0.96 +/- 0.19 ms (n = 122), and it was mediated by fibers with conduction velocities of less than 20 m/s. The projective area of the fast-rising component is organized somatotopically. Since it is more sensitive to membrane hyperpolarization than slow rising corticorubral EPSPs, it is mediated by synapses located more proximally than the corticorubral synapses of normal cats. The time course of facilitation by preceding cerebral peduncle stimulation of the nucleus interpositus (IP)-induced RN population responses was measured. It was characterized by a rapid, followed by a slower, rise time in the RN region where C-cells are concentrated. In contrast, the L-cell region was characterized by a slow rise time. In cats subjected to self-union of the peripheral flexor and extensor nerves, the majority of C-cells had CP-EPSPs with a time-to-peak within the normal range. Our results suggest that after cross-innervation sprouting and formation of functional synapses occur on the proximal portion of the soma-dendritic membrane of red nucleus neurons.

Animals↗
PubMed1985

Promotion of sprouting and synaptogenesis of cerebrofugal fibers by ganglioside application in the red nucleus.

The effect of gangliosides on sprouting of cerebrorubral synapses from the contralateral cerebral cortex was investigated following lesions of normal ipsilateral cerebrorubral synapses. It was found that, in cats in which ipsilateral cerebral ablations were performed at more than 2 months of age, the mean probability of occurrence of EPSPs induced in red nucleus neurons by stimulation of fibers from the contralateral cerebral cortex in the ganglioside-treated group was significantly higher than in the untreated group. Therefore, ganglioside application appears to promote sprouting and formation of functional synapses in the red nucleus.

Animals↗