Projections from the red nucleus to the parvicellular reticular formation and the cervical spinal cord in the rat, with special reference to innervation by branching axons

Application of Original Therapy for Stimulation of Oral Areas Innervated by the Trigeminal Nerve in a Child with Beckwith-Wiedemann Syndrome

About 90% of children diagnosed with classic BWS have macroglossia, and 40% of them are submitted to surgical tongue reduction. The purpose of our article is to present a case study of a 5-month-old child with BWS who was treated with an original therapy for stimulation of oral areas innervated by the trigeminal nerve. The therapy included stimulation of the upper and lower lip and muscles of the floor of the mouth. The treatment was provided by a therapist once a week. In addition, the child was stimulated every day at home by his mother. After 3 months, a significant improvement in oral alignment and function was achieved. Preliminary observations of therapy application for stimulation regions innervated by the trigeminal nerve in children with Beckwith-Wiedemann syndrome seem promising. The original therapy for stimulation of oral areas innervated by the trigeminal nerve is a good alternative to existing methods of surgical tongue reduction in children with BWS and macroglossia.

Role of the vestibular nuclear complex in facilitating the jaw-opening reflex following stimulation of the red nucleus

According to our previous studies, stimulation of the red nucleus (RN) facilitates the low-threshold afferent-evoked jaw-opening reflex (L-JOR). It has been reported that the RN projects to the superior (SVN), lateral (LVN) and inferior vestibular (IVN) nuclei. The SVN and the LVN have reciprocal intrinsic connections with the medial vestibular nucleus (MVN). Our previous study demonstrated that stimulation of the vestibular nuclear complex (VN) modulates the L-JOR. These facts suggest that RN-induced facilitation of the L-JOR is mediated via the VN. In the present work we investigated whether electrically induced lesions of the VN, or microinjection of muscimol into the VN, affects RN-induced facilitation of the L-JOR. The L-JOR was evoked by electrical stimulation of the inferior alveolar nerve. The stimulus intensity was 1.2 times the evocation threshold. Lesions of the MVN or the LVN or the SVN, and the muscimol injection into the MVN or the LVN or the SVN, reduced the RN-induced facilitation of the L-JOR. Conversely, lesions of the IVN, and the muscimol injection into the IVN, increased the RN-induced facilitation of the L-JOR. These results suggest that the RN-induced facilitation of the L-JOR is mediated by a relay in the VN.

Anatomical organization of descending cortical projections orchestrating the patterns of cortically induced rhythmical jaw muscle activity in guinea pigs

Repetitive electrical microstimulation to the cortical masticatory area (CMA) evokes distinct patterns of rhythmical jaw muscle activities (RJMAs) in animals. This study aimed to investigate the characteristics of the descending projections from the CMA, associated with distinct patterns of RJMAs, to the thalamus, midbrain, pons and medulla in guinea pigs. RJMAs with continuous masseter and digastric bursts (CB-RJMAs) and stimulus-locked digastric sub-bursts (SLB-RJMAs) were induced from the anterior and posterior areas of the rostral region of the lateral agranular cortex, and chewing-like RJMAs from the rostral region of the granular cortex. Anterograde tracer, biotinylated dextran amine, was injected into the three cortical areas. The cortical area inducing CB-RJMAs had strong ipsilateral projections to the motor thalamus, red nucleus, midbrain reticular formation, superior colliculus, parabrachial nucleus, and supratrigeminal region, and contralateral projections mainly to the lateral reticular formation around the trigeminal motor nucleus (Vmo). The cortical area inducing SLB-RJMAs had moderate projections to the motor thalamus and lateral reticular formation around the Vmo, but few projections to the midbrain nuclei. The cortical area inducing chewing-like RJMAs had strong projections to the ipsilateral sensory thalamus and contralateral trigeminal sensory nuclei, and moderate projections to the lateral reticular formation. The three cortical areas consistently had few projections to the ventromedial reticular formation. The present study demonstrates that multiple direct and indirect descending projections from the CMA onto the premotor systems connecting the trigeminal motoneurons represent the neuroanatomical repertoires for generating RJMAs during the distinct phases of natural ingestive behavior.

Suppression of the swallowing reflex by stimulation of the red nucleus

We study whether the red nucleus is involved in control of swallowing. The swallowing reflex was induced in anesthetized rats by repetitive electrical stimulation of the superior laryngeal nerve. The electromyographic activities of the mylohyoid and thyrohyoid muscles were recorded in order to identify the swallowing reflex. Repetitive electrical stimulation applied to the red nucleus reduced the number of swallows. The onset latency of the first swallow was increased during repetitive electrical stimulation applied to the magnocellular part of the red nucleus. Microinjection of monosodium glutamate into the red nucleus also reduced the number of swallows. The onset latency of the first swallow was increased after microinjection of monosodium glutamate into the magnocellular part of the red nucleus. These results imply that the red nucleus is involved in the control of swallowing.

Role of the red nucleus in suppressing the jaw-opening reflex following stimulation of the raphe magnus nucleus

In a previous study, we found that electrical and chemical stimulation of the red nucleus (RN) suppressed the high-threshold afferent-evoked jaw-opening reflex (JOR). It has been reported that the RN receives bilaterally projection fibers from the raphe magnus nucleus (RMg), and that stimulation of the RMg inhibits the tooth pulp-evoked nociceptive JOR. These facts imply that RMg-induced inhibition of the JOR could be mediated via the RN. The present study first examines whether stimulation of the RMg suppresses the high-threshold afferent-evoked JOR. The JOR was evoked by electrical stimulation of the inferior alveolar nerve (IAN), and was recorded as the electromyographic response of the anterior belly of the digastric muscle. The stimulus intensity was 4.0 (high-threshold) times the threshold. Conditioning electrical stimulation of the RMg significantly suppressed the JOR. A further study then examined whether electrically induced lesions of the RN or microinjection of muscimol into the RN affects RMg-induced suppression of the JOR. Electrically induced lesions of the bilateral RN and microinjection of muscimol into the bilateral RN both reduced the RMg-induced suppression of the JOR. These results suggest that RMg-induced suppression of the high-threshold afferent-evoked JOR is mediated by a relay in the RN.

Role of the lateral reticular nucleus in suppressing the jaw-opening reflex following stimulation of the red nucleus

We found in a previous study that stimulation of the red nucleus (RN) facilitated the low-threshold afferent-evoked jaw-opening reflex (JOR) and suppressed the high-threshold afferent-evoked JOR. It has been reported that the RN projections to the contralateral lateral reticular nucleus (LRt), and stimulation of the LRt inhibits the nociceptive JOR. These facts suggest that RN-induced modulation of the JOR is mediated via the LRt. We investigated whether electrically induced lesions of the LRt, or microinjection of muscimol into the LRt, affects RN-induced modulation of the JOR. The JOR was evoked by electrical stimulation of the inferior alveolar nerve (IAN), and was recorded as the electromyographic response of the anterior belly of the digastric muscle. The stimulus intensity was either 1.2 (low-threshold) or 4.0 (high-threshold) times the threshold. Electrically induced lesion of the LRt and microinjection of muscimol into the LRt reduced the RN-induced suppression of the high-threshold afferent-evoked JOR, but did not affect the RN-induced facilitation of the low-threshold afferent-evoked JOR. These results suggest that the RN-induced suppression of the high-threshold afferent-evoked JOR is mediated by a relay in the contralateral LRt.

Do spinocerebellar neurones forward information on spinal actions of neurones in the feline red nucleus?

We recently demonstrated that feline ventral spinocerebellar tract (VSCT) neurones monitor descending commands for voluntary movements initiated by pyramidal tract (PT) neurones as well as locomotor movements relayed by reticulospinal (RS) neurones. The aim of the present study was to examine whether VSCT neurones likewise monitor descending commands from the red nucleus (RN). Extracellular records from the spinal border (SB) subpopulation of VSCT neurons revealed that a third (31%) of SB neurones may be discharged by trains of stimuli applied in the RN. Moreover, when RN stimuli failed to discharge SB neurones they facilitated activation of some of these neurones by RS and/or PT neurones, while activation of other SB neurones was depressed. We propose that the facilitation and depression of actions of RS neurones by RN neurones might serve to reflect a higher or lower excitability of motoneurones and therefore a likely higher or lower efficacy of the RS descending commands, prompting the cerebellum to adjust the activation of reticulospinal neurones. Activation of SB neurones by RN stimuli alone would also allow monitoring and adjusting the RN descending commands. Intracellular records from SB neurones revealed both monosynaptic and disynaptic EPSPs and disynaptic IPSPs evoked by RN stimuli. The disynaptic actions remained following transection of axons of reticulospinal neurones within the medullary longitudinal fascicle (MLF) and were therefore taken to be relayed primarily by spinal neurones, in contrast to EPSPs and IPSPs evoked by PT stimuli found to be relayed by reticulospinal rather than spinal neurones.

The red nucleus and the rubrospinal projection in the mouse

We studied the organization and spinal projection of the mouse red nucleus with a range of techniques (Nissl stain, immunofluorescence, retrograde tracer injections into the spinal cord, anterograde tracer injections into the red nucleus, and in situ hybridization) and counted the number of neurons in the red nucleus (3,200.9 ± 230.8). We found that the rubrospinal neurons were mainly located in the parvicellular region of the red nucleus, more lateral in the rostral part and more medial in the caudal part. Labeled neurons were least common in the rostral and caudal most parts of the red nucleus. Neurons projecting to the cervical cord were predominantly dorsomedially placed and neurons projecting to the lumbar cord were predominantly ventrolaterally placed. Immunofluorescence staining with SMI-32 antibody showed that ~60% of SMI-32-positive neurons were cervical cord-projecting neurons and 24% were lumbar cord-projecting neurons. SMI-32-positive neurons were mainly located in the caudomedial part of the red nucleus. A study of vGluT2 expression showed that the number and location of glutamatergic neurons matched with those of the rubrospinal neurons. In the anterograde tracing experiments, rubrospinal fibers travelled in the dorsal portion of the lateral funiculus, between the lateral spinal nucleus and the calretinin-positive fibers of the lateral funiculus. Rubrospinal fibers terminated in contralateral laminae 5, 6, and the dorsal part of lamina 7 at all spinal cord levels. A few fibers could be seen next to the neurons in the dorsolateral part of lamina 9 at levels of C8-T1 (hand motor neurons) and L5-L6 (foot motor neurons), which is consistent with a view that rubrospinal fibers may play a role in distal limb movement in rodents.

Ipsilateral actions from the feline red nucleus on hindlimb motoneurones

The main aim of the study was to investigate whether neurones in the ipsilateral red nucleus (NR) affect hindlimb motoneurones. Intracellular records from motoneurones revealed that both EPSPs and IPSPs were evoked in them via ipsilaterally located premotor interneurones by stimulation of the ipsilateral NR in deeply anaesthetized cats in which only ipsilaterally descending tract fibres were left intact. When only contralaterally descending tract fibres were left intact, EPSPs mediated by excitatory commissural interneurones were evoked by NR stimuli alone while IPSPs mediated by inhibitory commissural interneurones required joint stimulation of the ipsilateral NR and of the medial longitudinal fascicle (MLF, i.e. reticulospinal tract fibres). Control experiments led to the conclusion that if any inadvertently coactivated axons of neurones from the contralateral NR contributed to these PSPs, their effect was minor. Another aim of the study was to investigate whether ipsilateral actions of NR neurones, pyramidal tract (PT) neurones and reticulospinal tract neurones descending in the MLF on hindlimb motoneurones are evoked via common spinal relay neurones. Mutual facilitation of these synaptic actions as well as of synaptic actions from the contralateral NR and contralateral PT neurones showed that they are to a great extent mediated via the same spinal neurones. A more effective activation of these neurones by not only ipsilateral corticospinal and reticulospinal but also rubrospinal tract neurones may thus contribute to the recovery of motor functions after injuries of the contralateral corticospinal tract neurones. No evidence was found for mediation of early PT actions via NR neurones.

Changes in cortically induced rhythmic jaw movements after lesioning of the red nucleus in rats

We study whether the red nucleus (RN) lesion can modify rhythmic jaw movements. Rhythmic jaw movements were induced by repetitive electrical stimulation of the two cortical masticatory areas (area A: the orofacial motor cortex; area P: the insular cortex). Lesions made by applied electric current in the RN were found to influence the rhythmic jaw movements induced by stimulation of A-area. The distance between the maximum and minimum jaw-opening positions was less after the lesions were induced. The duration of rhythmic jaw movements was shorter after lesioning. In contrast, lesions of the RN did not influence rhythmic jaw movements induced by stimulation of the P-area. Next, kainic acid (0.2 microl, lesion group) or phosphate-buffered saline (0.2 microl, control group) was injected into the left RN. Three days after injection, rhythmic jaw movements were induced by repetitive electrical stimulation of the A-area. The distance between the maximum and minimum jaw-opening positions in the lesion group was smaller than in the control group. The rhythmic jaw movements of the lesion group had shorter duration than the control group. These results suggest that the RN is involved in the modification of jaw movements induced by stimulation of the A-area.

Effect of orofacial motor cortex stimulation on neuronal activity in the red nucleus

We studied modulation of the activities of the red nucleus (RN) neurons under to electrical stimulation of the orofacial motor cortex (OfM) in urethane-anesthetized rats. Of 57 neurons studied, 30 (53%) neurons modulated the firing patterns. The firing patterns of the RN neurons were classified into four types: an excitation (E) type (n=4), a long inhibition (LI) type (n=4), a short inhibition (SI) type (n=22), and a no-effect type (n=27). These modulated neurons were intermingled in the dorso-ventral part of the RN. Our results suggest that the RN neurons receive excitatory or inhibitory inputs from the OfM.

Modulation of cortically induced rhythmical jaw movements by stimulation of the red nucleus in the rat

We study whether stimulation of the red nucleus (RN) can modulate rhythmical jaw movements in rats anesthetized by urethane. Rhythmical jaw movements were induced by repetitive electrical stimulation of the two cortical masticatory areas (area A: the orofacial motor cortex; area P: the insular cortex). Stimuli applied to the RN did influence rhythmical jaw movements induced by stimulation of the A-area. Stimuli applied in the jaw-closing phase increased the amplitude of the jaw-closing movement. Stimuli applied in the jaw-opening phase disturbed the rhythm of jaw movements and induced a small jaw-closing movement. Stimuli applied to the RN did not influence rhythmical jaw movements induced by stimulation of the P-area. These results indicate that the RN is involved in the modulation of rhythmical jaw movements induced by stimulation of the A-area.

Role of the parvicellular reticular formation in facilitating the jaw-opening reflex in rats by stimulation of the red nucleus

In a previous study, we have shown that electrical and chemical stimulation of the red nucleus (RN) facilitates the jaw-opening reflex (JOR). The RN sends projection fibers bilaterally, with contralateral dominance, to the part of the parvicellular reticular formation (RFp) containing premotor neurons projecting to the trigeminal motor nucleus. This implies that RN-induced facilitation of the JOR might be mediated via last-order neurons in the RFp. Here, we address this issue by investigating whether microinjection of lidocaine or l-glutamate into the RFp affects RN-induced modulation of the JOR. Experiments were performed on rats anesthetized with urethane-chloralose. The JOR was evoked by electrical stimulation of the inferior alveolar (IA) nerve and was recorded as an electromyographic response from the anterior belly of the digastric muscle. Conditioning stimulation was delivered unilaterally to the RN 12 ms before the IA test stimulation. We found that local injections of 2% lidocaine (0.5 microl) into the RFp, contralateral to the RN, significantly (P < 0.05) reduce RN-induced facilitation of the JOR, whereas corresponding injections of 0.1 mM l-glutamate (0.5 microl) significantly (P < 0.05) increase it. These results suggest that the facilitatory effect of RN stimulation on the JOR is mediated partly by a relay in the RFp.

Adeno-associated viral vector-mediated gene transfer of brain-derived neurotrophic factor reverses atrophy of rubrospinal neurons following both acute and chronic spinal cord injury

Rubrospinal neurons (RSNs) undergo marked atrophy after cervical axotomy. This progressive atrophy may impair the regenerative capacity of RSNs in response to repair strategies that are targeted to promote rubrospinal tract regeneration. Here, we investigated whether we could achieve long-term rescue of RSNs from lesion-induced atrophy by adeno-associated viral (AAV) vector-mediated gene transfer of brain-derived neurotrophic factor (BDNF). We show for the first time that AAV vectors can be used for the persistent transduction of highly atrophic neurons in the red nucleus (RN) for up to 18 months after injury. Furthermore, BDNF gene transfer into the RN following spinal axotomy resulted in counteraction of atrophy in both the acute and chronic stage after injury. These novel findings demonstrate that a gene therapeutic approach can be used to reverse atrophy of lesioned CNS neurons for an extended period of time.

Distinct temporal activity patterns in the rat M1 and red nucleus during skilled versus unskilled limb movement

The mammalian motor system contains multiple interconnected supraspinal networks, but little is known about their relative roles in producing different movements and behaviors, particularly given their apparently fused activity in primates. We tested whether the task context, as well as using a phylogenetically older mammal, rats, could distinguish the separate contributions of these networks. We obtained simultaneous multi-single neuron recordings from the forelimb motor cortex and magnocellular red nucleus as rats performed two contextually different, but kinematically similar, forelimb reach-like tasks: highly learned, skilled reaching for food through a narrow slot, a task requiring extensive training, versus the swing phases of treadmill locomotion. In both the M1 and the mRN, large subpopulations of neurons peaked in their spike firing rates near the onset and the end of the swing phase during treadmill locomotion. In contrast, neural subgroups in the two areas displayed different temporal sequences of activity during the skilled reaching task. In the mRN, the majority of task-modulated neurons peaked in their firing rate in the middle of the reach when the rat was preparing to project the arm through the slot, whereas large subgroups of M1 neurons displayed elevated firing rates during the initial and terminal phases of the reach. These results suggest that motor-behavioral context can alter the degree of overlapping activity in different supraspinal sensorimotor networks. Moreover, results for the skilled reaching task in rats may have highlighted a distinct processing role of the rubral complex: adapting natural muscle synergies across joints and limbs to novel task demands, in concert with cortically based learning.

Facilitation of the jaw reflexes by stimulation of the red nucleus in the rat

The effects of the red nucleus (RN) stimulation on the jaw-opening reflex (JOR) and the masseteric monosynaptic reflex (MMR) were studied in anesthetized rats. The JOR was evoked by electrical stimulation of the inferior alveolar nerve. The MMR was evoked by electrical stimulation of the mesencephalic trigeminal nucleus. The JOR and the MMR were recorded as electromyographic responses of the anterior belly of the digastric and the masseter muscles, respectively. The conditioning electrical stimulation of the RN facilitated both the JOR and the MMR bilaterally. The facilitatory effect on the JOR was much larger than that on the MMR. Additionally, microinjection of monosodium glutamate into the RN also elicited facilitation of the JOR and the MMR. The results suggest the RN plays an important role in reflex control of jaw movements.