The Cerebellar Cortex Receives Orofacial Proprioceptive Signals from the Supratrigeminal Nucleus via the Mossy Fiber Pathway in Rats.

Proprioceptive sensory information from muscle spindles is essential for the regulation of motor functions. However, little is known about the motor control regions in the cerebellar cortex that receive proprioceptive signals from muscle spindles distributed throughout the body, including the orofacial muscles. Therefore, in this study, we investigated the pattern of projections in the rat cerebellar cortex derived from the supratrigeminal nucleus (Su5), which conveys orofacial proprioceptive information from jaw-closing muscle spindles (JCMSs). Injections of an anterograde tracer into the Su5 revealed that many bilateral axon terminals (rosettes) were distributed in the granular layer of the cerebellar cortex (including the simple lobule B, crus II and flocculus) in a various sized, multiple patchy pattern. We could also detect JCMS proprioceptive signals in these cerebellar cortical regions, revealing for the first time that they receive muscle proprioceptive inputs in rats. Retrograde tracer injections confirmed that the Su5 directly sends outputs to the cerebellar cortical areas. Furthermore, we injected an anterograde tracer into the external cuneate nucleus (ECu), which receives proprioceptive signals from the forelimb and neck muscle spindles, to distinguish between the Su5- and ECu-derived projections in the cerebellar cortex. The labeled terminals from the ECu were distributed predominantly in the vermis of the cerebellar cortex. Almost no overlap was seen in the terminal distributions of the Su5 and ECu projections. Our findings demonstrate that the rat cerebellar cortex receives orofacial proprioceptive input that is processed differently from the proprioceptive signals from the other regions of the body.

Cerebellar Nuclei Receiving Orofacial Proprioceptive Signals through the Mossy Fiber Pathway from the Supratrigeminal Nucleus in Rats.

Proprioception from muscle spindles is necessary for motor function executed by the cerebellum. In particular, cerebellar nuclear neurons that receive proprioceptive signals and send projections to the lower brainstem or spinal cord play key roles in motor control. However, little is known about which cerebellar nuclear regions receive orofacial proprioception. Here, we investigated projections to the cerebellar nuclei from the supratrigeminal nucleus (Su5), which conveys the orofacial proprioception arising from jaw-closing muscle spindles (JCMSs). Injections of an anterograde tracer into the Su5 resulted in a large number of labeled axon terminals bilaterally in the dorsolateral hump (IntDL) of the cerebellar interposed nucleus (Int) and the dorsolateral protuberance (MedDL) of the cerebellar medial nucleus. In addition, a moderate number of axon terminals were ipsilaterally labeled in the vestibular group Y nucleus (group Y). We electrophysiologically detected JCMS proprioceptive signals in the IntDL and MedDL. Retrograde tracing analysis confirmed bilateral projections from the Su5 to the IntDL and MedDL. Furthermore, anterograde tracer injections into the external cuneate nucleus (ECu), which receives other proprioceptive input from forelimb/neck muscles, resulted in only a limited number of ipsilaterally labeled terminals, mainly in the dorsomedial crest of the Int and the group Y. Taken together, the Su5 and ECu axons almost separately terminated in the cerebellar nuclei (except for partial overlap in the group Y). These data suggest that orofacial proprioception is differently processed in the cerebellar circuits in comparison to other body-part proprioception, thus contributing to the executive function of orofacial motor control.

Comparison of rhythmic masticatory muscle activity during non-rapid eye movement sleep in guinea pigs and humans.

Rhythmic masticatory muscle activity can be a normal variant of oromotor activity, which can be exaggerated in patients with sleep bruxism. However, few studies have tested the possibility in naturally sleeping animals to study the neurophysiological mechanisms of rhythmic masticatory muscle activity. This study aimed to investigate the similarity of cortical, cardiac and electromyographic manifestations of rhythmic masticatory muscle activity occurring during non-rapid eye movement sleep between guinea pigs and human subjects. Polysomnographic recordings were made in 30 freely moving guinea pigs and in eight healthy human subjects. Burst cycle length, duration and activity of rhythmic masticatory muscle activity were compared with those for chewing. The time between R-waves in the electrocardiogram (RR interval) and electroencephalogram power spectrum were calculated to assess time-course changes in cardiac and cortical activities in relation to rhythmic masticatory muscle activity. In animals, in comparison with chewing, rhythmic masticatory muscle activity had a lower burst activity, longer burst duration and longer cycle length (P < 0.05), and greater variabilities were observed (P < 0.05). Rhythmic masticatory muscle activity occurring during non-rapid eye movement sleep [median (interquartile range): 5.2 (2.6-8.9) times per h] was preceded by a transient decrease in RR intervals, and was accompanied by a transient decrease in delta elelctroencephalogram power. In humans, masseter bursts of rhythmic masticatory muscle activity were characterized by a lower activity, longer duration and longer cycle length than those of chewing (P < 0.05). Rhythmic masticatory muscle activity during non-rapid eye movement sleep [1.4 (1.18-2.11) times per h] was preceded by a transient decrease in RR intervals and an increase in cortical activity. Rhythmic masticatory muscle activity in animals had common physiological components representing transient arousal-related rhythmic jaw motor activation in comparison to human subjects.

Exercise-induced enhancement of insulin sensitivity is associated with accumulation of M2-polarized macrophages in mouse skeletal muscle.

Exercise enhances insulin sensitivity in skeletal muscle, but the underlying mechanism remains obscure. Recent data suggest that alternatively activated M2 macrophages enhance insulin sensitivity in insulin target organs such as adipose tissue and liver. Therefore, the aim of this study was to determine the role of anti-inflammatory M2 macrophages in exercise-induced enhancement of insulin sensitivity in skeletal muscle. C57BL6J mice underwent a single bout of treadmill running (20 m/min, 90 min). Twenty-four hours later, ex vivo insulin-stimulated 2-deoxy glucose uptake was found to be increased in plantaris muscle. This change was associated with increased number of CD163-expressing macrophages (i.e. M2-polarized macrophages) in skeletal muscle. Systemic depletion of macrophages by pretreatment of mice with clodronate-containing liposome abrogated both CD163-positive macrophage accumulation in skeletal muscle as well as the enhancement of insulin sensitivity after exercise, without affecting insulin-induced phosphorylation of Akt and AS160 or exercise-induced GLUT4 expression. These results suggest that accumulation of M2-polarized macrophages is involved in exercise-induced enhancement of insulin sensitivity in mouse skeletal muscle, independently of the phosphorylation of Akt and AS160 and expression of GLUT4.

Efferent and afferent connections of supratrigeminal neurons conveying orofacial muscle proprioception in rats.

The supratrigeminal nucleus (Su5) is a key structure for controlling jaw movements; it receives proprioceptive sensation from jaw-closing muscle spindles (JCMSs) and sends projections to the trigeminal motor nucleus (Mo5). However, the central projections and regulation of JCMS proprioceptive sensation are not yet fully understood. Therefore, we aimed to reveal the efferent and afferent connections of the Su5 using neuronal tract tracings. Anterograde tracer injections into the Su5 revealed that the Su5 sends contralateral projections (or bilateral projections with a contralateral predominance) to the Su5, basilar pontine nuclei, pontine reticular nucleus, deep mesencephalic nucleus, superior colliculus, caudo-ventromedial edge of the ventral posteromedial thalamic nucleus, parafascicular thalamic nucleus, zona incerta, and lateral hypothalamus, and ipsilateral projections (or bilateral projections with an ipsilateral predominance) to the intertrigeminal region, trigeminal oral subnucleus, dorsal medullary reticular formation, and hypoglossal nucleus as well as the Mo5. Retrograde tracer injections into the Su5 demonstrated that the Su5 receives bilateral projections with a contralateral predominance (or contralateral projections) from the primary and secondary somatosensory cortices, granular insular cortex, and Su5, and ipsilateral projections (or bilateral projections with an ipsilateral predominance) from the dorsal peduncular cortex, bed nuclei of stria terminalis, central amygdaloid nucleus, lateral hypothalamus, parasubthalamic nucleus, trigeminal mesencephalic nucleus, parabrachial nucleus, juxtatrigeminal region, trigeminal oral and caudal subnuclei, and dorsal medullary reticular formation. These findings suggest that the Su5, which receives JCMS proprioception, has efferent and afferent connections with multiple brain regions that are involved in emotional and autonomic functions as well as orofacial motor functions.

Pathophysiology of current odontogenic maxillary sinusitis and endoscopic sinus surgery preceding dental treatment.

OBJECTIVE: The successful management of odontogenic maxillary sinusitis (OMS) involves a combination of medical treatment with dental surgery and/or endoscopic sinus surgery (ESS). However, there is no consensus for the optimal timing of ESS. Although several studies have emphasized dental surgery as the primary treatment modality for OMS, there is recent evidence to suggest that ESS alone may be an effective treatment approach. The purpose of this study is to retrospectively investigate the pathophysiology of the current intractable OMS and the role ESS, especially ESS preceding dental treatment, plays in its pathophysiology. METHODS: Ninety-seven adults (60 males and 37 females, 48 ± 12 years) who underwent ESS for intractable OMS were retrospectively examined. RESULTS: In a great deal of the cases (85 cases, 87.6%), causative teeth of OMS were periapical lesions after root canal treatment (endodontics). The root canal procedures were not sufficient; hence, the root-canal-treated teeth had periapical lesions causing OMS. In postoperative nasal endoscopy and cone-beam CT scans for all patients, the natural ostiums and the membranous portions of the maxillary sinuses were enlarged and the ostiomeatal complexes remained widely open. The ventilation and drainage of all patients' maxillary sinuses seemed to be successfully restored. Temporary acute sinusitis recurrence after primary ESS for OMS was observed in 10 cases (11.8%) when the patients caught a cold. However, since the natural ostium and the membranous portion of the maxillary sinuses and the ostiomeatal complexes remained widely open, antibiotic administration alone without dental treatment cured the temporary acute sinusitis. Regarding the causative teeth (endodontic treated teeth), in 83 out of 85 cases (97.6%), causative teeth were able to be preserved with only antibiotic treatment and without dental retreatment. In two cases, extraction of the teeth was necessary because the teeth became mobile. Regarding the causative teeth after dental restoration, in 2 out of 2 cases (100%), causative teeth were able to be preserved with antibiotic treatment alone. CONCLUSION: ESS is highly indicated for OMS requiring surgery. The treatment results of intractable OMS are exceptionally good once the ventilation and drainage of the maxillary sinus is successfully restored after surgery. Consequently, ESS can be considered the first-line therapy for intractable OMS caused by root canal treatment (endodontics) and dental restoration, followed by close dental follow-up and dental treatment when necessary.

Widespread corticopetal projections from the oval paracentral nucleus of the intralaminar thalamic nuclei conveying orofacial proprioception in rats.

The oval paracentral nucleus (OPC) was initially isolated from the paracentral nucleus (PC) within the intralaminar thalamic nuclei in rats. We have recently shown that the rat OPC receives proprioceptive inputs from jaw-closing muscle spindles (JCMSs). However, it remains unknown which cortical areas receive thalamic inputs from the OPC, and whether the cortical areas receiving the OPC inputs are distinct from those receiving inputs from the other intralaminar nuclei and sensory thalamic nuclei. To address this issue, we injected an anterograde tracer, biotinylated dextranamine (BDA), into the OPC, which was electrophysiologically identified by recording of proprioceptive inputs from the JCMSs. Many BDA-labeled axonal fibers and terminals from the OPC were ipsilaterally observed in the rostral and rostroventral regions of the primary somatosensory cortex (S1), the rostral region of the secondary somatosensory cortex (S2), and the most rostrocaudal levels of the granular insular cortex (GI). In contrast, a BDA injection into the caudal PC, which was located slightly rostral to the OPC, resulted in ipsilateral labeling of axonal fibers and terminals in the rostrolateral region of the medial agranular cortex and the rostromedial region of the lateral agranular cortex. Furthermore, injections of a retrograde tracer, Fluorogold, into these S1, S2, and GI regions, resulted in preferential labeling of neurons in the ipsilateral OPC among the intralaminar and sensory thalamic nuclei. These findings reveal that the rat OPC has widespread, but strong corticopetal projections, indicating that there exist divergent corticopetal pathways from the intralaminar thalamic nucleus, which process JCMS proprioceptive sensation.

Histopathology of maxillary sinus mucosa with odontogenic maxillary sinusitis.

OBJECTIVE: Histopathology of the maxillary sinus mucosa with intractable odontogenic maxillary sinusitis (OMS) was investigated and the role endoscopic sinus surgery (ESS) plays in its pathophysiology was clarified. STUDY DESIGN: Histopathological analysis of the OMS mucosa. METHODS: Surgical specimens were obtained from 20 patients who underwent ESS for intractable OMS. For rigid endoscopic observation of the mucosae, a 70° rigid endoscope 4 mm in diameter with an attached high definition surgical camera was used. Histopathological analyses of the maxillary sinus mucosa were conducted by light and scanning electron microscopy. RESULTS: All the maxillary sinuses were filled, not with viscous, but with purulent secretions. The high-definition camera showed that the maxillary sinus mucosa had gyrus-like appearance. Light microscopic histopathological studies revealed that the surface of the maxillary sinus mucosa was convoluted. Light and scanning electron microscopic histopathological studies revealed that the ciliated cells of the epithelium had not decreased and their goblet cells were not hypertrophic, indicating that the damage of the ciliated columnar epithelium was not severe and they were not injured irreversibly. CONCLUSION: The ciliated columnar epithelium with intractable OMS was not severely damaged and not irreversibly injured. Hence, the pathophysiology of intractable OMS is one of the reasons why ESS is highly indicated for maxillary sinusitis requiring surgery and the treatment results are exceptionally good when the ventilation and drainage of the maxillary sinus is successfully restored after surgery. LEVEL OF EVIDENCE: NA.

Ascending projection of jaw-closing muscle-proprioception to the intralaminar thalamic nuclei in rats.

An invasive intralaminar thalamic stimulation and a non-invasive application of oral splint are both effective in treating tic symptoms of patients with Tourette syndrome (TS). Therefore, these two treatments may exert some influence on the same brain region in TS patients. We thus hypothesized that the proprioceptive input arising from the muscle spindles of jaw-closing muscles (JCMSs), known to be increased by the application of oral splint, is transmitted to the intralaminar thalamic nuclei. To test this issue, we morphologically and electrophysiologically examined the thalamic projections of proprioceptive input from the JCMSs to the intralaminar thalamic nuclei of rats. We first injected an anterograde tracer, biotinylated dextranamine, into the electrophysiologically identified supratrigeminal nucleus, which is known to receive proprioceptive inputs from the JCMSs via the trigeminal mesencephalic neurons. A moderate number of biotinylated dextranamine-labeled axon terminals were bilaterally distributed in the oval paracentral nucleus (OPC) of the intralaminar thalamic nuclei. We also detected electrophysiological responses to the electrical stimulation of bilateral masseter nerves and to sustained jaw-opening in the OPC. After injection of retrograde tracer (cholera toxin B subunit or Fluorogold) into the OPC, neuronal cell bodies were retrogradely labeled in the rostrodorsal portion of the bilateral supratrigeminal nucleus. Here, we show that proprioceptive inputs from the JCMSs are conveyed to the OPC in the intralaminar nuclei via the supratrigeminal nucleus. This study can help to understand previously unrecognized pathways of proprioception ascending inputs from the brainstem to the thalamus, which may contribute to treatments of TS patients.

Proprioceptive thalamus receiving forelimb and neck muscle spindle inputs via the external cuneate nucleus in the rat.

Proprioceptive signals from body muscles have historically been considered to project to the rostrodorsal shell of the ventrobasal thalamic complex [the ventral posterolateral nucleus (VPL) and ventral posteromedial nucleus (VPM)]. However, we have recently found that proprioception from rat jaw-closing muscle spindles (JCMSs) is conveyed via the supratrigeminal nucleus to the caudo-ventromedial edge of the VPM, but not to the rostrodorsal shell of the VPM. Therefore, proprioception from other body muscles may also project to thalamic regions other than the rostrodorsal shell of the VPL. We thus examined the thalamic projection from the rat external cuneate nucleus (ECu), which receives proprioceptive inputs from forelimb and neck muscles. After injection of anterograde tracer into the ECu, axon terminals were contralaterally labeled in the ventromedial part (VPLvm) of the VPL, but not in the rostrodorsal shell of the VPL. After anterograde tracer injection into the cuneate nucleus (Cu), axon terminals were widely labeled in the contralateral VPL including the VPLvm. In the VPLvm, we electrophysiologically confirmed the proprioceptive inputs responsive to electrical stimulation of the ECu or median nerve and to the pressure of forelimb/neck muscles or wrist flexion. After retrograde tracer injection into the VPLvm, neurons were contralaterally labeled in the ECu and Cu. After retrograde tracer injection into the VPL where no such proprioceptive inputs were recorded, no ECu neurons were labeled. These findings indicate that proprioception from forelimb/neck muscle spindles and JCMSs is somatotopically transmitted to the ventromedial floor of the ventrobasal thalamic complex, but not to its rostrodorsal shell.

Endoscopic Sealing With a Polyglycolic Acid Sheet for Restoration of Vocal Fold Mucosa in Dogs.

OBJECTIVES/HYPOTHESIS: Voice outcomes of cordectomy for early glottic cancer are often poor due to vocal fold scarring and tissue defects. Improvements in this aspect could make cordectomy a more acceptable treatment option than radiotherapy. We hypothesized that a polyglycolic acid (PGA) sheet could be used to cover vocal fold defects. The present study aimed to prevent vocal fold scarring after cordectomy using the PGA sheet. STUDY DESIGN: Animal experiment. METHODS: Nine male beagles were divided into three groups including a control group (n = 3). Following cordectomy, the vocal fold defect was covered with the PGA sheet plus fibrin glue (PGA group; n = 3) or with the PGA sheet plus fibrin glue containing basic fibroblast growth factor (bFGF; the PGA-bFGF group, n = 3). Vocal folds were chronologically observed, and larynges were removed 6 months after surgery. Mucosal amplitude was measured using a high-speed camera, and histological analysis was performed. RESULTS: The re-epithelialization process was delayed in the PGA and PGA-bFGF groups compared with the control group. The mucosal amplitude was significantly more normalized and the thickness ratio significantly higher in the PGA and PGA-bFGF groups compared with the control group. The PGA-bFGF group had the highest elastic fiber density, followed by the PGA group and then the control group, with a significant difference between the PGA-bFGF and control groups. CONCLUSIONS: The PGA sheet plus fibrin glue could serve as an effective regenerative scaffold for reconstructing vocal fold morphology and function after cordectomy, with the potential benefit of establishing an endoscopic sealing method for vocal fold defects. LEVEL OF EVIDENCE: NA Laryngoscope, 130:E436-E443, 2020.

Transcortical descending pathways through granular insular cortex conveying orofacial proprioception.

Our motor behavior can be affected by proprioceptive information. However, little is known about which brain circuits contribute to this process. We have recently revealed that the proprioceptive information arising from jaw-closing muscle spindles (JCMSs) is conveyed to the supratrigeminal nucleus (Su5) by neurons in the trigeminal mesencephalic nucleus (Me5), then to the caudo-ventromedial edge of ventral posteromedial thalamic nucleus (VPMcvm), and finally to the dorsal part of granular insular cortex rostroventrally adjacent to the rostralmost part of secondary somatosensory cortex (dGIrvs2). Our next question is which brain areas receive the information from the dGIrvs2 for the jaw-movements. To test this issue, we injected an anterograde tracer, biotinylated dextranamine, into the dGIrvs2, and analyzed the resultant distribution profiles of the labeled axon terminals. Anterogradely labeled axons were distributed in the pontomedullary areas (including the Su5) which are known to receive JCMS proprioceptive inputs conveyed directly by the Me5 neurons and to contain premotoneurons projecting to the jaw-closing motoneurons in the trigeminal motor nucleus (Mo5). They were also found in and around the VPMcvm. In contrast, no labeled axonal terminals were detected on the cell bodies of Me5 neurons and motoneurons in the Mo5. These data suggest that jaw-movements, which are evoked by the classically defined jaw-reflex arc originating from the peripheral JCMS proprioceptive information, could also be modulated by the transcortical feedback connections from the dGIrvs2 to the VPMcvm and Su5.

Cortical and Subcortical Projections from Granular Insular Cortex Receiving Orofacial Proprioception.

We have recently revealed that the proprioceptive signal from jaw-closing muscle spindles (JCMSs) is conveyed to the dorsal part of granular insular cortex rostroventrally adjacent to the rostralmost part of secondary somatosensory cortex (dGIrvs2) via the caudo-ventromedial edge (VPMcvm) of ventral posteromedial thalamic nucleus (VPM) in rats. However, it remains unclear to which cortical or subcortical structures the JCMS proprioceptive information is subsequently conveyed from the dGIrvs2. To test this issue, we injected an anterograde tracer, biotinylated dextranamine, into the electophysiologically identified dGIrvs2, and analyzed the resultant distribution profiles of labeled axon terminals in rats. Labeled terminals were distributed with an ipsilateral predominance. In the cerebral cortex, they were seen in the primary and secondary somatosensory cortices, lateral and medial agranular cortices and dorsolateral orbital cortex. In the basal ganglia, they were found in the caudate putamen, core part of accumbens nucleus, lateral globus pallidus, subthalamic nucleus, and substantia nigra pars compacta and pars reticulata. They were also observed in the central amygdaloid nucleus and extended amygdala (the interstitial nucleus of posterior limb of anterior commissure and the juxtacapsular part of lateral division of bed nucleus of stria terminalis). In the thalamus, they were seen in the reticular nucleus, ventromedial nucleus, core VPM, parvicellular part of ventral posterior nucleus, oval paracentral nucleus, medial and triangular parts of posterior nucleus, and zona incerta as well as the VPMcvm. These data suggest that the JCMS proprioceptive information through the dGIrvs2 is transmitted to the emotional 'limbic' regions as well as sensorimotor regions.

Thalamo-insular pathway conveying orofacial muscle proprioception in the rat.

Little is known about how proprioceptive signals arising from muscles reach to higher brain regions such as the cerebral cortex. We have recently shown that a particular thalamic region, the caudo-ventromedial edge (VPMcvm) of ventral posteromedial thalamic nucleus (VPM), receives the proprioceptive signals from jaw-closing muscle spindles (JCMSs) in rats. In this study, we further addressed how the orofacial thalamic inputs from the JCMSs were transmitted from the thalamus (VPMcvm) to the cerebral cortex in rats. Injections of a retrograde and anterograde neuronal tracer, wheat-germ agglutinin-conjugated horseradish peroxidase (WGA-HRP), into the VPMcvm demonstrated that the thalamic pathway terminated mainly in a rostrocaudally narrow area in the dorsal part of granular insular cortex rostroventrally adjacent to the rostralmost part of the secondary somatosensory cortex (dGIrvs2). We also electrophysiologically confirmed that the dGIrvs2 received the proprioceptive inputs from JCMSs. To support the anatomical evidence of the VPMcvm-dGIrvs2 pathway, injections of a retrograde neuronal tracer Fluorogold into the dGIrvs2 demonstrated that the thalamic neurons projecting to the dGIrvs2 were confined in the VPMcvm and the parvicellular part of ventral posterior nucleus. In contrast, WGA-HRP injections into the lingual nerve area of core VPM demonstrated that axon terminals were mainly labeled in the core regions of the primary and secondary somatosensory cortices, which were far from the dGIrvs2. These results suggest that the dGIrvs2 is a specialized cortical region receiving the orofacial proprioceptive inputs. Functional contribution of the revealed JCMSs-VPMcvm-dGIrvs2 pathway to Tourette syndrome is also discussed.

Orofacial proprioceptive thalamus of the rat.

The ascending pathway mediating proprioception from the orofacial region is still not fully known. The present study elucidated the relay of jaw-closing muscle spindle (JCMS) inputs from brainstem to thalamus in rats. We injected an anterograde tracer into the electrophysiologically identified supratrigeminal nucleus (Su5), known to receive JCMS input. Many thalamic axon terminals were labeled and were found mainly contralaterally in a small, unpredicted area of the caudo-ventromedial edge (VPMcvm) of ventral posteromedial thalamic nucleus (VPM). Electrical stimulation of the masseter nerve and passive jaw movements induced large responses in the VPMcvm. The VPMcvm is far from the rostrodorsal part of ventral posterolateral thalamic nucleus (VPL) where proprioceptive inputs from the body are represented. After injection of a retrograde tracer into the electrophysiologically identified VPMcvm, many neurons were labeled almost exclusively in the contralateral Su5, whereas no labeled neurons were found in the principal sensory trigeminal nucleus (Pr5) and spinal trigeminal nucleus (Sp5). In contrast, after injection of a retrograde tracer into the core of VPM, many neurons were labeled contralaterally in the Pr5 and Sp5, but none in the Su5. We conclude that JCMS input excites trigeminothalamic projection neurons in the Su5 which project primarily to the VPMcvm in marked contrast to other proprioceptors and sensory receptors in the orofacial region which project to the core VPM. These findings suggest that lesions or deep brain stimulation in the human equivalent of VPMcvm may be useful for treatment of movement disorders (e.g., orofacial tremor) without affecting other sensations.

Direct projection from the lateral habenula to the trigeminal mesencephalic nucleus in rats.

Trigeminal mesencephalic nucleus (Vmes) neurons are primary afferents conveying deep sensation from the masticatory muscle spindles or the periodontal mechanoreceptors, and are crucial for controlling jaw movements. Their cell bodies exist in the brain and receive descending commands from a variety of cortical and subcortical structures involved in limbic (emotional) systems. However, it remains unclear how the lateral habenula (LHb), a center of negative emotions (e.g., pain, stress and anxiety), can influence the control of jaw movements. To address this issue, we examined whether and how the LHb directly projects to the Vmes by means of neuronal tract tracing techniques in rats. After injections of a retrograde tracer Fluorogold in the rostral and caudal Vmes, a number of neurons were labeled in the lateral division of LHb (LHbl) bilaterally, whereas a few neurons were labeled in the medial division of LHb (LHbm) bilaterally. After injections of an anterograde tracer, biotinylated dextranamine (BDA) in the LHbl, a small number of labeled axons were distributed bilaterally in the rostral and caudal levels of Vmes, where some labeled axonal boutons contacted the cell body of rostral and caudal levels of Vmes neurons bilaterally. After the BDA injection into the LHbm, however, no axons were labeled bilaterally in the rostral and caudal levels of Vmes. Therefore, the present study for the first time demonstrated the direct projection from the LHbl to the Vmes and the detailed projection patterns, suggesting that jaw movements are modulated by negative emotions that are signaled by LHbl neurons.

Distinct association between the antagonistic jaw muscle activity levels and cardiac activity during chewing and NREM sleep in the freely moving guinea pigs.

The aim of this study was to investigate the changes of the association between cardiac activity and the electromyographic (EMG) level of the antagonistic jaw muscles during chewing and NREM sleep in guinea pigs after systemic clonidine injections. Ten animals were prepared for chronic experiments to monitor sleep, cardiac activity and EMG activity of jaw-closing masseter (MAS) and jaw-opening anterior belly of digastric (ADG) muscles. The recordings were made for ten hours with the injections of saline or clonidine (10 µg/kg, i.p.). Integrated EMG activity of the two muscles and mean heart rate (mHR) were calculated for every 10-s epoch. During the two hours after clonidine injection, the duration of REM sleep and mHR were significantly reduced. During chewing, the high EMG activity level of the two muscles and the activity ratio between the two muscles were not modified although mHR was decreased. During NREM sleep, after clonidine injection, the low EMG activity level at baseline was further decreased by 20-30% in parallel to a decrease of mHR although the heterogeneity of the activity ratio remained unaltered. The results suggest that the maintenance of the activity level for the antagonistic jaw muscles are regulated by the distinct physiological mechanisms reflecting the behavioral states during conscious chewing and unconscious NREM sleep.

Jaw-opening and -closing premotoneurons in the nucleus of the solitary tract making contacts with laryngeal and pharyngeal afferent terminals in rats.

This study clarified the neural mechanisms underlying jaw movements in pharyngolaryngeal reflexes such as swallowing in rats. After retrograde tracer injections into the ventromedial division (Vmovm) of the trigeminal motor nucleus (Vmo) containing jaw-opening (JO) motoneurons or into the dorsolateral division (Vmodl) of Vmo containing jaw-closing (JC) motoneurons, JO and JC premotoneurons were labeled with an ipsilateral predominance in the medial and intermediate subnuclei of the rostrocaudal middle two-thirds of the nucleus of the solitary tract (Sol); JC premotoneurons were also in the lateral subnucleus of Sol. After anterograde tracer injections into the Sol, axons were labeled with an ipsilateral predominance in the Vmovm and Vmodl, prominently in the ipsilateral Vmovm. After transganglionic tracer applications to the superior laryngeal nerve (SLN) or the cervical trunk of the glossopharyngeal nerve (GpN-ct), labeled afferents were seen in the medial, intermediate, lateral and interstitial subnuclei of Sol at the rostral three-fourths of Sol, indicating considerable overlap with the JO and JC premotoneurons in the Sol. Double labeling experiments demonstrated contacts between the afferent terminals and the JO and JC premotoneurons. The present study has for the first time revealed the differential distribution of JO and JC premotoneurons in the Sol and features of their projections from the Sol, as well as their connections with SLN and GpN-ct afferent inputs. The JO and JC premotoneurons in the Sol may play an important role in generation and organization of jaw movements in pharyngolaryngeal reflexes evoked by SLN and GpN-ct inputs, such as swallowing.

Thalamic afferent and efferent connectivity to cerebral cortical areas with direct projections to identified subgroups of trigeminal premotoneurons in the rat.

The roles of supramedullary brain mechanisms involved in the control of jaw movements are not fully understood. To address this issue, a series of retrograde (Fluorogold, FG) and anterograde (biotinylated dextran amine, BDA) tract-tracing studies were done in rats. At first, we identified projection patterns from defined sensorimotor cortical areas to subgroups of trigeminal premotoneurons that are located in defined brainstem areas. Focal injections of FG into these brainstem areas revealed that the rostralmost part of lateral agranular cortex (rmost-Agl), the rostralmost part of medial agranular cortex (rmost-Agm), and the rostralmost part of primary somatosensory cortex (rmost-S1) preferentially project to brainstem areas containing jaw-closing premotoneurons, jaw-opening premotoneurons and a mixture of both types of premotoneurons, respectively. The thalamic reciprocal connectivities to rmost-Agl, rmost-Agm, and rmost-S1 were then investigated following cortical injections of FG or BDA. We found many retrogradely FG-labeled neurons and large numbers of axons and terminals labeled anterogradely with BDA in the dorsal thalamus mainly on the side ipsilateral to the injection sites. The rmost-Agl had strong connections with the ventral lateral nucleus (VL), ventromedial nucleus (VM), parafascicular nucleus, and posterior nucleus (Po); the rmost-Agm with the ventral anterior nucleus, VL, VM, central lateral nucleus, paracentral nucleus, central medial nucleus, mediodorsal nucleus and Po; and the rmost-S1 with the ventral posteromedial nucleus and Po. The present results suggest that the descending multiple pathways from the cerebral cortex to jaw-closing and jaw-opening premotoneurons have unique functional roles in jaw movement motor control.

Preparation and characterization of ceramide-based liposomes with high fusion activity and high membrane fluidity.

Liposomes are useful vesicles that deliver drugs effectively to various organs. For transdermal applications, liposomes with high membrane fluidity, high fusion activity, and comprising stratum corneum lipid have been used for drug delivery. With the aim to increase drug distribution to the skin, we developed new liposomes with three characteristics: high membrane fluidity, high fusion activity to the stratum corneum lipid liposomes (SCLL), and lipid compositions based on stratum corneum lipids. New liposomes were prepared based on SCLL. First, lipid compositions of SCLL were optimized. Second, the alkyl chain length of ceramides and fatty acids, and the saturation degree of fatty acids were altered. As a result, liposomes with the highest membrane fluidity and fusion activity to SCLL were composed of C-8 ceramide/cholesterol/linolenic acid/cholesterol sulfate = 45/5/5/45 (w/w%), and named C8L. C8L had 1.54-times greater membrane fluidity and 6.57-times greater fusion activity to SCLL than SCLL. Transmission electron microscopy revealed that C8L had a spherical structure. The surface charge and the particle size were approximately -47.7 mV and 184 nm, respectively. Thus, in the future, C8L will be used to facilitate drug delivery to the skin.