Excitatory pathways from the vestibular nuclei to the NTS and the PBN and indirect vestibulo-cardiovascular pathway from the vestibular nuclei to the RVLM relayed by the NTS.

Previous studies have confirmed the existence of vestibulo-sympathetic pathways in the central nervous system. However, the exact pathways and neurotransmitters underlying this reflex are unclear. The present study was undertaken to investigate whether the vestibulo-cardiovascular responses are a result of activated glutamate receptors in the caudal vestibular nucleus. We also attempt to verify the indirect excitatory pathways from the vestibular nucleus (VN) to the rostral ventrolateral medulla (RVLM) using a tracing method combined with a vesicular glutamate transporter (VGluTs) immunofluorescence. In anesthetized rats, unilateral injection of l-glutamate (5 nmol) into the medial vestibular nucleus (MVe) and spinal vestibular nucleus (SpVe) slightly increased the mean arterial pressure (MVe: 93.29+/-11.58 to 96.30+/-11.66, SpVe: 91.72+/-15.20 to 95.48+/-17.16). Local pretreatment with the N-methyl-D-aspartate (NMDA)-receptor antagonist MK-801 (2 nmol) significantly attenuated the pressor effect of L-glutamate injected into the MVe compared to the contralateral self-control. After injection of biotinylated dextran amine (BDA) into the MVe and SpVe, and fluorogold (FG) into the RVLM, some BDA-labeled fibres and terminals in the nucleus of solitary tract (NTS) and the parabrachial nucleus (PBN) were immunoreactive for VGluT1 and VGluT2. Several BDA-labeled fibres were closely apposed to FG-labeled neurons in the NTS. These results suggested that activation of caudal vestibular nucleus neurons could induce pressor response and NMDA receptors might contribute to this response in the MVe. The glutamatergic VN-NTS and VN-PBN pathways might exist, and the projections from the VN to the RVLM relayed by the NTS comprise an indirect vestibulo-cardiovascular pathway in the brain stem.

Glutamatergic vestibular neurons express Fos after vestibular stimulation and project to the NTS and the PBN in rats.

In this study, retrograde tracing method combined with phosphate-activated glutaminase (PAG) and Fos immunofluorescence histochemistry was used to identify glutamatergic vestibular nucleus (VN) neurons receiving vestibular inputs and projecting to the nucleus of the solitary tract (NTS) and the parabrachial nucleus (PBN). Conscious animals were subjected to 120 min Ferris-wheel like rotation stimulation. Neuronal activation was assessed by Fos expression in the nucleus of VN neurons. After Fluoro-gold (FG) injection into the caudal NTS, approximately 48% FG-labeled VN neurons were immunoreactive for PAG, and about 14% PAG/FG double-labeled neurons co-existed with Fos. Following FG injection into the PBN, approximately 56% FG-labeled VN neurons were double-labeled with PAG, and about 12% of the PAG/FG double-labeled neurons also expressed Fos. Careful examination of the typology and distribution pattern of these PAG-immunoreactive neurons indicated that the vast majority of these neurons were glutamatergic rather than GABAergic. These results suggest that PAG-immunoreactive VN neurons might constitute excitatory glutamatergic VN-NTS and VN-PBN transmission pathways and these pathways might be involved in vestibulo-autonomic reflexes during vestibular stimulation.

Visceral and orofacial somatic afferent fiber terminals converge onto the same neuron in paratrigeminal nucleus: An electron microscopic study in rats.

The paratrigeminal nucleus (Pa5) receives visceral sensory inputs through the vagus (X) and glossopharyngeal (IX) nerves and somatic sensory inputs through the trigeminal (V) nerve. In the present study, transganglionic transport of the WGA-HRP and Wallerian degeneration was used to identify whether two kinds of primary afferent fiber terminals converge onto a single neuron in the Pa5 at the utrastructural level. It was found that HRP-labeled and degenerated terminals originating from the IX and/or X nerves and infraorbital nerve formed asymmetrical synapses with unlabeled dendrites in the Pa5. Furthermore, approximately 7% (43/630) HRP-labeled and 31% (43/137) degenerated terminals formed synaptic connections with the same dendritic profiles simultaneously in the dorsal division of the Pa5. These results may provide a neuroanatomical substrate for integration of viscerosomatic sensory inputs associated with visceral and cardiovascular reflexes in the Pa5.

[Arthroscopic investigation of the status of temporomandibular joint in patients with temporomandibular joint pain].

OBJECTIVE: To investigate the status of the temporomandibular joint (TMJ) in patients with complaints of joint pain for improving clinical therapy. METHODS: Twenty three joints in twenty patients who complained of TMJ pain were examined radiographically and arthroscopically. RESULTS: There were at least one and more to six pathological changes could be found arthroscopically in the 23 temporomandibular joints, which were different in some respects with radiographic findings. CONCLUSION: TMJ related pain may be associated with pathological alterations in the TMJ, and synovitis may be one of the causes of TMJ pain.

[Behavioral changes of rats under rotation stimulation].

OBJECTIVE: To assess the specification and efficiency of rotation sickness indices by monitoring changes of behaviors in rats under rotation stimulation. METHOD: SD rats were stimulated by Crampton model with different time courses. Pica or kaolin consumption (KC), conditioned taste aversion (CTA) or saccharine water ingestion (SWI), 2 h food ingestion (2hFI), and open-field test (OFT) scores were observed. RESULT: Apparent changes of the four indices were observed after rotation stimulation. SWI, OFT scores and 2hFI decreased exponentially with increase of duration of the motion stimulation. KC increased linearly with the increase of time within 12 h stimulation. After 18 h stimulation, KC decreased to a level even lower than that after 6 or 12 h stimulation. The adjusted correlation between changes of the indices and duration of stimulation within 12 h are: 0.94 for KC, 0.54 for SWI, 0.44 for 2hFI and 0.34 for OFT. The maximum efficiency of the four indices appeared at 6-hour stimulation: 70% for KC, 90% for SWI, 80% for 2hFI and 95% for OFT. CONCLUSION: It is found that pica and CTA were more specific than the other indices. They may serve as primary indices and can be combined with the secondary indices such as 2hFI or OFT. Six hours is the optimal duration of stimulation by Crampton model for rotation sickness studies.

Calbindin D28k-containing neurons in the paratrigeminal nucleus receive convergent nociceptive information and project to nucleus of the solitary tract in rat.

The paratrigeminal nucleus (PTN) receives orofacial somatic and visceral afferent fibers and contains many calbindin-D28k neurons (CB-containing neurons) that project to nucleus of the solitary tract (NTS). In the present study, retrograde and transganglionic tracing methods combined with immunofluorescence histochemistry and confocal laser scanning microscopy were used. After Fluoro-gold (FG) injection into the unilateral NTS, 74.4% FG-labeled neurons of ipsilateral PTN were double-labeled with CB. Furthermore, 41.0% and 32.5% FG/CB double-labeled neurons co-existed with Fos induced by nociceptive stimulation of the lips and the upper alimentary tract, respectively. In the PTN unilateral to FG injection site, 26.6% CB-LI neurons were double-labeled with PAG, 61.5% and 79.0% CB/PAG double-labeled neurons were triple-labeled with FG and Fos, and 22.9% FG/CB double-labeled neurons were triple-labeled with PAG, 84.3% FG/PAG double-labeled neurons expressed Fos induced by the upper alimentary tract stimulation. In the intact animals, 62.8% CB-LI neurons and 88.3% PAG-LI neurons co-existed with GABA(B)R, respectively. In addition, some terminals from the inferior alveolar nerve (IAN) were closely apposed to CB/Fos double-labeled or CB single-labeled neurons. These results suggested that CB-containing neurons in the PTN receive the nociceptive information converge from the orofacial area and visceral organs, and comprising the glutamatergic excitatory transmission pathway from the PTN to the NTS. This pathway might be modulated by GABA via the GABA(B) receptor.

Somatic and visceral nociceptive inputs from the orofacial area and the upper alimentary tract converge onto CB-containing neurons in interstitial nucleus of the spinal trigeminal tract in rats.

The interstitial nucleus of the spinal trigeminal tract (INV) contains many calbindin-D28k-containing neurons (CB-neurons) receiving convergence information from the somatic and visceral structures. The purpose of the present study was to confirm whether the primary afferent terminals from the inferior alveolar nerve (IAN) make close contact and synaptic connections with the same CB-neurons receiving visceral nociceptive signals in INV. Biotinylated dextran amine (BDA) and horseradish peroxidase (HRP) tracing combined with CB and Fos proteins immunohistochemistry were used. After injections of BDA and formalin into unilateral IAN and upper alimentary tract, respectively, the transganglionic labeled afferent fibers and terminals from IAN were observed in the ipsilateral INV, especially in its enlarged part. A large number of CB- and Fos-like immunoreactive (LI) neurons were found in bilateral INV. These CB- and Fos-LI neurons mostly overlapped with BDA-labeled terminals in the enlarged part of INV. About one half of the CB-LI neurons were double labeled with Fos-LI nuclei (74/153). The terminals from IAN were to made close contacts with many CB/Fos-double labeled or CB-single labeled neurons. After injection of HRP into IAN, HRP-labeled fibers and terminals in INV were similar to that labeled with BDA. Under the electron microscope, a large number of CB-LI dendrites and a few soma in the enlarged part of INV were found to form asymmetrical axo-dendritic and axo-somal synapses with the HRP-labeled axon terminals. These results indicate that the orofacial somatic inputs from IAN and the visceral nociceptive inputs from the upper alimentary tract converge onto the same CB-containing neurons in INV. These CB-containing neurons in INV probably play an important role in information integration as well as visceral and cardiovascular activity.

[Calbindin D-28k-containing neurons receiving visceral and somatic nociceptive information in interstitial nucleus of the spinal trigeminal tract project to the parabrachial nuclei in the rat].

The calbindin D-28k (CB)-containing neurons in the interstitial nucleus of the spinal trigeminal tract (INV) that receive visceral and orofacial somatic nociceptive information and emanate projections to the parabrachial nuclei (PB) were investigated by the triple-labeled methods of fluorogold (FG) retrograde tracing combined with Fos and CB proteins immunofluorescence histochemistry in the rat. The results showed (1) in the perioral stimulation group, a large number of FG-retrograde labeled and Fos-immunoreactive neurons were found in the paratrigeminal nucleus (PaV) and the dorsal paramarginal nucleus (PaMd) of the INV ipsilateral to FG and formalin injection made to the PB and lips, respectively, while a lot of CB-immunoreactive neurons were distributed in the INV bilaterally; (2) a majority of the FG-retrograde labeled neurons (77.3%) were double-labeled with CB, and 40.7% of them were double-labeled with Fos; about 38.5% of FG/CB double-labeled neurons were FG/CB/Fos triple-labeled in the INV; and (3) in the upper alimentary tract stimulation group, the distribution and the numbers of FG-retrograde labeled, CB-immunoreactive neurons and FG/CB double-labeled neurons in the INV were similar to those of the perioral stimulation group as described above, except that the Fos immunoreactive neurons were distributed in the INV bilaterally, approximately 41.9% of the FG-retrograde labeled neurons were FG/Fos double-labeled, and over half (52.0%) of those double-labeled neurons were FG/CB/Fos triple-labeled. The results indicate that a part of CB-containing neurons in the INV receive orofacial somatic and visceral nociceptive information and that these neurons sent projections directly to the PB. The CB-containing neurons might play an important role in the transmission of the peripheral nociceptive information from INV to PB.

Origins of GABA(B) receptor-like immunoreactive terminals in the rat spinal dorsal horn.

By means of immunohistochemistry for gamma-aminobutyric acid receptor B subtype (GABA(B)R), the origins of GABA(B)R-like immunoreactive (GABA(B)R-LI) terminals in the rat spinal dorsal horn were investigated. After dorsal root rhizotomy and/or spinal cord hemisection, the densities of GABA(B)R-LI terminals were remarkably depleted in the ipsilateral superficial dorsal horn of relevant segments, whereas GABA(B)R-LI neurons and sparsely distributed GABA(B)R-LI terminals remained. After injection of Fluoro-Gold (FG) into the left side of superficial lumbar dorsal horn, FG retrograde-labeled neurons were mainly observed in the ipsilateral rostral ventromedial medulla (RVM) and brainstem raphe nuclei. Some of the FG-labeled neurons, especially in the RVM, exhibited GABA(B)R-like immunoreactivity. Additionally, immunofluorescence histochemical double-staining revealed that the majority of GABA(B)R-LI neurons in the periaqueductal gray (PAG), RVM and brainstem raphe nuclei showed 5-hydroxytryptamine (5-HT)-like immunoreactivity. The present study morphologically proves that GABA(B)R-LI terminals in the spinal dorsal horn originate from peripheral afferents, intrinsic neurons and supraspinal structures; GABA(B)R and 5-HT co-exist in many neurons in the PAG, RVM and brainstem raphe nuclei. Considering that PAG, RVM, brainstem raphe nuclei and spinal dorsal horn are important structures involved in the pain modulation, we suggest that the descending pain modulation system might be mediated, at least in part, by GABA(B)R.