Electrophysiological monitoring of pain afferent pathway of the trigeminal nerve and its functional plasticity in response to occlusal interference in rats / 南方医科大学学报

OBJECTIVE@#To observe the effect of occlusal interference on the afferent pathway of the trigeminal nerve and neuronal excitability in the trigeminal subnucleus caudalis (SPVC) of rats by electrical stimulation of the trigeminal ganglion (TG) and extracellular recordings of SPVC activities.@*METHODS@#Twenty male Wistar rats were randomly divided into control group and model group (=10). In the model group, occlusal interference for 30 consecutive days was induced using light-cured flowable resin on the right maxillary molars. During occlusal interference, the pain sensitivity was scored with von Frey Fibers in the masseter. Simultaneous recordings of electrical activities from the SPVC, electrocardiogram, body temperature and electromyogram of the breath muscles of the anesthetized rats were performed, and the responses evoked by electrical stimulation of the TG were analyzed.@*RESULTS@#Compared with the control rats, the rats in the model group showed significantly increased pain sensitivity scores ( 0.05). Train stimulation (0.2 ms, 1 mA, 30 s, 100 Hz) of the TG significantly increased the discharge frequency of the SPVC only in the rats in the model group ( < 0.05).@*CONCLUSIONS@#The functional activities of the pain afferent pathway of the trigeminal nerve can be electrophysiologically monitored by electrical stimulation of the TG and extracellular recordings of SPVC activities in rats. Occlusal interference can increase the excitability of the neurons in the SPVC and enhance their sensitivities to TG afferent activation, suggesting the neural plasticity of the pain afferent pathway.

Expression of KA1 kainate receptor subunit in the substantia gelatinosa of the trigeminal subnucleus caudalis in mice

The KA1 kainate receptor (KAR) subunit in the substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc) has been implicated in the processing of nociceptive information from the orofacial region. This study compared the expression of the KA1 KAR subunit in the SG of the Vc in juvenile, prepubescent and adult mice. RT-PCR, Western blot and immunohistochemistry analyses were used to examine the expression level in SG area. The expression levels of the KA1 KAR subunit mRNA and protein were higher in juvenile mice than in prepubescent or adult mice. Quantitative data revealed that the KA1 KAR subunit mRNA and protein were expressed at levels approximately two and three times higher, respectively, in juvenile mice than in adult mice. A similar expression pattern of the KA1 KAR subunit was observed in an immunohistochemical study that showed higher expression in the juvenile (59%) than those of adult (35%) mice. These results show that the KA1 KAR subunits are expressed in the SG of the Vc in mice and that the expression level of the KA1 KAR subunit decreases gradually with postnatal development. These findings suggest that age-dependent KA1 KAR subunit expression can be a potential mechanism of age-dependent pain perception.

Thoracic Vagal Ganglion and Referred Craniofacial Pain: a Case Report and Review / Ganglio Torácico Vagal y Dolor Craneofacial Referido: Reporte de Caso y Revisión

The presence of a ganglion-like tumefaction is reported in the mediastinal course of the right vagus nerve at Tl level in a cadaver in the Universidad Industrial de Santander's morphology laboratory. The vagal ganglion was located next to hyperplasic lymphoid nodes in para-tracheal and tracheal-bronchial levels, agglomerating in a large lymphoid mass in the carina and the pulmonary hilum. Anatomical-pathological study revealed a marked, diffusely distributed, predominantly histo-lymphocyte mixed inflammation, separating the epineurium, producing lysis of the vagus nerve fibers. This finding showed the degeneration of this cranial par by mediastinal pathology. This provided a possible explanation for the physiopathology of pain referring to the head and neck in inflammatory or neoplastic pathology involving compression and degeneration by inflammatory infiltration of the vagus nerve. Pons-medullar trigeminal afferent tracts and connectivity, supra-spinal pathways for processing somatic-visceral pain, possible somatic-vegetative responses and the integration of the trigeminal system in the physiology of pain concerning the vagus nerve are all discussed.

Se reporta la presencia de una tumefacción a manera de "ganglio" en el trayecto mediastínico del nervio vago derecho, a nivel de TI, en un cadáver en el Laboratorio de Morfología de la Universidad Industrial de Santander, Colombia. El "ganglio" vagal se encuentra adyacente a nodos linfoides hiperplásicos, en niveles para-traqueales y tráqueo-bronquiales que se aglomeran en una gran masa linfoide a la altura de la carina e hilio pulmonar. En el estudio anatomopatológico, se encontró marcado proceso inflamatorio mixto de predominio histo-linfocitario el cual se distribuye de manera difusa separando el epineuro y produciendo lisis de las fibras del nervio vago. Este hallazgo muestra la degeneración de este par craneal por patologías a nivel mediastínico. Esto brinda una posible explicación de la fisiopatología del dolor referido a cabeza y cuello, en patologías inflamatorias o neoplásicas que involucran la compresión y degeneración por infiltración inflamatoria del nervio vago. Se discute los tractos y la conectividad de las aferencias vagales a nivel ponto-medular, las vías supraespinales para el procesamiento del dolor sómato-visceral, las posibles respuestas sómato-vegetativas y la integración del sistema trigeminal en la fisiología del dolor en el nervio vago.

An Immunohistochemical and Immunoelectron Microscopic Study of Distribution of Neuropeptide Y in the Cat Spinal Trigeminal Subnucleus Caudalis after Pulpectomy / 대한해부학회지

The purpose of this study was to investigate the distribution of neuropeptide Y (NPY) in the cat spinal trigeminal subnucleus caudalis following pulpectomy of mandibular premolars and molar by means of an immunohistochemical and immunoelectron microscopic study. The animals were divided into normal and experimental group which were sacrificed at 14 days after pulpectomy. The results were as follows; 1. On the light microscopic observation of the spinal trigeminal subnucleus caudalis in normal group, NPY-immunoreactivity (IR) was weak within lamina I and lamina II outer. In pulpectomy group, NPY-IR was strong and appeared to extend into lamina I and lamina II inner at 14 days. 2. On the immunoelectron microscopic observation of the spinal trigeminal subnucleus caudalis in normal group, NPY-IR was revealed in axon terminals, dendrites, myelinated axons and unmyelinated axons. NPY-IR was associated with membrane structures within microtubules, synaptic vesicles, outer membrane of mitochondria and inner surface of the axolemma. In NPY-immunoreactive structure, there was a small amount of DAB precipita-tions. 3. On the immunoelectron microscopic observation of the spinal trigeminal subnucleus caudalis at 14 days in pulpectomy group, the number of NPY-immunoreactive axon terminals, dendrites, myelinated axons and unmyelinated axons was increased than normal group. DAB precipitations in NPY-immunoreactive structure was increased than normal group. Some NPY-immunoreactive axon terminal formed synaptic glomerulus and axoaxonic synapse. 4. The results indicate that NPY-IR was increased in the spinal trigeminal subnucleus caudalis after pulpectomy, and it is speculated that the increased NPY by injury of peripheral nerve may participate in the processing of nociception.

THE DISTRIBUTION OF LARGE GRANULAR VESICLES IN SUBSTANCE P AXON TERMINALS AND THEIR SYNAPTIC RELATIONS IN THE TRIGEMINAL SUBNUCLEUS CAUDALIS / 解剖学报

The ultrastructural localization of substance P (SP) immunoreactivity, especially the morphology, number and distribution of positive large granular vesicles (LGV) in SP axon terminals of the trigeminal subnucleus caudalis of the rat were studied by electron microscopic immunocytochemistry. This study revealed that SP immunoreactivity was mostly located in axon terminals and unmyelinated fibers. SP axon terminals contained both clear round vesicles and LGV. SP immunoreactivity was found in LGV, and on the surface of clear round vesicles and outer membrane of mitochondria. Positive LGV were spherical or oval in shape (60～120nm in diameter). The number of LGv was mostly 2～3 in a SP axon terminal. LGV often apposed to the axolemma or scattered in the centre of terminal. LGV were far from the presynaptic sites of the SP terminals which formed synapses. The number of LGV closed to the terminal membrane was significantly (P

ULTRASTRUCTURE OF THE DESCENDING RUBRAL FIBERS IN LAMINA V OF THE CAT TRIGEMINAL SUBNUCLEUS CAUDALIS——HRP LABELING AND DEGENERATION STUDY / 解剖学报

After a injection of kainic acid or WGA-HRP into the red nucleus, the degenerated or HRP labeled terminals in lamina V of the contralateral trigeminal subnucleus caudalis (Vc) were examined electron microscopically. It was found that the degenerated and HRP labeled terminals contained vesicles of spherical or mixed type, and formed symmetrical synapses with medium- or small-sized dendrites. These findings suggested that the descending rubral fibers might be inhibitory in regulating the activity of the neurons, and supposed to be sensory in nature. Thus the red nucleus might play certain role in modulation of the oro-facial somatosensory transmission (including pain) in lamina V of Vc, besides the rubrospinal influence on the involuntary motor functions of the spinal anterior horn. The technique for tracing neural connections with electron microscope was discussed as well.

MORPHOLOGICAL STUDIES OF LARGE DENSE CORE VESICLE NONSYNAPTIC EXOCYTOSIS AND MEMBRANE RECYCLING IN THE TRIGEMINAL SUBNUCLEUS CAUDALIS / 解剖学报

Large dense core vesicle in the trigeminal subnucleus caudalis of the rat has been observed electron microscopically. It is fixed in glutaraldehyde-osmium tetroxide following removal of the skin of the vibrissae areas. The findings of the present study are: 1.Morphological evidence for exocytosis of large dense core vesicle from non-synaptic sites of the axonal terminal has been presented.2. The large coated vesicles equipped with central densities derived from the invagination of the plasma membrane. These observations suggest that membrane recycling occur at location in the terminal via these coated vesicles.3.Some large dense core vesicles may also form the tubular structures which may represent smooth endoplasmic reticulum containing dense material. This study supports the hypothesis that release of the transmitter of the great dense core vesicles occur at nonsynaptic sites by exocytosis.