OBJECTIVETo explore the patterns of innervation of cervical facet joints and determine the pathways from facet joints to dorsal root ganglions (DRGs) in order to clarify the causes of diffuse neck pain, headache, and shoulder pain.

METHODSForty-two male-Sprague-Dawley rats, weighing 250-300 g, were randomly divided into three groups: Group A (n=18), Group B (n=18), and Group C (n=6). Under anesthesia with intraperitoneal pentobarbital sodium (45 mg/kg body weight), a midline dorsal longitudinal incision was made over the cervical spine to expose the left cervical facet joint capsule of all the rats under a microscope. The rats in Group A underwent sympathectomy, but the rats in Group B and Group C did not undergo sympathectomy. Then 0.6 microlitre 5% bisbenzimide (Bb) were injected into the C1-2, C3-4 and C5-6 facet joints of 6 rats respectively in Group A and Group B. The holes were immediately sealed with mineral wax to prevent leakage of Bb and the fascia and skin were closed. But in Group C, 0.9% normal saline was injected into the corresponding joint capsules. Then under deep re-anesthesia with intraperitoneal pentobarbital sodium (45 mg/kg body weight), C1-C8 left DRGs in all rats and the sympathetic ganglions in Group B were obtained and the number of the labeled neurons was determined.

RESULTSNeurons labeled with Bb were present in C1-C8 DRGs in both Group A and Group B, and sympathetic ganglions in Group B. In the C1-2 and C3-4 subgroups, labeled neurons were present from C1 to C8 DRGs, while in C5-6 subgroups they were from C3 to C8. The number of Bb(+) neurons after sympathectomy was not significantly different in the injected level from that without sympathectomy. But in the other levels, the number of Bb(+) neurons after sympathectomy was significantly less than that without sympathectomy.

CONCLUSIONSThe innervation of the cervical facet joints is derived from both sensory and sympathetic nervous system, and DRGs are associated with sympathetic ganglions through nerve fibers outside the central nerve system.

Animals ; Cervical Vertebrae ; innervation ; Ganglia, Spinal ; cytology ; Ganglia, Sympathetic ; cytology ; Male ; Neurons, Afferent ; cytology ; Rats ; Rats, Sprague-Dawley

Traumatic injury or inflammatory irritation of the peripheral nervous system often leads to persistent pathophysiological pain states. It has been well-documented that, after peripheral nerve injury or inflammation, functional and anatomical alterations sweep over the entire peripheral nervous system including the peripheral nerve endings, the injured or inflamed afferent fibers, the dorsal root ganglion (DRG), and the central afferent terminals in the spinal cord. Among all the changes, ectopic discharge or spontaneous activity of primary sensory neurons is of great clinical interest, as such discharges doubtless contribute to the development of pathological pain states such as neuropathic pain. Two key sources of abnormal spontaneous activity have been identified following peripheral nerve injury: the injured afferent fibers (neuroma) leading to the DRG, and the DRG somata. The purpose of this review is to provide a global account of the abnormal spontaneous activity in various animal models of pain. Particular attention is focused on the consequence of peripheral nerve injury and localized inflammation. Further, mechanisms involved in the generation of spontaneous activity are also reviewed; evidence of spontaneous activity in contributing to abnormal sympathetic sprouting in the axotomized DRG and to the initiation of neuropathic pain based on new findings from our research group are discussed. An improved understanding of the causes of spontaneous activity and the origins of neuropathic pain should facilitate the development of novel strategies for effective treatment of pathological pain.
Animals ; Axotomy ; Ganglia, Spinal ; cytology ; Humans ; Neuralgia ; physiopathology ; Neurons, Afferent ; cytology ; Peripheral Nerve Injuries ; physiopathology ; Spinal Cord ; cytology

The cell body or soma in the dosal root ganglion (DRG) is normally excitable and this excitability can increase and persist after an injury of peripheral sensory neurons. In a rat model of radicular pain, an intraforaminal implantation of a rod that chronically compressed the lumbar DRG ("CCD" model) resulted in neuronal somal hyperexcitability and spontaneous activity that was accompanied by hyperalgesia in the ipsilateral hind paw. By the 5th day after onset of CCD, there was a novel upregulation in neuronal expression of the chemokine, monocyte chemoattractant protein-1 (MCP-1 or CCL2) and also its receptor, CCR2. The neurons developed, in response to topically applied MCP-1, an excitatory response that they normally do not have. CCD also activated non-neuronal cells including, for example, the endothelial cells as evidenced by angiogenesis in the form of an increased number of capillaries in the DRG after 7 days. A working hypothesis is that the CCD induced changes in neurons and non-neuronal cells that may act together to promote the survival of the injured tissue. The release of ligands such as CCL2, in addition to possibly activating nociceptive neurons (maintaining the pain), may also act to preserve injured cells in the face of ischemia and hypoxia, for example, by promoting angiogenesis. Thus, somal hyperexcitability, as often said of inflammation, may represent a double edged sword.
Animals ; Chemokine CCL2 ; metabolism ; Ganglia, Spinal ; cytology ; pathology ; Hyperalgesia ; pathology ; Neuroglia ; cytology ; Nociceptors ; cytology ; Pain ; pathology ; Rats ; Rats, Sprague-Dawley ; Spinal Cord Compression ; physiopathology ; Up-Regulation

The aim of the paper is to study the effect of spontaneous firing of injured dorsal root ganglion (DRG) neuron in chronic compression of DRG (CCD) model on excitability of wide dynamic range (WDR) neuron in rat spinal dorsal horn. In vivo intracellular recording was done in DRG neurons and in vivo extracellular recording was done in spinal WDR neurons. After CCD, incidence of spontaneous discharge and firing frequency enhanced to 59.46% and (4.30 ± 0.69) Hz respectively from 22.81% and (0.60 ± 0.08) Hz in normal control group (P < 0.05). Local administration of 50 nmol/L tetrodotoxin (TTX) on DRG neuron in CCD rats decreased the spontaneous activities of WDR neurons from (191.97 ± 45.20)/min to (92.50 ± 30.32)/min (P < 0.05). On the other side, local administration of 100 mmol/L KCl on DRG neuron evoked spontaneous firing in a reversible way (n = 5) in silent WDR neurons of normal rats. There was 36.36% (12/33) WDR neuron showing after-discharge in response to innocuous mechanical stimuli on cutaneous receptive field in CCD rats, while after-discharge was not seen in control rats. Local administration of TTX on DRG with a concentration of 50 nmol/L attenuated innocuous electric stimuli-evoked after-discharge of WDR neurons in CCD rats in a reversible manner, and the frequency was decreased from (263 ± 56.5) Hz to (117 ± 30) Hz (P < 0.05). The study suggests that the excitability of WDR neurons is influenced by spontaneous firings of DRG neurons after CCD.
Action Potentials ; Animals ; Ganglia, Spinal ; physiology ; Neurons ; physiology ; Rats ; Rats, Sprague-Dawley ; Spinal Cord Dorsal Horn ; cytology

In this study, the expressions of growth hormone secretagogue receptor type 1a (GHS-R1a) in the rat dorsal root ganglion (DRG) and nodose ganglion (NG) were investigated by using immunohistochemistry and in situ hybridization. The results clearly showed the presence of GHS-R1a mRNA and GHS-R1a-positive neurons in the rat DRG and NG. GHS-R1a was also co-localized with calcitonin gene-related peptide (CGRP) in some DRG and NG neurons, indicating the existence of subpopulations of the visceral afferents. The extrinsic primary afferent visceroceptive DRG and NG neurons from the stomach were identified by retrograde tracing fluorogold and stained for GHS-R1a and CGRP. Some neurons both positive for CGRP and GHS-Rla were labled by fluorogold. Our results not only demonstrate the expression of GHS-R1a in the vagal afferents but also provide the first and direct morphological evidence for its presence in the spinal visceral afferents, and gherin might have a modulatory role in the visceral afferent signaling.
Afferent Pathways ; Animals ; Calcitonin Gene-Related Peptide ; metabolism ; Ganglia, Spinal ; cytology ; Immunohistochemistry ; Neurons, Afferent ; cytology ; Nodose Ganglion ; cytology ; Rats ; Receptors, Ghrelin ; metabolism ; Stomach ; innervation

Different physical and chemical stimuli are detected by the peripheral sensory receptors of dorsal root ganglion (DRG) neurons, and the generated inputs are transmitted via afferent fibers into the central nervous system. The gene expression profiles of DRG neurons contribute to the generation, transmission, and regulation of various somatosensory signals. Recently, the single-cell transcriptomes, cell types, and functional annotations of somatosensory neurons have been studied. In this review, we introduce our classification of DRG neurons based on single-cell RNA-sequencing and functional analyses, and discuss the technical approaches. Moreover, studies on the molecular and cellular mechanisms underlying somatic sensations are discussed.
Animals ; Ganglia, Spinal ; cytology ; Gene Regulatory Networks ; Humans ; Pain ; genetics ; metabolism ; pathology ; Sensory Receptor Cells ; metabolism ; Sequence Analysis, RNA ; Transcriptome

To study the acute and long-term effects of local gut inflammation on the sensitivity of the spinal sensory neurons, the expressions of vanilloid receptor 1 (VR1) and calcitonin gene-related peptide (CGRP) in the colon-innervated primary sensory neurons in dorsal root ganglia (DRG) were examined in rats with trinitrobenzenesulfonic acid (TNBS)-induced experimental colitis. The neurons projecting to the distal colon were identified by DiI(3) retrograde labelling. Macroscopic examination, mean damage score and myeloperoxidase (MPO) activity were determined to assess the inflammatory status of the colon tissue. The number of CGRP and VR1 immunoreactive neurons at different stages of inflammation (on days 7, 21 and 42 after TNBS treatment) were compared. On day 7 after TNBS treatment, macroscopic damage of the mucosa could be easily detected and the percentage of colon-innervated DRG neurons expressing CGRP and VR1 increased nearly two folds respectively [(95.38±9.45)% vs (42.86±.02)% for CGRP, (89.23±8.21)% vs (32.54±4.58)% for VR1]. When the colon inflammatory reaction was resolved on days 21 and 42 after TNBS treatment, the percentage of colon-innervated DRG neurons expressing CGRP and VR1 were still higher than that in the control group [(86.25±8.21)%, (68.28±7.12)% vs (42.86±5.02)% for CGRP; (67.22±6.52)%, (56.25±4.86)% vs (32.54±4.58)% for VR1]. These results suggest that the local gut inflammation increases the expressions of CGRP and VR1 in gut-innervated DRG sensory neurons. More importantly, this abnormal status persists even after the gut inflammatory reaction has been resolved for certain time.
Animals ; Calcitonin Gene-Related Peptide ; metabolism ; Colitis ; physiopathology ; Colon ; innervation ; Ganglia, Spinal ; cytology ; Inflammation ; physiopathology ; Neurons, Afferent ; cytology ; Rats ; Rats, Sprague-Dawley ; Sensory Receptor Cells ; cytology ; Spinal Cord ; cytology ; TRPV Cation Channels ; metabolism

OBJECTIVETo investigate the effects of ropivacaine on Gamma-aminobutyric acid(GABA)-activated currents in dorsal root ganglion (DRG) neurons in rats and discuss the analgesia mechanism of ropivacaine.

METHODSBy means of using whole-cell patch-clamp technique, to investigate the modulatory effects of ropivacaine on GABA-activated currents (I(GABA)) in acutely isolated dorsal root ganglion neurons.

RESULTS(1) In 48 out of 73DRG cells (65.7%, 48/73), to perfusion ropivacaine bromide (0.1 - 1 000 micromol/L) were sensitive. Which produce in 0 to 380 pA current. (2) The majority of the neurons examined (74.5%, 73/98) were sensitive to GABA. Concentration of 1 - 1 000 micromol/L GABA could activate a concentration-dependent inward current, which manifested obvious desensitization, and the inward currents could be blocked byGABA-receptor selective antagonist of bicuculline (100 micromol/L). (3) After the neurons were treated with ropivacaine (0.1 - 1000 micromol/L) prior to the application of GABA (100 micromol/L) 30 s, GABA currents were obviously increased. Ropivacaine could make dose-response curve of the GABA up, EC50 is 23.46 micromol/L. Ropivacaine shifted the GABA dose-response curve upward and increased the maximum response to the contrast about 153%.

CONCLUSIONThe enhancement of ropivacaine to DRG neurons activation of GABA current, can lead to enhancement of pre-synaptic inhibition at the spinal cord level. This may be one of the reasons for the anesthetic effect and analgesia for ropivacaine in epidural anesthesia.

Amides ; pharmacology ; Animals ; Ganglia, Spinal ; cytology ; physiology ; Membrane Potentials ; drug effects ; Neurons ; cytology ; drug effects ; physiology ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; Receptors, GABA-A ; physiology

OBJECTIVETo construct the co-culture models of salivarya denoid cystic carcinoma (SACC) cells and dorsal root ganglia (DRG) of chickens and investigate the promotive effects of SACC on neural tissue.

METHODSGlass-base culture dish was adopted to construct co-culture model of SACC-83 cells and DRG. SACC-83 cells were seeded in the medium pore with DRG around them. Outgrowth of neuronal processes was observed. Then DRG was cultured in the conditioned medium of SACC-83, with the groups of conditioned medium of MC3T3-E1 and HGF, the group of cell lysis buffer, the groups of serum-free medium and serum-plus medium as the controls. Outgrowth of neuronal processes was also recorded and compared with control groups.

RESULTSIn the co-culture model of tumor and neuronal tissue, SACC-83 cells produced a suitable microenvironment in which neuronal processes remarkably grow. Neuronal processes of most DRG displayed growth tendency toward SACC. The group of conditioned medium from SACC-83 manifested obvious promotive effects on DRG.

CONCLUSIONSCo-culture model of tumor and neuronal tissue was successfully constructed, with which the promotive effects of tumor on outgrowth of neuronal processes could be observed. So hypothesized that SACC could secrete some neurotrophic factors to guide peripheral nerves gemmating and to trigger the cascade of the neural invasion in succession.

Animals ; Carcinoma, Adenoid Cystic ; pathology ; Cell Line ; Cell Line, Tumor ; Chickens ; Coculture Techniques ; Culture Media ; Ganglia, Spinal ; growth & development ; Gingiva ; cytology ; Humans ; Osteoblasts ; cytology ; Salivary Gland Neoplasms ; pathology

It has proven difficult to use systemic administration of small molecules to selectively modulate nociception. Over the past decade, we and others have developed non-replicating herpes simplex virus (HSV)-based vectors to treat chronic pain. Subcutaneous inoculation of an HSV vector effectively transduces sensory neurons in the dorsal root ganglion; release of transgene-coded inhibitory neurotransmitters or anti-inflammatory peptides reduces pain-related behaviors in rodent models of chronic inflammatory and neuropathic pain. A phase 1 trial of this therapy in patients is set to begin soon.
Animals ; Chronic Pain ; therapy ; Disease Models, Animal ; Ganglia, Spinal ; cytology ; Gene Transfer Techniques ; Genetic Vectors ; Humans ; Neuralgia ; therapy ; Neurons, Afferent ; cytology ; Simplexvirus