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One of the physiological changes accompanying neuropathic pain from nerve injury is the spontaneous firing of primary afferent fibers. At least some of this activity is thought to arise from the dorsal root ganglion. We have investigated whether this activity is resident in the cell bodies of dorsal root ganglion neurons and if it is retained in vitro. Dorsal root ganglion neurons from rats with...
The efficacy of radiofrequency lesion treatment of the cervical dorsal root ganglion (RF-DRG) in cervicobrachialgia was investigated in 61 patients by a randomized prospective double blinded study. Before lesion treatment the putative pain provoking spinal root was identified by diagnostic blocks with a local anesthetic agent. One group of patients (n=32, group I) was treated with a radiofrequency...
Under anesthesia and sterile surgery, a small stainless steel rod (4 mm in length and 0.5-0.8 mm in diameter) was inserted into the L5 intervertebral foramen in the rat, developing intervertebral foramen stenosis and hence producing a chronic steady compression of the dorsal root ganglion (DRG). The hind paw on the injured side exhibited a significant reduction in the latency of foot withdrawal to...
Pulse radiofrequency has been recently described as a technique to apply a relatively high voltage near a nerve but with out the usual effects of a rise in temperature or subsequent nerve injury. In this set of case reports, the effect of pulsed radiofrequency (PRF) is described in patients with neuropathic pain syndromes which have been poorly controlled with other oral and invasive treatments. Whilst...
P 2X3 purinoceptor cellular distribution was studied in rat sensory neurons in naive animals and following peripheral nerve injury using immunohistochemical methods. Specific antiserum was raised in rabbits and characterized by Western blot, absorption assays and labeling of recombinant receptors. In naive animals, P 2X3 immunoreactivity was present predominantly...
Increased excitability of primary sensory neurons may be important for the generation of neuropathic pain from nerve injury. The currents underlying the action potentials of these neurons are largely carried by Na + , and changes in Na + currents have been postulated to contribute to this increased excitability. Using patch clamp in whole-cell mode, we recorded Na + currents...
The cell soma of primary afferent neurons in the dorsal root ganglion (DRG) is assigned by classical neurophysiology the role of a metabolic depot, charged with supporting the peripheral sensory ending, the conducting axon, and the central synaptic terminals. However, certain peculiarities of DRG morphology and physiology do not sit well with this being its only role. For example, why are DRG cell...
The pathways, synapses and molecules involved in pain processing in the newborn are not only required to trigger repair and recuperation but are also involved in the process of forming a mature nervous system. Sensory neurons in the dorsal root ganglion and dorsal horn express a phenomenal array of molecules which contribute to their structural and functional characteristics and many of these are...
The present study assessed the effect of a single subcutaneous injection of resiniferatoxin (RTX), an ultrapotent capsaicin analogue, on the activity of spinal cholecystokinin (CCK) systems, by using electrophysiological and in situ hybridization techniques. Subcutaneous RTX at 0.3 mg/kg, but not vehicle, produced marked thermal hypoalgesia in rats on the hot plate and tail flick tests. Partial recovery...
Injured afferent neurons produce spontaneous activity that is generated away from the normal impulse generation site. Since this activity, referred to as ectopic discharges, may play a significant role in neuropathic pain, it is important to systematically analyze the activity in various pain states. The present study used the segmental spinal nerve injury model of neuropathic pain to quantify the...
We examined the relation between ectopic afferent firing and tactile allodynia in the Chung model of neuropathic pain. Transection of the L5 spinal nerve in rats triggered a sharp, four- to six-fold increase in the spontaneous ectopic discharge recorded in vivo in sensory axons in the ipsilateral L5 dorsal root (DR). The increase, which was not yet apparent 16 h postoperatively, was complete by 24...
Transection of the L5 spinal nerve in rats results in allodynia- and hyperalgesia-like behavior to mechanical stimulation which are thought to be mediated by ectopic activity arising in lesioned afferent neurons mainly in the dorsal root ganglion (DRG). It has been suggested that the neuropathic pain behavior is dependent on the sympathetic nervous system. In rats 3-56 days after L5 spinal nerve lesion,...
Nerve growth factor (NGF) regulates the nociceptive properties including sensitivity to capsaicin of a subset of dorsal root ganglion neurons, which express the high-affinity NGF receptor, trkA. Capsaicin sensitivity co-localizes with the expression of a cloned capsaicin receptor, vanilloid receptor type 1 (VR-1), which displays properties similar to the native capsaicin response. To determine whether...
The aim of this study was to investigate the postnatal development of μ-(MOR) and δ-opioid receptor (DOR) immunoreactivity in rat dorsal root ganglia. Lumbar dorsal root ganglia (DRG) from postnatal day (P) 0, 3, 7 and 21 rat pups were immunostained for MOR and DOR. Proportions of MOR +ve and DOR +ve cells were calculated from profile counts. Diameters of MOR +ve and DOR +ve cells were measured and...
The P2X 3 receptor is a ligand-gated cation channel activated by the binding of extracellular adenosine 5'-triphosphate (ATP), an agent that has been suggested to have a role in the nociceptive pathway after tissue and nerve injury. After peripheral nerve injury, both down regulation and up regulation of the P2X 3 receptor in sensory ganglion neurons have been observed. The purpose...
Protein kinase A (PKA) can play a critical role in the modulation of neuronal excitability. We examined the role of PKA in the modulation of abnormal spontaneous activity (SA) originating from the chronically compressed dorsal root ganglion (CCD). The L 4 and L 5 dorsal root ganglia (DRGs) were compressed by inserting a stainless steel rod into each corresponding intervertebral foramen...
The release of cytosol from damaged cells has been proposed to be a chemical trigger for nociception. K + , H + , adenosine triphosphate (ATP), and glutamate are algogenic agents within cytosol that might contribute to such an effect. To examine which, if any, compounds in cytosol activate ion channels on nociceptors, we recorded currents in dissociated nociceptors when nearby skin...
To study the role of inflammatory cytokines in the initiation and persistence of radiculopathy as seen in humans, tumor necrosis factor α (TNF-α) was administered either to normal, uninjured L 5 dorsal root ganglia (DRG) of rats via a hole drilled through the transverse process, or to chronically compressed L 5 DRG via a hollow stainless steel rod inserted into the intervertebral foramen...
We investigated the expression of two candidate transducers of noxious stimuli in peripheral tissues, the vanilloid receptor subtype 1 (VR1) and the P2X 3 , a subunit of the ionotropic P2X receptor for ATP, in spared L4 DRG neurons following L5 spinal nerve ligation, a neuropathic pain model. VR1 mRNA expression increased in the small- and medium-sized DRG neurons from the first to 28th day...
A variety of molecules released by inflammatory reactions in the dorsal root and dorsal root ganglion (DRG) may play important roles in the pathology of neuronal abnormalities in lumbar disc herniation. In order to elucidate the pathophysiological mechanisms of painful radiculopathy, secondary to lumbar disc herniation, we evaluated pain-related behavior and the change of nerve growth factor (NGF)...
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