Pulsed radiofrequency treatment attenuates increases in spinal excitatory amino acid release in rats with adjuvant-induced mechanical allodynia

Ultrahigh frequency transcutaneous electrical nerve stimulation for neuropathic pain alleviation and neuromodulation

A challenging complication in patients with peripheral compressive neuropathy is neuropathic pain. Excessive neuroinflammation at the injury site worsens neuropathic pain and impairs function. Currently, non-invasive modulation techniques like transcutaneous electrical nerve stimulation (TENS) have shown therapeutic promise with positive results. However, the underlying regulatory molecular mechanism for pain relief remains complex and unexplored. This study aimed to validate the therapeutic effect of ultrahigh frequency (UHF)-TENS in chronic constriction injury of the rat sciatic nerve. Alleviation of mechanical allodynia was achieved through the application of UHF-TENS, lasting for 3 days after one session of therapy and 4 days after two sessions, without causing additional damage to the myelinated axon structure. The entire tissue collection schedule was divided into four time points: nerve exposure surgery, 7 days after nerve ligation, and 1 and 5 days after one session of UHF therapy. Significant reductions in pain-related neuropeptides, MEK, c-Myc, c-FOS, COX2, and substance P, were observed in the injured DRG neurons after UHF therapy. RNA sequencing of differential gene expression in sensory neurons revealed significant downregulation in Cables, Pik3r1, Vps4b, Tlr7, and Ezh2 after UHF therapy, while upregulation was observed in Nfkbie and Cln3. UHF-TENS effectively and safely relieved neuropathic pain without causing further nerve damage. The decreased production of pain-related neuropeptides within the DRG provided the therapeutic benefit. Possible molecular mechanisms behind UHF-TENS may result from the modulation of the NF-κB complex, toll-like receptor-7, and phosphoinositide 3-kinase/Akt signaling pathways. These results suggest the neuromodulatory effects of UHF-TENS in rat sciatic nerve chronic constriction injury, including alleviation of neuropathic pain, amelioration of pain-related neuropeptides, and regulation of neuroinflammatory gene expression. In combination with the regulation of related neuroinflammatory genes, UHF-TENS could become a new modality for enhancing the treatment of neuropathic pain in the future.

Novel Pulsed Ultrahigh-frequency Spinal Cord Stimulation Inhibits Mechanical Hypersensitivity and Brain Neuronal Activity in Rats after Nerve Injury

BACKGROUND

Spinal cord stimulation (SCS) is an important pain treatment modality. This study hypothesized that a novel pulsed ultrahigh-frequency spinal cord stimulation (pUHF-SCS) could safely and effectively inhibit spared nerve injury-induced neuropathic pain in rats.

METHODS

Epidural pUHF-SCS (± 3V, 2-Hz pulses comprising 500-kHz biphasic sinewaves) was implanted at the thoracic vertebrae (T9 to T11). Local field brain potentials after hind paw stimulation were recorded. Analgesia was evaluated by von Frey-evoked allodynia and acetone-induced cold allodynia.

RESULTS

The mechanical withdrawal threshold of the injured paw was 0.91 ± 0.28 g lower than that of the sham surgery (24.9 ± 1.2 g). Applying 5-, 10-, or 20-min pUHF-SCS five times every 2 days significantly increased the paw withdrawal threshold to 13.3 ± 6.5, 18.5 ± 3.6, and 21.0 ± 2.8 g at 5 h post-SCS, respectively (P = 0.0002, < 0.0001, and < 0.0001; n = 6 per group) and to 6.1 ± 2.5, 8.2 ± 2.7, and 14.3 ± 5.9 g on the second day, respectively (P = 0.123, 0.013, and < 0.0001). Acetone-induced paw response numbers decreased from pre-SCS (41 ± 12) to 24 ± 12 and 28 ± 10 (P = 0.006 and 0.027; n = 9) at 1 and 5 h after three rounds of 20-min pUHF-SCS, respectively. The areas under the curve from the C component of the evoked potentials at the left primary somatosensory and anterior cingulate cortices were significantly decreased from pre-SCS (101.3 ± 58.3 and 86.9 ± 25.5, respectively) to 39.7 ± 40.3 and 36.3 ± 20.7 (P = 0.021, and 0.003; n = 5) at 60 min post-SCS, respectively. The intensity thresholds for pUHF-SCS to induce brain and sciatic nerve activations were much higher than the therapeutic intensities and thresholds of conventional low-frequency SCS.

CONCLUSIONS

Pulsed ultrahigh-frequency spinal cord stimulation inhibited neuropathic pain-related behavior and paw stimulation evoked brain activation through mechanisms distinct from low-frequency SCS.

EDITOR’S PERSPECTIVE

Elucidating the Mechanisms of Pulsed Radiofrequency for Pain Treatment

Pulsed radiofrequency is a well-documented treatment option for multiple painful conditions where pulses of energy are delivered close to neural elements. Since its earliest adoption, this technique has gained increasing acceptance as a minimally invasive procedure, and new applications are evolving. Studies have shown microscopic and biochemical changes that reflect beneficial effects; however, the exact mechanism of action is not yet completely understood. To redress this paucity, 11,476 articles of scientific relevance published between 1980 and November 2022 were mined through a search of the PubMed database, arriving at 49 studies both in animals and humans. In general, the experimental studies examined have shown that pulsed radiofrequency induces multiple changes with antinociceptive and neuromodulatory effects. These modifications include changes in neural and glial cells, synaptic transmission, and perineural space. Studies also reveal that pulsed radiofrequency regulates inflammatory responses, cellular signaling proteins, and the expression of genes related to pain transmission, acting in biological processes in structures such as myelin, mitochondria, axons, glial cells, connective tissue, regulation of proteins, ion channels, and neurotransmitters.

Ultrasound-guided pulsed radiofrequency for neuromyelitis optica spectrum disorder-associated neuropathic pain: A case report

BACKGROUND

Neuropathic pain (NP) is one of the most prevalent and troublesome symptoms of neuromyelitis optica spectrum disorder (NMOSD), seriously affecting the patient's life. At present, effective treatment for NP induced by NMOSD does not exist. Pulsed radiofrequency (PRF), an emerging microinvasive therapy, alleviates pain and is widely used to treat various types of NP. This is the first report describing a patient with NMOSD-associated NP treated with PRF on the left cervical 6 nerve root.

METHODS

A 49-year-old female with NMOSD-associated severe NP in the left upper limb and left shoulder tried several medications, but none were effective. She was diagnosed with NP caused by NMOSD.To alleviate severe pain, we performed PRF on the left cervical nerve root under the guidance of ultrasound. This treatment was repeated 3 times.

RESULTS

The patient's pain was significantly relieved, with a visual analog scale score decreasing from 7-8/10 to 2-3/10, which was maintained during the 3-month follow-up period, without complications.

CONCLUSION

PRF might be effective for the management of intractable neuropathic pain caused by NMOSD.

Combined Continuous Radiofrequency Ablation and Pulsed Neuromodulation to Treat Cervical Facet Joint Pain and Alleviate Postcervical Radiofrequency Side Effects

Background

Continuous radiofrequency ablation (RFA) can effectively manage cervical facet joint pain related to neuropathic symptoms in the post-radiofrequency period. Additionally, pulse radiofrequency (PRF) provides relief of neuropathic symptoms. However, the effect of combined RFA and PRF has yet to be determined.

Objectives

The study aimed to compare the effectiveness and safety of RFA (CRF group) and combined RFA and PRF (CPRF group).

Methods

The study retrospectively reviewed the charts of patients with cervical facet joint pain undergoing RFA between June 1, 2014, and June 1, 2017, or combined RFA and PRF between June 1, 2017, and June 1, 2020, at a pain research center. Thirty-nine consecutive patients identified from charts meeting the inclusion criteria were included and classified in CRF (n = 22) and CPRF groups (n = 17). The results were evaluated using a Visual Analog Scale (VAS) and neck pain disability index (NDI) before procedures and 1, 3, and 6 months after the injections. Successful treatment was expressed as at least 80% pain relief from baseline and NDI score <15 points. The duration of pain relief was expressed as the period between pain relief and pain reoccurrence to 50% of the preprocedural pain level. The primary outcome was successful treatment in the groups, and the secondary outcome was the duration of pain relief and post-cervical radiofrequency side effects in the groups.

Results

Fourteen (66.7%) patients in the CRF group and 12 (66.7%) in the CPRF group experienced successful treatment at three and six-month follow-ups (P > 0.05). The median time to the reoccurrence of at least 50% of preprocedural pain level was 303.8 days in the CRF group and 270 days in the CPRF group (P = 0.395). However, the CPRF group showed significantly less postoperative numbness, dysesthesia, and hypersensitivity syndrome than the CRF group (P < 0.05).

Conclusions

Combined RFA and PRF can be complementary treatment for cervical facet joint pain, providing an adequate success rate and duration of pain relief as RFA alone but with significantly fewer post-radiofrequency side effects.

Behavioral Survey of Effects of Pulsed Radiofrequency on Neuropathic and Nociceptive Pain in Rats: Treatment Profile and Device Implantation

OBJECTIVES

Pulsed radiofrequency (PRF) stimulation is widely used for intractable pain; however, there is no consensus on treatment protocols and appropriate types of pain. We compared effectiveness of bipolar and unipolar PRF on neuropathic or inflammatory pains, and of targets at the dorsal root ganglion (DRG) and sciatic nerve (SN). We also examined efficacy of repetitive PRF stimulations. This preclinical study could serve as an extensive survey before human trials.

MATERIALS

Spare nerve injury (SNI)-induced neuropathic pain and complete Freund's adjuvant (CFA) injection-induced inflammatory pain were used. Behavioral responses were measured using von Frey test, acetone test, and Hargreave's test at preinjury and postinjury time points. In both models, we evaluated results of DRG stimulation with unipolar PRF (45 V) versus bipolar PRF (5 V), stimulation at DRG vs. SN, and repetitive stimulations.

RESULTS

Both unipolar and bipolar PRFs reduced SNI- or CFA-induced pain for a similar duration. In the SNI model, PRF-DRG had a stronger effect on tactile pain than PRF-SN but lower effect on cold allodynia, whereas in the CFA model PRF-DRG and PRF-SN showed similar effects. Repetitive PRF stimulation, by open technique or implantation method, produced analogous effect by each stimulus, and no evident analgesic tolerance or neurological deficit was shown.

CONCLUSIONS

PRF temporarily attenuates neuropathic and inflammatory pain. Bipolar PRF generates significant analgesia with a much lower electrical power than unipolar PRF. Meanwhile, the minor variant effects between PRF-DRG and PRF-SN may indicate distinct mechanisms. The sustained-analgesia by repetitive treatments suggests implantation technique could be a promising choice.

Microglial BDNF, PI3K, and p-ERK in the Spinal Cord Are Suppressed by Pulsed Radiofrequency on Dorsal Root Ganglion to Ease SNI-Induced Neuropathic Pain in Rats

Background

Pulsed radiofrequency (PRF) on the dorsal root ganglion (DRG) has been applied to alleviate neuropathic pain effectively, yet the mechanisms underlying pain reduction owing to this treatment are not clarified completely. The activated microglia, brain-derived neurotrophic factor (BDNF), phosphatidylinositol 3-kinase (PI3K), and phosphorylated extracellular signal-regulated kinase (p-ERK) in the spinal cord were demonstrated to be involved in developing neuropathic pain. Also, it has been just known that PRF on DRG inhibits the microglial activation in nerve injury rats. Here, we aim to investigate whether PRF treatment could regulate the levels of BDNF, PI3K, and p-ERK in the spinal cord of rats with spared nerve injury (SNI) via suppressing the spinal microglia activation to ease neuropathic pain.

Methods

The rats with SNI were intrathecally treated with minocycline (specific microglia inhibitor) or same volume of dimethyl sulfoxide once daily, beginning from 1 h before nerve transection to 7 days. PRF was applied adjacent to the L₄-L₅ DRG of rats with SNI at 45 V for 6 min on the seventh postoperative day, whereas the free-PRF rats were treated without PRF. The withdrawal thresholds were studied, and the spinal levels of ionized calcium-binding adapter molecule 1 (Iba1), BDNF, PI3K, and p-ERK were calculated by western blot analysis, reverse transcription-polymerase chain reaction, and immunofluorescence.

Results

The paw withdrawal mechanical threshold and paw withdrawal thermal latency decreased in the ipsilateral hind paws after SNI, and the spinal levels of Iba1, BDNF, PI3K, and p-ERK increased on day 21 after SNI compared with baseline (P < 0.01). An intrathecal injection of minocycline led to the reversal of SNI-induced allodynia and increase in levels of Iba1, BDNF, PI3K, and p-ERK. Withdrawal thresholds recovered partially after a single PRF treatment for 14 days, and SNI-induced microglia hyperactivity, BDNF upregulation, and PI3K and ERK phosphorylation in the spinal cord reduced on D14 due to the PRF procedure.

Conclusion

Microglial BDNF, PI3K, and p-ERK in the spinal cord are suppressed by the therapy of PRF on DRG to ease SNI-induced neuropathic pain in rats.

Clinical observation of CT-guided intra-articular conventional radiofrequency and pulsed radiofrequency in the treatment of chronic sacroiliac joint pain

Background

Sacroiliac joint pain (SIJP) is an important cause of low back pain and seriously affects the patients’ quality of life. Therefore, it is urgent to find effective treatment methods.

Objective

To observe the efficacy of intra-articular (IA) conventional radiofrequency (CRF) and pulsed radiofrequency (PRF) treatment of Sacroiliac joint syndrome (SIJS) under computed tomography (CT) guidance.

Study design

Retrospective comparative study.

Setting

Shengjing Hospital of China Medical University.

Patients and methods

Sixty-four patients with SIJS were enrolled in the Pain management. Patients were randomized into two groups: CRF (CRF group, n=32) and PRF (PRF group, n=32). At each observation time, the general condition, visual analog scale (VAS), the total efficiency rate, Oswestry disability index (ODI), and 36-item short-form health survey were followed up.

Results

Compared to the pretreatment value, the VAS and the ODI decreased in both groups after treatment (P<0.05). In the CRF group, the VAS and the ODI decreased significantly at 1 week after treatment (P<0.05); at 6 and 12 months after treatment, the VAS and the ODI were lower than that in the PRF group (P<0.05). The total efficiency rate in the CRF group and PRF group was 56.3% and 31.3%, respectively (P<0.05). After the relief of pain, both groups received different degrees of improvement in the quality of life. Compared to the pretreatment value, physical component summary (PCS) and the mental component summary (MCS) in both groups were increased after treatment (P<0.05); in the CRF group, PCS and MCS increased significantly at 1 week after treatment (P<0.05); and at 6 and 12 months after treatment, PCS and MCS were higher than those in the PRF group (P<0.05).

Conclusion

CT-guided IA PRF and CRF in the treatment of sacroiliac pain are safe and effective. CRF is superior to PRF in the early and late stage. It is recommended for the treatment of SIJP.

Efficacy and Safety of Computed Tomography-Guided Pulsed Radiofrequency Modulation of Thoracic Dorsal Root Ganglion on Herpes Zoster Neuralgia

OBJECTIVE

Pulsed radiofrequency (PRF) can relieve postherpetic neuralgia (PHN) caused by herpes zoster (HZ) infection. Nevertheless, its curative effect can vary and may be related to the duration of treatment period. The following study investigates the efficacy and safety of CT-guided PRF modulation on HZ neuralgia over different periods and different time points.

MATERIALS AND METHODS

A total of 150 patients with HZ/PHN were enrolled at the Pain Department, Shengjing Hospital of China Medical University between January 2013 and December 2016. According to the course of disease, the patients were randomly divided into group A, which included patients with acute stage (n = 50; course <1 m); group B, which included patients with subacute stage (n = 50; 1 m <course <3 m); and group C, which included patients with chronic stage (n = 50; course >3 m). The PRF therapy was performed in all patients by targeting thoracic dorsal root ganglion (DRG). The visual analogue scale (VAS), SF-36, total effective rate of treatment, and dosage of antiepileptic analgesic drugs were observed at different time points, before and after the surgery.

RESULTS

Compared to preoperative time, decreased VAS, improved SF-36, and the decreased dosage of antiepileptic analgesic drugs were observed at all time points, and in all groups after surgery (p < 0.05). In group A, pain relief lasted longer, and it further decreased over time. In addition, significantly lower VAS, higher SF-36, and lower dosage of antiepileptic analgesic drugs were found in group A compared to group B, and in group B compared to group C (all p < 0.05). Furthermore, the total effective rates in groups A, B, and C were 88, 72, and 52%, respectively.

CONCLUSIONS

CT-guided PRF targeting thoracic DRG for modulation of HZ neuralgia in different periods is safe and effective. It is recommended to perform early intervention therapy at the acute phase of HZ.

Transforaminal epidural steroid injection combined with pulsed radio frequency on spinal nerve root for the treatment of lumbar disc herniation

Background

Lumbar disc herniation (LDH) is a common disease in clinical practice. The symptoms recur and are aggravated by time; severe pain and long-term movement disorder cause physiological and psychological problems that affect the quality of life of patients. Therefore, relieving the pain symptoms and promoting functional recovery are the primary goals that have gained increased attention.

Objective

To assess the efficacy of CT-guided transforaminal epidural steroid injection (TFESI) combined with pulsed radio frequency (PRF) on spinal nerve root for the treatment of LDH.

Study design

Retrospective comparative study.

Setting

Shengjing Hospital of China Medical University.

Methods

A total of 135 patients with LDH were selected from the Department of Pain Management in the Shengjing Hospital of China Medical University between January 2014 and December 2016. All patients were divided into three groups according to the order of entry (n=45): TFESI (group A); PRF on spinal nerve root (group B); and TFESI combined with PRF on spinal nerve root (group C). The visual analog scale (VAS), Oswestry disability index (ODI), and global perceived effect (GPE) before treatment and at different time points after treatment were observed, and patients' satisfaction was assessed.

Results

At every point of observation, the VAS and ODI decreased significantly as compared to that before treatment in all groups (P<0.05). The VAS and ODI in group A at 3 and 6 months after treatment were significantly higher than that in the other two groups (P<0.05). At day 1, day 14, and 1 month after treatment, the VAS and ODI in group C were significantly lower than that in group B (P<0.05). The GPE in group C was high in the early days, while that at day 14 and 1 month after treatment was significantly higher than that in the other two groups (P<0.05); no significant difference was observed in GPE at 3 and 6 months after treatment between groups B and C (P>0.05).

Conclusion

TFESI combined with PRF for the treatment of LDH could effectively and rapidly relieve lumbago and radicular pain and achieve long-term remission. Although the method is widely applicable, the precise selection of patients is imperative.

Pulsed Radiofrequency Attenuates Complete Freund's Adjuvant-Induced Epigenetic Suppression of Potassium Chloride Cotransporter 2 Expression

Background

Pulsed radiofrequency (PRF) treatment offers pain relief for patients suffering from chronic pain who do not respond well to conventional treatments. We tested whether PRF treatment attenuated complete Freund's adjuvant (CFA)-induced inflammatory pain. Epigenetic modification of potassium-chloride cotransporter 2 (KCC2) gene expression was examined to elucidate the potential contributing mechanism.

Methods

Male Sprague-Dawley rats were injected with CFA into the plantar surface of the left hind paw to induce inflammation. PRF (20 minutes of 500-kHz RF pulses, delivered at a rate of 2 Hz, maximum temperature 42ºC) was delivered to the L5 and L6 anterior primary ramus just distal to the intervertebral foramen of adult CFA or saline rats. The hind paw withdrawal threshold to von Frey filament stimuli and withdrawal latency to radiant heat were determined before and after CFA. Acetyl-histone H3 and H4 was determined by chromatin immunoprecipitation in spinal dorsal horn. KCC2 expression was determined by Western blot. Inhibitory synaptic function was evaluated by patch clamp in lamina II neurons.

Results

KCC2 gene expression was suppressed through histone hypoacetylation, resulting in decreased efficacy of GABAergic signaling in CFA rats. PRF increased histone acetylation and KCC2 expression, partially restored the GABA synaptic function, and relieved sensitized pain behavior.

Conclusion

These findings suggest that PRF might be an alternative therapy for inflammatory pain. One of the underlying mechanisms is through modification of KCC2, which is an important determinant for the efficacy of inhibitory neurotransmission in the spinal cord, and its expression levels are regulated by histone acetylation epigenetically following inflammation.

A comprehensive review of pulsed radiofrequency in the treatment of pain associated with different spinal conditions

OBJECTIVE

The objective of this review was to evaluate the efficacy of pulsed radiofrequency (PRF) treatment of pain associated with different spinal conditions. The mechanisms of action and biological effects are shortly discussed to provide the scientific basis for this radiofrequency modality.

METHODS

We systematically searched for clinical studies on spinal clinical conditions using PRF. We searched the MEDLINE (PubMed) database. We classified the information in one table focusing on randomized controlled trials (RCTs) and other types of studies. Date of last electronic search was October 2016.

RESULTS

We found four RCTs that evaluated the efficacy of PRF on cervical radicular pain and five observational studies. Two trials and three observational studies were conducted in patients with facet pain. For disc-related pathology, we found one RCT with PRF applied intradiscally and three RCTs for dorsal root ganglia PRF modulation lumbosacral radicular pain. For sacroiliac joint pain, spondylolisthesis, malignancies and other minor spinal pathology, limited studies were conducted.

CONCLUSION

From the available evidence, the use of PRF to the dorsal root ganglion in cervical radicular pain is compelling. With regard to its lumbosacral counterpart, the use of PRF cannot be similarly advocated in view of the absence of standardization of PRF parameters, enrolment criteria and different methods in reporting results; but, the evidence is interesting. The use of PRF in lumbar facet pain was found to be less effective than conventional RF techniques. For the other different spinal conditions, we need further studies to assess the effectiveness of PRF. Advances in knowledge: The use of PRF in lumbar facet pain was found to be less effective than conventional RF techniques. For the other different spinal conditions, we need further studies to assess the effectiveness of PRF.

Epigenetic suppression of potassium-chloride co-transporter 2 expression in inflammatory pain induced by complete Freund's adjuvant (CFA)

BACKGROUND

Multiple mechanisms contribute to the stimulus-evoked pain hypersensitivity that may be experienced after peripheral inflammation. Persistent pathological stimuli in many pain conditions affect the expression of certain genes through epigenetic alternations. The main purpose of our study was to investigate the role of epigenetic modification on potassium-chloride co-transporter 2 (KCC2) gene expression in the persistence of inflammatory pain.

METHODS

Persistent inflammatory pain was induced through the injection of complete Freund's adjuvant (CFA) in the left hind paw of rats. Acetyl-histone H3 and H4 level was determined by chromatin immunoprecipitation in the spinal dorsal horn. Pain behaviour and inhibitory synaptic function of spinal cord were determined before and after CFA injection. KCC2 expression was determined by real time RT-PCR and Western blot. Intrathecal KCC2 siRNA (2 μg per 10 μL per rat) or HDAC inhibitor (10 μg per 10 μL per rat) was injected once daily for 3 days before CFA injection.

RESULTS

Persistent inflammatory pain epigenetically suppressed KCC2 expression through histone deacetylase (HDAC)-mediated histone hypoacetylation, resulting in decreased inhibitory signalling efficacy. KCC2 knock-down caused by intrathecal administration of KCC2 siRNA in naïve rats reduced KCC2 expression in the spinal cord, leading to sensitized pain behaviours and impaired inhibitory synaptic transmission in their spinal cords. Moreover, intrathecal HDAC inhibitor injection in CFA rats increased KCC2 expression, partially restoring the spinal inhibitory synaptic transmission and relieving the sensitized pain behaviour.

CONCLUSION

These findings suggest that the transcription of spinal KCC2 is regulated by histone acetylation epigenetically following CFA.

SIGNIFICANCE

Persistent pain suppresses KCC2 expression through HDAC-mediated histone hypoacetylation and consequently impairs the inhibitory function of inhibitory interneurons. Drugs such as HDAC inhibitors that suppress the influences of persistent pain on the expression of KCC2 may serve as a novel analgesic.

Pulsed radiofrequency attenuates diabetic neuropathic pain and suppresses formalin-evoked spinal glutamate release in rats

BACKGROUND

Pulsed radiofrequency (PRF) has been used to treat chronic pain for years, but its effectiveness and mechanism in treating diabetic neuropathic pain are still unexplored. The aim of this study was to elucidate the modulation of diabetic neuropathic pain induced by streptozotocin and the release of spinal excitatory amino acids by PRF.

METHODS

Diabetes was induced by intraperitoneal administration of streptozotocin. Pulsed radiofrequency was applied to L5 and L6 dorsal roots at 42 °C for 2 min. The responses of all of the groups to thermal, mechanical and cold stimuli were measured for a period of 6 d after this process. Seven days after PRF treatment, intrathecal microdialysis was used to examine the effect of pulsed radiofrequency on the formalin-evoked spinal release of excitatory amino acids and concurrent behaviour responses from diabetic rats.

RESULTS

Three weeks after intraperitoneal streptozotocin treatment and before PRF application, mechanical, thermal and cold hypersensitivity occurred. Application of PRF significantly alleviated hyperglycaemia-induced mechanical, thermal and cold hypersensitivity and also attenuated the increase in formalin-evoked CSF glutamate concentration, compared with sham treated diabetic rats.

CONCLUSION

It may be concluded that PRF has an analgesic effect on neuropathic pain by suppressing the nociception-induced release of excitatory neurotransmitters. PRF may provide a novel promising therapeutic approach for managing diabetic neuropathic pain.

Establishment of a rat model of adjuvant-induced osteoarthritis of the lumbar facet joint

To study the establishment of adjuvant-induced osteoarthritis of the lumbar facet joint in a rat model. Complete Freund's adjuvant (experimental group) and saline (control group) were randomly injected into the right and left side of rat, respectively. The rats were killed, and degeneration of lumbar facet joint was evaluated at macroscopic level and scored based on OARSI scores system. Moreover, Interleukin-1β and tumor necrosis factor-α levels in the synovium were measured. The macroscopic scores and OARSI scores of experimental group were higher than the control group (P < 0.05). The concentration of tumor necrosis factor-α was significantly increased only on 3- and 7-day post-surgery when compared with controls, and interleukin-1β was increased on days 3,7 and 14 post-surgery (P < 0.05). The rat model of adjuvant can induce degeneration of the lumbar facet joint. It can be useful for studies on mechanisms and treatment of lumbar facet joint osteoarthritis.

Pulsed radiofrequency reduced complete Freund's adjuvant-induced mechanical hyperalgesia via the spinal c-Jun N-terminal kinase pathway

Pulsed radiofrequency (PRF) treatment involves the pulsed application of a radiofrequency electric field to a nerve. The technology offers pain relief for patients suffering from chronic pain who do not respond well to conventional treatments. We tested whether PRF treatment attenuated complete Freund's adjuvant (CFA) induced inflammatory pain. The profile of spinal c-Jun N-terminal kinases (JNKs) phosphorylation was evaluated to elucidate the potential mechanism. Injection of CFA into the unilateral hind paw of rats induced mechanical hyperalgesia in both the ipsilateral and contralateral hind paws. We administered 500-kHz PRF treatment in 20-ms pulses, at a rate of 2 Hz (2 pulses per second) either to the sciatic nerve in the mid-thigh, or to the L4 anterior primary ramus just distal to the intervertebral foramen in both the CFA group and no-PRF group rats. Tissue samples were examined at 1, 3, 7, and 14 days following PRF treatments. Behavioral studies showed that PRF applied close to the dorsal root ganglion (DRG) significantly attenuated CFA-induced mechanical hyperalgesia compared to no-PRF group (P < .05). And western blotting revealed significant attenuation of the activation of JNK in the spinal dorsal horn compared to no-PRF group animals (P < .05). Application of PRF close to DRG provides an effective treatment for CFA-induced persistent mechanical hyperalgesia by attenuating JNK activation in the spinal dorsal horn.