Prediction of the Efficacy of Lumbar Sympathetic Block in Patients with Lower Extremity Complex Regional Pain Syndrome Type 1 Based on the Sympathetic Skin Response

INTRODUCTION

Complex regional pain syndrome type 1 (CRPS-1) is prevalent after trauma, with intractable pain being the most prominent clinical symptom. The impact of sympathetic block on CRPS is unclear. The goal of this study was to explore the characteristics that predict successful symptom relief with lumbar sympathetic block (LSB) in patients with lower extremity CRPS-1.

METHODS

The study was designed as a prospective cohort study. Ninety-eight patients diagnosed with lower extremity CRPS-1 between March 2021 and March 2022 were enrolled as participants. All of the patients received two LSB treatments within a month. Sympthetic skin response (SSR) and numeric rating scale (NRS) were recorded before and after LSB treatment. The procedure was judged as a clinically positive response if the patients a 50% or greater reduction in NRS scores. Patients were divided into positive response and negative response groups after LSB treatment: LSB (+) and LSB (-), and the different characteristics and examination findings of the two groups of patients were compared. Furthermore, a multivariable logistic regression model was utilized to evaluate the predictors of successful symptom relief following LSB treatment.

RESULTS

A total of 43.9% (43/98) of patients experienced successful symptom relief, while 56.1% (55/98) had unsuccessful symptom relief. After LSB treatment of all subjects, the overall NRS score decreased, the SSR amplitude increased, and the SSR latency shortened in the affected extremity (P < 0.05). There was a significant difference in the change in SSR amplitude between the LSB (-) and LSB (+) groups (P = 0.000). A 12-month disease duration had an OR (odds ratio) of 4.477 (P = 0.009), and a 510-µV baseline SSR amplitude of the affected extremity had an OR of 7.508 (P = 0.000) in the multivariable analysis that included these explanatory variables.

CONCLUSIONS

Patients with lower extremity CRPS-1 can experience significant pain relief after LSB treatment. The predictors of successful symptom relief after LSB treatment were a baseline SSR amplitude of the affected extremity < 510 µV and a disease duration < 12 months.

TRIAL REGISTRATION

The study was registered in the Chinese Clinical Trial Registry (ID: ChiCTR2000037755, date of registration: September 4, 2020).

Musical therapy attenuates neuroma pain by modifying leptin expression

BACKGROUND

Accumulating evidence reveals that music therapy appears to help patients with pain. However, there is a limited understanding of the underlying mechanisms. Several studies indicate that leptin level has a crucial relationship with acute and chronic pain. Herein, we evaluated the effects of music stimulation and the potential roles of adipokines (leptin) in pain behaviors.

METHODS

We used a tibial neuroma transposition (TNT) rat model to mimic neuroma pain. Adult male Sprague-Dawley rats were randomly assigned to one of the three groups (n = 6):group 1 (GC), TNT with white noise; group 2(GM), TNT with music; and group 3(GH), TNT. White noise and music stimulation was given once a day following surgery until the end of the study (42^nd day). Pain behavioral tests were carried out before surgery and on the 3^rd, 10^th, 14^th, 21^st, 28^th, 35^th, and 42^nd days after surgery. At the end of the observation period, we analyzed the histological samples of blood, spinal cord, and prefrontal cortex to investigate the role of leptin in pain behaviors modulated by white noise and sound stimulation.

RESULT

Music therapy might improve the pain of TNT rats. Music stimulation ameliorated paw withdrawal thermal latency (PWTL) from the 3^rd day after the surgery while the mechanical pain was improved 21 days after the operation.Music stimulation also increased leptin expression in the spinal cord, prefrontal cortex.White noise had no obvious effect.

CONCLUSION

Music therapy might improve the pain of TNT rats. Besides, music stimulation ameliorated TNT-induced pain behaviors and affected leptin expression.

Visualizing stellate ganglion with US imaging for guided SGB treatment: A feasibility study with healthy adults

Objective

As for ultrasound (US) guided stellate ganglion (SG) block, unsatisfactory curative outcomes and complications still remain. This problem could be greatly improved by identifying and monitoring SG. To the best of our knowledge, there are few reports to directly visualize SG in literature. This study explored the feasibility of detection of SG and summarized the findings of SG through US.

Methods

Fifty healthy adults with 100 SGs were enrolled. The size, shape, echogenicity, margin, the inferior pole of SG, the relationship between the superior pole of SG and the transverse process, the relationship between the superior pole of SG and the inferior thyroid artery, and the relationships between SG and other surrounding tissues were evaluated by US.

Results

The SG was identified in 79% of the participants. No significant differences were found between the right and left sides regarding thickness, cross-sectional area (CSA), and position (all p > 0.05); however, there was a significant difference in the width of the right and left sides (p < 0.05). Side was associated with SG visibility (p < 0.05), however, the gender was not (p > 0.05). A total of 42% of SGs were oval-shaped. All SGs were hyperechogenic and had an ill-defined margin. In fact, 63% of SGs were located in the C7 transverse process level, 77% of SGs were located under the inferior thyroid artery, and all of these SGs were located lateral to the thyroid and medial to the anterior scalene muscle and the vagus nerve.

Conclusion

Our preliminary study demonstrates that US imaging provides the capability of detecting SG. This may be helpful in minimizing complications and improving the accuracy of US-guided SG block.

Mechanosensitive Ion Channel TMEM63A Gangs Up with Local Macrophages to Modulate Chronic Post-amputation Pain

Post-amputation pain causes great suffering to amputees, but still no effective drugs are available due to its elusive mechanisms. Our previous clinical studies found that surgical removal or radiofrequency treatment of the neuroma at the axotomized nerve stump effectively relieves the phantom pain afflicting patients after amputation. This indicated an essential role of the residual nerve stump in the formation of chronic post-amputation pain (CPAP). However, the molecular mechanism by which the residual nerve stump or neuroma is involved and regulates CPAP is still a mystery. In this study, we found that nociceptors expressed the mechanosensitive ion channel TMEM63A and macrophages infiltrated into the dorsal root ganglion (DRG) neurons worked synergistically to promote CPAP. Histology and qRT-PCR showed that TMEM63A was mainly expressed in mechanical pain-producing non-peptidergic nociceptors in the DRG, and the expression of TMEM63A increased significantly both in the neuroma from amputated patients and the DRG in a mouse model of tibial nerve transfer (TNT). Behavioral tests showed that the mechanical, heat, and cold sensitivity were not affected in the Tmem63a^-/- mice in the naïve state, suggesting the basal pain was not affected. In the inflammatory and post-amputation state, the mechanical allodynia but not the heat hyperalgesia or cold allodynia was significantly decreased in Tmem63a^-/- mice. Further study showed that there was severe neuronal injury and macrophage infiltration in the DRG, tibial nerve, residual stump, and the neuroma-like structure of the TNT mouse model, Consistent with this, expression of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β all increased dramatically in the DRG. Interestingly, the deletion of Tmem63a significantly reduced the macrophage infiltration in the DRG but not in the tibial nerve stump. Furthermore, the ablation of macrophages significantly reduced both the expression of Tmem63a and the mechanical allodynia in the TNT mouse model, indicating an interaction between nociceptors and macrophages, and that these two factors gang up together to regulate the formation of CPAP. This provides a new insight into the mechanisms underlying CPAP and potential drug targets its treatment.

The Tourniquet Ischemia Test Effectively Predicts the Efficacy of Lumbar Sympathetic Block in Patients with Lower Extremity Complex Regional Pain Syndrome Type 1

Background

Neuropathic pain is the most common clinical sign of complex regional pain syndrome (CRPS). Currently, lumbar sympathetic block (LSB) is commonly utilized in lower extremity CRPS that has failed to respond to medication therapy and physical therapy, but its effectiveness is unknown. The tourniquet ischemia test (IT) can distinguish between two types of CRPS: IT-positive CRPS and IT-negative CRPS.

Objective

The aim of the study was to investigate whether LSB improves pain scores in patients with lower extremity CRPS-1 and to screen factors to predict its efficacy.

Study Design

Prospective clinical observational study.

Setting

Pain management center.

Subjects

Forty-three patients diagnosed with lower extremity CRPS-1 using the Budapest criteria were included as participants.

Methods

Forty-three CRPS-1 patients were treated with LSB therapy, and all of them underwent a tourniquet ischemia test (IT) before undergoing LSB therapy. LSB therapy was performed using a combination of ultrasonography and fluoroscopy. Then, numeric rating scale (NRS) scores and the symptom relief rates of patients were evaluated at 1, 4, and 12 weeks. Finally, peripheral blood inflammatory cytokine samples were collected before and after the LSB treatment.

Results

At 4 weeks after the treatment, the total effective symptom relief rate of LSB on CRPS-1 was 25.6% (11/43), with 52.6% (10/19) of IT(+) patients and 4.2% (1/24) of IT(-) patients. There was a significant difference between the IT(-) and IT(+) groups (P = 0.001). The multivariate binary logistic regression analysis revealed that the response to the tourniquet IT was the only significant independent predictor of sympathetic block success (p = 0.007).

Conclusion

Tourniquet IT is a simple, safe and effective test to distinguish patients with lower extremity CRPS-1. The response to the tourniquet IT is a reliable predictor of LSB effectiveness in lower extremity CRPS-1 patients.

Ultrasound-Guided Extraforaminal Thoracic Nerve Root Block Through the Midpoint of the Inferior Articular Process and the Parietal Pleura: A Clinical Application of Thoracic Paravertebral Nerve Block

Purpose

Thoracic nerve root (TNR) block is performed primarily under computed tomography or X-ray fluoroscopy but is associated with radiation exposure. Ultrasound requires no radiation and distinguishes vessels, nerves, pleura, and other tissues. Few reports of ultrasound-guided TNR (US-TNR) block have been described, and the puncture end point has not been clearly defined. Herein, we evaluated the feasibility of US-TNR block using the midpoint of the inferior articular process (IAP) and parietal pleura (PP) as the puncture end point.

Patients and Methods

A prospective series of 10 patients with Herpes Zoster-associated pain underwent US-TNR-guided block performed using an in-plane technique with the midpoint of thoracic IAP and PP as the puncture end points of ultrasonography. The US-TNR block procedure was performed with ultrasound as the primary imaging tool followed by fluoroscopic confirmation.

Results

In all patients, the needle tips were visible at the lateral margin of the pedicle in the anteroposterior view and at the extraforaminal zone in the lateral view. The TNR and dorsal root ganglion (DRG) were delineated in all 10 patients. Furthermore, 2 mL of radiopaque agent could delineate the epidural space in 8 patients and the thoracic paravertebral (TPV) space in the other 2 patients. All patients developed numbness along the corresponding dermatome 30 min after injection of local anesthetics. The numeric rating scale (NRS) score at baseline, and at two- and four-week follow-ups were 6.50 ± 1.35, 3.50 ± 0.85 (vs NRS at baseline, P < 0.01), and 4.00 ± 0.82 (vs NRS at baseline, P < 0.01), respectively.

Conclusion

This study demonstrated the feasibility of US-TNR block using the in-plane technique with the midpoint of thoracic IAP and PP as the puncture end point to effectively block the TNR and DRG. This technique is an accurate clinical application of TPV nerve block and provides a potential therapeutic option for the treatment of neuropathic pain.

US-Guided Transforaminal Cervical Nerve Root Block: A Novel Lateral in-Plane Approach

OBJECTIVE

The aim of the present study was to investigate the effectiveness and safety of a novel lateral in-plane approach for ultrasound-guided transforaminal cervical nerve root block (US-guided TF-CNRB) in the treatment of cervical radiculopathic pain.

DESIGN

The design of the present study consisted of an institutional, retrospective case series.

SETTING

The present study was conducted at a university hospital.

SUBJECTS

Thirty-two patients with cervical radiculopathy who were resistant to conservative therapies and regular US-guided CNRB were included as participants.

METHODS

The included patients were treated with US-guided TF-CNRB. During the treatments, using real-time fluoroscopy, we monitored the spreading patterns of a contrast medium and double confirmed the positions of needle tips. Pain numeric rating scales (NRS) and symptom relief grades were determined via telephone interviews at one, four, and 12 weeks after the procedures.

RESULTS

US-guided TF-CNRB was performed at the C5 level in six patients, the C6 level in 18 patients, and the C7 level in eight patients. Compared with NRS at baseline, pain scores decreased throughout the observation period. Symptom relief rates of US-guided TF-CNRB at one, four, and 12 weeks were 72%, 69%, and 63%, respectively. Venous blood was aspirated during the procedures in two patients, and the needle tips were corrected. No intravascular injections or neurologic injuries were observed.

CONCLUSION

US-guided TF-CNRB produced circumferential spreading around the involved cervical nerve root and showed significant clinical effectiveness in patients resistant to regular US-guided CNRB.

Radar-based sleep stage classification in children undergoing polysomnography: a pilot-study

STUDY OBJECTIVES

Unobtrusive monitoring of sleep and sleep disorders in children presents challenges. We investigated the possibility of using Ultra-Wide band (UWB) radar to measure sleep in children.

METHODS

Thirty-two children scheduled to undergo a clinical polysomnography participated; their ages ranged from 2 months to 14 years. During the polysomnography, the children's body movements and breathing rate were measured by an UWB-radar. A total of 38 features were calculated from the motion signals and breathing rate obtained from the raw radar signals. Adaptive boosting was used as machine learning classifier to estimate sleep stages, with polysomnography as gold standard method for comparison.

RESULTS

Data of all participants combined, this study achieved a Cohen's Kappa coefficient of 0.67 and an overall accuracy of 89.8% for wake and sleep classification, a Kappa of 0.47 and an accuracy of 72.9% for wake, rapid-eye-movement (REM) sleep, and non-REM sleep classification, and a Kappa of 0.43 and an accuracy of 58.0% for wake, REM sleep, light sleep and deep sleep classification.

CONCLUSION

Although the current performance is not sufficient for clinical use yet, UWB radar is a promising method for non-contact sleep analysis in children.

Tamoxifen attenuates reactive astrocyte-induced brain metastasis and drug resistance through the IL-6/STAT3 signaling pathway

Brain metastasis affects approximately 20%-30% of patients with triple-negative breast cancers (TNBCs). Even small metastatic lesions in the brain can trigger severe neurological impairments and result in extremely short survival time. Recently, active astrocytes were reported to be associated with brain metastases. However, how activated astrocytes regulate the behaviors of disseminated breast cancer cells in the brain remains unknown. In this study, human primary astrocytes were stimulated with IL-1β to form active astrocytes to study the cross-talk between stromal cells (astrocytes) and TNBC cells in brain metastases. Our results showed that active astrocytes significantly increase the malignancy of TNBC cells and prevent them from undergoing apoptosis caused by doxorubicin. We also found that the high level of IL-6 secreted by activated astrocytes was responsible for the drug resistance of breast cancer, which could be abolished by treatment of astrocytes with tamoxifen (TAM). The blockage of active astrocyte-derived IL-6 by a neutralizing antibody resulted in the attenuation of drug resistance, consequently enhancing the sensitivity of breast cancer cells to doxorubicin. Furthermore, the possible involved TAM-modulated drug resistance mechanism may be associated with a decrease in IL-6 expression in astrocytes and the downregulation of MAPK and JAK2/STAT3 signaling in cancer cells. Our data suggested that TAMs might reduce drug resistance through the IL-6/JAK2/STAT3 signaling pathway, providing a possible therapy to treat brain metastasis in TNBCs, as estrogen receptor inhibitors (TAMs, etc.) can cross the blood-brain barrier.

Ultrasonography-Guided Radiofrequency Ablation for Painful Stump Neuromas to Relieve Postamputation Pain: A Pilot Study

Objective

Postamputation pain (PAP) is a serious problem, and thus far, there is no perfect treatment strategy. Clinically, minimally invasive treatments for peripheral neuromas are simple and feasible. This study aimed to investigate the immediate and long-term effects of ultrasonography-guided radiofrequency ablation (RFA) on PAP.

Methods

Eighteen PAP subjects with painful peripheral neuromas were treated with ultrasonography-guided RFA.

Results

A total of 18 PAP subjects were included in the final analyses. Fourteen of the 17 subjects with residual limb pain (RLP) (82.4%) had successful outcomes. A successful outcome was noted in 9 of the 13 subjects with phantom limb pain (PLP) (69.2%). There were no significant associations between symptom relief and sex, age, or the duration of symptoms. There were no severe complications.

Conclusions

Ultrasonography-guided RFA for painful stump neuromas can effectively relieve stump pain and PLP in amputees with PAP (follow-up time was 12 months). Ultrasonography-guided RFA is easy and safe and does not involve radiation exposure, making it very suitable for clinical applications.

Deficiency of SHANK3 isoforms impairs thermal hyperalgesia and dysregulates the expression of postsynaptic proteins in the spinal cord

SHANK3 is one of the scaffolding proteins in the postsynaptic density (PSD). Pain perception and underlying mechanisms were investigated in Shank3 exon 21 deficient (Shank3^△C) mice. Sixty-six mice were attributed according to their genotype to three groups: (1) wild-type (WT), (2) heterozygous Shank3^△C/+, and (3) homozygous Shank3^△C/△C. Complete Freund's adjuvant (CFA) was used to induce inflammatory pain, and thermal hyperalgesia was determined. CFA treatment reduced the thermal threshold in the WT group; groups expressing mutations of Shank3 (^△C/+ and ^△C/△C) had higher thresholds after CFA administration compared to the WT group. Mice with Shank3 mutations (^△C/+ or ^△C/△C) had a lower expression of GluN2A and IP₃R proteins and a higher expression of mGluR5 protein in the PSD compared to WT mice without changes in GluN1, GluN2B, and Homer expression. The crosslinking of Homer-IP₃R, but not Homer-mGluR5, was decreased in the total lysate. Deficit of Shank3 exon 21 may lead to impaired perception of thermal pain in mice under inflammatory conditions. This impairment may result from protein dysregulation in the PSD like downregulation of the GluN2A subunit, which may reduce NMDAR-mediated currents, and/or decreased crosslinking between Homer and IP₃R, which may reduce the release of Ca²⁺ from intracellular stores.

The effectiveness of ultrasound-guided cervical transforaminal epidural steroid injections in cervical radiculopathy: a prospective pilot study

Background

Cervical transforaminal epidural steroid injection (CTFESI) is used to provide pain relief and restore function in patients with cervical radiculopathy. Traditionally, it is performed under the guidance of fluoroscopy or computed tomography. Here, we introduce a novel technique - ultrasound-guided CTFESI - with which operators can easily distinguish the close soft tissue (nerve, vessels) around the cervical foramina to avoid intravascular injection during the procedure.

Objective

To present the immediate and long-term effectiveness of ultrasound-guided CTFESI in patients with cervical radiculopathy in an academic pain-management center with prospective clinic experiments.

Methods

Fifteen patients with cervical radiculopathy who were resistant to conservative therapies and ultrasound-guided selective cervical spinal nerve-root injections, were treated with ultrasound-guided CTFESI. During the injection procedures, the needle tips were reconfirmed by real-time fluoroscopy. Pain numeric rating-scale and neck-disability-index scores were assessed from onset to six months after the procedures.

Results

During the procedures, based on real-time fluoroscopic confirmation, the injection solution outlined the spinal nerve root and spread into the epidural space in most cases (14 of 15). All patients reported pain relief within 10 minutes after the injection. The majority of patients (eleven of 15) experienced pain relief and neck-disability index-score improvement throughout the 6-month study period. No patient experienced any complication.

Conclusion

We suggest that ultrasound-guided CTFESI is an effective, safe, and simple procedure free of radiation or magnetization and provides sustained pain relief in patients with cervical radiculopathy who have failed previous conservation therapies.

Effects of ultrasound-guided stellate ganglion block on cervical vascular blood flow: study protocol for a randomized controlled trial

BACKGROUND

The stellate ganglion block (SGB) can lead to vasodilation of the head and neck. However, controversy remains concerning the changes in extracerebral blood flow. The objective of this study is to assess the effects of SGB on the blood flow to the neck.

METHODS

A randomized controlled crossover trial with 38 participants will be conducted. Participants who have primary headaches will be assigned to either group A or B. Patients in group A will receive SGB with 6 ml 1% lidocaine, and after a one-week washout period, they will undergo the second SGB with 6 ml normal saline. In contrast, patients in group B will receive the opposite protocol. Data will be collected at baseline (T0) and at 15 min after the first intervention (T1), 15 min before the second intervention (T2), 15 min after the second intervention (T3) and at a 3-week follow up (T4). T1 is the primary time point for the primary outcome analysis. The primary outcomes include the peak systolic velocity (PSV), the end diastolic velocity (EDV), resistance index (RI) and vessel diameter of the common carotid artery (CCA) and vertebral artery (VA). The secondary outcomes include the rate of ptosis, the rate of conjunctival flushing, and the numerical rating scale (NRS) pain score. Additionally, adverse events (AEs) or serious adverse events (SAEs) will be collected at each assessment point.

DISCUSSION

This study will comprehensively investigate the efficacy of SGB in extracerebral blood flow. Our research may also suggest that SGB will be effective in reducing pain in patients with primary headaches.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, identifier ChiCTR-IOR-17011536 . Registered on 1 June 2017.

Swimming Training Reduces Neuroma Pain by Regulating Neurotrophins

Introduction

Neuroma formation after peripheral nerve transection leads to severe neuropathic pain in amputees. Previous studies suggested that physical exercise could bring beneficial effect on alleviating neuropathic pain. However, the effect of exercise on neuroma pain still remained unclear. In addition, long-term exercise can affect the expression of neurotrophins (NT), such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), which play key roles in nociceptor sensitization and nerve sprouting after nerve injury. Here, we investigated whether long-term swimming exercise could relieve neuroma pain by modulating NT expression.

Methods

We used a tibial neuroma transposition (TNT) rat model to mimic neuroma pain. After TNT surgery, rats performed swimming exercise for 5 wk. Neuroma pain and tactile sensitivities were detected using von Frey filaments. Immunofluorescence was applied to analyze neuroma formation. NGF and BDNF expressions in peripheral neuroma, dorsal root ganglion, and the spinal cord were measured using enzyme-linked immunosorbent assay and Western blotting.

Results

TNT led to neuroma formation, induced neuroma pain, and mechanical allodynia in hind paw. Five-week swimming exercise inhibited neuroma formation and relieved mechanical allodynia in the hind paw and neuroma pain in the lateral ankle. The analgesic effect lasted for at least 1 wk, even when the exercise ceased. TNT elevated the expressions of BDNF and NGF in peripheral neuroma, dorsal root ganglion, and the spinal cord to different extents. Swimming also decreased the elevation of NT expression.

Conclusions

Swimming exercise not only inhibits neuroma formation induced by nerve transection but also relieves pain behavior. These effects might be associated with the modulation of NT.

Ultrasound-guided alcohol neurolysis and radiofrequency ablation of painful stump neuroma: effective treatments for post-amputation pain

BACKGROUND

Post-amputation pain (PAP) is highly prevalent after limb amputation, and stump neuromas play a key role in the generation of the pain. Presently, PAP refractory to medical management is frequently treated with minimally invasive procedures guided by ultrasound, such as alcohol neurolysis and radiofrequency ablation (RFA).

OBJECTIVE

To record the immediate and long-term efficacy of alcohol neurolysis and RFA. We first used alcohol neurolysis and then, when necessary, we performed RFA on PAP patients.

STUDY DESIGN

Prospective case series.

SETTING

Pain management center.

METHODS

Thirteen subjects were treated with ultrasound-guided procedures.

RESULTS

All patients were treated with neurolysis using alcohol solutions guided by ultrasound. Seven (54%) of 13 subjects achieved pain relief after 1-3 alcohol injection treatments. The remaining 6 subjects obtained pain relief after receiving 2 administrations of ultrasound-guided RFA. After a 6-month follow-up evaluation period, pain quantities were also assessed. Both stump pain (including intermittent sharp pain and continuous burning pain) and phantom pain were relieved. The frequency of intermittent sharp pain was decreased, and no complications were noted during the observation.

CONCLUSION

The use of ultrasound guidance for alcohol injection and RFA of painful stump neuromas is a simple, radiation-free, safe, and effective procedure that provides sustained pain relief in PAP patients. In this case series, RFA was found to be an effective alternative to alcohol injection.

Anti-nociceptive roles of the glia-specific metabolic inhibitor fluorocitrate in paclitaxel-evoked neuropathic pain

Paclitaxel (Taxol) is a powerful chemotherapy drug used in breast cancers, but it often causes neuropathic pain, leading to the early cessation of therapy and poor treatment outcomes. Approaches for the management of paclitaxel-induced neuropathic pain are urgently needed. The involvement of spinal astrocytes in the pathogenesis of paclitaxel-induced neuropathy has been reported, but little is known about the role of fluorocitrate (FC), a selective inhibitor of astrocyte activation, during neuropathic pain related to paclitaxel treatment. In this study, we investigated the effects of FC on paclitaxel-induced neuropathic pain. Glial fibrillary acidic protein (GFAP) expression was determined to assess astrocyte activation. To explore the mechanisms involved, the expression of glial glutamate transporter 1 (GLT-1) and the activation of mitogen-activated protein kinases in the spinal dorsal horn were analyzed. The results showed that paclitaxel decreased the mechanical nociceptive thresholds and increased GFAP expression, leading to spinal astrocyte activation. After paclitaxel treatment, GLT-1 was significantly down-regulated, and the phosphorylation of ERK1/2 and JNK were obviously up-regulated. However, paclitaxel treatment did not increase p38 phosphorylation. Additional studies showed that paclitaxel-evoked mechanical hypersensitivity was reduced by FC treatment. Moreover, FC treatment inhibited the activation of astrocytes and reversed the changes in GLT-1 expression and MAPK phosphorylation. Further study indicated that FC did not influence the antitumor effect of paclitaxel, suggesting that FC blocked paclitaxel-induced neuropathic pain without antagonizing its antitumor effect. Together, these results suggested that paclitaxel induced astrocyte-specific activation, which may contribute to mechanical allodynia and hyperalgesia, and that FC could be a potential therapeutic agent for paclitaxel-induced neuropathic pain.

Circulating microRNA expression profile: a novel potential predictor for chronic nervous lesions

The mechanisms of chronic neuropathic pain are not clear. Serum microRNAs (miRNAs) might show a special feature for chronic nervous lesions. However, little is known about the changes in circulating miRNAs for the neuropathic pain. Therefore, changes in the circulating miRNAs expression profile for the neuropathic pain were investigated. Serum was collected from rats before and after spinal nerve ligation (SNL) surgery, and a microarray analysis was performed to determine the changes in miRNA expression profile. The expression of inflammatory cytokines in serum from the same individuals, including interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and monocyte chemotactic protein-1 (MCP-1), was also measured. The results showed that the expression levels of IL-6, TNF-α, and MCP-1 were significantly elevated in SNL rats which were significantly correlated with pain levels. Nine miRNAs with significantly different expression levels before and after SNL surgery were identified by microarray analysis, which were further validated by quantitative real-time polymerase chain reaction analyses. Compared with naive rats without SNL surgery, the expression of five miRNAs (hsa-miR-221, hsa-miR-34c, hsa-miR-21, hsa-miR-30a-5p, and hsa-miR-206) in the serum of rats after SNL surgery was decreased and four miRNAs (hsa-miR-31-5p, hsa-miR-133b, hsa-miR-22, and hsa-miRPlus-A1087) were increased, suggesting that miRNA changes may involve in the regulation of neuropathic pain. TargetScan was used to predict mRNA targets for these miRNAs, and the results showed that the transcripts with multiple predicted target sites belonged to neurologically important pathways. Bioinformatics analysis revealed that several target genes are related to the activation of cell signaling associated with nervous lesions. In this study, the changes to miRNA profiles in serum under neuropathic pain conditions were shown for the first time, suggesting that circulating miRNAs profile in serum is a potential predictor for neuropathic pain.

Positive feedback loop of autocrine BDNF from microglia causes prolonged microglia activation

BACKGROUND/AIMS

Microglia, which represent the immune cells of the central nervous system (CNS), have long been a subject of study in CNS disease research. Substantial evidence indicates that microglial activation functions as a strong neuro-inflammatory response in neuropathic pain, promoting the release of pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-α. In addition, activated microglia release brain-derived neurotrophic factor (BDNF), which acts as a powerful cytokine. In this study, we performed a series of in vitro experiments to examine whether a positive autocrine feedback loop existed between microglia-derived BDNF and subsequent microglial activation as well as the mechanisms underlying this positive feedback loop.

METHODS

Because ATP is a classic inducer of microglial activation, firstly, we examined ATP-activated microglia in the present study. Secondly, we used TrkB/Fc, the BDNF sequester, to eliminate the effects of endogenous BDNF. ATP-stimulated microglia without BDNF was examined. Finally, we used exogenous BDNF to further determine whether BDNF could directly activate BV2 microglia. In all experiments, to quantify BV2 microglia activation, the protein levels of CD11b, a microglial activation marker, were measured by western blot. A Transwell migration assay was used to examine microglial migration. To assess the synthesis and release of proinflammatory cytokines, western blot was used to measure BDNF synthesis, and ELISA was used to quantify TNF-α release.

RESULTS

In our present research, we have observed that ATP dramatically activates microglia, enhancing microglial migration, increasing the synthesis of BDNF and up-regulating the release of TNF-α. Microglial activation is inhibited following the sequestration of endogenous BDNF, resulting in impaired microglial migration and decreased TNF-α release. Furthermore, exogenous BDNF can also activate microglia to subsequently enhance migration and increase TNF-α release.

CONCLUSION

Therefore, we suggest that microglial activation increases the synthesis of BDNF and that the release of BDNF can, in turn, activate microglia. A positive autocrine BDNF feedback loop from microglia may contribute to prolonged microglial activation.

Brain-derived neurotrophic factor-activated astrocytes produce mechanical allodynia in neuropathic pain

Neuropathic pain management is challenging for physicians and a vexing problem for basic researchers. Recent studies reveal that activated spinal astrocytes may play a vital role in nerve injury-induced neuropathic pain, although the mechanisms are not fully understood. We have found increased glial fibrillary acidic protein (GFAP) expression, a hallmark of reactive gliosis, and elevated brain-derived neurotrophic factor (BDNF) expression in the dorsal horn in a rat model of allodynia induced by spinal nerve ligation (SNL). The high GFAP expression and mechanical allodynia that SNL induces were prevented by the intrathecal injection of the BDNF-sequestering fusion protein TrkB/Fc. Additionally, mechanical allodynia and GFAP overexpression was induced by the spinal administration of exogenous BDNF to naive rats, and exogenous BDNF given together with fluorocitrate, an astrocytic metabolism inhibitor, inhibited allodynia and GFAP upregulation. Exogenous BDNF also activated the astrocytes directly when tested in vitro. Furthermore, intrathecal administration of BDNF-stimulated astrocytes also induced mechanical allodynia in naive rats. All of these results indicate that astrocytes activated by BDNF might contribute to mechanical allodynia development in neuropathic pain in rats.

The effect of intrathecal administration of glial activation inhibitors on dorsal horn BDNF overexpression and hind paw mechanical allodynia in spinal nerve ligated rats

Recent studies have suggested that activated glia in the spinal cord may play a vital role at different times during spinal nerve ligation (SNL)-induced neuropathic pain; therefore, glial activation inhibitors have been used as effective painkillers. Brain-derived neurotrophic factor (BDNF) is also known to be a powerful pain modulator, but it remains unclear how it contributes to the glial activation inhibitor-based treatment. This study revealed the following results: (1) intrathecal administration of minocycline (a microglial activation inhibitor) could prevent mechanical allodynia during the initiation of SNL-induced neuropathic pain, and its action was associated with the elimination of BDNF overexpression in the dorsal horn; (2) the spinal injection of fluorocitrate (an astrocytic activation inhibitor) but not minocycline could reverse mechanical allodynia during the maintenance phase of SNL-induced pain, and its action was also related to a decrease in BDNF overexpression in the dorsal horn; and (3) treatment with TrkB/Fc (a BDNF-sequestering protein) had a similar effect during both the early development and maintenance periods. These results led to the following conclusions: (1) elevated BDNF expression in the dorsal horn was required to develop and maintain neuropathic pain; (2) minocycline could only prevent mechanical allodynia in the early stages, possibly by inhibiting BDNF release from microglia; and (3) fluorocitrate could reverse existing mechanical allodynia, and its action was associated with the inhibition of BDNF upregulation induced by astrocytic activation.

p38/MAPK inhibitor modulates the expression of dorsal horn GABA(B) receptors in the spinal nerve ligation model of neuropathic pain

BACKGROUND

Neuropathic pain is one of the most challenging clinical problems due to a lack of understanding the mechanisms. Recent studies have suggested that activated microglia in spinal cord may play a vital role in nerve injury-induced neuropathic pain, but the exact mechanisms have not been fully determined.

METHODS

First, we investigated the changes of dorsal horn GABA(B) receptor 1 (R1) expression in spinal nerve ligation rats. Second, we explored whether activated microglia contributed to such neuron changes by intrathecal administration of the p38 inhibitor, SB203580.

RESULTS

In this study, we found a dynamic change of GABA(B)R1a protein expression after spinal nerve ligation, and the peripheral nerve injury-induced downregulation of GABA(B)R1a expression in the spinal dorsal horn could be prevented by intrathecal administration of a p38/MAPK inhibitor SB203580.

CONCLUSIONS

Our results provide valuable information for a better understanding of neuropathic pain and may contribute to developing effective treatments in future studies.

The characteristics of placental transfer and tissue concentrations of nickel in late gestational rats and fetuses

The dynamics of nickel (Ni) uptake, transfer, retention and clearance in fetuses and late gestational rats were investigated by assessing its distributions in placenta, maternal and fetal organs and tissues during the 24 h period after a single dose of (63)Ni intraperitoneal injection on gestational day 20. Peak (63)Ni radioactivity was detected at 0.5 h in maternal blood, at 3 h in placenta, fetal membranes, fetal blood, fetal heart, maternal kidney, lung, stomach, liver and brain, at 9 h in fetal kidney, stomach, liver and brain, and lastly at 24 h in fetal lung and amniotic fluid. The maximal (63)Ni radioactivity among all samples was detected consistently in the fetal membranes and placenta. The (63)Ni radioactivity in fetal blood was higher than that in maternal blood from 3 to 24 h. The fetal liver, heart, stomach and brain exhibited higher (63)Ni radioactivity than the corresponding maternal organs from 6 to 24 h. However, maternal kidney consistently exhibited significantly higher (63)Ni radioactivity than the fetal kidney. The (63)Ni in fetal lung and amniotic fluid increased throughout the period of experimental observation. These observations corroborated previous finding that nickel is actively transferred across the blood-placenta-barrier into fetus, but hardly from fetus to mother. Moreover, these results suggest that the placenta has a high affinity for nickel and its barrier does not protect the fetus from nickel exposure. The fact that nickel concentrations are higher in most fetal organs and tissues than in corresponding maternal organs and tissues in late gestation indicates that, unlike the dam, fetuses lack effective means for getting rid of excessive nickel due to its confined environment and relatively weak kidney functions. The situation is exacerbated by mother-to-fetus unidirectional transfer. Consequently, the fetuses are particularly vulnerable to the damaging effects of nickel.

A GABA-neuropeptide Y (NPY) interplay in LH release

Neuropeptide Y (NPY) stimulates and gamma-amino butyric acid (GABA) inhibits LH release in the rat. Since a sub-population of NPY-producing neurons in the arcuate nucleus (ARC) of the hypothalamus co-express GABA, the possibility of an interplay between NPY and GABA in the release of LH was investigated in two ways. First by employing light and electron microscopic double staining for NPY and GABA, using pre and post-immunolabeling on rat brain sections, we detected GABA in NPY immunoreactive axon terminals in the MPOA, one of the primary sites of action of these neurotransmitters/neuromodulators in the regulation of LH release. These morphological findings raised the possibility that inhibitory GABA co-released with NPY may act to restrain the excitatory effects of NPY on LH release. Muscimol (MUS, 0.44 or 1.76 nmol/rat), a GABA(A) receptor agonist, administered intracerebroventricularly (icv), alone failed to affect LH release, but NPY (0.47 nmol/rat icv) alone stimulated LH release in ovarian steroid-primed ovariectomized rats. On the other hand, administration of MUS blocked the NPY-induced stimulation of LH release in a dose-dependent manner. Similarly, administration of MUS abolished the excitatory effects on LH release of 1229U91, a selective NPY Y4 receptor agonist. These results support the possibility that in the event of co-release of these neurotransmitters/neuromodulators, GABA may act to restrain stimulation of LH release by NPY during the basal episodic and cyclic release of LH in vivo.

Neuropeptide Y counteracts the anorectic and weight reducing effects of ciliary neurotropic factor

Ciliary neurotrophic factor (CNTF), a cytokine of the interleukin-6 superfamily, has been shown to induce hypophagia and weight loss. Neuropeptide Y (NPY) and orexin are potent orexigenic signals in the hypothalamus. Anorexia, normally seen in response to infection, injury and inflammation, may result from diminished hypothalamic orexigenic signalling caused by persistently elevated cytokines, including CNTF. To test this hypothesis, we first examined the effects of chronic intracerebroventricular (i.c.v.) infusion of CNTF for 6-7 days on food intake and body weight as well as hypothalamic NPY and orexin gene expression in male rats. Subsequently, the effectiveness of NPY replacement to counteract the effects of CNTF by coinfusion of NPY and CNTF was evaluated. Chronic i.c.v. infusion of CNTF (2.5 microg/day) reduced body weight (14.3% vs control) at the end of 7 days. Food intake remained suppressed for 5 days postinfusion and subsequently gradually returned to the control range by day 7. Serum leptin concentrations in these rats were in the same range seen in control rats. Chronic i.c.v. infusion of higher doses of CNTF (5.0 microg/day) produced sustained anorexia and body weight loss (29% vs controls) through the entire duration of the experiment. This severe anorexia was accompanied by markedly suppressed serum leptin concentrations. Furthermore, CNTF infusion alone significantly reduced hypothalamic NPY gene expression (P < 0. 05) without affecting orexin gene expression. As expected, in fusion of NPY alone (18 microg/day) augmented food intake (191.6% over the initial control, P < 0.05) and produced a 25.1% weight gain in conjunction with a 10-fold increase in serum leptin concentrations at the end of the 7-day period. Interestingly, coinfusion of this regimen of NPY with the highly effective anorectic and body reducing effects of CNTF (5.0 microg/day) not only prevented the CNTF-induced anorexia and weight loss, but also normalized serum leptin concentrations and hypothalamic NPY gene expression. These results demonstrate that chronic central infusion to produce a persistent elevation of the cytokine at pathophysiological levels (a situation that may normally manifest during infection, injury and inflammation) produced severe anorexia and weight loss in conjunction with reduction in both serum leptin concentrations and hypothalamic NPY gene expression. Reinstatement of hypothalamic NPY signalling by coinfusion of NPY counteracted these CNTF-induced responses.

Regulation of leptin secretion: effects of aging on daily patterns of serum leptin and food consumption

We have investigated the effects of age on the daily rise in serum leptin levels during the dark-phase of the light-dark cycle. The results show that in young 7-week-old rats, serum leptin levels increase significantly at 2300 h from the levels at 1500 h in association with increased food consumption. However, in middle-aged rats 25 weeks old, the dark-phase increase in serum leptin is absent despite retention of the daily dark-phase increase in food consumption. When compared to our earlier published results, these finding show that the loss of dark-phase rise in serum leptin occurred despite the daily increase in adipocyte leptin gene expression. These results are in accord with the view that the daily pattern in serum leptin is unlikely to be a contributor to the daily patterning of food consumption.

Central infusion of interleukin-1 receptor antagonist fails to alter feeding and weight gain

Interleukin-1 (IL-1) administered either i.p. or i.c.v. provokes sickness behaviors, including suppression of feeding. As well, the possibility exists that IL-1 contributes to the cascade of factors that regulate feeding under basal conditions. The current study assessed the contribution of IL-1 in the control of food intake and body weight under physiological conditions in male rats. Pretreatment with an IL- I receptor antagonist (IL-1ra, 16 mg/kg, i.p.) completely blocked the suppression of food intake produced by injection of IL-1beta (4 microg/kg, i.p.). However, neither daily injections of IL-1ra (16 mg/kg, i.p.) for 4 consecutive days nor infusion of IL-1ra (500 microg/day, i.c.v.) for 7 days altered daily food intake and the rate of body weight gain. These findings suggest while IL-1 may play a role in anorexia associated with sickness, this cytokine likely does not play a physiological role in the regulation of daily food intake and long-term energy balance.

Melanocortin signaling is decreased during neurotoxin-induced transient hyperphagia and increased body-weight gain

Hypothalamic neuropeptides play critical roles in the regulation of feeding behavior and body weight (BW). Disruption of signaling in the ventromedial nucleus by microinjection of the neurotoxin, colchicine (COL), produces transient hyperphagia with corresponding BW gain lasting for 4 days. Because the melanocortin system exerts an inhibitory control on food intake, we hypothesized that hyperphagia in COL-treated rats is due to decreased melanocortin-induced restraint on feeding. Melanocortin restraint is exerted through alpha-melanocortin-stimulating hormone derived from proopiomelanocortin (POMC) and is antagonized by agouti-related peptide produced in neurons located in the arcuate nucleus (ARC). COL (4 microg/0.5 microl saline) or saline was microinjected bilaterally into the ventromedial nucleus of adult male rats. In conjunction with BW gain, blood leptin levels were elevated, whereas POMC mRNA in the ARC was significantly decreased in COL-injected rats. Levels of alpha-melanocortin-stimulating hormone were also decreased in the micropunched paraventricular nucleus, dorsomedial nucleus, and perifornical hypothalamus, sites implicated in the control of food intake. That diminution in melanocortin signaling underlies hyperphagia was supported by the observation that intracerebroventricular injection of the MC3/MC4 melanocortin receptor agonist, MTII, prevented the hyperphagia and BW gain. Surprisingly, however, mRNA levels of the orexigenic peptide agouti-related peptide in the ARC were decreased perhaps due to the action of elevated leptin. These results show that transient hyperphagia and BW gain induced by disruption of signaling in the ventromedial nucleus results from two neurochemical rearrangements: development of leptin resistance in POMC neurons and diminution in melanocortin signaling as reflected by decreased POMC gene expression in the ARC and decreased availability of alpha-melanocortin-stimulating hormone for release in feeding relevant sites.

Evidence that stimulation of two modalities of pituitary luteinizing hormone release in ovarian steroid-primed ovariectomized rats may involve neuropeptide Y Y1 and Y4 receptors

A large body of evidence indicates that neuropeptide Y (NPY) is involved in stimulation of basal and cyclic release of hypothalamic LHRH and pituitary LH. To identify the NPY receptor subtypes that mediate the excitatory effects of NPY in these two modalities of LH release, we studied the effects of 1229U91, a selective Y1 receptor antagonist and Y4 receptor agonist, in two experimental paradigms that reproduce the two modalities of LH secretion in steroid-primed ovariectomized (OVX) rats. Rats were ovariectomized and implanted with a permanent cannula into the lateral cerebroventricle. In the first experiment, rats received estradiol benzoate (EB, 30 microg/rat) on day 5, followed 2 days later with progesterone (2 mg/rat) at 1000 h to induce an afternoon LH surge. 1229U91 (30 microg/3 microl) or vehicle (control) was injected intracerebroventricularly into these rats either once at 1300 h or twice (15 microg/injection) at 1100 and 1200 h. Blood samples were collected before progesterone injection at 1000 h and at hourly intervals from 1300 -1800 h via an intrajugular cannula implanted on the previous day. In control rats, serum LH levels rose significantly at 1400 h, and these high levels were maintained until 1700 h. After two injections of 1229U91, LH levels displayed a tendency to rise at 1300-1400 h, as in controls, but thereafter, decreased rapidly below the control range. In the second experiment, the acute effect of 1229U91 on LH release was evaluated in OVX rats pretreated with EB alone. Saline alone or saline containing 1, 3, 10, or 30 microg 1229U91 was injected intracerebroventricularly at 1000 h, and the effects on LH release were analyzed at 10, 20, 30, and 60 min. 1229U91 elicited a dose-dependent stimulation of LH release, with maximal response (950% of basal levels) occurring at 10 min after the 30-microg dose; elevated levels were maintained for 1 h. Because 1229U91 is a potent Y4 agonist with some affinity for Y5 receptors, these results raised the possibility that activation of Y4/Y5 receptors by 1229U91 may augment LH release. Therefore, we examined the effects of icv administration of rat pancreatic polypeptide, a Y4-selective agonist, and [D-Trp32]-NPY, a Y5 agonist on LH release in EB-primed rats. Rat pancreatic polypeptide (0.5-2 microg/rat) stimulated LH release in a dose-related manner, and peak levels (280% of basal levels) were seen at 10-20 min; the response evoked by a higher dose (10 microg) was smaller than that induced by 0.5 or 2 microg. [D-Trp32]-NPY was relatively less effective, because only the highest (10-microg) dose elicited a modest stimulation (244% of basal levels). These results demonstrate that 1229U91, a Y1 antagonist and Y4 agonist, evokes two types of responses; it suppresses the protracted ovarian steroid-induced LH surge, and acutely, it also stimulates LH. These results imply that normally two different types of NPY receptors may mediate the stimulation of LH release. Because 1229U91 is a Y1 receptor antagonist, inhibition of the steroid-induced LH surge by 1229U91 suggests that Y1 receptors may mediate the cyclic release of LH. On the other hand, acute stimulation of LH by 1229U91 implies that the Y4 agonist-like activity of 1229U91 may mediate the basal release of LH and that either NPY or a yet-to-be-identified endogenous Y4 receptor agonist may activate Y4 receptors in the hypothalamus to stimulate LH release.

Relationship between remodeling and function of left ventricle and angiotensin II AT1 receptor expression after myocardial infarction in rats

OBJECTIVE

To determine the relationship between remodeling and dysfunction of left ventricle (LV) and the expression of the angiotensin II AT1 receptor mRNA after myocardial infarction (MI) in rats.

METHODS

Nine MI rats (Group A) and 8 sham-operated rats (Group B) were studied by both Doppler echocardiography and Dot blot using Digoxingenin-labelled cDNA probes.

RESULTS

Compared with Group B, Group A showed the increase in LV internal diastolic diameter (0.87 +/- 0.06 mm vs 0.66 +/- 0.03 mm, respectively, P < 0.01) and volume (0.73 +/- 0.09 ml vs 0.51 +/- 0.05 ml, P < 0.01). In addition, thinning of anterior wall, thickening of posterior wall, increasing of peak early filling velocity (peak E), decreasing of late filling velocity (peak A) and increasing of the E/A were demonstrated in MI rats 7 weeks after MI. The levels of the cardiac angiotensin II AT1 receptor mRNA in Group A were higher than those of Group B (2.2-fold).

CONCLUSIONS

Seven weeks after MI in rats, character of LV remodeling and dysfunction were developed and the expression of cardiac angiotensin II AT1 receptor mRNA was increased.

Interactions between neuropeptide Y and gamma-aminobutyric acid in stimulation of feeding: a morphological and pharmacological analysis

Neuropeptide Y (NPY) produced in neurons in the arcuate nucleus and brain stem and released in the paraventricular nucleus (PVN) and surrounding areas is involved in stimulation of feeding in rats. We recently reported that gamma-aminobutyric acid (GABA) is coexpressed in a subpopulation of NPY neurons in the arcuate nucleus. To determine whether GABA is colocalized in NPY terminals in the PVN, the site of NPY action, light and electron microscopic double staining for NPY and GABA using pre- and postembedding immunolabeling was performed on rat brain sections. GABA was detected in NPY-immunopositive axons and axon terminals within both the parvocellular and magnocellular divisions of the PVN. These morphological findings suggested a NPY-GABA interaction in the hypothalamic control of feeding. Therefore, the effects of muscimol (MUS), a GABA(A) receptor agonist, on NPY-induced food intake were examined in sated rats. When injected intracerebroventricularly, both NPY and MUS elicited dose-dependent feeding responses that were blocked by the administration of 1229U91 (a putative Y1 receptor antagonist) or bicuculline (a GABA(A) receptor antagonist), respectively. Coadministration of NPY and MUS intracerebroventricularly amplified the feeding response over that evoked by NPY or MUS alone. Similarly, microinjection of either NPY or MUS into the PVN stimulated food intake in a dose-related fashion, and coinjection elicited a significantly higher response than that evoked by either individual treatment. These results suggest that GABA and NPY may coact through distinct receptors and second messenger systems in the PVN to augment food intake.

Interacting appetite-regulating pathways in the hypothalamic regulation of body weight

Various aspects of the complex spatio-temporal patterning of hypothalamic signaling that leads to the development of synchronized nocturnal feeding in the rat are critically examined. Undoubtedly, as depicted in Fig. 7, a distinct ARN in the hypothalamus is involved in the control of nocturnal appetite. At least four basic elements operate within this ARN. These are: 1) A discrete appetite-driving or orexigenic network of NPY, NE, GABA, GAL, EOP, and orexin transduces and releases appetite-stimulating signals. 2) Similarly, anorexigenic signal-producing pathways (e.g., CRH, GLP-1, alpha MSH, and CART) orchestrate neural events for dissipation of appetite and to terminate feeding, possibly by interrupting NPY efflux and action at a postsynaptic level within the hypothalamus. It is possible that some of these may represent the physiologically relevant "off" switches under the influence of GABA alone, or AgrP alone, or in combination with NPY released from the NPY-, GABA-, and AgrP-coproducing neurons. 3) Recent evidence shows that neural elements in the VMN-DMN complex tonically restrain the orexigenic signals during the intermeal interval; the restraint is greatly aided by leptin's action via diminution of orexigenic (NPY) and augmentation of anorexigenic (GLP-1, alpha MSH, and CART) signals. Since interruption of neurotransmission in the VMN resulted in hyperphagia and development of leptin resistance, it seems likely that the VMN is an effector site for the restraint exercised by leptin. The daily rhythms in leptin synthesis and release are temporally dissociable because the onset of daily rise in leptin gene expression in adipocytes precedes that in leptin secretion. Nevertheless, these rhythms are in phase with daily ingestive behavior because the peak in circulating leptin levels occurs during the middle of the feeding period. These observations, coupled with the fact that circulating levels of leptin are directly related to adiposity, pose a new challenge for elucidating the precise role of leptin in daily patterning of feeding in the rat. 4) A neural timing mechanism also operates upstream from the ARN in the daily management of energy homeostasis. Although the precise anatomical boundaries are not clearly defined, this device is likely to be composed of a group of neurons that integrate incoming internal and external information for the timely onset of the drive to eat. Evidently, this network operates independently in primates, but it is entrained to the circadian time keeper in the SCN of rodents. Apart from its role in the onset of drive to eat, the circadian patterns of gene expression of NPY, GAL, and POMC denote independent control of the timing device on the synthesis and availability for release of orexigenic signals. The VMN-DMN-PVN complex is apparently an integrated constituent of the timing mechanism in this context, because lesions in each of these sites result in loss of regulated feeding. The accumulated evidence points to the PVN and surrounding neural sites within this framework as the primary sites of release and action of various orexigenic and anorexigenic signals. A novel finding is the identification of the interconnected wiring of the DMN-mPVN axis that may mediate leptin restraint on NPY-induced feeding. The chemical phenotypes of leptin and NPY target neurons in this axis remain to be identified. These multiple orexigenic and anorexigenic pathways in the hypothalamic ARN appear to represent redundancy, a characteristic of regulated biological systems to provide a "fail-safe" neural mechanism to meet an organism's constant energy needs for growth and maintenance. Within this formulation, the coexisting orexigenic signals (NPY, NE, GAL, GABA, and AgrP) represent either another level of redundancy or it is possible that these signals operate within the ARN as reinforcing agents to varying degrees under different circumstances. (ABSTRACT TRUNCATED)

Interacting appetite-regulating pathways in the hypothalamic regulation of body weight

Various aspects of the complex spatio-temporal patterning of hypothalamic signaling that leads to the development of synchronized nocturnal feeding in the rat are critically examined. Undoubtedly, as depicted in Fig. 7, a distinct ARN in the hypothalamus is involved in the control of nocturnal appetite. At least four basic elements operate within this ARN. These are: 1) A discrete appetite-driving or orexigenic network of NPY, NE, GABA, GAL, EOP, and orexin transduces and releases appetite-stimulating signals. 2) Similarly, anorexigenic signal-producing pathways (e.g., CRH, GLP-1, alpha MSH, and CART) orchestrate neural events for dissipation of appetite and to terminate feeding, possibly by interrupting NPY efflux and action at a postsynaptic level within the hypothalamus. It is possible that some of these may represent the physiologically relevant "off" switches under the influence of GABA alone, or AgrP alone, or in combination with NPY released from the NPY-, GABA-, and AgrP-coproducing neurons. 3) Recent evidence shows that neural elements in the VMN-DMN complex tonically restrain the orexigenic signals during the intermeal interval; the restraint is greatly aided by leptin's action via diminution of orexigenic (NPY) and augmentation of anorexigenic (GLP-1, alpha MSH, and CART) signals. Since interruption of neurotransmission in the VMN resulted in hyperphagia and development of leptin resistance, it seems likely that the VMN is an effector site for the restraint exercised by leptin. The daily rhythms in leptin synthesis and release are temporally dissociable because the onset of daily rise in leptin gene expression in adipocytes precedes that in leptin secretion. Nevertheless, these rhythms are in phase with daily ingestive behavior because the peak in circulating leptin levels occurs during the middle of the feeding period. These observations, coupled with the fact that circulating levels of leptin are directly related to adiposity, pose a new challenge for elucidating the precise role of leptin in daily patterning of feeding in the rat. 4) A neural timing mechanism also operates upstream from the ARN in the daily management of energy homeostasis. Although the precise anatomical boundaries are not clearly defined, this device is likely to be composed of a group of neurons that integrate incoming internal and external information for the timely onset of the drive to eat. Evidently, this network operates independently in primates, but it is entrained to the circadian time keeper in the SCN of rodents. Apart from its role in the onset of drive to eat, the circadian patterns of gene expression of NPY, GAL, and POMC denote independent control of the timing device on the synthesis and availability for release of orexigenic signals. The VMN-DMN-PVN complex is apparently an integrated constituent of the timing mechanism in this context, because lesions in each of these sites result in loss of regulated feeding. The accumulated evidence points to the PVN and surrounding neural sites within this framework as the primary sites of release and action of various orexigenic and anorexigenic signals. A novel finding is the identification of the interconnected wiring of the DMN-mPVN axis that may mediate leptin restraint on NPY-induced feeding. The chemical phenotypes of leptin and NPY target neurons in this axis remain to be identified. These multiple orexigenic and anorexigenic pathways in the hypothalamic ARN appear to represent redundancy, a characteristic of regulated biological systems to provide a "fail-safe" neural mechanism to meet an organism's constant energy needs for growth and maintenance. Within this formulation, the coexisting orexigenic signals (NPY, NE, GAL, GABA, and AgrP) represent either another level of redundancy or it is possible that these signals operate within the ARN as reinforcing agents to varying degrees under different circumstances. (ABSTRACT TRUNCATED)

Disruption of neural signaling within the hypothalamic ventromedial nucleus upregulates galanin gene expression in association with hyperphagia: an in situ hybridization analysis

Hypothalamic neuropeptides play critical roles in the regulation of appetite and body weight. We recently reported that disruption of neural signaling in the ventromedial nucleus (VMN) by microinjection of the neurotoxin, colchicine (COL), produced transient hyperphagia with attendant body weight gain lasting for 4 days. The neural mechanism(s) underlying this temporary shift in energy homeostasis is still unknown. Galanin (GAL) is produced in several hypothalamic nuclei and since microinjection of GAL into these sites stimulates feeding, we tested the hypothesis that galaninergic signaling is upregulated in COL-treated rats. COL (4 microgram in 0.5 microliter saline) or saline alone was microinjected into the VMN of adult male rats and GAL mRNA was evaluated in the basal hypothalamus by ribonuclease protection assay on day 1, day 2 and day 4 after injection. Whereas in saline-treated rats body weight and GAL mRNA remained unaffected, they were significantly increased in COL-injected rats through the period of observation. To identify the specific neuronal subpopulations involved, GAL mRNA levels were analyzed in feeding-related hypothalamic nuclei using semiquantitative in situ hybridization histochemistry on day 4 after microinjection of COL or saline into the VMN. In COL-treated rats, GAL mRNA levels increased dramatically over controls in the supraoptic nucleus, paraventricular nucleus (PVN), dorsomedial nucleus (DMN), arcuate nucleus (ARC) and lateral hypothalamic area (LHA); no significant change was observed in the central nucleus of amygdala. These results indicated that disruption of neurotransmission in the VMN upregulated GAL gene expression in those hypothalamic sites (PVN, DMN, LHA and ARC) that are implicated in regulation of feeding, and since GAL stimulates feeding, this neurochemical rearrangement may contribute to the over-eating in these animals. These results also suggest that, normally, neurons in the VMN may suppress GAL neurotransmission in feeding-regulating hypothalamic neural circuits.

Orexins, a novel family of hypothalamic neuropeptides, modulate pituitary luteinizing hormone secretion in an ovarian steroid-dependent manner

Orexin A and orexin B are a newly described family of orexigenic hypothalamic neuropeptides. The distribution of orexin immunoreactive fibers overlaps with the luteinizing hormone-releasing hormone (LHRH) neuronal system in the septo-preoptic area and the arcuate nucleus-median eminence region. To test the hypothesis that orexins may be involved in the regulation of pituitary LH secretion by influencing LHRH release, the effects of orexin A and orexin B on LH secretion were evaluated in ovariectomized (ovx) and ovarian steroid-treated ovx rats. Intracerebroventricular injection of orexin A or orexin B rapidly stimulated LH secretion in a dose- (0.3 and 3.0 nmol) and time-related fashion in estradiol benzoate- (EB) and progesterone (P)-pretreated ovx rats. Peak plasma LH concentration at 10 min were significantly higher in orexin A- than in orexin B-injected rats. On the other hand, both orexins (3 nmol) inhibited LH release in unprimed ovx rats. This ovarian steroid-dependent bimodal LH response is reminiscent of that of other orexigenic neuropeptides, such as neuropeptide Y. These findings show that orexins belong to a group of hypothalamic messengers that neurochemically bridge the regulatory networks that controls reproduction and energy balance.

Diurnal rhythm in cyclic GMP/nitric oxide efflux in the medial preoptic area of male rats

Since nitric oxide (NO) is implicated in the neuroendocrine control of luteinizing hormone-releasing hormone (LHRH) secretion and sexual behavior which show diurnal variations, we monitored cGMP levels (an index of NO activity) in the extracellular compartment of the medial preoptic area (MPOA) using microdialysis. It was observed that MPOA cGMP levels rose significantly in the afternoon in both castrated and intact male rats, thereby suggesting the existence of a diurnal rhythm in MPOA cGMP/NO efflux which may participate in eliciting the well-known diurnal variations in LHRH neuronal activity and male sexual behavior.

Ovarian steroid-independent diurnal rhythm in cyclic GMP/nitric oxide efflux in the medial preoptic area: possible role in preovulatory and ovarian steroid-induced LH surge

The aim of this study was to evaluate the relationship between cyclic LH hypersecretion and nitric oxide (NO) release in the medial preoptic area (MPOA), the hypothalamic site implicated in induction of LH hypersecretion. The MPOA extracellular cyclic GMP (cGMP) efflux (an index of NO release), was monitored by microdialysis. Quite unexpectedly, we observed a daily afternoon rise in the MPOA cGMP efflux in cycling female rats on proestrus and diestrus II, in ovariectomized (ovx) rats and in ovx rats treated with ovarian steroids to induce the LH surge. The daily rise in cGMP efflux occurred earlier in diestrous and in estradiol benzoate (EB)-treated ovx rats than in ovx rats. Progesterone (P) injection to estrogen-primed ovx rats further advanced the onset of the rise close to the earliest time of rise as seen on proestrus. The afternoon increase in the cGMP efflux in proestrous rats was abolished by pentobarbital treatment that blocked the LH surge. Intracerebroventricular (i.c.v.) injection of 1 H-[1,2,4]oxadiazo[4,3-a]quinoxalin-one (ODQ), a selective inhibitor of soluble guanylyl cyclase, suppressed the P-induced LH surge in EB-primed ovx rats, but not basal LH secretion in unprimed ovx rats. Analysis of brain NOS (bNOS) levels in the POA by Western blotting showed that the morning bNOS levels were higher in the POA of EB-treated rats than in unprimed ovx rats. Further, with the exception of ovx rats treated with sequential EB and P treatment, the POA bNOS levels rose significantly in the afternoon in unprimed ovx and EB-treated ovx rats. Collectively, these findings reveal a diurnal rhythm in the MPOA cGMP/NO efflux that is ovarian steroid-independent. Ovarian steroids apparently shift the timing of the afternoon rise in cGMP/NO efflux to synchronize with the activation of steroid-dependent neuronal systems responsible for the LH surge.

Neural substrates for leptin and neuropeptide Y (NPY) interaction: hypothalamic sites associated with inhibition of NPY-induced food intake

Intracerebroventricular (i.c.v.) injection of leptin, the adipocyte hormone, inhibits neuropeptide Y (NPY)-induced feeding in the rat. To identify the neural substrate for leptin and NPY interaction in the hypothalamus, we evaluated the expression of c-fos-like immunoreactivity (FLI), an early marker of neuronal activation, in response to icv administration of leptin, NPY and leptin plus NPY. As expected, leptin significantly decreased NPY-induced feeding in leptin plus NPY-treated rats. A comparative evaluation of the number of FLI-positive neurons in hypothalamic sites showed that both leptin and NPY activated FLI in the parvocellular subdivision of the paraventricular nucleus (pPVN), dorsomedial nucleus (DMN) and ventromedial nucleus (VMN). NPY also augmented the FLI response in the magnocellular PVN (mPVN) and supraoptic nucleus (SON), two sites where leptin alone was ineffective. Combined leptin and NPY treatment significantly decreased the number of FLI-positive neurons in the magnocellular PVN but increased their number in the dorsomedial nucleus as compared to the number of FLI-expressing neurons in these sites after NPY and leptin alone. Because there is morphologic evidence of a link between magnocellular PVN and dorsomedial nucleus, these results suggest the functional involvement of leptin plus NPY responsive elements in these sites in reduction of NPY-induced feeding by leptin.

Comparative effects of losartan and captopril on ventricular remodeling and function after myocardial infarction in the rat

OBJECTIVE

To determine the effects of losartan and captopril treatment on ventricular remodeling and function after myocardial infarction in rats.

METHODS

Thirty-two rats with MI induced by coronary ligation after seven days were divided into four groups randomly and treated with captopril(2 g.liter-1, group A), losartan(10 mg.kg-1.d-1, group B), losartan(30 mg.kg-1.d-1, group C) and placebo (no drug, group D) for six weeks, respectively. Sham-operated rats(group E) served as controls. Echocardiography was performed at 1 and 7 weeks after MI, respectively.

RESULTS

Compared with the results before treatment, both LV end-diastolic internal diameter and volume decreased significantly and the thickened posterior wall was reversed in group A, B and C; the peak early filling velocity decreased whereas the peak velocity was increased in these three groups. There are no significant difference among the three treated groups. However, LV end-diastolic internal diameter and the E/A were still increased, whereas the thickness of anterior wall and the peak velocity of LV outflow were decreased in group A, B, and C after treatment comparing with group E.

CONCLUSION

Both angiotensin converting enzyme inhibitor and angiotensin II receptor antagonist can prevent the ventricular remodeling and improve the ventricular function.

The interactive language of the hypothalamus for the gonadotropin releasing hormone (GNRH) system

The enormous diversity in neurochemical signals employed within the network of afferents to GnRH neurons is well-documented. An examination of novel and accumulating knowledge on the operation of these messengers indicates the presence of an interactive language governing GnRH secretion. The basic operational structures identified to date to affirm this interactive form of communication summarized in this review are the following: (i) the demonstration of interconnections within various components of the afferent network; (ii) coexistence and possible co-release of excitatory and inhibitory neurotransmitters/neuromodulators; (iii) co-action of various messengers at synaptic targets, and (4) modulation by gonadal steroids of the synthesis and release of signals and their receptors, and induction of synaptic plasticity for the timely relay of signals for GnRH secretion. Unraveling the molecular sequelae that promote this interactive communication to elicit periodic GnRH secretion is now a new challenge.

Evidence showing that beta-endorphin regulates cyclic guanosine 3',5'-monophosphate (cGMP) efflux: anatomical and functional support for an interaction between opiates and nitric oxide

Nitric oxide (NO) is now recognized as a diffusible messenger molecule that normally augments intercellular communication in the central nervous system, but is neurotoxic if released in excessive amounts. NO is synthesized from L-arginine by the Ca2+/calmodulin-dependent neuronal isoform NO synthase (NOS) localized in sub-populations of neurons throughout the brain, including the hypothalamus. In the hypothalamus, NO stimulates the release of GnRH, the primary neurohormone governing reproduction in mammals. Although the excitatory amino acid, glutamate, acting through the N-methyl-D-aspartate (NMDA) receptor is believed to be responsible for stimulation of NO release, the neuronal system(s) that inhibits NO efflux is unknown. As the endogenous opioids, primarily beta-endorphin (betaEND), exert a tonic restraint on GnRH secretion, we sought evidence for a possible functional link between betaEND and NOS pathways in the hypothalamus. We observed that restraining the opioid influence with the opiate receptor antagonist, naloxone, in intact, but not in castrated, rats rapidly augmented extracellular cGMP/NO efflux in the medial preoptic area, where GnRH, NOS, and betaEND immunoreactive pathways are coextensive. Pituitary LH secretion increased in conjunction with this augmented cGMP/NO response and pretreatment with the mu opiate receptor agonist, morphine, suppressed these naloxone-induced responses. Further, visualization of hypothalamic sections immunostained for both betaEND and NOS revealed betaEND-immunoreactive axon terminals in close proximity to NOS-positive cell bodies and dendrites in a number of hypothalamic subdivisions, including the medial preoptic area. These close appositions represented conventional synapses between betaEND nerve terminals and NOS-positive perikarya and dendrites under the electron microscope. Clearly, the experimental data, corroborated by morphological evidence, point to a direct inhibitory control of betaEND on NOS-immunoreactive neurons in monitoring cGMP/NO release. These findings together with the previous observations that the glutamate neurotransmitter acting through NMDA receptors located on NOS-immunopositive cells stimulates cGMP/NO efflux and plasma LH selectively in intact rats document the existence of a dual control comprised of the excitatory NMDA and the inhibitory mu opiate receptors in modulating cGMP/NO release, a response also directed by gonadal steroids. This new knowledge of an inhibitory opioid influence on cGMP/NO release is probably extremely important both in the generation of periodicities in GnRH secretion that underlie hypothalamic control of reproduction and in protecting against neurotoxic overstimulation of NO release by excitatory amino acids.

An interactive physiological role of neuropeptide Y and galanin in pulsatile pituitary luteinizing hormone secretion

Both neuropeptide Y (NPY) and galanin (GAL) systems have been implicated in the excitatory regulation of pulsatile LH secretion in the ovariectomized rat. The present studies were designed to examine the possible interaction of these two neuropeptides in controlling episodic LH release by testing the effects of central infusion of antibodies (Ab) to NPY and GAL, alone or in combination; additional studies tested the effects of central administration of an antisense oligodeoxynucleotide (ODN) to NPY and GAL messenger RNA. Rats were ovariectomized, implanted with a cannula in the third ventricle, and used in experiments 2 weeks later. Central infusion, via Alzet osmotic minipumps, of IgG purified from an NPY Ab produced a dose-related suppression of pulsatile LH secretion. Although an Ab dilution of 1:10 was ineffective, a maximal inhibitory effect was obtained using an NPY Ab dilution of 1:1, which decreased the mean levels, pulse frequency, and pulse amplitude of LH. These parameters of episodic LH secretion were also significantly reduced by central injection of antisense NPY ODN compared to those in vehicle- or missense ODN-treated controls. Similar dose-related inhibitory effects on the parameters of LH secretion were seen after central infusion of GAL Ab. Furthermore, infusion of a combination of NPY Ab and GAL Ab, each at the ineffective dilution of 1:10, resulted in a profound inhibition of LH secretion equivalent to the pattern seen with the maximally effective 1:1 Ab dilution. These results strengthen the idea of a physiological role for both NPY and GAL systems in the mechanism underlying the LHRH pulse generator activity and further suggest that these two excitatory neuropeptides act in concert to generate pulsatile LHRH release.