Lights at night mediate depression-like behavioral and molecular phenotypes in a glucocorticoid-dependent manner in male rats

Nocturnal light pollution, an underappreciated mood manipulator, disturbs the circadian rhythms of individuals in modern society. Preclinical and clinical studies have suggested that exposure to lights at night (LANs) results in depression-like phenotypes. However, the mechanism underlying the action of LANs remains unclear. Therefore, this study explored the potential influence of LANs on depression-related brain regions by testing brain-derived neurotrophic factor (BDNF), synaptic transmission, and plasticity in male Sprague-Dawley rats. Depression-related behavioral tests, enzyme-linked immunosorbent assays, and intracellular and extracellular electrophysiological recordings were performed. Resultantly, rats exposed to either white or blue LAN for 5 or 21 days exhibited depression-like behaviors. Both white and blue LANs reduced BDNF expression in the medial prefrontal cortex (mPFC) and ventrolateral periaqueductal gray (vlPAG). Moreover, both lights at night (LANs) elevated the plasma corticosterone levels. Pharmacologically, the activation of glucocorticoid receptors mimics the LAN-mediated effects on depression-like behaviors and reduces BDNF levels, whereas the inhibition of glucocorticoid receptors blocks LAN-mediated behavioral and molecular actions. Electrophysiologically, both LANs attenuated the stimulation-response curve, increased the paired-pulse ratio, and decreased the frequency and amplitude of miniature excitatory postsynaptic currents in the vlPAG. In the mPFC, LANs attenuate long-term potentiation and long-term depression. Collectively, these results suggested that white and blue LANs disturbed BDNF expression, synaptic transmission, and plasticity in the vlPAG and mPFC in a glucocorticoid-dependent manner. The results of the present study provide a theoretical basis for understanding the effects of nocturnal light exposure on depression-like phenotypes.

Protein Arginine Methyltransferase 5 Contributes to Paclitaxel-Induced Neuropathic Pain by Activating Transient Receptor Potential Vanilloid 1 Epigenetic Modification in Dorsal Root Ganglion

BACKGROUND

Paclitaxel (PTX), which is a first-line chemotherapy drug used to treat various types of cancers, exhibits peripheral neuropathy as a common side effect that is difficult to treat. Protein arginine methyltransferase 5 (PRMT 5) is a key regulator of the chemotherapy response, as chemotherapy drugs induce PRMT5 expression. However, little is known about the PRMT5-mediated epigenetic mechanisms involved in PTX-induced neuropathic allodynia.

METHODS

Sprague-Dawley rats were intraperitoneally given PTX to induce neuropathic pain. Biochemical analyses were conducted to measure the protein expression levels in the dorsal root ganglion (DRG) of the animals. The von Frey test and hot plate test were used to evaluate nociceptive behaviors.

RESULTS

PTX increased the PRMT5 (mean difference [MD]: 0.68, 95% confidence interval [CI], 0.88-0.48; P < .001 for vehicle)-mediated deposition of histone H3R2 dimethyl symmetric (H3R2me2s) at the transient receptor potential vanilloid 1 ( Trpv1 ) promoter in the DRG. PRMT5-induced H3R2me2s recruited WD repeat domain 5 (WDR5) to increase trimethylation of lysine 4 on histone H3 (H3K4me3) at Trpv1 promoters, thus resulting in TRPV1 transcriptional activation (MD: 0.65, 95% CI, 0.82-0.49; P < .001 for vehicle) in DRG in PTX-induced neuropathic pain. Moreover, PTX increased the activity of NADPH oxidase 4 (NOX4) (MD: 0.66, 95% CI, 0.81-0.51; P < .001 for vehicle), PRMT5-induced H3R2me2s, and WDR5-mediated H3K4me3 in the DRG in PTX-induced neuropathic pain. Pharmacological antagonism and the selective knockdown of PRMT5 in DRG neurons completely blocked PRMT5-mediated H3R2me2s, WDR5-mediated H3K4me3, or TRPV1 expression and neuropathic pain development after PTX injection. Remarkably, NOX4 inhibition not only attenuated allodynia behavior and reversed the above-mentioned signaling but also reversed NOX4 upregulation via PTX.

CONCLUSIONS

Thus, the NOX4/PRMT5-associated epigenetic mechanism in DRG has a dominant function in the transcriptional activation of TRPV1 in PTX-induced neuropathic pain.

Methylone produces antidepressant-relevant actions and prosocial effects

Methylone (3,4-methylenedioxy-N-methylcathinone) is a rapid-acting entactogen that has been shown to have significant benefits in patients with post-traumatic stress disorder and major depressive disorder and is well tolerated in phase 1 clinical trials. A recent preclinical study reported that methylone produced robust antidepressant-like actions in naïve rats. However, its antidepressant effects on various stress-related psychopathologies and other neuropsychological actions remain unclear. In the present study, we examined the antidepressant-relevant effects of methylone in learned helplessness (LH) and social defeat stress C57BL/6J male mouse models and further explored its sociability-relevant neuropsychological actions. Our results indicate that methylone produces antidepressant-relevant effects on the helpless phenotype, LH-evoked depressive-like behaviors, and psychosocial stress-induced social avoidance, and induced depressive-like behaviors. In addition, methylone was found to enhance social preference and increase various social behaviors, including social contact, sniffing, allogrooming, and following. Moreover, methylone appeared to elevate empathy-like phenotypes and was also found to increase helping-like behavior. Overall, the present results suggest that methylone plays an antidepressant-like role in various stress-relevant psychopathologies and could be an ideal antidepressant candidate. In addition, novel findings on the elevated tendencies of social preference and empathy-like and helping-like phenotypes reveal that methylone may have potential application in patients with social deficits.

Blue light at night produces stress-evoked heightened aggression by enhancing brain-derived neurotrophic factor in the basolateral amygdala

Light is an underappreciated mood manipulator. People are often exposed to electronic equipment, which results in nocturnal blue light exposure in modern society. Light pollution drastically shortens the night phase of the circadian rhythm. Preclinical and clinical studies have reported that nocturnal light exposure can influence mood, such as depressive-like phenotypes. However, the effects of blue light at night (BLAN) on other moods and how it alters mood remain unclear. Here, we explored the impact of BLAN on stress-provoked aggression in male Sprague‒Dawley rats, focusing on its influence on basolateral amygdala (BLA) activity. Resident-intruder tests, extracellular electrophysiological recordings, and enzyme-linked immunosorbent assays were performed. The results indicated that BLAN produces stress-induced heightened aggressive and anxiety-like phenotypes. Moreover, BLAN not only potentiates long-term potentiation and long-term depression in the BLA but also results in stress-induced elevation of brain-derived neurotrophic factor (BDNF), mature BDNF, and phosphorylation of tyrosine receptor kinase B expression in the BLA. Intra-BLA microinfusion of BDNF RNAi, BDNF neutralizing antibody, K252a, and rapamycin blocked stress-induced heightened aggressive behavior in BLAN rats. In addition, intra-BLA application of BDNF and 7,8-DHF caused stress-induced heightened aggressive behavior in naïve rats. Collectively, these results suggest that BLAN results in stress-evoked heightened aggressive phenotypes, which may work by enhancing BLA BDNF signaling and synaptic plasticity. This study reveals that nocturnal blue light exposure may have an impact on stress-provoked aggression. Moreover, this study provides novel insights into the BLA BDNF-dependent mechanism underlying the impact of the BLAN on mood.

Melatonin Relieves Paclitaxel-Induced Neuropathic Pain by Regulating pNEK2-Dependent Epigenetic Pathways in DRG Neurons

The neurohormone melatonin (MLT) demonstrates promising potential in ameliorating neuropathic pain induced by paclitaxel (PTX) chemotherapy. However, little is known about its protective effect on dorsal root ganglion (DRG) neurons in neuropathic pain resulting from the chemotherapeutic drug PTX. Here, PTX-treated rats revealed that intrathecal administration of MLT dose-dependently elevated hind paw withdrawal thresholds and latency, indicating that MLT significantly reversed PTX-induced neuropathic pain. Mechanistically, the analgesic effects of MLT were found to be mediated via melatonin receptor 2 (MT2), as pretreatment with an MT2 receptor antagonist inhibited these effects. Moreover, intrathecal MLT injection reversed the pNEK2-dependent epigenetic program induced by PTX. All of the effects caused by MLT were blocked by pretreatment with an MT2 receptor-selective antagonist, 4P-PDOT. Remarkably, multiple MLT administered during PTX treatment (PTX+MLTs) exhibited not only rapid but also lasting reversal of allodynia/hyperalgesia compared to single-bolus MLT administered after PTX treatment (PTX+MLT). In addition, PTX+MLTs exhibited greater efficacy in reversing PTX-induced alterations in pRSK2, pNEK2, JMJD3, H3K27me3, and TRPV1 expression and interaction in DRG neurons than PTX+MLT. These results indicated that MLT administered during PTX treatment reduced the incidence and/or severity of neuropathy and had a better inhibitory effect on the pNEK2-dependent epigenetic program compared to MLT administered after PTX treatment. In conclusion, MLT/MT2 is a promising therapy for the treatment of pNEK2-dependent painful neuropathy resulting from PTX treatment. MLT administered during PTX chemotherapy may be more effective in the prevention or reduction of PTX-induced neuropathy and maintaining quality.

Phosphate NIMA-Related Kinase 2-Dependent Epigenetic Pathways in Dorsal Root Ganglion Neurons Mediates Paclitaxel-Induced Neuropathic Pain

BACKGROUND

The microtubule-stabilizing drug paclitaxel (PTX) is an important chemotherapeutic agent for cancer treatment and causes peripheral neuropathy as a common side effect that substantially impacts the functional status and quality of life of patients. The mechanistic role for NIMA-related kinase 2 (NEK2) in the progression of PTX-induced neuropathic pain has not been established.

METHODS

Adult male Sprague-Dawley rats intraperitoneally received PTX to induce neuropathic pain. The protein expression levels in the dorsal root ganglion (DRG) of animals were measured by biochemical analyses. Nociceptive behaviors were evaluated by von Frey tests and hot plate tests.

RESULTS

PTX increased phosphorylation of the important microtubule dynamics regulator NEK2 in DRG neurons and induced profound neuropathic allodynia. PTX-activated phosphorylated NEK2 (pNEK2) increased jumonji domain-containing 3 (JMJD3) protein, a histone demethylase protein, to specifically catalyze the demethylation of the repressive histone mark H3 lysine 27 trimethylation (H3K27me3) at the Trpv1 gene, thereby enhancing transient receptor potential vanilloid subtype-1 (TRPV1) expression in DRG neurons. Moreover, the pNEK2-dependent PTX response program is regulated by enhancing p90 ribosomal S6 kinase 2 (RSK2) phosphorylation. Conversely, intrathecal injections of kaempferol (a selective RSK2 activation antagonist), NCL 00017509 (a selective NEK2 inhibitor), NEK2-targeted siRNA, GSK-J4 (a selective JMJD3 inhibitor), or capsazepine (an antagonist of TRPV1 receptor) into PTX-treated rats reversed neuropathic allodynia and restored silencing of the Trpv1 gene, suggesting the hierarchy and interaction among phosphorylated RSK2 (pRSK2), pNEK2, JMJD3, H3K27me3, and TRPV1 in the DRG neurons in PTX-induced neuropathic pain.

CONCLUSIONS

pRSK2/JMJD3/H3K27me3/TRPV1 signaling in the DRG neurons plays as a key regulator for PTX therapeutic approaches.

Pressure-Volume Loop Analysis of Voiding Workload: An Application in Trans-Vaginal Mesh-Repaired Pelvic Organ Prolapse Patients

Although trans-vaginal mesh (TVM) offers a successful anatomical reconstruction and can subjectively relieve symptoms/signs in pelvic organ prolapse (POP) patients, its objective benefits to the voiding function of the bladder have not been well established. In this study, we investigated the therapeutic advantage of TVM on bladder function by focusing on the thermodynamic workload of voiding. The histories of 31 POP patients who underwent TVM repair were retrospectively reviewed. Cystometry and pressure volume analysis (PVA) of the patients performed before and after the operation were analyzed. TVM postoperatively decreased the mean voiding resistance (mRv, p < 0.05, N = 31), reduced the mean and peak voiding pressure (mPv, p < 0.05 and pPv, p < 0.01, both N = 31), and elevated the mean flow rate (mFv, p < 0.05, N = 31) of voiding. While displaying an insignificant effect on the voided volume (Vv, p < 0.05, N = 31), TVM significantly shortened the voiding time (Tv, p < 0.05, N = 31). TVM postoperatively decreased the loop-enclosed area (Apv, p < 0.05, N = 31) in the PVA, indicating that TVM lessened the workload of voiding. Moreover, in 21 patients who displayed postvoiding urine retention before the operation, TVM decreased the residual volume (Vr, p < 0.01, N = 21). Collectively, our results reveal that TVM postoperatively lessened the workload of bladder voiding by diminishing voiding resistance, which reduced the pressure gradient required for driving urine flow.

BTRX-246040 acts through the ventrolateral periaqueductal gray to exert antidepressant-relevant actions in mice

BACKGROUND

BTRX-246040, a nociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptor antagonist, is being developed for the treatment of depressive patients. However, the underlying mechanism of this potential antidepressant is still largely unclear. Here, we studied the antidepressant-related actions of BTRX-246040 in the ventrolateral periaqueductal gray (vlPAG).

METHODS

The tail suspension test (TST), forced swim test (FST), female urine sniffing test (FUST), sucrose preference test (SPT), and learned helplessness (LH) combined with pharmacological approaches were employed to examine the antidepressant-like effects and the drug effects on LH-induced depressive-like behavior in C57BL/6J mice. Electrophysiological recordings in vlPAG neurons were used to study synaptic activity.

RESULTS

Intraperitoneal administration of BTRX-246040 produced antidepressant-like behavioral effects in a dose-dependent manner. Systemic BTRX-246040 (10 mg/kg) resulted in an increased frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs) in the vlPAG. Moreover, slice perfusion of BTRX-246040 directly elevated the frequency and amplitude of mEPSCs and enhanced the evoked excitatory postsynaptic currents (EPSCs) in the vlPAG, which were blocked by pretreatment with the NOP receptor agonist Ro 64-6198. In addition, intra-vlPAG application of BTRX-246040 produced antidepressant-like behavioral effects in a dose-dependent manner. Moreover, intra-vlPAG pretreatment with CNQX reversed both systemic and local BTRX-246040-mediated antidepressant-like behavioral effects. Furthermore, both systemic and local BTRX-246040 decreased the LH phenotype and reduced LH-induced depressive-like behavior.

CONCLUSIONS

The results suggested that BTRX-246040 may act through the vlPAG to exert antidepressant-relevant actions. The present study provides new insight into a vlPAG-dependent mechanism underlying the antidepressant-like actions of BTRX-246040.

Phosphorylated Upstream Frameshift 1-dependent Nonsense-mediated μ-Opioid Receptor mRNA Decay in the Spinal Cord Contributes to the Development of Neuropathic Allodynia-like Behavior in Rats

BACKGROUND

Nonsense-mediated messenger RNA (mRNA) decay increases targeted mRNA degradation and has been implicated in the regulation of gene expression in neurons. The authors hypothesized that nonsense-mediated μ-opioid receptor mRNA decay in the spinal cord is involved in the development of neuropathic allodynia-like behavior in rats.

METHODS

Adult Sprague-Dawley rats of both sexes received spinal nerve ligation to induce neuropathic allodynia-like behavior. The mRNA and protein expression contents in the dorsal horn of animals were measured by biochemical analyses. Nociceptive behaviors were evaluated by the von Frey test and the burrow test.

RESULTS

On Day 7, spinal nerve ligation significantly increased phosphorylated upstream frameshift 1 (UPF1) expression in the dorsal horn (mean ± SD; 0.34 ± 0.19 in the sham ipsilateral group vs. 0.88 ± 0.15 in the nerve ligation ipsilateral group; P < 0.001; data in arbitrary units) and drove allodynia-like behaviors in rats (10.58 ± 1.72 g in the sham ipsilateral group vs. 1.19 ± 0.31 g in the nerve ligation ipsilateral group, P < 0.001). No sex-based differences were found in either Western blotting or behavior tests in rats. Eukaryotic translation initiation factor 4A3 (eIF4A3) triggered SMG1 kinase (0.06 ± 0.02 in the sham group vs. 0.20 ± 0.08 in the nerve ligation group, P = 0.005, data in arbitrary units)-mediated UPF1 phosphorylation, leading to increased nonsense-mediated mRNA decay factor SMG7 binding and µ-opioid receptor mRNA degradation (0.87 ± 0.11-fold in the sham group vs. 0.50 ± 0.11-fold in the nerve ligation group, P = 0.002) in the dorsal horn of the spinal cord after spinal nerve ligation. Pharmacologic or genetic inhibition of this signaling pathway in vivo ameliorated allodynia-like behaviors after spinal nerve ligation.

CONCLUSIONS

This study suggests that phosphorylated UPF1-dependent nonsense-mediated μ-opioid receptor mRNA decay is involved in the pathogenesis of neuropathic pain.

EDITOR’S PERSPECTIVE

(2R,6R)-hydroxynorketamine targeting the basolateral amygdala regulates fear memory

(2R,6R)-Hydroxynorketamine (HNK), a ketamine metabolite, has been proposed as an ideal next-generation antidepressant due to its rapid-acting and long-lasting antidepression-relevant actions. Interestingly, recent studies have shown that (2R,6R)-HNK may have diverse impacts on memory formation. However, its effect on fear memory extinction is still unknown. In the present study, we assessed the effects of (2R,6R)-HNK on synaptic transmission and plasticity in the basolateral amygdala (BLA) and explored its actions on auditory fear memory extinction. Adult male C57BL/6J mice were used in this study. The extracellular electrophysiological recording was conducted to assay synaptic transmission and plasticity. The auditory fear conditioning paradigm was performed to test fear extinction. The results showed that (2R,6R)-HNK at 30 mg/kg increased the number of c-fos-positive cells in the BLA. Moreover, (2R,6R)-HNK enhanced the induction and maintenance of long-term potentiation (LTP) in the BLA in a dose-dependent manner (at 1, 10, and 30 mg/kg). In addition, (2R,6R)-HNK at 30 mg/kg and directly slice perfusion of (2R,6R)-HNK enhanced BLA synaptic transmission. Furthermore, intra-BLA application and systemic administration of (2R,6R)-HNK reduced the retrieval of recent fear memory and decreased the retrieval of remote fear memory. Both local and systemic (2R,6R)-HNK also inhibited the spontaneous recovery of remote fear memory. Taken together, these results indicated that (2R,6R)-HNK could regulate BLA synaptic transmission and plasticity and act through the BLA to modulate fear memory. The results revealed that (2R,6R)-HNK may be a potential drug to treat posttraumatic stress disorder (PTSD) patients.

[Effects and mechanism of pressure treatment on hemodynamic changes in patients with hypertrophic scar secondary to extensive burns]

Objective: To investigate the hemodynamic changes of the main arteries and veins of the extremities and the heart in patients with hypertrophic scar secondary to extensive burns after pressure treatment, and to analyze the relevant mechanisms. Methods: A retrospective before-after self-control study was conducted. From January 2017 to February 2022, 37 patients with hypertrophic scar secondary to extensive burns who met the inclusion criteria were hospitalized in the Burn Rehabilitation Department of Guangdong Industrial Injury Rehabilitation Hospital, including 25 males and 12 females, aged 23-52 years. The patients were admitted to the hospital within 12 weeks after wound healing, and within one week after admission, rehabilitation therapists, occupational therapists, and tailors custom-made pressure products such as full-body pressure garment, pressure pants, vests, split finger gloves, split finger socks, hoods, and plastic collars, with the pressure at each part maintained at 2.67-4.00 kPa when wearing. Before the first treatment with pressure products (hereinafter referred to as before pressure treatment) and at 1 h of the first treatment with pressure products (hereinafter referred to as 1 h of pressure treatment), color Doppler ultrasonography was performed to check the pulse rate of the axillary artery, the lumen diameter, peak systolic velocity (PSV), and resistance index of the axillary artery and femoral artery on the left side, the lumen diameter, cross-sectional area, and average blood flow velocity of the axillary vein and femoral vein, and the mitral valve E peak, mitral valve A peak, tricuspid valve E peak, aortic valve PSV, and pulmonary valve PSV of the heart; an optical chromatographic skin detector was used to detect the red color, red pigment, and surface brightness of the scar on the back of the hand to reflect the filling and distribution of the scar microvessels. Data were statistically analyzed with paired sample t test. Results: Compared with those before pressure treatment, the PSV of the axillary artery of patients was significantly slowed down at 1 h of pressure treatment (t=55.42, P<0.01); the average blood flow velocity of the axillary vein was significantly accelerated (t=-60.50, P<0.01); the pulse rate, lumen diameter, and resistance index of the axillary artery, as well as the lumen diameter and cross-sectional area of the axillary vein did not change obviously (P>0.05); the average blood flow velocity of the femoral vein was significantly accelerated (t=-80.52, P<0.01); the lumen diameter, PSV, and resistance index of the femoral artery, as well as the lumen diameter and cross-sectional area of the femoral vein had no significant change (P>0.05); the mitral valve E peak and mitral valve A peak of the heart decreased significantly (with t values of 10.71 and 21.96, respectively, P<0.01); the tricuspid valve E peak of the heart increased significantly (t=7.57, P<0.01); the PSV of the aortic valve and pulmonary valve of the heart did not change obviously (P>0.05). At 1 h of pressure treatment, the red color and red pigment values of the scar on the back of the hand of patients were 15.3±1.1 and 16.8±1.2, respectively, which were significantly lower than 24.5±1.3 and 23.8±1.2 before pressure treatment (with t values of 8.32 and 8.04, respectively, P<0.01). The brightness value of the scar surface on the back of the hand of patients at 1 h of pressure treatment was similar to that before pressure treatment (P>0.05). Conclusions: After pressure treatment for the hypertrophic scar in patients secondary to extensive burn, the average blood flow velocity of the axillary vein and femoral vein in patients are obviously accelerated, the PSV of the axillary artery is significantly slowed down, the peak values of mitral valve E and mitral valve A of the heart are significantly decreased, and the tricuspid valve E peak is significantly increased. These hemodynamic changes may be related to the reduction of microvascular blood flow in the local area of scar after systemic pressure treatment.

Modification of bladder thermodynamics in stress urinary incontinence patients submitted to trans-obturator tape: A retrospective study based on urodynamic assessment

Importance: It needs to be clarified whether trans-obturator tape (TOT)-enhanced urethral resistance could impact the voiding function.

Objective: Although TOT has been well-recognized for enhancing urethral resistance to restore continence in stress urinary incontinence (SUI) patients, whether the bladder’s voiding functions adapt to the TOT-enhanced resistance has not been adequately investigated. This study thereby aimed to investigate whether TOT impacts the bladder’s thermodynamic efficacy during the voiding phase.

Design: A retrospective analysis of urodynamics performed before and after TOT was assessed.

Setting: A tertiary referral hospital in Taiwan.

Participants: A total of 26 female SUI patients who underwent urodynamic investigations before and after TOT.

Main outcomes and measures: The area enclosed by the pressure-volume loop (Apv), which represents the work performed by the bladder during voiding, in a pressure-volume analysis established by plotting the detrusor pressure versus intra-vesical volume was retrospectively analyzed. Paired Student’s t-tests were employed to assess the difference in values before and after the operation. Significance in difference was set at p &lt; 0.05.

Results: TOT increased Apv in 20 of 26 (77%) patients and significantly increased the mean Apv compared to the preoperative control (2.17 ± 0.18 and 1.51 ± 0.13 × 103 cmH2O-ml, respectively p &lt; 0.01). TOT also increased the mean urethral resistance (1.03 ± 0.30 vs. 0.29 ± 0.05 cmH2O-sec/ml, p &lt; 0.01) and mean voiding pressure (25.87 ± 1.72 and 19.30 ± 1.98 cmH2O p &lt; 0.01) but did not affect the voided volume and voiding time. Moreover, the TOT-induced Apv increment showed a moderate correlation with the changes in urethral resistance and voiding pressure (both r &gt; 0.5) but no correlation with changes in voided volume or voiding time. It is remarkable that the TOT-induced urethral resistance increment showed a strong correlation with changes in voiding pressure (r &gt; 0.7).

Conclusion and Relevance: The bladder enhances thermodynamic efficacy by adapting the voiding mechanism to increased urethral resistance caused by TOT. Further studies with higher case series and longer follow-ups should assess whether this effect could be maintained over time or expire in a functional detrusor decompensation, to define diagnostic criteria that allow therapeutic interventions aimed at its prevention during the follow-up.

Clinical Trial Registration: (clinicaltrials.gov), identifier (NCT05255289)

MicroRNA-489-3p attenuates neuropathic allodynia by regulating oncoprotein DEK/TET1-dependent epigenetic modification in the dorsal horn

Originally characterized as an oncoprotein overexpressed in many forms of cancer that participates in numerous cellular pathways, DEK has since been well described regarding the regulation of epigenetic markers and transcription factors in neurons. However, its role in neuropathic allodynia processes remain elusive and intriguingly complex. Here, we show that DEK, which is induced in spinal dorsal horn neurons after spinal nerve ligation (SNL), is regulated by miR-489-3p. Moreover, SNL-induced decrease in miR-489-3p expression increased the expression of DEK, which recruited TET1 to the promoter fragments of the Bdnf, Grm5, and Stat3 genes, thereby enhancing their transcription in the dorsal horn. Remarkably, these effects were also induced by intrathecally administering naïve animals with miR-489-3p inhibitor, which could be inhibited by knockdown of TET1 siRNA or DEK siRNA. Conversely, delivery of intrathecal miR-489-3p-mimic into SNL rats attenuated allodynia behavior and reversed protein expression coupled to the promoter segments in the dorsal horn. Thus, a spinal miR-489-3p/DEK/TET1 transcriptional axis may contribute to neuropathic allodynia. These results may provide a new target for treating neuropathic allodynia.

Shoulder transcutaneous electric nerve stimulation decreases heart rate via potentiating vagal tone

By enhancing vagal activity, auricle transcutaneous electric nerve stimulation (TENS) is developed as a non-invasive therapy for heart failure. Nevertheless, though shoulder TENS used for treating adhesive capsulitis could affect vagal tone, its potential impact on heart functions remains unclear. In this study, electrocardiogram (ECG) and heart rate (HR) of subjects in response to sham, right-sided, or left-sided shoulder TENS (TENS-S, TENS-R, and TENS-L, respectively; 5 min) were recorded and analyzed. During the stimulation period, TENS-R constantly and TENS-L transiently decreased the HR of subjects; both TENS-R and TENS-L increased powers of the low- and high-frequency spectra. While TENS-R exhibiting no effect, TENS-L increased the ratio of low/high-frequency power spectrum indicating TENS-R decreased the HR through potentiating cardiac vagal tone. Collectively, these results suggest TENS could be an early and non-invasive therapy for heart failure patients before considering implant devices or devices are not feasible; moreover, therapists/physicians need to carefully monitor the potential adverse events during treatment for patient safety.

Trial registration: The study protocol was registered in ClinicalTrials.gov (NCT03982472; 11/06/2019).

Protective Effects of Fucoxanthin Dampen Pathogen-Associated Molecular Pattern (PAMP) Lipopolysaccharide-Induced Inflammatory Action and Elevated Intraocular Pressure by Activating Nrf2 Signaling and Generating Reactive Oxygen Species

Inflammation and oxidative stress are closely related processes in the pathogenesis of various ocular diseases. Uveitis is a disorder of the uvea and ocular tissues that causes extreme pain, decreases visual acuity, and can eventually lead to blindness. The pharmacological functions of fucoxanthin, isolated from brown algae, induce a variety of therapeutic effects such as oxidative stress reduction and repression of inflammation reactions. However, the specific anti-inflammatory effects of fucoxanthin on pathogen-associated molecular pattern (PAMP) lipopolysaccharide-induced uveitis have yet to be extensively described. Therefore, the aim of present study was to investigate the anti-inflammatory effects of fucoxanthin on uveitis in rats. The results showed that fucoxanthin effectively enhanced the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) in ocular tissues. Furthermore, fucoxanthin significantly increased the ocular activities of superoxide dismutase and decreased the levels of malondialdehyde stimulated by PAMP-induced uveitis. Ocular hypertension and the levels of inflammatory cells and proinflammatory cytokine tumor necrosis factor-alpha in the aqueous humor were alleviated with fucoxanthin treatment. Consequently, compared to the observed effects in lipopolysaccharide groups, fucoxanthin treatment significantly preserved iris sphincter innervation and pupillary function. Additionally, PAMP-induced corneal endothelial disruption was significantly inhibited by fucoxanthin treatment. Overall, these findings suggest that fucoxanthin may protect against inflammation from PAMP-induced uveitis by promoting the Nrf2 pathway and inhibiting oxidative stress.

Solifenacin/Mirabegron Induces an Acute Compliance Increase in the Filling Phase of the Capacity-Reduced Urinary Bladder: A Pressure-Volume Analysis in Rats

Aims: Pressure in the bladder, which is a high compliance organ, is only slightly elevated to a considerable filling volume during storage. Although cystometry off-line offers mean compliance, no protocol is available for real-time assays of the dynamics of bladder compliance, and the potential impact of solifenacin and mirabegron on dynamic bladder compliance has not been established.

Methods: Along with constantly infused cystometry, a pressure-volume analysis (PVA) was performed by plotting intra-vesical volume against pressure in Sprague-Dawley rats. The instant compliance was assayed as the slope of the trajectory, and the mean compliance (Cm) was determined by the slope of the line produced by regression of the data points at the end of the first, second, and third quarters of the filling phase.

Results: Under a steady-state, the PVA trajectory moved clockwise which shaped coincident enclosed loops with stable compliance. Though administering to naïve animals solifenacin, but not mirabegron (both 1 × 10⁻⁵−1 × 10⁻¹ mg/kg, i.a.) decreased the peak pressure, both of these reagents exhibited acute increments in the trajectory slope and Cm of the filling phase in a dose-dependent manner (ED₅₀ = 1.4 × 10⁻⁴ and 2.2 × 10⁻⁵ mg/kg, respectively). Resembling urine frequency/urgency in OAB patients, the voiding frequency of a capacity-reduced bladder was increased in association with decreased compliance which was ameliorated by both acute solifenacin and mirabegron injections (both 1 × 10−1 mg/kg).

Conclusion: In addition to their well-known anti-inotropic/relaxative effects, solifenacin, and mirabegron induce an acute increase in bladder compliance to ameliorate OAB-like syndromes. Together with time-domain cystometry, PVA offers a platform for investigating the physiology/pathophysiology/pharmacology of bladder compliance which is crucial for urine storage.

Blocking the Spinal Fbxo3/CARM1/K+ Channel Epigenetic Silencing Pathway as a Strategy for Neuropathic Pain Relief

Many epigenetic regulators are involved in pain-associated spinal plasticity. Coactivator-associated arginine methyltransferase 1 (CARM1), an epigenetic regulator of histone arginine methylation, is a highly interesting target in neuroplasticity. However, its potential contribution to spinal plasticity-associated neuropathic pain development remains poorly explored. Here, we report that nerve injury decreased the expression of spinal CARM1 and induced allodynia. Moreover, decreasing spinal CARM1 expression by Fbxo3-mediated CARM1 ubiquitination promoted H3R17me2 decrement at the K+ channel promoter, thereby causing K+ channel epigenetic silencing and the development of neuropathic pain. Remarkably, in naïve rats, decreasing spinal CARM1 using CARM1 siRNA or a CARM1 inhibitor resulted in similar epigenetic signaling and allodynia. Furthermore, intrathecal administration of BC-1215 (a novel Fbxo3 inhibitor) prevented CARM1 ubiquitination to block K+ channel gene silencing and ameliorate allodynia after nerve injury. Collectively, the results reveal that this newly identified spinal Fbxo3-CARM1-K+ channel gene functional axis promotes neuropathic pain. These findings provide essential insights that will aid in the development of more efficient and specific therapies against neuropathic pain.

Pressure-volume analysis of rat's micturition cycles in vivo

AIMS

Though the pressure-volume analysis (PVA), a method based on thermodynamics, is broadly used for assaying cardiac functions, its potential application on the physiology/pathophysiology of the urinary bladder, which processes resemble thermodynamic cycles to the heart, has not been established.

METHODS

Cystometry recording intravesical pressure (IVP) and intravesical volume (IVV) of rhythmic voiding contractions caused by a constant saline infusion (0.04 mL/min) were carried out in forty urethane-anesthetized female Sprague-Dawley rats, and the PVA was established by plotting IVP against IVV.

RESULTS

Pressure-volume points shaped coincident enclosed loops, and loop-associated urodynamic parameters kept stable under a constant infusion rate (0.04 mL/min). Enhancing preload (by elevating infusion rates to 0.08 and 0.12 mL/min) increased the area enclosed by the loop (Apv) and shifted loops to the right and slightly upward. Augmenting afterload (by enhancing resistances using 1/4 and 1/2 urethra clamping) increased Apv and shifted loops markedly to the right and upward. Without affecting Apv, muscarine (0.01 and 0.1 mM)-induced inotropic states shifted loop to the left and upward that was as opposed to the atropine (0.01 and 0.1 mM)-induced anti-inotropic state.

CONCLUSIONS

Not only consistently assayed baseline bladder functions, PVA but also validly measured modified bladder functions due to altered extrinsic environment and intrinsic contractility of the bladder itself. In accompanied by cystometry, PVA could provide a clear concept about the relationship between time, pressure, and volume in the voiding activity.

Protective Effects of Fucoxanthin on Ultraviolet B-Induced Corneal Denervation and Inflammatory Pain in a Rat Model

Fucoxanthin is a carotenoid with many pharmaceutical properties that is found in brown seaweed. However, the effects of fucoxanthin on corneal innervation and intense eye pain have not been extensively examined. To clarify the protective roles and underlying mechanisms of fucoxanthin on ocular lesions, we investigated the beneficial effects and mechanisms by which fucoxanthin ameliorates ultraviolet B (UVB)-induced corneal denervation and trigeminal pain. Treatment with fucoxanthin enhanced the expression of nuclear factor erythroid 2-related factor 2 in the cornea. Inhibition of typical denervation and epithelial exfoliation in the cornea were observed in rats treated with fucoxanthin following UVB-induced nerve disorders. Moreover, the active phosphorylated form of p38 MAP kinase (pp38) and the number of glial fibrillary acidic protein (GFAP)-positive neural cells were significantly reduced. Decreased expression of neuron-selective transient receptor potential vanilloid type 1 (TRPV1) in the trigeminal ganglia neurons was also demonstrated in rats treated with fucoxanthin after UVB-induced keratitis. Symptoms of inflammatory pain, including difficulty in opening the eyes and eye wipe behaviour, were also reduced in fucoxanthin-treated groups. Pre-treatment with fucoxanthin may protect the eyes from denervation and inhibit trigeminal pain in UVB-induced photokeratitis models.

Spinal TNF-α impedes Fbxo45-dependent Munc13-1 ubiquitination to mediate neuropathic allodynia in rats

Presynaptic active zone proteins play a crucial role in regulating synaptic plasticity. Although the ubiquitin–proteasome system underlying the degradation of the presynaptic active zone protein is well established, the contribution of this machinery to regulating spinal plasticity during neuropathic pain development remains unclear. Here, using male Sprague Dawley rats, we demonstrated along with behavioral allodynia, neuropathic injury induced a marked elevation in the expression levels of an active zone protein Munc13-1 in the homogenate and synaptic plasma membrane of the ipsilateral dorsal horn. Moreover, nerve injury-increased Munc13-1 expression was associated with an increase in the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs) in ipsilateral dorsal horn neurons. This neuropathic injury-induced accumulation of Munc13-1 colocalized with synaptophysin but not homer1 in the dorsal horn. Focal knockdown of spinal Munc13-1 expression attenuated behavioral allodynia and the increased frequency, not the amplitude, of mEPSCs in neuropathic rats. Remarkably, neuropathic injury decreased spinal Fbxo45 expression, Fbxo45-Munc13-1 co-precipitation, and Munc13-1 ubiquitination in the ipsilateral dorsal horn. Conversely, focal knockdown of spinal Fbxo45 expression in naive animals resulted in behavioral allodynia in association with similar protein expression and ubiquitination in the dorsal horn as observed with neuropathic injury rats. Furthermore, both neuropathic insults and intrathecal injection of tumor necrosis factor-α (TNF-α) impeded spinal Fbxo45-dependent Munc13-1 ubiquitination, which was reversed by intrathecal TNF-α-neutralizing antibody. Our data revealed that spinal TNF-α impedes Fbxo45-dependent Munc13-1 ubiquitination that accumulates Munc13-1 in the presynaptic area and hence facilitates the synaptic excitability of nociceptive neurotransmission underlying neuropathic pain.

Periaqueductal Gray Glutamatergic Transmission Governs Chronic Stress-Induced Depression

The mechanisms underlying chronic stress-induced dysfunction of glutamatergic transmission that contribute to helplessness-associated depressive disorder are unknown. We investigated the relationship of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and stress, and the neuroplastic changes of stress-induced depression-like behavior in the ventrolateral periaqueductal gray (vlPAG). We conducted whole-cell patch-clamp electrophysiological recordings in the vlPAG neurons. Depression-like behavior was assayed using tail suspension test and sucrose preference test. Surface and cytosolic glutamate receptor 1 (GluR1) AMPA receptor expression was analyzed using western blotting. Phosphorylated GluR1 expression was quantified using western blotting and immunohistochemical analysis. Unpredictable inescapable foot shock stress caused reduction in glutamatergic transmission originating from both presynaptic and postsynaptic loci in the vlPAG that was associated with behavioral despair and anhedonia in chronic stress-induced depression. Pharmacological inhibition of GluR1 function in the vlPAG caused depression-like behavior. Diminished glutamatergic transmission was due to reduced glutamate release presynaptically and enhanced GluR1-endocytosis from the cell surface postsynaptically. Chronic stress-induced neuroplastic changes and maladaptive behavior were reversed and mimicked by administration of glucocorticoid receptor (GR) antagonist and agonist, respectively. However, chronic stress did not affect γ-aminobutyric acid (GABA)-mediated inhibitory synaptic transmission in the vlPAG. These results demonstrate that depression-like behavior is associated with remarkable reduction in glutamatergic, but not GABAergic, transmission in the vlPAG. These neuroplastic changes and maladaptive behavior are attributed to GR-dependent mechanisms. As reduced GluR1-associated responses in the vlPAG contribute to chronic stress-induced neuroplastic changes, this cellular mechanism may be a critical component in the pathogenesis of stress-associated neuropsychiatric disorders.

Melatonin impedes Tet1-dependent mGluR5 promoter demethylation to relieve pain

Melatonin (N-acetyl-5-methoxytryptamine)/MT2 receptor-dependent epigenetic modification represents a novel pathway in the treatment of neuropathic pain. Because spinal ten-eleven translocation methylcytosine dioxygenase 1 (Tet1)-dependent epigenetic demethylation has recently been linked to pain hypersensitivity, we hypothesized that melatonin/MT2-dependent analgesia involves spinal Tet1-dependent demethylation. Here, we showed that spinal Tet1 gene transfer by intrathecal delivery of Tet1-encoding vectors to naïve rats produced profound and long-lasting nociceptive hypersensitivity. In addition, enhanced Tet1 expression, Tet1-metabotropic glutamate receptor subtype 5 (mGluR5) promoter coupling, demethylation at the mGluR5 promoter, and mGluR5 expression in dorsal horn neurons were observed. Rats subjected to spinal nerve ligation and intraplantar complete Freund's adjuvant injection displayed tactile allodynia and behavioral hyperalgesia associated with similar changes in the dorsal horn. Notably, intrathecal melatonin injection reversed the protein expression, protein-promoter coupling, promoter demethylation, and pain hypersensitivity induced by Tet1 gene transfer, spinal nerve ligation, and intraplantar complete Freund's adjuvant injection. All the effects caused by melatonin were blocked by pretreatment with a MT2 receptor-selective antagonist. In conclusion, melatonin relieves pain by impeding Tet1-dependent demethylation of mGluR5 in dorsal horn neurons through the MT2 receptor. Our findings link melatonin/MT2 signaling to Tet1-dependent epigenetic demethylation of nociceptive genes for the first time and suggest melatonin as a promising therapy for the treatment of pain.

Melatonin relieves neuropathic allodynia through spinal MT2-enhanced PP2Ac and downstream HDAC4 shuttling-dependent epigenetic modification of hmgb1 transcription

Melatonin (MLT; N-acetyl-5-methoxytryptamine) exhibits analgesic properties in chronic pain conditions. While researches linking MLT to epigenetic mechanisms have grown exponentially over recent years, very few studies have investigated the contribution of MLT-associated epigenetic modification to pain states. Here, we report that together with behavioral allodynia, spinal nerve ligation (SNL) induced a decrease in the expression of catalytic subunit of phosphatase 2A (PP2Ac) and enhanced histone deacetylase 4 (HDAC4) phosphorylation and cytoplasmic accumulation, which epigenetically alleviated HDAC4-suppressed hmgb1 gene transcription, resulting in increased high-mobility group protein B1 (HMGB1) expression selectively in the ipsilateral dorsal horn of rats. Focal knock-down of spinal PP2Ac expression also resulted in behavioral allodynia in association with similar protein expression as observed with SNL. Notably, intrathecal administration with MLT increased PP2Ac expression, HDAC4 dephosphorylation and nuclear accumulation, restored HDAC4-mediated hmgb1 suppression and relieved SNL-sensitized behavioral pain; these effects were all inhibited by spinal injection of 4P-PDOT (a MT2 receptor antagonist, 30 minutes before MLT) and okadaic acid (OA, a PP2A inhibitor, 3 hr after MLT). Our findings demonstrate a novel mechanism by which MLT ameliorates neuropathic allodynia via epigenetic modification. This MLT-exhibited anti-allodynia is mediated by MT2-enhanced PP2Ac expression that couples PP2Ac with HDAC4 to induce HDAC4 dephosphorylation and nuclear import, herein increases HDAC4 binding to the promoter of hmgb1 gene and upregulates HMGB1 expression in dorsal horn neurons.

Inhibition of Ultraviolet B-Induced Expression of the Proinflammatory Cytokines TNF-α and VEGF in the Cornea by Fucoxanthin Treatment in a Rat Model

Ultraviolet B (UVB) irradiation is the most common cause of radiation damage to the eyeball and is a risk factor for human corneal damage. We determined the protective effect of fucoxanthin, which is a carotenoid found in common edible seaweed, on ocular tissues against oxidative UVB-induced corneal injury. The experimental rats were intravenously injected with fucoxanthin at doses of 0.5, 5 mg/kg body weight/day or with a vehicle before UVB irradiation. Lissamine green for corneal surface staining showed that UVB irradiation caused serious damage on the corneal surface, including severe epithelial exfoliation and deteriorated epithelial smoothness. Histopathological lesion examination revealed that levels of proinflammatory cytokines, including tumor necrosis factor-α (TNF-α) and vascular endothelial growth factor (VEGF), significantly increased. However, pretreatment with fucoxanthin inhibited UVB radiation-induced corneal disorders including evident preservation of corneal surface smoothness, downregulation of proinflammatory cytokine expression, and decrease of infiltrated polymorphonuclear leukocytes from UVB-induced damage. Moreover, significant preservation of the epithelial integrity and inhibition of stromal swelling were also observed after UVB irradiation in fucoxanthin-treated groups. Pretreatment with fucoxanthin may protect against UVB radiation-induced corneal disorders by inhibiting expression of proinflammatory factors, TNF-α, and VEGF and by blocking polymorphonuclear leukocyte infiltration.

Glucocorticoid mediates water avoidance stress-sensitized colon-bladder cross-talk via RSK2/PSD-95/NR2B in rats

Unexpected environmental and social stimuli could trigger stress. Although coping with stress is essential for survival, long-term stress impacts visceral functions, and therefore, it plays a role in the development and exacerbation of symptoms of gastrointestinal/urogenital disorders. The aim of this study is to characterize the role of corticosterone in stress-sensitized colon-bladder cross-talk, a phenomenon presumed to underlie the comorbidity of functional bowel and bladder disorders. Cystometry and protein/mRNA expression in the lumbosacral dorsal horn (L6-S1) in response to intracolonic mustard oil (MO) instillation were analyzed in female Wistar-Kyoto rats subjected to water avoidance stress (WAS; 1 h/day for 10 days) or sham stress (WAsham). Whereas it had no effect on baseline-voiding function, chronic stress upregulated plasma corticosterone concentration and dorsal horn spinal p90 ribosomal S6 kinase 2 (RSK2) protein/mRNA levels, and RSK2 immunoreactivity colocalized with NeuN-positive neurons. Intracolonic MO dose-dependently decreased intrercontraction intervals and threshold pressure, provoked spinal RSK2 and NR2B phosphorylation, and enhanced PSD-95-RSK2 and PSD-95-NR2B coupling. Intrathecal kaempferol (a RSK2 activation antagonist; 30 min before MO instillation), bilateral adrenalectomy (7 days prior the stress paradigm), and subcutaneous RU-38486 (a glucocorticoid receptor antagonist; 30 min daily before stress sessions), but not RU-28318 (a mineralocorticoid receptor antagonist), attenuated MO-induced bladder hyperactivity, protein phosphorylation, and protein-protein interactions in the WAS group. Our results suggest that stress-associated glucocorticoid release mediates WAS-dependent sensitization of colon-bladder cross-talk via the spinal RSK2/PSD-95/NR2B cascade and offer a possibility for developing pharmacological strategies for the treatment of stress-related pelvic pain.

Cyclophosphamide induces NR2B phosphorylation-dependent facilitation on spinal reflex potentiation

It is well-established that cyclophosphamide (CYP) can sensitize the pelvic afferent nerve arising from the urinary bladder and therefore induce suprapubic pain. To test the possibility that CYP might mediate the development of visceral hypereflexia/hyperalgesia by facilitating spinal activity-dependent neural plasticity, we compared the pelvic-urethra reflex activity and spinal N-methyl-d-aspartate receptor NR2B subunit (NR2B) phosphorylation in rats treated with vehicle solution and CYP. Compared with vehicle solution, when accompanied by upregulation of phosphorylated NR2B expression in the lumbosacral (L6–S2) dorsal horn, CYP increased the evoked spikes in spinal reflex potentiation induced by repetitive stimulation (1 stimulation/1 s). Moreover, intraperitoneal pretreatments with NG-nitro-l-arginine methyl ester and roscovitine, nitric oxide synthase and cyclin-dependent protein kinase 5 (Cdk5) antagonists, respectively, overwrote CYP-enhanced reflex potentiation and NR2B phosphorylation. When compared with the untreated group, the treatment with small-interfering RNA of NR2B, which decreased the expression of NR2B expression, abolished CYP-dependent reflex facilitation and spinal NR2B phosphorylation. These results suggested that CYP might facilitate spinal reflex potentiation mediated by N-methyl-d-aspartate receptors and participate in the development of visceral hypereflexia/hyperalgesia through nitric oxide- and Cdk5-dependent NR2B phosphorylation at the lumbosacral dorsal horn.

EphrinB2 induces pelvic-urethra reflex potentiation via Src kinase-dependent tyrosine phosphorylation of NR2B

Recently, the role of EphB receptor (EphBR) tyrosine kinase and their ephrinB ligands in pain-related neural plasticity at the spinal cord level have been identified. To test whether Src-family tyrosine kinase-dependent glutamatergic N-methyl-d-aspartate receptor NR2B subunit phosphorylation underlies lumbosacral spinal EphBR activation to mediate pelvic-urethra reflex potentiation, we recorded external urethra sphincter electromyogram reflex activity and analyzed protein expression in the lumbosacral (L(6)-S(2)) dorsal horn in response to intrathecal ephrinB2 injections. When compared with vehicle solution, exogenous ephrinB2 (5 μg/rat it)-induced reflex potentiation, in associated with phosphorylation of EphB1/2, Src-family kinase, NR2B Y1336 and Y1472 tyrosine residues. Both intrathecal EphB1 and EphB2 immunoglobulin fusion protein (both 10 μg/rat it) prevented ephrinB2-dependent reflex potentiation, as well as protein phosphorylation. Pretreatment with PP2 (50 μM, 10 μl it), an Src-family kinase antagonist, reversed the reflex potentiation, as well as Src kinase and NR2B phosphorylation. Together, these results suggest the ephrinB2-dependent EphBR activation, which subsequently provokes Src kinase-mediated N-methyl-d-aspartate receptor NR2B phosphorylation in the lumbosacral dorsal horn, is crucial for the induction of spinal reflex potentiation contributing to the development of visceral pain and/or hyperalgesia in the pelvic area.

Dopaminergic D2 receptors activate PKA to inhibit spinal pelvic-urethra reflex in rats

To clarify the role of descending dopaminergic innervation in reflexive urethral closure, the impacts of dopaminergic D2 receptor (DR2)-selective agonists and antagonists on repetitive stimulation-induced pelvic-to-urethra spinal reflex potentiation (SRP) were tested using in vivo rat preparations. Pelvic afferent nerve test stimulation (TS; 1 pulse/30 s for 30 min) evoked baseline reflex activity with single spikes in the external urethral sphincter electromyogram (EUSE), whereas, repetitive stimulation (RS; 1 pulse/s for 30 min) induced SRP. Intrathecal application of quinelorane dihydrochloride (Q110; 10, 30, and 100 nM, 10 μl, a selective DR2 agonist) dose dependently inhibited the RS-induced SRP. Pretreatment with L135 (100 nM, 10 μL it, a selective DR2 antagonist) antagonized the Q110-dependent inhibition (100 nM, 10 μl it). Intrathecal AMPA (10 μM, 10 μl, a selective glutamatergic AMPA receptor agonist), and NMDA (10 μM, 10 μl, a selective glutamatergic NMDA receptor agonist) reversed the Q110-dependent inhibition. Intrathecal forskolin (100 nM, 10 μl, a PKA activator) prevented the Q110-dependent inhibition that was reversed by CNQX (10 μM, 10 μl it, a selective glutamate AMPA receptor antagonist) and APV (10 μM, 10 μl it , a selective glutamate NMDA receptor antagonist). Our results suggest that DR2 activation, which inactivates intracellular PKA, may be involved in descending dopaminergic inhibition of NMDA/AMPA receptor-dependent SRP at the lumbosacral spinal cord, which is thought to be involved in reflexive urethral closure.

Acute neurosteroids inhibit the spinal reflex potentiation via GABAergic neurotransmission

Recently, we demonstrated a chronic neurosteroid-dependent inhibition of activity-dependent spinal reflex potentiation (SRP), but it remains unclear whether neurosteroids acutely modulate SRP induction. This study shows progesterone as well as two of its 3alpha,5alpha-derivatives, allopregnalonone and 3alpha,5alpha-tetrahydrodeoxycorticosterone (THDOC), to be capable of producing acute GABA(A) receptor (GABA(A)R)-dependent inhibition of SRP. When compared with test simulation (1 stimulation/30 s) of pelvic afferent nerves that evoked a baseline reflex activity in an external urethra sphincter electromyogram, repetitive stimulation (RS; 1 stimulation/1 s) induced SRP characterized by an increase in the evoked activity. Intrathecal progesterone (3-30 muM, 10 microl) at 10 min before stimulation onset dose dependently prevented RS induction. Intrathecal allopregnalonone (10 muM, 10 microl it) and THDOC (10 microM, 10 microl it) also prevented the SRP caused by RS. Pretreatment with the GABA(A)R antagonist bicuculline (10 microM, 10 microl it) at 1 min before progesterone/neurosteroid injection attenuated the inhibition of SRP caused by progesterone, allopregnanolone, and THDOC. Results suggest that progesterone and its neurosteroid metabolites may be crucial to the development of pelvic visceral neuropathic/postinflammatory pain and imply clinical use of neurosteroids, such as allopregnanolone and THDOC, for visceral pain treatment.

Balloon kyphoplasty versus vertebroplasty for treatment of osteoporotic vertebral compression fracture: a prospective, comparative, and randomized clinical study

Bone pain and spinal axial deformity are major concerns in aged patients suffering from osteoporotic vertebral compression fracture (VCF). Pain can be relieved by vertebroplasty or kyphoplasty procedures, in which the compressed vertebral body is filled with substitutes. We randomly assigned 100 patients with osteoporotic compression fracture at the thoraco-lumbar (T-L) junction into two groups: vertebroplasty and kyphoplasty; we used polymethylmethacrylate (PMMA) as the bone filler. Pain before and after treatment was assessed with visual analog scale (VAS) scores and vertebral body height and kyphotic wedge angle were measured from reconstructed computed tomography images. More PMMA was used in the kyphoplasty group than in the vertebroplasty group (5.56 +/- 0.62 vs. 4.91 +/- 0.65 mL, p < 0.001). Vertebral body height and kyphotic wedge angle of the T-L spine were also improved (p < 0.001). VAS pain scores did not differ significantly between the treatment groups. The duration of follow-up was 6 months. Two patients in the kyphoplasty group had an adjacent segment fracture. In terms of clinical outcome there was little difference between the treatment groups. Thus, owing to the higher cost of the kyphotic balloon procedure, we recommend vertebroplasty over kyphoplasty for the treatment of osteoporotic VCFs.

INTRODUCTION

Spinal axial deformities are major concerns in aged patients suffering from osteoporotic vertebral compression fracture. Pain may be relieved by vertebroplasty or kyphoplasty. We investigated the radiological and clinical outcomes of these procedures.

METHODS

One hundred cases of VCF at the thoraco-lumbar junction were randomly assigned into two groups: vertebroplasty or kyphoplasty (50 cases each). We used polymethylmethacrylate as the bone filler. Pain before and after treatment was assessed with visual analog scale scores and vertebral body height and kyphotic wedge angle were measured from reconstructed computed tomography images.

RESULTS

More PMMA was used in the kyphoplasty group than in the vertebroplasty group (5.56 +/- 0.62 vs. 4.91 +/- 0.65 mL, p < 0.001). Vertebral body height and kyphotic wedge angle of the T-L spine were also improved (p < 0.001). VAS pain scores did not differ significantly between the treatment groups. The duration of follow-up was 6 months. Two patients in the kyphoplasty group had an adjacent segment fracture.

CONCLUSIONS

In terms of clinical outcome there was little difference between the treatment groups. Thus, with the higher cost of the kyphotic balloon procedure, we recommend vertebroplasty over kyphoplasty for the treatment of osteoporotic VCFs.

Endogenous ephrinB2 mediates colon-urethra cross-organ sensitization via Src kinase-dependent tyrosine phosphorylation of NR2B

Recently, the role of EphB receptor (EphBR) tyrosine kinase and their ephrinB ligands in spinal pain-related neural plasticity has been identified. To test whether Src-family non-receptor tyrosine kinase-dependent glutamatergic N-methyl-d-aspartate receptor (NMDAR) NR2B subunit phosphorylation underlies lumbosacral spinal EphBR activation to mediate cross-organ sensitization between the colon and the urethra, external urethra sphincter electromyogram activity evoked by pelvic nerve stimulation and protein expression in the lumbosacral (L6-S2) dorsal horn were studied before and after intracolonic mustard oil (MO) instillation. We found MO instillation produced colon-urethra reflex sensitization along with an upregulation of endogenous ephrinB2 expression as well as phosphorylation of EphB 1/2, Src-family kinase, and NR2B tyrosine residues. Intrathecal immunoglobulin fusion protein of EphB1 and EphB2 as well as PP2 reversed the reflex sensitization and NR2B phosphorylation caused by MO. All these results suggest that EphBR-ephrinB interactions, which provoke Src-family kinase-dependent NMDAR NR2B phosphorylation at the lumbosacral spinal cord level, are involved in cross-organ sensitization, contributing to the development of viscero-visceral referred pain between the bowel and the urethra.

Neuromodulation on cervical spinal cord combined with hyperbaric oxygen in comatose patients--a preliminary report

BACKGROUND

Because both SCS and HBO therapy have shown some promise in treating patients with states of reduced consciousness, we evaluated the combination of therapies in a prospective trial in comatose patients.

METHODS

Twelve patients who had received median nerve stimulation for 3 months without improvement in consciousness received cSCS for 1 year combined with simultaneous HBO therapy for the first 3 months. Another group enrolled 12 patients who received median nerve stimulation only were served as control.

RESULTS

Six patients emerged from coma at 1 year (after conclusion of treatment). Glasgow Coma Scale score, SPECT imaging, and PVS scores (state and reaction subscores) of the 12 patients were all significantly increased at 1 year compared with enrollment (P < .05). Neither respirator nor tracheostomy was needed to assist respiration in any patient. Only 1 of 12 patients still needed nasogastric tube feeding at 1 year. By contrast, control patients (without cSCS and HBO therapy) showed no apparent improvement.

CONCLUSION

Increase of GCS score, cerebral blood perfusion, and PVS scores were observed in comatose patients treated with combined cSCS and HBO therapy.

Estrogen-dependent facilitation on spinal reflex potentiation involves the Cdk5/ERK1/2/NR2B cascade in anesthetized rats

Cyclin-dependent kinase-5 (Cdk5), a proline-directed serine/threonine kinase, may alter pain-related neuronal plasticity by regulating extracellular signal-related kinase-1/2 (ERK1/2) activation. This study investigated whether Cdk5-dependent ERK activation underlies the estrogen-elicited facilitation on the repetitive stimulation-induced spinal reflex potentiaton (SRP) that is presumed to be involved in postinflammatory/neuropathic hyperalgesia and allodynia. Reflex activity of the external urethra sphincter electromyogram evoked by pelvic afferent nerve test stimulation (TS; 1 stimulation/30 s for 10 min) and repetitive stimulation (RS; 1 stimulation/1 s for 10 min) was recorded in anesthetized rats. TS evoked a baseline reflex activity, whereas RS produced SRP. Intrathecal (it) beta-estradiol facilitated the repetitive stimulation-induced SRP that was reversed by pretreatment with the estrogen receptor anatogonist ICI 182,780 (10 nM, 10 microl it), Cdk5 inhibitor roscovitine (100 nM, 10 microl it), ERK inhibitor (U-0126; 100 microM, 10 microl it) and N-methyl-D-aspartate (NMDA) NR2B subunit antagonist (Co-101244; 100 nM, 10 microl it). Moreover, ERalpha (propylpyrazoletriol; 100 nM, 10 microl it) and ERbeta (diarylpropionitrile; 100 microM, 10 microl it) agonists both facilitated the SRP, similar to results with a beta-estradiol injection. In association with the facilitated RS-induced SRP, an intrathecal beta-estradiol injection elicited ERK1/2 and NR2B subunit phosphorylation that were both reversed by intrathecal roscovitine and U-0126. These results indicated that the Cdk/ERK cascade, which is activated by ERalpha and ERbeta, may subsequently phosphorylate the NR2B subunit to develop NMDA-dependent postinflammatory hyperalgesia and allodynia to maintain the protective mechanisms of the body.

Neuroactive steroids inhibit spinal reflex potentiation by selectively enhancing specific spinal GABA(A) receptor subtypes

Recently, we demonstrated a spinal GABA(A) receptor (GABA(A)R)-dependent inhibition on the induction of repetitive stimulation-induced spinal reflex potentiation. However, it remains unclear whether steroid hormones modulate such an inhibition. Here, we show that progesterone is capable of producing GABA(A)Rs-dependent inhibition of the induction of spinal reflex potentiation by actions through neurosteroid metabolites. Progesterone (5mg/kg, twice daily for 4 days) up-regulates the expression of GABA(A)R alpha2, alpha3, alpha4 and delta subunits, and is associated with attenuated repetitive stimulation-induced spinal reflex activity in ovariectomized rats. These changes were blocked by finasteride (50mg/kg, twice daily), an antagonist of neurosteroid synthesis from progesterone, but not by the progesterone receptor antagonist, RU486 (100mg/kg, twice daily). The induction of spinal reflex potentiation was attenuated after a short (30 min) intrathecal treatment with the neurosteroids, allopregnanolone (ALLOP, 10 microM, 10 microL) and 3 alpha,5 alpha-tetrahydrodeoxycorticosterone (THDOC, 10 microM, 10 microL). Acute intrathecal administration of the GABA(A)R antagonist, bicuculline (10 microM, 10 microL) reversed the inhibition produced by progesterone, THDOC and allopregnanolone. These results imply that progesterone-mediated effects on GABA(A)R expression and neural inhibition are regulated by neurosteroids synthesis rather than progesterone receptor activation.

Colon mustard oil instillation induced cross-organ reflex sensitization on the pelvic-urethra reflex activity in rats

We investigated the participation of cyclin-dependent kinase-5 (Cdk5)-mediated N-methyl-D-aspartate receptor (NMDAR) NR2B subunit phosphorylation in cross-organ reflex sensitization caused by colon irritation. The external urethral sphincter electromyogram (EUSE) reflex activity evoked by the pelvic afferent nerve test stimulation (TS, 1 stimulation/30s) and protein expression in the spinal cord and dorsal root ganglion tissue (T13-L2 and L6-S2 ipsilateral to the stimulation) in response to colon mustard oil (MO) instillation were tested in anesthetized rats. When compared with a baseline reflex activity with a single action potential evoked by the TS before the administration of test agents, MO instillation into the descending colon sensitized the evoked activity characterized by elongated firing in the reflex activity in association with increased protein levels of Cdk5, PSD95, and phosphorylated NR2B (pNR2B) but not of total NR2B (tNR2B) in the spinal cord tissue. Both cross-organ reflex sensitization and increments in protein expression were reversed by intra-colonic pretreatments with ruthenium red (a non-selective transient receptor potential vanilloid, TRPV, antagonist), capsaizepine (a TRPV1-selective antagonist), lidocaine (a nerve conduction blocker) as well as by the intra-thecal pretreatment with APV (a NRMDR antagonist) Co-101244 (a NR2B-selective antagonist) and roscovitine (a Cdk5 antagonist). Moreover, compared with the control group, both the increase in pNR2B and the cross-organ reflex sensitization were attenuated in the si-RNA of NR2B rats. All these results suggested that Cdk-dependent NMDAR NR2B subunit phosphorylation mediates the development of cross-organ pelvic-urethra reflex sensitization caused by acute colon irritation which could possibly underlie the high concurrence of pelvic pain syndrome with irritable bowel syndrome.

TRPV1 mediates the uterine capsaicin-induced NMDA NR2B-dependent cross-organ reflex sensitization in anesthetized rats

Spinal cord-mediated cross-organ sensitization between the uterus and the lower urinary tract may underlie the high concurrence of obstetrical/gynecological inflammation and chronic pelvic pain syndrome characterized by urogenital pain. However, the neural pathway and the neurotransmitters involved are still unknown. We tested the hypothesis that the excitation of capsaicin-sensitive primary afferent fibers arising from the uterus through the stimulation of transient receptor potential vanilloid 1 (TRPV1) induces cross-organ sensitization on the pelvic-urethra reflex activity. Capsaicin (1–1,000 μM, 0.05 ml) was instilled into the uterus to induce cross-organ reflex sensitization. Activation of capsaicin-sensitive primary afferent fibers by capsaicin instillation into the uterine horn sensitized the pelvic-urethra reflex activity that was reversed by an intrauterine pretreatment with capsaizepine, a TRPV1-selective antagonist. Intrathecal injection of AP5, a glutamatergic N-methyl-d-aspartate (NMDA) antagonist, and Co-101244, an NMDA NR2B-selective antagonist, both abolished the cross-organ reflex sensitization caused by capsaicin instillation. These results demonstrated that TRPV1 plays a crucial role in contributing to the capsaicin-sensitive primary afferent fibers mediating the glutamatergic NMDA-dependent cross-organ sensitization between the uterus and the lower urinary tract when there is a tissue injury.

Effect of single botulinum toxin A injection to the external urethral sphincter for treating detrusor external sphincter dyssynergia in spinal cord injury

OBJECTIVE

To evaluate the effect of a single cystoscopic injection of botulinum toxin to the external urethral sphincter in treating detrusor external sphincter dyssynergia.

DESIGN

An open treatment trial with pre- and post-treatment evaluations.

SUBJECTS

A total of 20 suprasacral spinal cord injured patients with pure detrusor external sphincter dyssynergia.

METHODS

A single dose of 100 IU botulinum toxin A was applied into the external urethral sphincter via cystoscopy. Outcome measurements included maximal detrusor pressure, maximal urethral pressure, detrusor leak point pressure, integrated electromyography, and maximal pressure on static urethral pressure profilometry obtained 4 weeks post-treatment. Post-voiding residuals were checked pre- and post-injection.

RESULTS

There were significant reductions in integrated electro notmyography and static and maximal urethral pressure, but not in maximal detrusor pressure and detrusor leak point pressure after treatment. Post-voiding residuals were significantly decreased at all evaluation periods. In the sub-group analysis, patients who showed good effects of treatment had significantly lower baseline integrated electro-myography (p<0.05).

CONCLUSION

This study demonstrates the effect of a single cystoscopic injection of botulinum toxin in detrusor external sphincter dyssynergia. Integrated electromyography is a good evaluation tool for the net effect and dosage of botulinum toxin. Patients with severe spasticity over the external urethral sphincter may require repeated injections or higher doses.

Acute anal stretch inhibits NMDA-dependent pelvic-urethra reflex potentiation via spinal GABAergic inhibition in anesthetized rats

The impact of acute anal stretch on the pelvic-urethra reflex potentiation was examined in urethane-anesthetized rats by recording the external urethra sphincter electromyogram activity evoked by the pelvic afferent stimulation. Test stimulation (1 stimulation/30 s) evoked a baseline reflex activity with a single action potential that was abolished by gallamine (5 mg/kg iv). On the other hand, the repetitive stimulation (1 stimulation/1 s) induced spinal reflex potentiation (SRP) that was attenuated by intrathecal 6-cyano-7-nitroquinoxaline-2,4-dione (a glutamatergic α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionat receptor antagonist, 100 μM, 10 μl) and d-2-amino-5-phosphonovalerate [a glutamatergic N-methyl-d-aspartate (NMDA) antagonist, 100 μM, 10 μl]. Acute anal stretch using a mosquito clamp with a distance of 4 mm exhibited no effect, whereas distances of 8 mm attenuated and 12 mm abolished the repetitive stimulation-induced SRP. Intrathecal NMDA (100 μM, 10 μl) reversed the abolition on SRP caused by anal stretch. On the other hand, pretreated bicuculline [γ-aminobutyric acid (GABA) A receptor antagonist, 100 μM, 10 μl] but not hydroxysaclofen (GABAB receptor antagonist) counteracted the abolition on the repetitive stimulation-induced SRP caused by the anal stretch. All of the results suggested that anal stretch may be used as an adjunct to assist voiding dysfunction in patients with overactive urethra sphincter and that GABAergic neurotransmission is important in the neural mechanisms underlying external urethra sphincter activity inhibited by anal stretch.

Estrous cycle variation of TRPV1-mediated cross-organ sensitization between uterus and NMDA-dependent pelvic-urethra reflex activity

Cross-organ sensitization between the uterus and the lower urinary tract (LUT) underlies the high concurrence of pelvic pain syndrome and LUT dysfunctions, and yet the role of gonadal steroids is still unknown. We tested the hypothesis that cross-organ sensitization on pelvic-urethra reflex activity caused by uterine capsaicin instillation is estrous cycle dependent. When compared with the baseline reflex activity (1.00 +/- 0.00 spikes/stimulation), uterine capsaicin instillation significantly increased reflex activity (45.42 +/- 9.13 spikes/stimulation, P < 0.01, n = 7) that was corroborated by an increase in phosphorylated NMDA NR2B (P < 0.05, n = 4) but not NR2A subunit (P > 0.05, n = 4) expression. Both intrauterine pretreatment with capsazepine (5.02 +/- 2.11 spikes/stimulation, P < 0.01, n = 7) and an intrathecal injection of AP5 (3.21 +/- 0.83 spikes/stimulation, P < 0.01, n = 7) abolished the capsaicin-induced cross-organ sensitization and the increment in the phosphorylated NR2B level (P < 0.05, n = 4). The degrees of the cross-organ sensitization increased in a dose-dependent manner with the concentration of instilled capsaicin from 100 to 300 microM in both the proestrus and metestrus stages, whereas they weakened when the concentrations were higher than 1,000 microM. Moreover, the cross-organ sensitization caused by the uterine capsaicin instillation increased significantly in the rats during the proestrus stage when compared with the metestrus stage (P < 0.01, n = 7). These results suggest that estrogen levels might modulate the cross-organ sensitization between the uterus and the urethra and underlie the high concurrence of pelvic pain syndrome and LUT dysfunctions.

Orexin-A modulates glutamatergic NMDA-dependent spinal reflex potentiation via inhibition of NR2B subunit

Glucose-sensitive neurons in the lateral hypothalamic area produce orexin-A (OxA) as well as orexin-B (OxB) and send their axons to the spinal dorsal horn, which predominantly expresses orexin receptor-1 (OX-1), showing a higher sensitivity to OxA. The purpose of the present study was to assess the effects of OxA on the induction of a novel form of activity-dependent reflex potentiation, spinal reflex potentiation (SRP), in the pelvic-urethral reflex activity. External urethra sphincter electromyogram in response to pelvic afferent nerve test stimulation (TS; 1/30 Hz) or repetitive stimulation (RS; 1 Hz) was recorded in anesthetized rats. TS evoked a baseline reflex activity, whereas RS produced SRP, which was abolished by intrathecal OxA (30 nM, 10 mul). Intrathecal SB-408124 (10 muM, 10 mul), an OX-1 antagonist, reversed the abolition on SRP caused by OxA. Although there is, so far, no NR2A- and NR2B-specific agonist available, N-methyl-d-aspartate (NMDA) reversed the abolition on the RS-induced SRP caused by the co-administration of OxA and Co-101244 (30 nM, 10 mul; an NMDA NR2B subunit antagonist), but it did not reverse the abolition by the co-administration of OxA and PPPA (300 nM, 10 mul; an NMDA NR2A subunit antagonist). In conclusion, the activation of descending orexinergic fibers may inhibit the repetitive afferent input-induced central sensitization of pelvic-urethral reflex activity and urethra hyperactivity, indicating that spinal orexinergic neural transmission may be a novel target for the treatment of patients with neuropathetic or postinflammatory pain of pelvic origin.

Nicotine-activated descending facilitation on spinal NMDA-dependent reflex potentiation from pontine tegmentum in rats

This study was conducted to investigate the possible neurotransmitter that activates the descending pathways coming from the dorsolateral pontine tegmentum (DPT) to modulate spinal pelvic-urethra reflex potentiation. External urethra sphincter electromyogram (EUSE) activity in response to test stimulation (TS, 1/30 Hz) and repetitive stimulation (RS, 1 Hz) on the pelvic afferent nerve of 63 anesthetized rats were recorded with or without microinjection of nicotinic cholinergic receptor (nAChR) agonists, ACh and nicotine, to the DPT. TS evoked a baseline reflex activity with a single action potential (1.00 ± 0.00 spikes/stimulation, n = 40), whereas RS produced a long-lasting reflex potentiation (16.14 ± 0.96 spikes/stimulation, n = 40) that was abolished by d-2-amino-5-phosphonovaleric acid (1.60 ± 0.89 spikes/stimulation, n = 40) and was attenuated by 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo (F) quinoxaline (7.10 ± 0.84 spikes/stimulation, n = 40). ACh and nicotine microinjections to DPT both produced facilitation on the RS-induced reflex potentiation (23.57 ± 2.23 and 28.29 ± 2.36 spikes/stimulation, P < 0.01, n = 10 and 20, respectively). Pretreatment of selective nicotinic receptor antagonist, chlorisondamine, reversed the facilitation on RS-induced reflex potentiation caused by nicotine (19.41 ± 1.21 spikes/stimulation, P < 0.01, n = 10) Intrathecal WAY-100635 and spinal transection at the T1level both abolished the facilitation on reflex potentiation resulting from the DPT nicotine injection (12.86 ± 3.13 and 15.57 ± 1.72 spikes/stimulation, P < 0.01, n = 10 each). Our findings suggest that activation of nAChR at DPT may modulate N-methyl-d-aspartic acid-dependent reflex potentiation via descending serotonergic neurotransmission. This descending modulation may have physiological/pathological relevance in the neural controls of urethral closure.

Impairment of cerebral hemodynamic response to the cold pressor test in patients with Parkinson's disease

BACKGROUND AND PURPOSE

Disturbance of the autonomic nervous system (ANS) is frequently encountered in Parkinson's disease (PD). In this study, we examined changes in systemic and cerebral hemodynamics during the cold pressor test (CPT) to determine whether cerebrovascular reactivity, controlled by the sympathetic nervous system, is intact or impaired in patients with PD.

METHODS

Forty-nine patients with PD and 49 sex- and age-matched non-PD subjects were evaluated. Measurements were performed in the resting state and over a period of 1min of CPT. The cerebral blood flow velocity (CBFV) and pulsatility index (PI) of the middle cerebral artery (MCA) were recorded by transcranial color-coded Doppler ultrasonography (TCCS). Mean arterial blood pressure (MAP), heart rate (HR), and end-tidal CO(2) (Et-CO(2)) were investigated simultaneously. The resistance of the cerebrovascular bed (CVR) was calculated as the ratio of mean arterial blood pressure to mean cerebral blood flow velocity (Vm). Changes of Vm, PI and CVR in response to the cold pressor test were evaluated.

RESULTS

Baseline values for control and PD subjects showed no statistical difference. CPT induced a significant increase in MAP, HR, and Vm in both groups. Pulsatility index (PI) and CVR were decreased in both groups during CPT. Percent increases of Vm (P<0.001) and MAP (P=0.011) were significantly higher while the percent decreases of PI (P=0.002) and CVR (P=0.007) were significantly decreased more in the non-PD group.

CONCLUSIONS

This study indirectly shows that ANS-mediated cerebrovascular reactivity is impaired in patients with PD. Further investigations are needed to confirm the hypothesis that using the cold pressor test to evaluate cerebrovascular reactivity might be beneficial in early diagnosis of impairment of ANS-mediated cerebrovascular autoregulation in patients with PD.