Time Of Nerve Injury Research Articles

D20. Agrin Nanoparticles in a Nanofiber Hydrogel-based Drug Delivery System Improve Neuromuscular Junction Reinnervation following Chronic Denervation

PURPOSE: Following peripheral nerve injury, neuromuscular junctions (NMJs) within denervated muscle rapidly destabilize. Agrin, a proteoglycan essential to NMJ formation, may have an essential role in preserving NMJ receptivity to reinnervation. This study aimed to evaluate the efficacy of agrin-NP therapy in a rodent chronic denervation model. METHODS: Agrin was encapsulated in biodegradable polyelectrolyte:polymer NPs and embedded within a hyaluronic acid/PCL nanofiber hydrogel composite (NHC). The effect of locally delivered agrin-NP/NHC on NMJ reinnervation was assessed using a forelimb chronic denervation nerve injury model. Animals were injected with agrin-NP/NHC, free agrin, or empty-NP/NHC every six weeks from time of nerve injury and underwent 16 weeks of functional assessment. RESULTS: Agrin-NP/NHC animals exhibited significantly increased functional recovery compared to free agrin (p<0.01) and empty-NP/NHC animals (p<0.01) At Week 15, Agrin-NP/NHC animals demonstrated an increase of 21.2% compared to free agrin (p=0.056) and of 26.8% compared to empty-NP/NHC (p<0.05). Agrin-NP/NHC animals demonstrated significantly greater NMJ reinnervation than free agrin (78.9% vs 66.8%, p<0.05) and empty-NP/NHC groups (78.9% vs 39.2%, p<0.001). No significant differences were seen in myofibril cross-sectional area between treatment groups. No foreign body response was detected in empty-NP/NHC or agrin-NP/NHC animals. Agrin levels were undetectable in serum and were significantly higher in agrin-NP/NHC than free agrin animals. CONCLUSION: Agrin-NP/NHC treatment in vivo promotes neuromuscular junction reinnervation and improves functional recovery of forelimb grip strength.

Tumor Necrosis Factor- α (TNF-α) and Rho-Associated Kinase 2 (ROCK2) Inhibitors Improve Erectile Function in a Bilateral Cavernous Nerve Injury Rat Model

ABSTRACT Introduction Prior studies suggest Rho-kinase (ROCK) upregulation and pro-inflammatory cytokines such as Tumor Necrosis Factor-α as causative factors of axonal degeneration, neuropathy, and penile fibrosis following peripheral cavernous nerve (CN) injury. We hypothesize, the combination therapy using inhibitors/antagonists of ROCK and TNF-α may prevent end-organ damage and neuroinflammation in the penis. The current study was designed to investigate selective inhibition of ROCK2 (SAR407899) and TNF-α (Infliximab) in a pre-clinical model of post-radical prostatectomy ED to prevent penile neuroinflammation, fibrosis, and preserve penile hemodynamics. Objective This study investigates the effect of FDA approved TNF- α inhibitor (Infliximab) in combination with ROCK2 selective inhibitor (SAR407899) on erectile function restoration in the bilateral crush nerve injury (BCNI) rat model. Methods Sprague Dawley rats were randomized to undergo either sham (6) or BCNI (28). The BCNI rats were further randomly stratified to receive saline (6), Infliximab (5 mg/kg once weekly) (6), low dose of SAR407899 (1.5 mg/kg QD) (5), high dose of SAR407899 (3 mg/kg QD) (5), or combination treatment SAR407899 (1.5 mg/kg QD) + Infliximab (5 mg/kg once weekly) (6). At 14 days after injury rats underwent cavernous nerve stimulation to determine erectile function. Penes were collected and immune infiltrate analyses were performed using multicolor flow-cytometry. Results Erectile response studies demonstrated that rodents treated with combination of Infliximab and SAR407899 had significantly improved (p&amp;lt;0.05) erectile function (ICP/MAP) at all voltages compared to BCNI alone (2V: 0.243 vs 0.051, 4V: 0.321 vs 0.0782, 6V: 0.456 vs 0.091, p &amp;lt;0.05). Peak ICP and total ICP were also significantly (p&amp;lt;0.05) improved compared to BCNI rats. Combination therapy, however, did not show a significant change compared to each treatment alone. Likewise, there was no significant difference between low and high dose SAR407899. Flow cytometry showed that Infliximab and SAR407899 significantly (p&amp;lt;0.05) decreased % of CD11b+ CD45+ monocytes in the penis. While combination therapy had no effect. The percent of CD11b+ MHCII+ CD45+ macrophages were increased (p&amp;lt;0.05) in the penes of rats treated with Infliximab and SAR407899 while combination therapy decreased penile macrophage population. We found no change in TNF- α+ monocytes and macrophages compared in penes from all groups investigated. Conclusions Our study suggests that treatment with commercially available TNF-α and ROCK2 inhibitors result in mitigation of erectile dysfunction in a BCNI rat model when administered at the time of nerve injury. The mechanism of the beneficial effects may involve reduction in macrophage population in the penis. Disclosure No

PD62-07 TUMOR NECROSIS FACTOR ALPHA (TNF- Α) INHIBITOR IMPROVED ERECTILE FUNCTION IN A BILATERAL CAVERNOUS NERVE INJURY RAT MODEL

You have accessJournal of UrologySexual Function/Dysfunction: Basic Research & Pathophysiology (PD62)1 Sep 2021PD62-07 TUMOR NECROSIS FACTOR ALPHA (TNF- Α) INHIBITOR IMPROVED ERECTILE FUNCTION IN A BILATERAL CAVERNOUS NERVE INJURY RAT MODEL James Liu, Hotaka Matsui, Kara Lombardo, Serkan Karakus, Arthur Burnett, and Trinity Bivalacqua James LiuJames Liu More articles by this author , Hotaka MatsuiHotaka Matsui More articles by this author , Kara LombardoKara Lombardo More articles by this author , Serkan KarakusSerkan Karakus More articles by this author , Arthur BurnettArthur Burnett More articles by this author , and Trinity BivalacquaTrinity Bivalacqua More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002099.07AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Erectile dysfunction (ED) after injury to the peripheral cavernous nerves (CN) is partially the result of an increase in neuroinflammation in the pelvic ganglia. Inflammatory cytokines have been implicated in axonal degeneration and neuropathy. This study examines the role of the inflammatory cytokine, tumor necrosis factor –alpha (TNF- α), after bilateral CN injury (BCNI) in vivo. We also investigate the effect of commercially available TNF- α inhibitors (Infliximab) on erectile function restoration in the BCNI rodent model. METHODS: Seventy male Sprague Dawley rats were randomized to undergo either BCNI or sham surgery. Sham rats major pelvic ganglion (MPG) were harvested after 48 hours, whereas the BCNI groups had MPG harvested at 6 hours, 12 hours, 24 hours, 48 hours, 7 days, or 14 days after BCNI. MPGs were analyzed by qPCR to evaluate gene expression of TNF-α, TNF- αR1, TNF- αR2 and markers of macrophages (CD11b and CD68). Western blot of MPGs were also performed to confirm these finding. Additionally, 25 Sprague Dawley rats were randomized to three groups: sham surgery, BCNI, or BCNI treated with TNF- α inhibitor (Infliximab) (5mg/kg weekly) for two weeks and then underwent cavernous nerve stimulation and erectile parameters were measured (peak ICP, ICP/MAP, and total ICP). RESULTS: BCNI significantly increased (p<0.05) gene and protein expression of TNF- α and its receptors (R1, R2) in rat MPGS, with peak levels were observed at 2 and 7 days, respectively. Corresponding macrophage markers (CD11b and CD68) were significantly increased (p<0.05) following BCNI with maximal expression at 48 hours. Erectile response studies demonstrated that rodents treated with TNF- α inhibitors had significantly improved (p<0.05) erectile function (ICP/MAP) at all voltages compared to BCNI alone (2V: 0.203 vs 0.057, 4V: 0.279 vs 0.081, 6V: 0.317 vs 0.166. Control 2V: 0.347, 4V: 0.414, 6V: 0.486). Peak ICP and total ICP were also significantly (p<0.05) improved compared to BCNI rats. CONCLUSIONS: TNF- α is a key inflammatory cytokine which contributes to neuroinflammation following BCNI. Treatment with commercially available TNF- α inhibitor results in mitigation of erectile dysfunction in a BCNI rat model when administered at the time of nerve injury. Source of Funding: None © 2021 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 206Issue Supplement 3September 2021Page: e1074-e1075 Advertisement Copyright & Permissions© 2021 by American Urological Association Education and Research, Inc.MetricsAuthor Information James Liu More articles by this author Hotaka Matsui More articles by this author Kara Lombardo More articles by this author Serkan Karakus More articles by this author Arthur Burnett More articles by this author Trinity Bivalacqua More articles by this author Expand All Advertisement Loading ...

Asparagine Endopeptidase (δ Secretase), an Enzyme Implicated in Alzheimer's Disease Pathology, Is an Inhibitor of Axon Regeneration in Peripheral Nerves.

Asparagine endopeptidase (AEP) is a lysosomal protease implicated in the pathology of Alzheimer’s disease (AD). It is known to cleave the axonal microtubule associated protein, Tau, and amyloid precursor protein (APP), both of which might impede axon regeneration following peripheral nerve injury (PNI). Active AEP, AEP-cleaved fragments of Tau (Tau N368), and APP (APP N585) were found in injured peripheral nerves. In AEP null mice, elongation of regenerating axons after sciatic nerve transection and repair was increased relative to wild-type (WT) controls. Compound muscle action potentials (M responses) were restored in reinnervated muscles twice as fast after injury in AEP knock-out (KO) mice as WT controls. Neurite elongation in cultures of adult dorsal root ganglion (DRG) neurons derived from AEP KO mice was increased significantly relative to cultures from WT controls. In AEP KO mice exposed to 1 h of 20-Hz electrical stimulation (ES) at the time of nerve injury, no further enhancement of axon regeneration was observed. These findings support inhibition of AEP as a therapeutic target to enhance axon regeneration after PNI.

Oxycodone, fentanyl, and morphine amplify established neuropathic pain in male rats.

Opioids are widely prescribed for chronic pain, including neuropathic pain, despite growing evidence of long-term harm. Previous preclinical studies have documented exacerbation of nociceptive hypersensitivity, including that induced by peripheral nerve injury, by morphine. The present series of behavioral studies sought to replicate and extend our prior research, which demonstrated a multimonth exacerbation of nociceptive hypersensitivity by a 5-day course of morphine initiated 10 days after nerve injury. The current studies demonstrate that enduring exacerbation of nociceptive hypersensitivity is not restricted to morphine, but rather is also created by the clinically relevant opioids fentanyl and oxycodone when these are likewise administered for 5 days beginning 10 days after nerve injury. Furthermore, enduring exacerbation of nociceptive hypersensitivity is also observed when the same dosing regimen for either morphine, fentanyl, or oxycodone begins 1 month after nerve injury. Finally, a striking result from these studies is that no such exacerbation of nociceptive hypersensitivity occurs when either morphine, fentanyl, or oxycodone dosing begins at the time of nerve injury. These results extend our previous findings that morphine exacerbates nociceptive hypersensitivity to the clinically relevant opioids fentanyl and oxycodone when administered after the development of nociceptive hypersensitivity, while also providing possible clinically relevant insight into when these opioids can be safely administered and not exacerbate neuropathic pain.

Assessment of anti-nociceptive effect of allopurinol in a neuropathic pain model

BackgroundThis study aimed to investigate the antinociceptive effect of allopurinol, a xanthine oxidase inhibitor, in the chronic constriction injury (CCI) to sciatic nerve rat model of neuropathic pain. MethodsAllopurinol administration (30, 60, 90 mg/kg, i.p.) was started at the time of nerve injury, and given for 14 continuous days. Behavioural tests (von Frey filaments, acetone drop, hot plate) were conducted on days 0, 3, 7, 10 and 14. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis was performed on the spinal cord of CCI animals on day 14. The contribution of adenosine (A) receptors was tested using the methylxanthine theophylline, a non-selective A receptor antagonist and 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), a selective A1 receptor antagonist, administered 30 min before allopurinol on day 10. ResultsCCI of the sciatic nerve resulted in a persistent mechanical allodynia, cold allodynia, and heat hyperalgesia, together with increased iNOS, bax/bcl2, iba-1 and TNF-α expression in the lumbar spinal cord of animals. The highest-dose group of allopurinol (90 mg/kg) attenuated pain-like behaviors compared with the normal saline treated group, and this was accompanied by normalization of iNOS, bax/bcl2, caspase 3, iba-1 and TNF-α gene expression changes. DPCPX and theophylline reversed the thermal anti-hyperalgesic effect of allopurinol. In contrast, the mechanical anti-allodynic effect was only prevented by theophylline. ConclusionAllopurinol through interacting with different aspects of neuropathic pain, via anti-oxidant effects, protection against neuroinflammation, and activating adenosine receptors, could be useful in the treatment of patients with neuropathic pain.

(351) The Opioids Oxycodone, Fentanyl, and Morphine Amplify Neuropathic when Given after Chronic Pain is Established

Neuropathic pain affects approximately 4 million people in the U.S. and remains refractory to analgesics in many patients. We have previously shown that a short course of morphine given at the time of initial chronic pain development results in amplification of the intensity and/or duration of neuropathic pain. However, it is unknown whether this effect is exclusive to morphine, or whether this effect is dependent on the time of dosing relative to the time of nerve injury. To test whether other common, clinically used opioids also exacerbate neuropathic pain, we tested the effects of fentanyl and oxycodone compared to morphine in a rat model of neuropathic pain, chronic constriction injury (CCI). Male Sprague Dawley rats received CCI surgery and were dosed with oxycodone (s.c. 2 mg/kg, b.i.d.), fentanyl (0.01mg/kg/hr s.c. osmotic minipump), morphine (s.c. 5 mg/kg, b.i.d.), or vehicle beginning 1 hour, 10 days, or 28 days post-CCI for 5 days. Previous experiments have shown that pain amplification occurs when morphine administration begins at day 10 after CCI (at the time of chronic pain development). We found that dosing with morphine, oxycodone, or fentanyl that begins at either day 10 or day 28 after injury results in prolonged magnitude and duration of chronic pain. This effect is not observed when the 5-day administration of these opioids began one-hour post CCI, before chronic pain onset. This suggests that opioids administered after the development of chronic pain can produce detrimental and counterproductive increases in pain, whereas a short course of opioids administered at the time of injury may not produce such effects. Whether patients with ongoing neuropathic pain (relative to those with acute nerve injury) are particularly sensitive to the deleterious effects of opioids warrants investigation. Supported by Dept of the Army Log No. 14001001. Opioids provided by the NIDA Drug Repository.

Insulin-Like Growth Factor-1–Loaded Polymeric Poly(Lactic-Co-Glycolic) Acid Microspheres Improved Erectile Function in a Rat Model of Bilateral Cavernous Nerve Injury

BackgroundPrevious studies have documented improvement in erectile function after bilateral cavernous nerve injury (BCNI) in rats with the use of pioglitazone. Our group determined this improvement to be mediated by the insulin-like growth factor-1 (IGF-1) pathway. AimTo eliminate the systemic effects of pioglitazone and evaluate the local delivery of IGF-1 by polymeric microspheres after BCNI in the rat. MethodsMale Sprague–Dawley rats aged 10–12 weeks were assigned at random to 3 groups: sham operation with phosphate buffered saline (PBS)-loaded microspheres (sham group), crush injury with PBS-loaded microspheres (crush group), and crush injury with IGF-1–loaded microspheres (IGF-1 group). Poly(lactic-co-glycolic) acid microspheres were injected underneath the major pelvic ganglion (MPG). IGF-1 was released at approximately 30 ng/mL/day per MPG per rat. OutcomesFunctional results were demonstrated by maximal intracavernosal pressure (ICP) normalized to mean arterial pressure (MAP). Protein-level analysis data of IGF-1 receptor (IGF-1R), extracellular signal–regulated kinase (ERK)-1/2, and neuronal nitric oxide synthase (nNOS) were obtained using Western blot analysis and immunohistochemistry for both the cavernosal tissue and the MPG and cavernous nerve (CN). ResultsAt 2 weeks after nerve injury, animals treated with IGF-1 demonstrated improved erectile functional recovery (ICP/MAP) at all voltages compared with BCNI (2.5V, P = .001; 5V, P < .001; 7.5V, P < .001). Western blot results revealed that up-regulation of the IGF-1R and ERK-1/2 in both the nervous and erectile tissue was associated with improved erectile function recovery. There were no significant between-group differences in nNOS protein levels in cavernosal tissue, but there was an up-regulation of nNOS in the MPG and CN. Immunohistochemistry confirmed these trends. Clinical TranslationLocal up-regulation of the IGF-1R in the neurovascular bed at the time of nerve injury may help men preserve erectile function after pelvic surgery, such as radical prostatectomy, eliminating the need for systemic therapy. Strengths & LimitationsThis study demonstrates that local drug delivery to the MPG and CN can affect the CN tissue downstream, but did not investigate the potential effects of up-regulation of the growth factor receptors on prostate cancer tissue. ConclusionStimulating the IGF-1R at the level of the CN has the potential to mitigate erectile dysfunction in men after radical prostatectomy, but further research is needed to evaluate the safety of this growth factor in the setting of prostate cancer.Haney NM, Talwar S, Akula PK, et al. Insulin-Like Growth Factor-1–Loaded Polymeric Poly(Lactic-Co-Glycolic) Acid Microspheres Improved Erectile Function in a Rat Model of Bilateral Cavernous Nerve Injury. J Sex Med 2019;16:383–393.

The role of the GABA-A receptor of the adjacent intact dorsal root ganglion neurons in rats with neuropathic pain.

We aim to investigate the changes of The γ-aminobutyric acid (GABA) signals in the adjacent intact dorsal root ganglion (DRG) and the contribution of these changes to the development and maintenance of neuropathic pain (NPP). After establishment of neuropathic pain model with the lumbar 5 spinal nerve ligation (L5 SNL), the GABA-evoked currents were recorded in the acutely dissociated L4 DRG neurons using whole-cell patch clamp. Moreover, Muscimol or Bicuculline were respectively topically injected to the L4 DRG at the time of nerve injury and post-operative 5 days (POD5). The pain thresholds of hind paw were recorded. We found that the incidence and amplitude of GABA currents significantly decreased in the large and medium L4 DRG neurons after SNL (P<0.05). Furthermore, in the L5 SNL rats, 20 μg Muscimol injected immediately after injury caused a long-lasting attenuation of mechanical allodynia (P<0.05), whereas the thermal hyperalgesia was not alleviated (P>0.05). 0.15 μg Bicuculline further decreased the pain thresholds (P<0.05) and reversed the pain-alleviating effects of Muscimol. However, at POD5, 20 μg Muscimol only exhibited transient alleviating effects (P<0.05). In conclusion, the decrease of inhibition signal mediated by GABA-A receptor in the adjacent intact DRG neurons may be crucial in the development of hyperalgesia in NPP.

Endogenous analgesic action of the pontospinal noradrenergic system spatially restricts and temporally delays the progression of neuropathic pain following tibial nerve injury

Pontospinal noradrenergic neurons form part of an endogenous analgesic system that suppresses acute pain, but there is conflicting evidence about its role in neuropathic pain. We investigated the chronology of descending noradrenergic control during the development of a neuropathic pain phenotype in rats following tibial nerve transection (TNT). A lumbar intrathecal cannula was implanted at the time of nerve injury allowing administration of selective α-adrenoceptor (α-AR) antagonists to sequentially assay their effects upon the expression of allodynia and hyperalgesia. Following TNT animals progressively developed mechanical and cold allodynia (by day 10) and subsequently heat hypersensitivity (day 17). Blockade of α2-AR with intrathecal yohimbine (30μg) revealed earlier ipsilateral sensitization of all modalities while prazosin (30μg, α1-AR) was without effect. Established allodynia (by day 21) was partly reversed by the re-uptake inhibitor reboxetine (5μg, i.t.) but yohimbine no longer had any sensitising effect. This loss of effect coincided with a reduction in the descending noradrenergic innervation of the ipsilateral lumbar dorsal horn. Yohimbine reversibly unmasked contralateral hindlimb allodynia and hyperalgesia of all modalities and increased dorsal horn c-fos expression to an innocuous brush stimulus. Contralateral thermal hyperalgesia was also reversibly uncovered by yohimbine administration in a contact heat ramp paradigm in anaesthetised TNT rats. Following TNT there is an engagement of inhibitory α2-AR-mediated noradrenergic tone which completely masks contralateral and transiently suppresses the development of ipsilateral sensitization. This endogenous analgesic system plays a key role in shaping the spatial and temporal expression of the neuropathic pain phenotype after nerve injury.

High-dose remifentanil prevents development of thermal hyperalgesia in a neuropathic pain model

Intraoperative nerve lesions can lead to chronic postoperative pain. There are conflicting data as to whether or not anaesthetics administered intraoperatively are beneficial. We investigated if remifentanil administered at the time of nerve injury was able to attenuate neuropathic hypersensitivity. Rats were anaesthetized with isoflurane, endotracheally intubated, and a tail vein catheter was inserted. Rats received an i.v. infusion of either saline or low- or high-dose remifentanil (2 or 20 μg kg(-1) min(-1), respectively) for 20 min. During this time, rats received a spinal nerve L5 transection to induce neuropathic pain or a sham procedure. Behavioural tests to assess mechanical and cold allodynia and heat hyperalgesia were performed on postoperative days 1, 3, 7, 14, 21, and 28. Sham-operated animals exhibited no hypersensitivity regardless of the intraoperative remifentanil dose. In rats which received spinal nerve L5 transection, mechanical and cold allodynia developed with no significant differences between treatment groups. However, thermal hyperalgesia was reduced in rats given high-dose remifentanil: mean (standard deviation) area under the curve 426 (53) compared with 363 (34) and 342 (24) in saline or low-dose remifentanil treated rats, respectively (P<0.05). High-dose remifentanil administered at the time of transection of the spinal nerve at L5 prevents subsequent thermal hyperalgesia.

Evaluating the timing of injection laryngoplasty for vocal fold paralysis in an attempt to avoid future type 1 thyroplasty

ObjectivesTo determine whether immediate (less than 3 months from time of nerve injury), early (from 3 to 6 months from time of nerve injury) or late (more than 6 months from time of nerve injury) vocal fold injection influences the long-term outcomes for patients with permanent unilateral vocal fold paralysis.MethodsA total of 250 patients with documented unilateral vocal fold paralysis were identified in this retrospective chart review. 66 patients met the inclusion criteria, having undergone awake trancervical injection with gelfoam™, collagen, perlane™ or a combination. Patients with documented recovery of vocal fold mobility, or patients with less than one year of follow-up after the onset of paralysis were excluded. Patients were stratified into immediate (<3 months), early (3-6 months) and late (>6 months) groups denoting the time from suspected injury to injection. The need for open surgery as determined by a persistently immobile vocal fold with insufficient glottic closure following injection was the primary outcome.Results1 out of 21 (4.8%) in the immediate group, 2 out of 17 (11.8%) in the early group and 20 out of 28 (71.4%) in the late group required type 1 thyroplasty procedures to restore glottic competence. There was significance when comparing late injection to both early and immediate injection (p < 0.001). No statistically significant differences were seen when comparing the number of injections needed to restore glottic competence.ConclusionsThis 10-year longitudinal assessment revealed that early medialization of a permanent paralyzed, abducted vocal fold with a temporary material appears to diminish the likelihood of requiring permanent laryngeal framework surgery.

Causes and prevention of chronic postsurgical pain

Surgical incision invariably causes some measure of nerve damage and inflammatory response that, in most cases, heals quickly without long-term negative consequence. However, a subset of these patients go on to develop lasting neuropathic pain that is difficult to treat and, in many cases, prevents the return to normal activities of life. It remains unknown why two patients with identical surgical interventions may go on to develop completely divergent pain phenotypes or no pain at all. Aggressive, early analgesic therapy has been shown to reduce the incidence of chronic postsurgical pain (CPSP), but no specific regional anesthetic technique or systemic pharmacologic therapy has been shown to prevent CPSP. Inflammation and glial cell activation have recently been shown to be just as important in the transition from normal acute pain to pathologic chronic pain as nerve injury itself and that central sensitization may not be solely due to repetitive nociceptive firing at the time of nerve injury. This has opened a number of new therapeutic possibilities for prevention of CPSP. Here, we discuss the causes of CPSP and current useful preventive strategies in the perioperative period. We also discuss future potential disease-modifying treatments of CPSP.

Early versus late injection medialization for unilateral vocal cord paralysis

To evaluate whether the timing of early (≤6 months from time of nerve injury) vs. late (>6 months) injection medialization laryngoplasty impacts the need for subsequent open-neck reconstruction to restore vocal function in patients with unilateral vocal cord paralysis. Retrospective chart review. A total of 112 outpatient or hospitalized adults with dysphonia resulting from postsurgical or idiopathic unilateral vocal cord paralysis were identified who were injected as initial treatment within 1 year of onset of their paralysis. All subjects underwent awake, transoral, paraglottic injection with absorbable hyaluronic-acid gel. Patients with documented recovery of vocal cord mobility (22), active disease directly affecting the recurrent laryngeal nerve (8), <3 months of follow-up after injection (time for gel to be reabsorbed) (34), or deaths within 1 year after the onset of paralysis (13) were excluded, leaving a study population of 35 patients. Twenty of 32 (62.5%) patients with early injection medialization maintained an adequate voice, obviating the need for open-neck phonosurgical reconstruction; their follow-up from onset of paralysis ranged from 4.0 to 41.8 months (mean 15.2). None of the three patients undergoing late injection (>6 months postparalysis) avoided phonosurgical reconstruction (P = .03, χ2 test). Patients receiving early injection medialization for vocal cord paralysis were less likely to require transcervical reconstruction. We believe that early medialization creates a more favorable vocal cord position for phonation that can be maintained by synkinetic reinnervation, in contrast to the final position of a lateralized vocal cord being determined solely by reinnervation.

Characterisation of the Nociceptive Phenotype of Suppressible Galanin Overexpressing Transgenic Mice

The neuropeptide galanin is widely expressed in both the central and peripheral nervous systems and is involved in many diverse biological functions. There is a substantial data set that demonstrates galanin is upregulated after injury in the DRG, spinal cord and in many brain regions where it plays a predominantly antinociceptive role in addition to being neuroprotective and pro-regenerative. To further characterise the role of galanin following nerve injury, a novel transgenic line was created using the binary transgenic tet-off system, to overexpress galanin in galaninergic tissue in a suppressible manner. The double transgenic mice express significantly more galanin in the DRG one week after sciatic nerve section (axotomy) compared to WT mice and this overexpression is suppressible upon administration of doxycycline. Phenotypic analysis revealed markedly attenuated allodynia when galanin is overexpressed and an increase in allodynia following galanin suppression. This novel transgenic line demonstrates that whether galanin expression is increased at the time of nerve injury or only after allodynia is established, the neuropeptide is able to reduce neuropathic pain behaviour. These new findings imply that administration of a galanin agonist to patients with established allodynia would be an effective treatment for neuropathic pain.

Unity vs. diversity of neuropathic pain mechanisms: Allodynia and hyperalgesia in rats selected for heritable predisposition to spontaneous pain

Do contrasting neuropathic pain diagnoses share common pathophysiological mechanisms? Selective breeding was used to derive rat lines with a common genetic background but a striking difference in the degree of spontaneous pain behavior expressed in the neuroma model of neuropathic pain (HA rats (high autotomy) and LA rats (low autotomy)). The contrasting pain phenotype in these lines is attributable to allelic differences at a small number of genetic loci. Here we show that HA and LA rats also differ in their nocifensive response to applied stimuli in the Chung (spinal nerve ligation, SNL) model of neuropathic pain. This includes tactile allodynia and hyperalgesia, and heat allodynia. The degree of hypersensibility varied with sex, age at the time of nerve injury, and the extent of the nerve lesion. F1 crosses of HA and LA rats and inbred Lewis rats showed low levels of autotomy but variable levels of hypersensibility to applied stimuli. Results indicate that alleles which predispose to spontaneous neuropathic pain also predispose to stimulus-evoked pain (allodynia and hyperalgesia). This, in turn, suggests that despite contrasting etiology and behavioral endpoints, pain phenotype in the neuroma and the SNL models shares common pathophysiological mechanisms.

Age-Dependent Development Of Chronic Neuropathic Pain, Allodynia and Sensory Recovery after Upper Limb Nerve Injury in Children

Forty-nine children with distal upper limb nerve injury were studied at a mean follow-up of 2 years 3 months. Patients who were aged 5 years or younger at the time of nerve injury (15/49) had no chronic neuropathic pain symptoms or allodynia. Patients with allodynia on quantitative sensory testing but no spontaneous pain (8/49) were all older than 5 years and those reporting spontaneous chronic neuropathic pain (5/49) were all older than 12 years at the time of injury. Previous studies of adults with similar nerve injuries report chronic hyperaesthesia in up to 40% of cases. Semmes-Weinstein monofilament testing showed a positive correlation between age at injury and abnormal sensory threshold (r = 0.60, P<0.0001). These findings indicate that young children show better sensory recovery and are less likely to develop long-term chronic neuropathic pain syndromes than adults following nerve injury.

Effect of acute and chronic administration of caffeine on pain-like behaviors in rats with partial sciatic nerve injury

Caffeine, used in many pain medications as an adjuvant analgesic, is an adenosine A 1 and A 2A receptor antagonist. Here we examined the effects of acute or chronic caffeine administration in rats after partial sciatic nerve injury. The hindpaw response to mechanical or cold stimulation was assessed following photochemically induced sciatic nerve injury which leads to hypersensitivity to these stimuli. Caffeine was administered i.p. acutely or in the drinking water chronically. The mechanical and cold hypersensitivity of sciatic nerve-injured rats was dose-dependently alleviated by acute systemic administration of caffeine (10–80 mg/kg). The effect of caffeine was, however, associated with side effects including locomotor stimulation or depression. Chronic oral administration (average daily doses 27.5 mg/kg/day or 61.5 mg/kg/day for 2 weeks) of caffeine starting at the time of nerve injury did not significantly affect the development of pain-like behaviors. Thus, acute, but not long term, caffeine intake reduced neuropathic pain state in nerve-injured rats, but only at very high doses. The potential hyperalgesic effect of chronic A 1 adenosine receptor blockade may have been compensated for by an antinociceptive effect of caffeine through antagonism of A 2A receptors and tolerance development.

Abstracts

Abstracts

Macrophage-Derived Factors Stimulate Optic Nerve Regeneration

After optic nerve injury in mature mammals, retinal ganglion cells (RGCs) are normally unable to regenerate their axons and undergo delayed apoptosis. However, if the lens is damaged at the time of nerve injury, many RGCs survive axotomy and regenerate their axons into the distal optic nerve. Lens injury induces macrophage activation, and we show here that factors secreted by macrophages stimulate RGCs to regenerate their axons. When macrophages were activated by intravitreal injections of Zymosan, a yeast cell wall preparation, the number of RGC axons regenerating into the distal optic nerve was even greater than after lens injury. These effects were further enhanced if Zymosan was injected 3 d after nerve crush. In a grafting paradigm, intravitreal Zymosan increased the number of RGCs that regenerated their axons through a 1.5 cm peripheral nerve graft twofold relative to uninjected controls and threefold if injections were delayed 3 d. In cell culture, media conditioned by activated macrophages stimulated adult rat RGCs to regenerate their axons; this effect was potentiated by a low molecular weight factor that is constitutively present in the vitreous humor. After gel-filtration chromatography, macrophage-derived proteins > or =30 kDa were found to be toxic to RGCs, whereas proteins <30 kDa reversed this toxicity and promoted axon regeneration. The protein(s) that stimulated axon growth is distinct from identified polypeptide trophic factors that were tested. Thus, macrophages produce proteins with both positive and negative effects on RGCs, and the effects of macrophages can be optimized by the timing of their activation.