A Síndrome de Ardência Bucal (SAB) caracteriza - se por sensação de ardor, com ausência de sinais clínicos ou laboratoriais associados. A etiopatogenia é desconhecida, inexistindo protocolo terapêutico satisfatório. O objetivo deste trabalho foi avaliar a eficácia da aplicação tópica de capsaicina, como alternativa terapêutica, em um grupo de pacientes portadores da SAB, além de investigar, nessa população, indicativos de ansiedade e depressão, correlacionando estes últimos aspectos com a resposta à terapêutica aplicada. Constituiu-se um grupo de vinte indivíduos portadores da síndrome, todos de acordo com os termos do consentimento esclarecido. Quinze sujeitos constituíram o grupo teste (GT) e foram tratados com capsaicina, em aplicações diárias, durante três semanas, repetindo-se o ciclo por quatro semanas após uma semana de intervalo. O grupo controle (GC) foi tratado com o creme base utilizado como veículo da capsaicina, durante o mesmo período. Ambos foram controlados após 30 dias do término da medicação. A evolução dos sintomas foi controlada por escala visual de sintomatologia (EVS) e questionário acerca do efeito global percebido (EGP). A intensidade média do sintoma de ardência antes do início dos ciclos de tratamento, mensurado pela EVS, foi de 5,1 (GT) e 4,4 (GC). Ao final da quarta semana o GT mostrou redução dos sintomas (EVS=3,6), enquanto o GC declarou aumento da sintomatologia (EVS=4,8). No GT, entre a quarta e a oitava semana houve redução dos sintomas da ordem de 8,3%, e entre a oitava e a décima segunda semana observou-se aumento de 13,5% da sintomatologia. No GC houve 22.8% de piora (EVS=5,75) entre o início e a décima segunda semana. Ao EGP houve pelo menos algum alívio do sintoma em seis pacientes (40%) do GT e em um paciente do GC (20%). Quatro pacientes (26,6%) reportaram remissão total do sintoma após tratamento com capsaicina e um paciente (20%) do controle. Para três pacientes do GT e dois do GC não houve modificações do sintoma. Houve relato de piora em dois pacientes (13,3%) do GT e um (20%) do GC. Oito pacientes do GT apresentaram alto nível de ansiedade e sete níveis médios. No GC um paciente apresentou nível baixo, três mostraram valores médios e um classificou-se como alto. Ao CES-D valores indicativos de depressão foram registrados por dez pacientes (66,6%) do GT e 40% (02) do GC. Concluímos que a capsaicina apresentou efetividade no controle da sintomatologia da SAB, parecendo haver correlação com a intensidade inicial de sintomas e manutenção do uso do medicamento. Além disso, houve correlação entre alto nível de ansiedade e indicativos de depressão, embora não se tenha percebido influência destes aspectos sobre a resposta terapêutica. / Burning mouth syndrome (BMS) is characterized by an oral burning sensation, with no corresponding clinical signs or laboratory abnormalities. The etiology is unknown, and there was no satisfactory treatment available. The objective of this study was to evaluate the effectiveness of topical use of capsaicin, as an alternative therapy in a group of BMS patients, as well as to correlate anxiety and depression levels to response to the therapy applied. Twenty BMS individuals in accordance to the terms to informed consent comprised the study group. Fifteen subjects were allocated to the test group (TG) and were treated with capsaicin, in daily applications for three weeks, one-week interval and an additional treatment cycle of four weeks. The control group (CG) was treated with the cream base used as a vehicle of capsaicin preparation, during the same period. All patients were examined 30 days after discontinuation of the medication. Results were assessed through a visual analogue scale (VAS) and a questionnaire on the global perceived effect (GPE). The average symptoms intensity before treatment, on EVS, was 5.1 (TG) and 4.4 (CG). At the fourth week control, TG presented reduction on the level of symptoms (EVS = 3.6), while CG presented an increase of symptoms intensity (VAS = 4.8). In the TG, between fourth and eighth week of follow-up, symptoms decreased around 8.3%, and between the eighth and twelfth week there was an increase of 13.5% on symptoms intensity. In the CG it was registered 22.8% of worsening (EVS = 5.75) between the beginning of the study and the twelfth week of control. On GPE assessment, six patients (40%) of TG and one patient of CG (20%), presented some relief of symptoms; four patients TG (26.6%) reported total remission of symptoms after treatment with capsaicin and one patient (20%) of control; three patients of TG and two of the CG remained unaltered. There were reports of worsening in two patients (13.3%) of TG and one (20%) of the CG. Eight patients of TG showed a high level of anxiety and seven moderate levels. In CG one patient presented low level, three showed a moderate level and one was ranked as having a high level of anxiety. CES-D suggested traits of depression in ten patients (66.6%) of TG and 40% (2) of the CG. We concluded that capsaicin is effective in controlling the burning symptom of BMS, suggesting some correlation with initial symptoms intensity and the maintenance of drug use. Moreover, there was some correspondence between high levels of anxiety and traits of depression, but it was not perceived influence of these aspects to the therapeutic response.

Dor neuropática (DN) é definida como “dor iniciada ou causada por lesão primária ou disfunção em sistema nervoso”, porém sua prevalência depende do tipo de trauma e da disfunção relacionada. Apesar desta condição dolorosa ser considerada altamente prevalente e debilitante, os tratamentos disponíveis são relacionados a efeitos adversos dificultando a adesão. Devido a isso, buscam-se alternativas não farmacológicas para o tratamento deste tipo de dor, entre elas, as técnicas de neuromodulação periférica, como acupuntura (AC) e eletroacupuntura (EA). Estas técnicas podem ser combinadas com intervenções farmacológicas e não farmacológicas e têm apresentado resultados promissores no tratamento da dor neuropática. No entanto, seus mecanismos de ação não estão totalmente elucidados, desta forma a utilização de modelos animais é de grande valia para o estudo destes mecanismos no tratamento da dor neuropática e da patofisiologia deste tipo de dor crônica. É importante salientar que a aplicação de AC e EA em animais acordados é complexa, visto que gera desconforto e pode alterar a analgesia induzida pelo tratamento. Em muitos estudos a anestesia com isoflurano é utilizada durante a aplicação dos tratamentos, porém sua utilização pode gerar um viés no estudo, considerando a possível interferência do fármaco nos resultados comportamentais e neuroquímicos. Outro importante foco de estudo consiste em comparar as duas técnicas, AC e EA, buscando determinar qual destas é a mais eficaz no tratamento da dor neuropática. Considerando o exposto acima, os objetivos desta tese foram: 1) avaliar os parâmetros comportamentais e neuroquímicos dos efeitos da utilização de anestesia na aplicação de AC e EA em ratos submetidos ao modelo de DN; 2) comparar os efeitos da AC e EA em modelo animal de DN por meio de parâmentros comportamentais, neuroquímicos e histológicos. Considerando os resultados obtidos nesta tese, concluímos que o isoflurano aumenta a analgesia promovida por AC e EA, provavelmente diminuindo o efeito do estresse gerado pela aplicação dos tratamentos em animais acordados, resultado que é corroborado pela diminuição do nível de S100β periférico (marcador de morte neuronal central); Por outro lado, o isoflurano diminuiu os níveis de fator de crescimento neuronal (NGF) no nervo periférico lesado, indicando diminuição do processo de regeneração neural, enquanto a EA aumentou. Ao mesmo tempo, o isoflurano alterou os efeitos dos tratamentos nos comportamentos exploratórios e nos níveis de N-metil D-aspartato em tronco encefáfio e medula espinhal. A AC apresentou-se mais eficaz no tratamento da DN em comparação à EA, porém nenhum dos tratamentos foi capaz de alterar os danos causados pela indução da DN no músculo gastrocnemio esquerdo dos animais demonstrado na histologia. Todavia, este resultado não alterou a analgesia gerada pelos tratamentos. / Neuropathic pain (NP) is defined as "pain initiated or caused by primary injury or dysfunction in the nervous system," but its prevalence depends on the type of trauma and related dysfunction. Although this painful condition is considered to be highly prevalent and debilitating, the available treatments are related to adverse effects, making adherence difficult. Because of this, non-pharmacological alternatives for the treatment of this type of pain are sought, among them, the techniques of peripheral neuromodulation, such as acupuncture (AC) and electroacupuncture (EA). These techniques can be combined with pharmacological and non-pharmacological interventions and have shown promising results in the treatment of neuropathic pain. However, its mechanisms of action are not fully elucidated, so the use of animal models is of great value for the study of these mechanisms in the treatment of neuropathic pain and the pathophysiology of this type of chronic pain. It is important to emphasize that the application of AC and EA in awake animals is complex, since it generates discomfort and can alter the analgesia induced by the treatment. In many studies, anesthesia with isoflurane is used during the application of the treatments, but its use may generate a bias in the study, considering the possible interference of the drug in the behavioral and neurochemical results. Another important focus of the study is to compare the two techniques, AC and EA, seeking to determine which is the most effective in the treatment of neuropathic pain. Considering the above, the objectives of this thesis were: 1) to evaluate the behavioral and neurochemical parameters of the effects of the use of anesthesia in the application of AC and EA in rats submitted to the DN model; 2) to compare the effects of AC and EA on animal model of DN by means of behavioral, neurochemical and morphological parameters. Considering the results obtained in this thesis, we conclude that isoflurane increases the analgesia promoted by AC and EA, probably decreasing the effect of the stress generated by the application of the treatments in agreed animals, a result that is corroborated by the decrease in the level of peripheral S100β (biomarker of central neuronal injury); On the other hand, isoflurane decreased the levels of neural grown factor (NGF) in the injured peripheral nerve, indicating a decrease in the neural regeneration process, while the EA increased. At the same time, isoflurane altered the effects of treatments on exploratory behaviors and N-metil-D-aspartato (NMDA) levels in the brainstem and spinal cord. AC was more effective in the treatment of DN compared to EA, but none of the treatments was able to alter the damage caused by DN induction in the left gastrocnemius muscle of the animals showed in histology. However, this result did not alter the analgesia generated by the treatments.

Background Chemotherapy-induced peripheral neuropathy (CIPN) is a common dose-limiting toxicity with significant sequelae impacting prognosis and quality of life. The natural history and pathophysiological mechanisms of CIPN are unclear. Equally, the lack of systematic approach to diagnosis and assessments contribute to difficulty identifying at risk patients with implications on symptom burden. Effective management of CIPN is also difficult due to limited treatment options. To try and address this challenging clinical problem, this thesis aimed to adopt a translational approach to: 1) characterisation and early identification of the development of CIPN in cancer patients receiving neurotoxic chemotherapy and 2) explore topical treatment options in patients with chronic peripheral neuropathic pain. Methodology In the CIPN study, a mixed cohort of colorectal, gynaecological and lung cancer patients receiving neurotoxic chemotherapy (platinum agents and taxanes) were assessed prospectively, at baseline (prior to initiating chemotherapy), during cycles (every 3 weeks) and post-treatment (every 3 months) for up to 12 months (cumulative 261 assessments). Comprehensive longitudinal clinical characterisation consisted of the integration of quantitative sensory testing (QST), objective measure of function (grooved pegboard test), patient-reported outcomes and in vivo confocal microscopy to provide insight into the clinical course and potential psychophysical biomarkers of CIPN during and after chemotherapy. In the pilot intervention study, patients with chronic, complex cancer treatment related peripheral neuropathic pain received a single application of high concentration 8% capsaicin patch. Assessments conducted at baseline, 4 weeks and 12 weeks included patient-reported outcomes and QST with an exploratory application of in vivo confocal microscopy in a case. Results In the CIPN study, 33 patients when compared to 33 age and gender matched healthy controls displayed thermal hyperalgesia, sensorimotor impairment and increased resting heart rate prior to initiating neurotoxic chemotherapy. Characterisation of somato-sensory profile demonstrated dysfunction of the various types of primary afferent nerves (Aβ, Aδ and C). Assessing the change over time from baseline to during cycles and post-treatment follow up, revealed signs and symptoms as early as cycle 2 with an increase in the later cycles and 3 months post-treatment follow up. A greater burden was observed at 12 months in comparison to baseline. Significant changes were observed in QST parameters indicating both small and large fibre deficits. Interesting associations were observed for example with tactile deficits in the upper and lower limb and patient-reported outcomes. The repeated measures model provided an opportunity to distil the relationship between subjective and objective measures of CIPN. The subclinical findings at baseline however did not translate to obvious predictors of CIPN development. The exploratory use of in vivo confocal microscopy (45 healthy controls, 9 patients) demonstrated correlation with current assessment tools (QST). Analysis from the pilot intervention study of 20 patients revealed clinically significant improvement in pain in a subset at 4 and 12 weeks post-treatment. Conclusion Overall the combination of subjective and objective measures utilised in the prospective characterisation of this mixed cohort of cancer patients provided a useful paradigm for qualifying and quantifying the trajectory of CIPN related peripheral nerve damage and symptom burden with additional contribution from the novel in vivo confocal microscopy work. In capturing the varied spectrum of phenotypes, this approach may provide insight into the complexities of the underlying neurobiological mechanisms. The baseline subclinical sensory, motor and autonomic nerve dysfunction implicate a cancer-mediated process possibly contributing to CIPN. Although the preliminary investigation of baseline predictors of CIPN was inconclusive, thermal pain threshold warrant further investigation. These findings highlight the need to further address prediction and risk stratification in larger studies. The exploratory intervention study suggests that patients with chronic neuropathic pain may receive some benefit in pain severity, function and mood with effect continuing at 12 weeks post-treatment. This research warrants further investigation in larger cohorts.

<p>Neuropathic pain of central and peripheral origin presents a substantial clinical problem as it is often resistant to pharmacological treatment.</p><p>The health related quality of life of 126 patients with peripheral neuropathic pain was studied, to provide a cross sectional description from this point of view. Two generic health-related quality of life instruments; the SF-36 and the Nottingham Health Profile were used together with pain assessments, global rating of health and verbal rating scales of pain and other symptoms, as well as patient descriptors.</p><p>The analgesic effect of ketamine, lidocaine and morphine were assessed in a double blind, placebo-controlled, randomized study design. Three groups of patients were studied: patients with peripheral neuropathic pain of traumatic origin, patients with central post-stroke pain and patients with neuropathic pain after spinal cord injury. Somatosensory function was examined to see if this could predict response to treatment and to investigate if the drugs caused changes in thermal or mechanical sensibility.</p><p>The results shows that the intense pain, limited efficacy and tolerability of available treatments, the low overall rating of health, reduced work status and troublesome symptoms constitute a substantial impact on the quality of life for patients with peripheral neuropathic pain.</p><p>The NMDA-antagonist ketamine yielded substantial pain relief to patients with peripheral neuropathic pain and patients with neuropathic pain after spinal cord injury. However, the reported side effects limit the clinical usefulness of the treatment. Lidocaine did not give significant pain relief to the patients in the three studied groups. Morphine may represent a therapeutic alternative for some patients with central post-stroke pain, although only a small group of this category of patients responded with analgesia.</p><p>Assessment of baseline somatosensory functions could not be used to identify responders to treatment with either drug, nor did ketamine, lidocaine or morphine cause any changes in thermal or mechanical sensibility.</p>

Introduction. Painful diabetic peripheral neuropathy (DPN) is a common complication of diabetes that interferes with daily living and causes severe pain. Pharmacotherapy is the accepted treatment strategy, however, this strategy is associated with high cost, minimal reductions in pain, and adverse side effects. Thus, a critical need exists to develop alternative treatment strategies. Purpose. To determine if a 12-week whole-body vibration (WBV) intervention reduces pain in adults with DPN. Methods. Twenty-one adults with physician confirmed painful DPN volunteered to take part in a 26-week time series design study. Pain was assessed with the Brief Pain Inventory Short Form [BPI-sf] and a 0-10 numeric rating scale [NRS]. The BPI-sf contains two indices that respectively measure how pain interferes with daily living and severity. The intervention began after a 12-week control period. At week 13, participants were asked to stand on a WBV machine 3 d/week for 4, 3-min bouts at 30-50 Hz with 1-min rest intervals between bouts. Pain levels were reported using the NRS before and after each bout. Results. Comparing post- to pre-intervention, BPI-sf pain interference scores decreased from 5.61±1.40 to 2.39±1.82 (p≤0.001). BPI-sf pain severity scores decreased from 5.1±0.64 to 3.1±1.87 (p≤0.01). Analyses of the NRS scores indicate that pain decreased each week following WBV and that between weeks, pain continued to decrease. Conclusion. These findings demonstrate that whole-body vibration was effective at reducing pain in a sample of adults with painful DPN. / Graduation date: 2012

Prior work from our laboratory has shown that the spinal cord is capable of supporting a simple form of instrumental (response-outcome) learning. In a typical experiment, animals are given a spinal transection at the second thoracic vertebra, and tested 24 h after surgery. If animals are given shock when their leg is in a resting position (controllable shock), they quickly learn to maintain the leg in a flexed position, thereby minimizing shock exposure. Animals exposed to shock that is independent of leg position (uncontrollable shock) fail to learn. This learning deficit can be induced by as little as 6 minutes of shock to either limb or to the tail, and lasts for up to 48 h. The aim of this dissertation was to explore whether the deficit shares behavioral features and pharmacological mechanisms similar to those involved in the induction of neuropathic pain. Work within the pain literature has identified a spinal hyperexcitability that is induced by intense stimulation of pain fibers. This phenomenon, known as central sensitization, is characterized by an increase in tactile reactivity (allodynia) that can be induced by shock or peripheral inflammation. Pharmacological findings have revealed that central sensitization depends on the activation of the N-methyl-D-aspartate (NMDA) and group I metabotropic glutamate receptors (mGluRs). Experiment 1 showed that uncontrollable shock induces a tactile allodynia similar to that observed in central sensitization. Experiment 2 showed that peripheral inflammation caused by a subcutaneous injection of formalin generates a dose-dependent deficit. Experiment 3 indicated that the formalin-induced deficit was observed 24 h after delivery of the stimulus. Experiments 4-8 revealed that the NMDA and group I mGluRs are involved in the deficit. The NMDA receptor was found to be necessary (Experiment 4), but only sufficient to induce a deficit at neurotoxic doses (Experiment 5). Both of the group I mGluRs (subtypes, mGluR1 and mGluR5) were found to be necessary (Experiments 6 & 7). A general group I mGluR agonist summated with a subthreshold intensity of shock to produce a robust deficit (Experiment 8), suggesting shock and mGluR activation produce a deficit through a common mechanism.

Neuropathic pain of central and peripheral origin presents a substantial clinical problem as it is often resistant to pharmacological treatment. The health related quality of life of 126 patients with peripheral neuropathic pain was studied, to provide a cross sectional description from this point of view. Two generic health-related quality of life instruments; the SF-36 and the Nottingham Health Profile were used together with pain assessments, global rating of health and verbal rating scales of pain and other symptoms, as well as patient descriptors. The analgesic effect of ketamine, lidocaine and morphine were assessed in a double blind, placebo-controlled, randomized study design. Three groups of patients were studied: patients with peripheral neuropathic pain of traumatic origin, patients with central post-stroke pain and patients with neuropathic pain after spinal cord injury. Somatosensory function was examined to see if this could predict response to treatment and to investigate if the drugs caused changes in thermal or mechanical sensibility. The results shows that the intense pain, limited efficacy and tolerability of available treatments, the low overall rating of health, reduced work status and troublesome symptoms constitute a substantial impact on the quality of life for patients with peripheral neuropathic pain. The NMDA-antagonist ketamine yielded substantial pain relief to patients with peripheral neuropathic pain and patients with neuropathic pain after spinal cord injury. However, the reported side effects limit the clinical usefulness of the treatment. Lidocaine did not give significant pain relief to the patients in the three studied groups. Morphine may represent a therapeutic alternative for some patients with central post-stroke pain, although only a small group of this category of patients responded with analgesia. Assessment of baseline somatosensory functions could not be used to identify responders to treatment with either drug, nor did ketamine, lidocaine or morphine cause any changes in thermal or mechanical sensibility.

The pharmacologic treatment of painful neuropathy continues to pose problems and challenges in clinical practice. This is largely due to a limited understanding of the underlying etiologies of such neuropathic pain and insufficient knowledge of the optimal effective doses that would cause only minimal systemic side effects. The use of molecular methods, such as gene deletion from knockout mice and the development of cellular mini-pumps for the delivery of biologic antinociceptive molecules have led to a better understanding of the underlying mechanisms involved in the induction of intractable neuropathic pain. It is now known that the initiation of an excitatory cascade after injury or disease leads to the induction of various second messenger systems, and the loss or down-regulation of the endogenous inhibitory spinal system and central sensitization, both of which cause such pain. Currently, there are novel approaches that use genetic therapy in the management of neuropathic pain. Two such approaches which have been determined to be safe are proposed to be investigated in this study using animal models of pain. The first approach involves cell-mediated delivery of antinociceptive molecules to the cerebrospinal fluid using cultivated spinal progenitor cells transplanted into the subarachnoid space. Chronic constriction injury (CCI) of the sciatic nerve was used to induce chronic neuropathic pain in the hind paw of rats. 1x106 spinal progenitor cells (SPCs) were implanted intrathecally on the third day after the CCI surgery. The behavioral response to thermal hyperalgesia was observed and recorded during the 14 days post surgery. Various techniques were utilized to trace the progenitor cells, confirm the differentiation, and identify the neurotransmitters involved. Glutamic acid decarboxylase (GAD) immunoreactivity was revealed for 65% of the cultivated SPCs in our study. We also determined that transplanted cells could survive more than four weeks post intrathecal implantation. Significant reductions were demonstrated for responses to thermal stimuli for the CCI rats that had received intrathecal SPC transplantation. A novel intrathecal delivery with SPCs reduced CCI-induced neuropathic pain. The second approach involves the use of a newly developed intrathecal electroporation probe in the delivery of antinociceptive peptides to reduce expression of endogenous nociceptive molecules in the spinal cord. To investigate the feasibility of delivering exogenous genes into spinal cord using direct in vivo electrotransfection, pE-GFP C1 vector was used to achieve the goal. Gene transfer to the spinal cord was accomplished via direct intrathecal injection of, followed by 5 electric pulses for 50 ms at 200 V delivered intrathecally. The spinal cords were retrieved and analyzed with fluorescence microscopy, reverse transcription polymerase chain reaction (RT-PCR), and western blotting. At day 1, 3 or 7 following electroporation a clear green fluorescence protein (GFP) expression in spinal cord tissue was detected. The most prominent transfection occurred in the meningeal cells and superficial layer of the spinal cord. Successful transfection was also confirmed with RT-PCR and western blotting. The expression of GFP protein was peaked between 3-7 days after electroporation and significantly decreased at 14 days. No behavioral or spinal neurodegenerative changes were detected at any time point. This study demonstrates that direct in vivo electrotransfection represents an effective and simple method for spinal gene delivery. Furthermore, the optimal pulse characteristics (voltage, pulse duration, number of shocks) were investigated for in vivo electroporation for gene transfer into the spinal cord. The expression of pre-opiomelanocortin (POMC) gene from electroporated plasmid DNA was then evaluated in this study using RT-PCR and western blot. We conclude that the optimal conditions for electroporation are a pulse voltage of 200 V, 75-ms duration, 925-ms interval, for five iterations. Also, electroporation treatment for neuropathic pain was attempted for CCI rats using plasmid DNA that expresses the POMC gene. Intrathecal administrations of the POMC plasmid elevated spinal beta-endorphin levels, as manifested in significantly elevated pain threshold for the CCI limbs. We also tested whether intrathecal electric stimulation would reduce the tolerance of chronic morphine usage and the severity of precipitated morphine withdrawal symptoms. Rats received intrathecal electrode catheter implantation and a continuous intrathecal infusion of morphine (2 nmol/hr) or saline for seven days. Intrathecal electric stimulations (0, 20V, 200V) were performed once daily during the same period. Daily tail flick and intrathecal morphine challenge tests were performed to assess the effect of intrathecal electric stimulation on antinociception and tolerance of morphine. Naloxone withdrawal (2mg/kg) was performed to assess morphine dependence, and changes in spinal neurotransmitters were monitored by microdialysis. The antinoceptive effect of intrathecal morphine was increased by 200V electric stimulation. The magnitude of tolerance was decreased in the rats receiving 2 nmol/hr infusion with daily intrathecal electric stimulation. The severity of naloxone-induced withdrawal symptom was lower in the rats receiving 200V stimulation. Intrathecal stimulation thus enhances analgesia and attenuates naloxone-induced withdrawal symptoms in rats receiving chronic intrathecal morphine infusion. Increases in spinal glycine release may be the underlying mechanisms. The promise is that, both approaches attenuate or reverse persistent nociceptive states; they could be exploited for use in the development of gene therapy for the management of pain.

Prior work from our laboratory has shown that the spinal cord is capable of supporting a simple form of instrumental (response-outcome) learning. In a typical experiment, animals are given a spinal transection at the second thoracic vertebra, and tested 24 h after surgery. If animals are given shock when their leg is in a resting position (controllable shock), they quickly learn to maintain the leg in a flexed position, thereby minimizing shock exposure. Animals exposed to shock that is independent of leg position (uncontrollable shock) fail to learn. This learning deficit can be induced by as little as 6 minutes of shock to either limb or to the tail, and lasts for up to 48 h. The aim of this dissertation was to explore whether the deficit shares behavioral features and pharmacological mechanisms similar to those involved in the induction of neuropathic pain. Work within the pain literature has identified a spinal hyperexcitability that is induced by intense stimulation of pain fibers. This phenomenon, known as central sensitization, is characterized by an increase in tactile reactivity (allodynia) that can be induced by shock or peripheral inflammation. Pharmacological findings have revealed that central sensitization depends on the activation of the N-methyl-D-aspartate (NMDA) and group I metabotropic glutamate receptors (mGluRs). Experiment 1 showed that uncontrollable shock induces a tactile allodynia similar to that observed in central sensitization. Experiment 2 showed that peripheral inflammation caused by a subcutaneous injection of formalin generates a dose-dependent deficit. Experiment 3 indicated that the formalin-induced deficit was observed 24 h after delivery of the stimulus. Experiments 4-8 revealed that the NMDA and group I mGluRs are involved in the deficit. The NMDA receptor was found to be necessary (Experiment 4), but only sufficient to induce a deficit at neurotoxic doses (Experiment 5). Both of the group I mGluRs (subtypes, mGluR1 and mGluR5) were found to be necessary (Experiments 6 & 7). A general group I mGluR agonist summated with a subthreshold intensity of shock to produce a robust deficit (Experiment 8), suggesting shock and mGluR activation produce a deficit through a common mechanism.

Neuronal-glial interactions play an important role in the development of neuropathic (NP) pain states. Earlier studies in our laboratory suggest a role for activated glia in morphine-induced delta opioid receptor (DOR) trafficking by altering DOR functional competence. Thus, chronic treatment with the glial inhibitor, propentofylline (PF) blocks the anti-allodynic and anti-hyperalgesic effects of the DOR agonist deltorphin II. The present study aimed to determine whether NP pain-induced changes in DOR function and trafficking are dependent on glial activation. The first global aim of this study was to determine the molecular and behavioural effects of glial activation by two glial inhibitors, PF and PJ34 in a model of neuropathic pain. Glial activation was assessed via changes in specific proteins using fluorescent immunohistochemistry (IHC). Neuropathy-induced c-Fos activation was assessed by IHC and pain hypersensitivity was assessed, including mechanical allodynia and spontaneous pain. The second global aim determined the role of activated glia in changes in neuropathy-induced increases in DOR function and DOR subcellular localization using immunogold IHC and transmission electron microscopy (EM). Chronic PJ34 attenuated chronic constriction injury (CCI)-induced mircoglial, but not astrocyte activation. Chronic administration of either PF or PJ34 attenuated the CCI-induced increase in c-Fos immunoreactive expression. However, neither drug attenuated CCI-induced mechanical allodynia or spontaneous pain. Both chronic PF and PJ34 administration in NP animals attenuated the anti-allodynic effects of the DOR-selective agonist deltorphin II, suggesting glial inhibition blocks DOR function. However, chronic PF, but not PJ34, blocked the anti-allodynic effects of another DOR agonist, SNC80. These data suggest that SNC80 might be targeting a different DOR molecular species that is not affected by factors released from microglia. Finally, EM experiments revealed that chronic PF treatment prevented the CCI-induced increase in DOR trafficking providing a positive correlation between behaviour and receptor localization. This study suggests that activated glia contribute to changes in DOR function and trafficking in NP pain states. It also suggests that there is a dissociation between glial inhibition and pain hypersensitivity. / Thesis (Master, Pharmacology & Toxicology) -- Queen's University, 2010-08-31 14:45:47.888