Migraine patients often demonstrate cutaneous allodynia, defined as a hypersensitivity of the skin to touch or mechanical stimuli that is considered non-noxious under normal circumstances. The allodynia sometimes begins intracranially and spreads, via unknown mechanisms, to extracranial regions. The goal of the study was to develop and validate a model of cutaneous allodynia triggered by dural inflammation for pain associated with headaches, and to explore neuronal and glial mechanisms underlying generalized allodynia. Inflammatory mediators (IM) were applied to the dura of unanesthetized rats via previously implanted cannulas and sensory thresholds of the face and hindpaws were characterized. IM elicited robust and time-related facial and hindpaw allodynia which peaked after approximately three hours as well as FOS expression in the trigeminal nucleus caudalis (TNC), indicative of central sensitization. These effects were reminiscent of cutaneous allodynia seen in patients with migraine or other primary headache conditions, and were reversed by agents used clinically in the treatment of migraine including sumatriptan, naproxen, CGRP-antagonist, and morphine. Consistent with clinical observations, the allodynia was unaffected by an NK-1 antagonist. Having established facial and hindpaw allodynia as a useful animal surrogate of headache-associated allodynia, we next showed that blocking pain-facilitating processes from the rostral ventromedial medulla (RVM) interfered with its expression. Inactivation of the RVM with local anesthetic, destruction of putative pain-facilitation cells, and blockade of cholecystokinin receptors all prevented or significantly attenuated IM-induced allodynia. Electrophysiological studies confirmed activation of pain-facilitating "ON" cells and transient suppression of "OFF" cells in the RVM following IM. Additionally, microinjection of the RVM with a microglial inhibitor or sumatriptan also inhibited the expression of IM-induced cutaneous allodynia as well as microglial activation. Facial and hindpaw allodynia associated with dural stimulation is a useful surrogate of pain associated with primary headache including migraine and may be exploited mechanistically for the development of novel therapeutic strategies for headache pain. The data also demonstrate a requirement for activation of descending facilitation from the RVM, likely reliant on neuronal-glial interactions, for the expression of cranial and extracranial cutaneous allodynia. Consequently, the findings are consistent with a brainstem generator of allodynia associated with headache disorders.

Cortical Spreading Depression (CSD) is characterized by a wave of neuronal and glial depolarization followed by depression of bioelectrical activity that slowly propagates through the cortex of many species, including humans. CSD is associated with brain disorders such as stroke, head trauma and migraine. Many earlier studies have provided compelling evidence that CSD is the underlying mechanism of aura in migraine; however, whether CSD can elicit headache associated with migraine is not fully understood. Cutaneous allodynia is highly prevalent in the peri-orbital area and extracephalic sites of migraine patients, suggesting that sensitization of primary afferents and central trigeminovascular neurons in these patients could be initiated by the underlying mechanism of aura.Unlike previous reports on the interaction between CSD and the trigeminal system, in which nociceptive behavior could not be measured since they employed anesthetized animals, we designed a model in which freely moving rats could be monitored for both CSD events and behavior responses due to pinprick plus KCl injection to the occipital cortex. We show that significant tactile hypersensitivity of the periorbital region of the face and hindpaws develop in a time-dependent manner following CSD. Enhanced expression of Fos protein and increased mRNA levels of the inflammatory cytokines IL-1beta and IL-6 are found within the trigeminal nucleus caudalis (TNC) two hours following cortical injection. We further show that systemic administration of anti-migraine drugs such as sumatriptan, naproxen and CGRP(8-37) (a CGRP antagonist) attenuate the generalized allodynia that ensue following cortical stimulation by KCl. Microinjection of bupivacaine in the ipsilateral trigeminal ganglion or in the rostral ventromedial medulla (RVM) prior to cortical pinprick plus KCl injection reversibly diminishes tactile hypersensitivity, suggesting that RVM pain-facilitating cells become activated by a trigeminal-RVM pathway following CSD. In addition we demonstrate that cortical pinprick plus KCl injection induced CSD events in 24/28 (85%) rats, among which 66% and 87% developed allodynia in the face and hindpaw, respectively.These studies suggest a potential association between CSD and development of hypersensitivity in rats, indicating that this model can be used to investigate the role of CSD-evoked migraine-related pain and to explore novel therapeutic strategies.

Thesis (M.Phil.) - University of Queensland, 2005. / Includes bibliography.

We performed greater occipital nerve blocks on 24 migraineurs with unilateral migraine and trigeminal nerve distribution allodynia. Using a visual analog scale for migraine pain, brush allodynia in the trigeminal nerve distribution and photophobia were reduced 64%, 75%, and 67%, respectively, after 5 minutes. Allodynia improved faster than headache. The results of this study suggest that greater occipital nerve blocks initiate an inhibitory process that shuts down several symptom generators.

BACKGROUND: Containing a brain for signal processing and decision making, and a peripheral component for sensation and response, the nervous system provides higher organisms a powerful method of interacting with their environment. The specific neurons involved in pain sensation are known as nociceptors and are the source of normal nociceptive pain signaling to prompt appropriate responses. Though acute hypersensitization can be advantageous by encouraging an organism to allow an injured area to heal, chronic pain conditions can be pathological and can markedly reduce quality of life. While a variety of genes have been associated with congenital pain conditions, two rare cases examined in this study have not had their mutated genes identified. Potassium voltage-gated channel subfamily H member 8, or KCNH8, is involved in regulating action potential production and propagation, and has not been linked with pain processing of any kind to date. Here, a male patient evaluated at Boston Children’s Hospital contains a novel single-base KCNH8 mutation and possesses an extremely low sensitivity to cold temperatures and mechanical pain, but a higher sensitivity to warmer temperatures. A separate protein, intersectin-2, or ITSN2, normally functions in clathrin-mediated endocytosis and exocytosis. A second patient at Boston Children’s Hospital expresses a previously-unseen point mutation in ITSN2 and experiences erythromelalgia, characterized by episodes of intense pain and red, swollen limbs during ambient warm temperatures. Through the use of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 genome editing, this study will produce these specific genetic mutations in mouse lines to explore their effects on mammalian behavior. OBJECTIVES: This project employs two transgenic mouse models to study the behavioral phenotypes associated with rare potentially damaging mutations in KCNH8 and ITSN2 exhibited in the human patients. Through these experiments, a greater understanding of neural pain signaling and sensitivity changes can occur. METHODS: The differences in temperature preference of KCNH8 and ITSN2 mutant mice compared to wild type mice lacking these mutations was studied using thermal plates under cold and warm conditions. Direct application of acetone and von Frey filaments to mouse paws was used to study cold and mechanical sensitivity. Further testing of stamina, anxiety, coordination, and strength were also evaluated. RESULTS: A marked decrease in sensitivity to von Frey stimulation (p<0.01) and acetone administration (p<0.05) was observed in KCNH8 mutant mice. Thermal preference testing demonstrated a decreased preference for warmer temperatures as compared to wild type mice. In addition, anxiety levels were also observed to be slightly higher in these mutant KCNH8 mice (p<0.05). The mutant ITSN2 mice spent less time at cooler temperatures, though surprisingly they significantly preferred warmer conditions as compared to their wild type littermates. A full and partial reversal of these temperature preferences was demonstrated in cold and heat thermal conditions respectively after intraperitoneal gabapentin injection, which normalized the mice toward wild type behavior. CONCLUSIONS: Data from the KCNH8 mutant mouse model indicates an aversion to warmer temperatures and a decreased ability to detect cold or mechanical pressure, much like the human patient. The mutant ITSN2 mice were less likely to spend time at cooler temperatures, indicating heightened sensory sensitivity, but their preference for warmer temperatures suggests a possible desensitization of the affected nociceptors. These results often mirror the patient’s phenotype, but the preference for ambient warmer environments appears opposite to the patient. As the ITSN2 mice feel discomfort at cooler temperatures, a proposed desensitization at warmer temperatures would result in a more comfortable environment and could explain the observed preference. The trends toward normal neural firing rates achieved through gabapentin injection suggest that the aberrant responses in mutant ITSN2 mice is due to altered sensitization, but additional examination under these conditions with a larger group of mice is necessary to further unravel these signaling pathways. However, these extremely encouraging data introduce two new molecular targets for acute pain control.

O objetivo foi realizar a adaptação transcultural do 12 item Allodynia Symptom Checklist para a população brasileira e testar a confiabilidade dessa versão, já que não havia nenhum questionário de avaliação da alodínia cutânea em migranosos, sintoma que tem sido apontado como sinalizador da sensibilização central e como fator de cronificação dessa doença. A adaptação transcultural foi realizada em seis estágios: tradução, síntese, retrotradução, revisão pelo comitê de especialistas na área, pré-teste e submissão dos documentos ao comitê de especialistas. No estágio do pré-teste, foram aplicados 30 questionários em migranosos de ambos os sexos, que relataram dificuldades de compreensão e, dessa maneira, uma segunda versão foi criada e aplicada em mais 30 sujeitos, para a qual não foram relatadas dificuldades adicionais. O tempo médio de preenchimento foi de 336 e a consistência interna foi considerada adequada demonstrando uma boa correlação entre os itens ( de Cronbach = 0,77). Para testar a confiabilidade, outros 30 sujeitos preencheram o questionário, em dois momentos, sendo que para 15 deles o questionário foi autoaplicável e para os outros 15 a avaliação foi feita no formato de entrevista. A confiabilidade foi classificada como moderada (kappa ponderado linear = 0,58) e excelente ( kappa ponderado linear =0,84) respectivamente. Portanto, foi possível através desse estudo, disponibilizar em língua portuguesa um questionário válido, confiável e de fácil aplicação para a avaliação da alodínia em migranosos da população brasileira. / Since there was no portuguese questionnaire to evaluate cutaneous allodynia in migraine population, which has been pointed out as a central sensibilization flag and as risk factor of migraine chronification we aimed to perform the cross-cultural adaptation of the 12 item Allodynia Symptom Checklist for the Brazilian population and to test its reliability. It consisted in six stages: translation, synthesis, back translation, revision by a specialist committee, pretest, and submission the documents to the committee. In the pretest stage, the questionnaire was applied to 30 migraineurs of both sexes, who had some difficulty in understanding it. Thus, a second version was applied to 30 additional subjects, with no others difficulties being reported. The mean filling out time was 336and the internal consistency was considered adequate showing a good interrelation between items (Cronbachs = 0,77). To test reliability, 30 other subjects filled out the questionnaire at two different times, 15 of them in a self-report administration and 15 in a structured interview. It was classified as moderate (linear weighted kappa = 0.58) and as excellent (linear weighted kappa = 0.84) respectively. In this study, it was possible to make available in portuguese a valid, reliable and easy tool for cutaneous allodynia assessment in Brazil.

O objetivo foi realizar a adaptação transcultural do 12 item Allodynia Symptom Checklist para a população brasileira e testar a confiabilidade dessa versão, já que não havia nenhum questionário de avaliação da alodínia cutânea em migranosos, sintoma que tem sido apontado como sinalizador da sensibilização central e como fator de cronificação dessa doença. A adaptação transcultural foi realizada em seis estágios: tradução, síntese, retrotradução, revisão pelo comitê de especialistas na área, pré-teste e submissão dos documentos ao comitê de especialistas. No estágio do pré-teste, foram aplicados 30 questionários em migranosos de ambos os sexos, que relataram dificuldades de compreensão e, dessa maneira, uma segunda versão foi criada e aplicada em mais 30 sujeitos, para a qual não foram relatadas dificuldades adicionais. O tempo médio de preenchimento foi de 336 e a consistência interna foi considerada adequada demonstrando uma boa correlação entre os itens ( de Cronbach = 0,77). Para testar a confiabilidade, outros 30 sujeitos preencheram o questionário, em dois momentos, sendo que para 15 deles o questionário foi autoaplicável e para os outros 15 a avaliação foi feita no formato de entrevista. A confiabilidade foi classificada como moderada (kappa ponderado linear = 0,58) e excelente ( kappa ponderado linear =0,84) respectivamente. Portanto, foi possível através desse estudo, disponibilizar em língua portuguesa um questionário válido, confiável e de fácil aplicação para a avaliação da alodínia em migranosos da população brasileira. / Since there was no portuguese questionnaire to evaluate cutaneous allodynia in migraine population, which has been pointed out as a central sensibilization flag and as risk factor of migraine chronification we aimed to perform the cross-cultural adaptation of the 12 item Allodynia Symptom Checklist for the Brazilian population and to test its reliability. It consisted in six stages: translation, synthesis, back translation, revision by a specialist committee, pretest, and submission the documents to the committee. In the pretest stage, the questionnaire was applied to 30 migraineurs of both sexes, who had some difficulty in understanding it. Thus, a second version was applied to 30 additional subjects, with no others difficulties being reported. The mean filling out time was 336and the internal consistency was considered adequate showing a good interrelation between items (Cronbachs = 0,77). To test reliability, 30 other subjects filled out the questionnaire at two different times, 15 of them in a self-report administration and 15 in a structured interview. It was classified as moderate (linear weighted kappa = 0.58) and as excellent (linear weighted kappa = 0.84) respectively. In this study, it was possible to make available in portuguese a valid, reliable and easy tool for cutaneous allodynia assessment in Brazil.

Research into the mechanisms of hyperalgesia is ongoing with the goal of improving clinical management of chronic pain. One animal model of chronic musculoskeletal pain uses two injections of acidic saline into a lateral gastrocnemius muscle to induce a long-lasting bilateral decrease in paw withdrawal thresholds. This study tested whether the two injections need to occur in the same muscle. Male Sprague-Dawley rats were injected with acidic saline (pH 4.0) in either the lateral or medial head of gastrocnemius or the contralateral gastrocnemius (lateral head). All animals received a second injection in the ipsilateral gastrocnemius (lateral head). Mechanical withdrawal thresholds were reduced in all groups when tested 24 hours after the second injection. Animals in which the first muscle injection was substituted with a non-specific treatment (intraperitoneal injection of lipopolysaccharide) developed bilateral hyperalgesia after a single acidic saline injection. Thus, the mechanism of hyperalgesia in this model is not restricted to the injected tissues and may include central nervous system structures. Consistent with this, an inhibitor of glia cell activation (minocycline) blocked the development of bilateral hyperalgesia. These data indicate that the central nervous system may play a large role in mediating chronic musculoskeletal pain. / October 2007

Thesis (M.Sc.)--Memorial University of Newfoundland, School of Pharmacy, 1997. / Typescript. Bibliography: leaves 104-121.

Research into the mechanisms of hyperalgesia is ongoing with the goal of improving clinical management of chronic pain. One animal model of chronic musculoskeletal pain uses two injections of acidic saline into a lateral gastrocnemius muscle to induce a long-lasting bilateral decrease in paw withdrawal thresholds. This study tested whether the two injections need to occur in the same muscle. Male Sprague-Dawley rats were injected with acidic saline (pH 4.0) in either the lateral or medial head of gastrocnemius or the contralateral gastrocnemius (lateral head). All animals received a second injection in the ipsilateral gastrocnemius (lateral head). Mechanical withdrawal thresholds were reduced in all groups when tested 24 hours after the second injection. Animals in which the first muscle injection was substituted with a non-specific treatment (intraperitoneal injection of lipopolysaccharide) developed bilateral hyperalgesia after a single acidic saline injection. Thus, the mechanism of hyperalgesia in this model is not restricted to the injected tissues and may include central nervous system structures. Consistent with this, an inhibitor of glia cell activation (minocycline) blocked the development of bilateral hyperalgesia. These data indicate that the central nervous system may play a large role in mediating chronic musculoskeletal pain.