<p>Because the interactions between feedforward influences are inextricably linked during many motor outputs (including but not limited to walking), the contribution of descending inputs to the generation of movements is difficult to study. Here we take advantage of the relatively small number of descending neurons (DNs) in the Drosophila melanogaster model system. We first characterize the number and distribution of the DN populations, then present a novel load free preparation, which enables the study of descending control on limb movements in a context where sensory feedback can be is reduced while leaving the nervous system, musculature, and cuticle of the animal relatively intact. Lastly we use in-vivo whole cell patch clamp electrophysiology to characterize the role of individual DNs in response to specific sensory stimuli and in relationship to movement. We find that there are approximately 1100 DNs in Drosophila that are distributed across six clusters. Input from these DNs is not necessary for coordinated motor activity, which can be generated by the thoracic ganglion, but is necessary for the specific combinations of joint movements typically observed in walking. Lastly, we identify a particular cluster of DNs that are tuned to sensory stimuli and innervate the leg neuromeres. We propose that a multi-layered interaction between these DNs, other DNs, and motor circuits in the thoracic ganglia enable the diverse but well-coordinated range of motor outputs an animal might exhibit.</p> / Dissertation

This thesis aims to examine how hindbrain spinal projection neurons (SPNs), namely RoV3, MiV1 and MiV2 control tail undulations during turning behaviors. I find that phototaxic turns differ from forward swims by an increased tail bend and a prolonged cycle period during the first undulation, while the later undulations are largely identical. Interestingly, laser ablation of RoV3, MiV1 and MiV2 neurons specifically affects the first undulation cycle by reducing the tail bend and the cycle period. Thus fish without the SPNs mainly perform forward swims in response to the turn-inducing phototaxic cues. These results suggest that the descending motor command that generates turns in larval zebrafish are composed of two pathways: one generates symmetric tail undulations, and the other, mediated by RoV3, MiV1 and MiV2 neurons, provides a brief and biased effect that modulates the first cycle of tail movement. Furthermore, fish whose unilateral SPNs are ablated are unable to perform turns toward the ablated side during the phototaxis, the optomotor response, the dark-flash response, and spontaneous swims, indicating the universal role of the SPNs in controlling visually-induced and spontaneous turns. Simultaneous two-photon calcium imaging and motor nerve recording in paralyzed fish show that RoV3, MiV2 and most MiV1 neurons on the turning side are active during turns, and that these activities are linearly correlated to the vigor of the intended turns. However, some MiV1 neurons are broadly tuned for all swimming directions. Computer simulations suggest that unilateral descending innervations to a specific type of spinal interneurons, namely commissural inhibitory interneurons, can generate a two-fold increase in the spinal network’s cycle period. This suggests that the SPNs could potentially innervate two types of spinal interneurons, namely \(CoBL_{gly}\) and CoLo, in order to control the rhythm during turns. An additional chapter of this thesis examines the ontogeny of operant and classical learning behaviors in zebrafish. Using strategically positioned visual cues paired with electroshocks, I find that both learning behaviors are expressed reliably around week 3, and reach adult performance levels at week 6. These memories are behaviorally expressed in adults for 6 hours and retrievable for 12 hours.

The neuropeptides dynorphin and cholecystokinin (CCK), and their associated pronociceptive effects were investigated in the RVM. Utilizing a nerve-injury model (SNL), RT-PCR analysis revealed increases (p<0.05) of prodynorphin mRNA, and bradyinkin, B1- and B2-receptor mRNA, post-SNL, 14-days, 2-days, and 14-days, respectively. Administration of dynorphin into the RVM produced both acute and long-lasting (>30-days) tactile hypersensitivity. Administration of the B1-antagonist, DALBK and the B2-antagonist, Hoe-140, into the RVM significantly attenuated dynorphin-induced tactile hypersensitivity. Nerve-injury induced tactile hypersensitivity was significantly reversed by RVM administration of dynorphin antiserum or the B2-antagonist, Hoe-140. These data suggest that dynorphin is up-regulated in the RVM in nerve-injury, and via the activation of bradykinin receptors in the RVM, produces abnormal pain. Like dynorphin, CCK is up-regulated in the RVM in nerve-injury, with studies suggesting that elevated levels of CCK in the RVM mediate pronociceptive activity through CCK2 receptor activation, resulting in enhanced spinal nociceptive transmission. At present, it is unknown what key neurotransmitters are mediating this RVM CCK-driven effect at the level of the spinal cord. Here, spinal cerebrospinal fluid (CSF) levels of serotonin (5-HT) and prostaglandin E2 (PGE2) were measured in the lumbar spinal cord in naïve rats following CCK administration into the RVM. Following RVM CCK microinjection, an approximate 5-fold increase in spinal (CSF) PGE2 levels was observed, as compared to baseline controls. PGE2 levels showed a progressive increase with peak levels observed at the 80-minute post-CCK injection timepoint, whereas 5-HT levels in the spinal CSF remained unchanged following CCK administration into the RVM. This release of PGE2 coincided with the timecourse for CCK-induced mechanical hypersensitivity. Administration of the CCK2-antagonist YM022 prior to CCK into the RVM, significantly attenuated (>50%) the release of PGE2 in the spinal cord. The non-selective COX-inhibitor naproxen and the 5-HT3 antagonist ondansetron, both administered intrathecally, significantly attenuated RVM CCK-induced hindpaw tactile hypersensitivity. In summary, these data suggest a bradykinin- or CCK2-receptor antagonist could be used alone or in conjunction with current therapies in the treatment of chronic pain.

No description available.

Morphine is the most widely prescribed opiate for alleviation of persistent pain; however, it is becoming increasingly clear that morphine is less potent in women compared to men. Morphine primarily binds mu opioid receptors, which are densely localized in the midbrain periaqueductal gray (PAG). Anatomical and physiological studies conducted in the 1960s identified the PAG, and its projections to the rostral ventromedial medulla (RVM) and spinal cord dorsal horn, as an essential neural circuit mediating opioid-based analgesia. Remarkably, the majority of studies since then were conducted in males with the implicit assumption that this circuit was the same in females; this is not the case. It is now well established that morphine produces greater analgesia in males compared to females in a wide range of vertebrates, however, the mechanism(s) driving this sex difference is not clear. Our recent studies indicate that two factors appear to be contributing to the sexually dimorphic effects of morphine. First, there are sex differences in the anatomy and physiology of the descending inhibitory pathway on which morphine acts to produce analgesia. Specifically, the projections from the PAG to the RVM are sexually dimorphic and activated to a greater degree by both inflammatory pain and systemic morphine in males. In the absence of pain, the PAG-RVM circuit is activated to a greater degree in males compared to females, while this activation steadily declines during the development of tolerance in males only. We also have evidence of a sexually dimorphic expression of mu opioid receptor within the PAG that appears to contribute to sex differences in morphine potency. Microinjection of morphine directly into the PAG produces significantly greater analgesia in males, indicating that the PAG is sufficient for eliciting this sexually dimorphic behavior. Furthermore, mu opioid receptor-expressing PAG neurons are necessary for eliciting a sexually dimorphic response to morphine as lesioning mu opioid receptor-expressing neurons attenuates analgesia in males only. Together, these data indicate that the PAG-RVM pathway and mu opioid receptor expression in the PAG is sexually dimorphic and provides a primary mechanism for sex differences in morphine potency.

The sound ascending is a musical theater work for two actors, four singers and piano. This project was a collaboration with playwright, Jason Tremblay. The story is a loose adaptation of Orpheus descending, by Tennessee Williams. Displaced from the rural, American South, most of our story takes place in Mazer, Afghanistan. Jason and I attempted to create an untraditional model. The work lies somewhere between a musical, oratorio and a song cycle. We both walked away with mixed feelings about the success of the work, following a preliminary premiere. I believe that the work is successful in its drama and storytelling. But in such a confined presentation, the work needs more diversity of material and character strength. Although complete for now, Jason and I plan on revising The sound ascending in the coming year. Most significantly, this project has been a learning experience. We both take away valuable lessons about writing and collaboration. / text

Morphine is the most widely prescribed opiate for alleviation of persistent pain; however, it is becoming increasingly clear that morphine is less potent in women compared to men. Morphine primarily binds mu opioid receptors, which are densely localized in the midbrain periaqueductal gray (PAG). Anatomical and physiological studies conducted in the 1960s identified the PAG, and its projections to the rostral ventromedial medulla (RVM) and spinal cord dorsal horn, as an essential neural circuit mediating opioid-based analgesia. Remarkably, the majority of studies since then were conducted in males with the implicit assumption that this circuit was the same in females; this is not the case. It is now well established that morphine produces greater analgesia in males compared to females in a wide range of vertebrates, however, the mechanism(s) driving this sex difference is not clear. Our recent studies indicate that two factors appear to be contributing to the sexually dimorphic effects of morphine. First, there are sex differences in the anatomy and physiology of the descending inhibitory pathway on which morphine acts to produce analgesia. Specifically, the projections from the PAG to the RVM are sexually dimorphic and activated to a greater degree by both inflammatory pain and systemic morphine in males. In the absence of pain, the PAG-RVM circuit is activated to a greater degree in males compared to females, while this activation steadily declines during the development of tolerance in males only. We also have evidence of a sexually dimorphic expression of mu opioid receptor within the PAG that appears to contribute to sex differences in morphine potency. Microinjection of morphine directly into the PAG produces significantly greater analgesia in males, indicating that the PAG is sufficient for eliciting this sexually dimorphic behavior. Furthermore, mu opioid receptor-expressing PAG neurons are necessary for eliciting a sexually dimorphic response to morphine as lesioning mu opioid receptor-expressing neurons attenuates analgesia in males only. Together, these data indicate that the PAG-RVM pathway and mu opioid receptor expression in the PAG is sexually dimorphic and provides a primary mechanism for sex differences in morphine potency.

Background: Pain is frequently reported by people with multiple sclerosis (MS). It has been associated with decreased quality of life, psychiatric morbidity, interference with day to day activities, and frequent healthcare attendance. It has been reported by people with multiple sclerosis to be one of their most important symptoms, and available treatments are limited in their effectiveness. Despite this, our understanding of the epidemiology and mechanisms of pain in people with MS are limited. Our understanding of the interactions of central nervous system mechanisms and pain states overall is growing. However, the application of this knowledge to MS is incomplete. Previous studies have shown that the descending pain modulatory system (DPMS) is an endogenous network of cortical and subcortical brain structures which act to limit, or accentuate, an individual’s perception of pain, via descending brainstem pathways. Associated clinical measures include depression, anxiety, and cognitive flexibility. Our understanding of the function or dysfunction of this system in MS is limited. We do not know if the MS disease process may adversely affect the structure or function of the DPMS. Hypothesis: In people with neuropathic limb pain in relapsing remitting MS (RRMS), compared to people with RRMS who do not have pain, there will be disruption of the endogenous descending pain modulatory system. This will manifest as impaired descending inhibition of pain. Aims and Methods Establishing the background using systematic reviews: The first aim of this thesis was to establish the prevalence, natural history and associations of pain (and pain syndromes) occurring in people with MS. The second aim was to explore existing knowledge of how the MS disease process may contribute to pain states, using a systematic review of neuroimaging studies. Prospective clinical study: A case-control study of 47 people with RRMS was then carried out. 31 of these had neuropathic pain in the limbs, and 16 did not have pain. Using targeted assessments, function of the descending pain modulatory system was assessed in the following ways: First: Detailed clinical, behavioural and neuropsychological assessment, focussing on cognitive, behavioural and affective features known to be closely related to the DPMS. Second: MRI imaging of brain structure, focussing on the volume and location of MS lesions, as well as the volume of key grey-matter structures involved in the DPMS. Third: Resting state functional MRI imaging of the brain, focussing on functional connectivity between the rostral anterior cingulate cortex and two other key DPMS structures (dorsolateral prefrontal cortex, and periaqueductal gray). Results: Systematic reviews: Meta-analysis of existing prospective studies confirmed that pain is very common in MS, affecting about 63% of people with MS on average (95%CI between 55 and 70%). Many different types of pain contribute to this overall estimate. No significant associations with disease course or stage emerged. Several neuroimaging studies have assessed people with MS-associated pain using MRI. These studies were often small, and with associated methodological issues. It is likely that location of MS lesions is implicated in aetiology of pain syndromes in some cases, though our overall knowledge is limited. Prospective study: In a prospective study, people with and without pain were matched for age and gender. Furthermore, groups were balanced for a range of other variables. The pain group more frequently received gabapentinoid medications. The presence of pain was significantly associated with increased scores for depression, fatigue and catastrophising, as well as with specific impairments at neuropsychological assessment, including cognitive flexibility. Many of these impairments are directly relevant to existing models of the DPMS. Overall volume of MS lesions was not different in people with pain, though lesions were more likely to occur in the brainstem. Some alterations of grey-matter volumes in people with pain which mirrored studies of pain disorders outside MS were found, but these did not involve structures key to the DPMS. Affected structures included trigeminothalamic nucleus (relative volume increase in pain group), posterior cingulate cortex and parahippocampal gyrus (volume decrease in pain group). Functional connectivity of the rostral anterior cingulate cortex to the periaqueductal grey matter, a key structure in the descending modulation of pain, was stronger in the group without pain. Conversely, functional connectivity to the dorsolateral prefrontal cortex, repeatedly implicated in the DPMS and thought to be involved in cognitive evaluation and flexibility, was stronger in the pain group. MS lesion volume appeared to account for some of this difference in a multivariate analysis. Limitations: Key limitations of this work include cross-sectional design, small sample size, and number of statistical comparisons carried out. Conclusions: Systematic reviews examined the prevalence, natural history and associations of pain in MS, as well as examining existing neuroimaging studies which investigated how the MS disease process could contribute to pain states. A prospective study found evidence of both emotional/affective and cognitive dysfunctions relevant to the hypothesis of dysfunction in the DPMS. Higher likelihood of MS lesions in the brainstem could be relevant to DPMS function. Separately, there were structural grey-matter volume alterations reflecting those found in many pain studies outside MS. Importantly, however, these did not affect key DPMS structures. Resting state functional MRI however demonstrated altered connectivity of core DPMS structures, which may be partly mediated by MS lesion volume. Functional connectivity findings could be consistent with the hypothesis of impaired descending pain inhibition, in people with relapsing remitting MS affected by neuropathic limb pain.

Made available in DSpace on 2014-06-11T19:23:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-04-20Bitstream added on 2014-06-13T20:30:37Z : No. of bitstreams: 1 teixeira_lg_me_jabo.pdf: 1248709 bytes, checksum: abf07304609e643fddd58d8b10e9193e (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Avaliou-se por meio de análises clínico-laboratoriais e morfológicas, a evolução cicatricial de dois segmentos distintos do cólon descendente. Os equinos foram alocados em um único grupo e submetidos a três fases experimentais: obstrução experimental (F I), seguida de 13 dias pós-operatórios; anastomose término-terminal (F II) e videolaparoscopia (F III), ambas seguidas, cada uma, de seis dias pós-operatórios. O segmento distendido (SD) foi submetido a 240 minutos de distensão intraluminal, com pressão de 40 mmHg. O segmento controle (SC) não sofreu distensão. Colheram-se amostras do cólon descendente antes da obstrução (M0), após a desobstrução (M1) e durante a anastomose (M2). Realizou-se exame clínico antes de cada cirurgia (M0a, M0b e M0) e nos dias pós-operatórios (M12a-M312a, M24b-M120b e M24-M120). A colheita de sangue foi realizada antes de cada cirurgia (M0a, M0b e M0), durante a obstrução (M2a-M4a) e nos respectivos momentos pós-operatórios (M6a-M240a, M24b- M120b e M24-M120). Dois animais foram a óbito, sendo um durante F I e outro na F II. Verificou-se que a as alterações morfológicas e morfométricas intestinais foram mais evidentes na camada serosa no M2, no SD e SC, com muita semelhança entre os dois segmentos. Não houve diferença (p>0,5) na quantidade de colágeno determinada histologicamente e dosagem espectrofotométrica de hidroxiprolina. Durante a F II e F III, três e dois equinos, respectivamente, apresentaram aderências intestinais. Foram observadas diferenças (p>0,5) nos parâmetros clínicos e hematológicos apenas durante F I e F II. Concluiu-se que os equinos submetidos à obstrução experimental apresentaram pior prognóstico em relação à enteroanastomose... / The healing progression of two distinct segments of equine descending colon was evaluated by clinical, laboratorial and morphological analysis. Horses were allocated in only one group and submitted to three following experimental stages: experimental obstruction (F I) followed by thirteen days of postoperative care; end-toend anastomosis (F II) and the videolaparoscopy (F III), both last stages followed by six days of postoperative care. The distended segment (DS) underwent 40 mmHg intraluminal distension pressure for 240 minutes long. The control segment (CS) didn’t suffer any distension. Samples of the tissue of the descending colon was obtained before the obstruction (M0), after the desobstruction (M1) and during the anastomosis (M2). Clinical exam was done before each surgery (M0a, M0b and M0) and during the postoperative care days (M12a-M312a, M24b-M120b e M24-M120). Two animals died, one during F I and the other during F II. The intestinal morphological and morphometric changes were observed markedly on the serous layer on the M2 stage, on the DS and the CS, and it had similarity among the two segments. There was no difference (p>0,5) in the amount of collagen determined by histology and hydroxyproline spectrophotometric analysis. During F II and F III, three and two horses respectively, presented intestinal adhesions. Differences (p<0,5) in some of the clinical and hematological parameters were only observed during F I and F II. In conclusion, the horses that underwent experimental obstruction presented poor prognosis compared to the enteroanastomosis. The serialized clinical exams and the laboratory analyses provided good monitoring of the physiological immune responses during and after the intestinal obstruction or the anastomosis

Made available in DSpace on 2014-06-11T19:29:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-12-18Bitstream added on 2014-06-13T20:38:15Z : No. of bitstreams: 1 sarzedas_lpm_me_assis.pdf: 946351 bytes, checksum: 6d67a25b01ffeb8750957b1d2b880fed (MD5) / Para se estudar as relações raciais no Brasil é imprescindível reconhecer a construção social e histórica das etnias que formaram, e formam, a nação brasileira. Ter por objetivo conhecer a visão que a escola, a família, as crianças e a própria criança negra tem em ser negra é adentrar um espaço constituído numa sociedade na qual os dizeres sobre o negro são permeados por ideologias e saberes desprovidos de uma visão histórica do problema. Atualmente, a implantação das Ações Afirmativas no Brasil despertou discussões ao redor da polêmica de se reconhecer, ou não, a condição desigual a que se vê submetido o negro brasileiro. A escola, como um espaço da vida cotidiana, está permeada por conceitos e pré-conceitos, podendo tornar-se um espaço de manutenção do racismo. Tendo por orientação teórica a Psicologia Sócio-Histórica, essa pesquisa teve por objetivo conhecer a visão que se tem da criança negra no espaço escolar. Foram realizadas observações livres registradas em um diário de campo, segundo uma metodologia etnográfica, tendo por foco uma turma de 1ª. série do Ensino Fundamental de uma escola pública da Cidade de Londrina, estado do Paraná. A pesquisa compreendeu, também, um levantamento das principais leis que respaldam o anti-racismo no Brasil tendo por foco a educação. O que se pôde verificar, a partir das observações livres, foi um discurso que culpabiliza o negro por sua condição, corroborando a idéia de mito da democracia racial, assim como a busca por atingir um ideal estético branco devido ao mesmo estar associado a um ideal de caráter e beleza... / To study the racial relations in Brazil is indispensable to recognize the social and historical from the ethnical constructions that were formed, and still are forming, the brazilian nation. To have as objective to know the opinion that the school, the family, the children and the afrodescending child have about being a afro-descending person is to get inside of a space constituted in a society where the words about the subject “being black” are full of ideologies and speechs without a historical vision of the problem. At present, the implementation of affirmative actions in Brazil brought discussions around the polemical subject about to recognize or not the disproportional condition that seems a afrodescending person is submitted in Brazil. The school, as a space of the routine life, is surrounded by conceptions and preconceptions, becoming this way possible the maintenance of the racism. Having as theoretical orientation the social-historical psychology, this research has as objective to know the vision that people have about the afro-brazilian infant at the school place. There were made free recorded observations in some sort of a field’s diary, following an ethnographic methodology, having as focus a 1st grade’s group of the public school’s fundamental education of Londrina, a city that belong to the state of Paraná. The research agglomerates a selection of the main laws that uphold the anti-racism in Brazil, having as focus the education. What could be verified from the free observations was a speech that blames the afro-descending person by his condition, corroborating the idea of the racial democracy myth, such as the seek to reach a white esthetic ideal due to the fact that this last one is associated to a character and beauty ideal, despite of the most recent... (Complete abstract click electronic access below)