O Labirinto em Cruz Elevado (LCE) é um modelo animal para o estudo da ansiedade, suas bases biológicas e os efeitos de diferentes tipos de fármacos sobre o comportamento. Diferentes métodos têm sido usados para estudá-lo, dentro dos quais encontra-se a modelagem computacional. O presente trabalho junta-se a esses estudos utilizando as ferramentas da modelagem computacional para desenvolver dois modelos computacionais e índices que permitiram avaliá-lo. O primeiro deles estuda a maneira como os animais exploram o labirinto usando cadeias de Markov. Esta abordagem rendeu um método de caracterização capaz de identificar os efeitos de certos tipos de fármacos sobre a maneira como o animal explora o LCE, ao mesmo tempo que levanta alguns indícios sobre a quantidade de informação que o rato usa para tomar uma decisão. O segundo foi construído baseado na ideia do conflito como o determinante do comportamento do rato no LCE, adaptando um modelo de rede neural usado para avaliar informação conflitante: o modelo de dipolo chaveado de Grossberg. O objetivo desse segundo modelo foi avaliar a viabilidade de um modelo de competição de três forças: uma que insta explorar locais considerados amedrontadores, uma outra que insta procurar proteção e a última que representa o vigor do animal. Cada uma das forças que compõem o modelo recebe sinais vindos do ambiente e a maneira como processam esses sinais pode ser afetada pelos efeitos de um determinado fármaco. O modelo reproduz os efeitos esperados dos três tipos de fármacos fazendo mudanças em no máximo dois de seus parâmetros. Da mesma maneira, o modelo reproduz parte do comportamento esperado na Arena, precisando apenas de um pequeno ajuste para reproduzir as trajetórias que o animal costuma fazer em torno das paredes desse labirinto. Pode-se concluir que o modelo computacional descreve uma possível maneira de como as variáveis que controlam o comportamento do rato no LCE interagem e de como os fármacos interagem com essas variáveis, permitindo a reprodução do comportamento do rato no LCE e em outros labirintos como a Arena. O modelo foi construído para reproduzir os efeitos de três tipos de fármacos, porém, a maneira como esses tipos de fármacos interagem com o modelo não foi condicionada a um local ou maneira específico. Esta abordagem permite procurar outras interações que não somente reproduzam os efeitos de fármacos conhecidos, mas também possam predizer os efeitos de fármacos ainda não estudados. / The Elevated Plus Maze (EPM) is an animal model for the study of anxiety, its biological foundations, and the effects of different kinds of drugs on behavior. A group of different modeling methods have been used to study the rat behavior in the EPM. One of them characterizes rat behavior the EPM using directed graphs and proposes an index which can be used to classify the drug type and dosis. The other two methods were used to construct computational models for the rat behavior. The first of these models used Markov chains to reproduce the rat behavior. This approach offers a method to characterize the rat behavior, which is able to identify the effects of certain kinds of drugs on the way the rat explores the maze and, at the same time, raises some clues on how much information is used by the animal to take a decision. The second one was built based on the idea that conflict determines the rat behavior in the EPM. Conflict was introduced in the model via an adapted version of Grossberg\'s gated dipole artificial neural network model. The goal was to evaluate the viability of a competition-based model with three kind of drives: a drive to explore threatening places, a drive to seek protection, and a drive to move, related to the energy of the animal. The model receives and processes signals from the environment according to the states of these three drives, and the way in which the signals are processed can be influenced by effects of specific drugs. This model reproduces the expected effects of three types of drugs with modifications of up to two parameters. The model also reproduces part of the expected behavior of the animal in the Arena, a different maze, by requiring only small adjustments to reproduce the trajectory of the rat around the walls. It is possible to conclude that this computational model captures elements of the interaction of variables which control the rat behavior in the EPM and how drugs interact with these variables. These elements may also be present in the rat behavior in the Arena. The tools and models presented here offer new paradigms to study rat behavior in the EPM. They can offer new benchmarks to characterize rat behavior and can be used to study the effects of different drugs and their interactions.

Situações ameaçadoras (p.ex., exposição ao labirinto em cruz elevado LCE) induzem respostas comportamentais e neurovegetativas, geralmente acompanhadas por antinocicepção e da ativação do eixo hipotálamo-pituitária-adrenais (HPA). Além disso, é conhecido que a matéria cinzenta periaquedutal (MCP) faz parte do substrato neural para a expressão de alterações comportamentais e neurovegetativas em resposta a estímulos aversivos e que essa estrutura mesencefálica é longitudinalmente dividida em quatro colunas (dorsomedial, dorsolateral, lateral e ventrolateral) que estão envolvidas em coordenar estratégias distintas para o animal lidar com diferentes tipos de estresse, ameaça e dor. No presente estudo foram analisados os níveis plasmáticos de corticosterona em camundongos expostos a 3 tipos de LCE, o fechado (LCEf: 4 braços fechados - situação não aversiva), o padrão (LCEp: 2 braços abertos e 2 braços fechados - situação aversiva com a possibilidade de esquiva/fuga) ou o aberto (LCEa: 4 braços abertos - situação aversiva sem a possibilidade de esquiva/fuga). O perfil da resposta hormonal foi também avaliado em animais concomitantemente submetidos à injeção de formalina 2,5% no dorso da pata traseira direita (teste de nocicepção). O estudo também avaliou a duração da antinocicepção induzida pela exposição ao LCEa em animais mantidos ou não neste ambiente aversivo. A caracterização da participação da MCP neste tipo de antinocicepção foi avaliada pela lesão irreversível (produzida pela injeção de NMDA) uni ou bilateral da porção dorsal (MCPd: colunas dorsolateral e dorsomedial) e bilateral da porção ventrolateral (MCPvl) desta estrutura mesencefálica sobre a resposta nociceptiva induzida pela injeção de formalina na pata traseira direita em camundongos expostos ao LCEf ou ao LCEa. Finalmente, os efeitos da lesão da MCPd ou da MCPvl nos índices de ansiedade foram avaliados no labirinto em cruz elevado padrão (LCEp) em camundongos com ou sem a injeção prévia de formalina. Os resultados mostraram que a exposição aos três tipos de LCE aumentou a secreção plasmática de corticosterona (CORT), porém os níveis foram superiores nos animais expostos ao LCEp ou LCEa quando comparados ao LCEf. Além disso, quando os animais foram submetidos ao teste de formalina níveis elevados, porém semelhantes, de CORT foram verificados após a exposição aos diferentes LCE, sugerindo que o estímulo nociceptivo elevou as concentrações plasmáticas desse glicocorticóide para valores máximos. Na avaliação da duração da antinocicepção induzida pela exposição ao LCEa, verificou-se que esta reação defensiva cessou imediatamente após a retirada do animal deste ambiente, mas perdurou por até 20 minutos quando o animal foi mantido nesta condição ameaçadora. Por fim, a lesão das diferentes porções da MCP mostrou que tanto a MCPd como a MCPvl parecem não estar envolvidas na antinocicepção induzida pela exposição ao LCEa. Curiosamente, a lesão da MCPvl reduziu a resposta nociceptiva de animais submetidos ao LCEf e aumentou a locomoção durante a exposição ao LCEf e LCEa. Além disso, a lesão bilateral da MCPd reduziu seletivamente os índices de ansiedade (% de entradas e de tempo nos braços abertos do LCEp) somente em camundongos que não foram submetidos ao teste da formalina, o que sugere que a nocicepção prejudicou o efeito ansiolítico produzido pela lesão desta porção da MCP. No entanto, é importante destacar que a lesão da MCPvl não alterou os índices de ansiedade e a locomoção de camundongos não submetidos a estimulação sensorial nociceptiva concomitante. / Threatening situations (e.g., exposure to an elevated plus-maze with four open arms oEPM) induce behavioral and neurovegetative responses generally accompanied by antinociception and activation of the hypothalamus-pituitary-adrenal (HPA) axis. Furthermore, it is known that the midbrain periaqueductal gray (PAG) is part of the neural substrate for the expression of behaviorally and neurovegetative alterations in response to aversive stimuli. In addition, the PAG is longitudinally divided into four columns (dorsomedial, dorsolateral, lateral and ventrolateral) that are involved in coordinating distinct strategies for animals coping with different types of stress, threat and pain. The present study analyzed the plasmatic levels of corticosterone when mice with or without prior 2.5% formalin injection into the right hind paw (nociception test) were exposed in one of the 3 types of EPM, the enclosed (eEPM: 4 enclosed arms - non-aversive situation), the standard (sEPM: two open and two closed arms - aversive situation with the possibility of avoidance/flight) or the open (oEPM: 4 open arms - aversive situation without the possibility of avoidance/flight) EPM. The study also investigated the temporal evaluation of the oEPM-induced antinociception when mice were kepted in (for 30 min) or removed from (after 10 min of exposure) that aversive environment (i.e., the oEPM). The characterization of the PAG participation in this type of antinociception was evaluated by irreversible (produced by NMDA injection) uni or bilateral lesion of dorsal PAG portion (dPAG: dorsolateral and dorsomedial columns) and bilateral ventrolateral PAG lesion (vlPAG). Finally, the effects of dPAG or vlPAG lesion on the anxiety indices were investigated in mice with or without prior formalin injection during the exposure to the sEPM. Results showed that the eEPM exposure increased the plasmatic concentration of corticosterone (CORT), however sEPM or oEPM exposure animals showed higher levels of CORT than eEPM-exposed mice. Moreover, when animals were submitted to the formalin test high, but similar levels of this glucocorticoid were verified after the exposure to the different EPM, suggesting that nociception also has provoked a ceiling effect on plasma corticosterone concentration. Results also showed that the oEPM-induced antinociception ceased immediately after mice withdrawal from the aversive situation. However, this pain inhibition response remained unchanged for approximately 20 min in animals that were kept in the threatening condition. Finally, the lesions of different portions of PAG showed that neither dPAG nor vlPAG appear to be involved in the modulation of the oEPM-induced antinociception. Curiously, vlPAG lesion reduced the nociceptive response in animals submitted to the eEPM and increased the locomotion during eEPM and oEPM exposure. Moreover, bilateral dPAG lesion reduced anxiety indices (% of open arm entries and % of open arm time) only in mice that had not received prior injection of formalin, suggesting that nociception impaired the anxiolytic-like effect produced by dPAG lesion. It is important to highlight that vlPAG lesion did not alter the anxiety-like indices and the locomotion in mice not submitted to the concurrent nociceptive stimulation.

O protocolo de teste/reteste no labirinto em cruz elevado (LCE) mostra que a experiência prévia no labirinto produz alterações duradouras nas respostas comportamentais de roedores. Nesse contexto, ratos submetidos ao LCE pela primeira vez apresentam um aumento característico na exploração dos braços abertos e uma redução dos comportamentos de avaliação de risco após a administração de drogas ansiolíticas. Na reexposição ao labirinto, porém, essas drogas tornam-se ineficazes em alterar as medidas tradicionais do LCE. Esse fenômeno foi inicialmente observado com o benzodiazepínico clordiazepóxido e referido como one-trial tolerance (tolerância de um ensaio OTT). A proposta do presente estudo é compreender a OTT por meio do exame dos fatores hormonais, cognitivos e neuroanatômicos envolvidos nesse fenômeno. A administração sistêmica do benzodiazepínico midazolam ou de metirapona, um bloqueador da síntese de glicocorticóides, reduziu a frequência dos comportamentos de avaliação de risco e dos níveis plasmáticos de corticosterona quando injetados antes das sessões teste ou reteste. Além disso, a reexposição de ratos ao LCE foi caracterizada por uma avaliação de risco mais proeminente, de acordo com a análise fatorial, e pela ativação de estruturas límbicas envolvidas com aspectos cognitivos do medo, como a região ventral do córtex pré-frontal medial (CPFm) e a amígdala, mostrada por meio da distribuição da proteína Fos. Midazolam administrado antes da primeira exposição ao LCE produziu uma redução significativa do número de neurônios Fos-positivos no córtex cingulado anterior, área 1 (Cg1) e nos núcleos anterior e pré-mamilar dorsal do hipotálamo. Por outro lado, midazolam causou uma redução no número de neurônios Fos-positivos no CPFm, amígdala, núcleo dorsomedial do hipotálamo e núcleos da rafe em ratos reexpostos ao LCE. Cg1 foi a única estrutura-alvo do benzodiazepínico em ambas as sessões. Resultados comportamentais similares aos produzidos pelo tratamento sistêmico foram obtidos com infusões de midazolam intra-Cg1. Esses resultados apontam para um papel crucial dos comportamentos de avaliação de risco no desenvolvimento da OTT e indicam o Cg1 como um importante sítio de ação ansiolítica dos benzodiazepínicos em roedores. / The elevated plus maze (EPM) test/retest protocol has shown that prior experience to the maze produces enduring changes in behavioral responses of rodents. In this context, rats submitted for the first time to the EPM display a characteristic increase in open arm exploration and reduced risk assessment behaviors after the administration of anxiolytic drugs. Upon re-exposure to the maze, however, these drugs become unable to change the traditional measures of the EPM. This phenomenon was initially observed with the benzodiazepine chlordiazepoxide and referred to as one-trial tolerance (OTT). The purpose of the present study is to understand the OTT through the exam of the hormonal, cognitive and neuroanatomical factors involved in this phenomenon. The systemic administration of the benzodiazepine midazolam or metyrapone, a glucocorticoids synthesis blocker, reduced the frequency of risk assessment behaviors and the corticosterone levels when injected before the test or retest sessions. Moreover, the re-exposure of rats to the EPM was characterized by more prominent risk assessment behaviors, according to the factor analysis, and by activation of limbic structures involved with cognitive aspects of fear, such as the ventral regions of the medial prefrontal cortex (mPFC) and amygdala, as shown through the distribution of the Fos protein. Midazolam injected before the first exposure to the EPM produced a significant decrease in the number of Fos-positive neurons in the anterior cingulate cortex, area 1 (Cg1), anterior and dorsal premammillary nuclei of hypothalamus. On the other hand, midazolam caused a decrease in the number of Fos-positive neurons in the mPFC, amygdala, dorsomedial nucleus of hypothalamus and raphe nuclei in rats re-exposed to the EPM. Cg1 was the only structure targeted by the benzodiazepine in both sessions. Behavioral results similar to those produced by systemic treatment were obtained with intra-Cg1 infusions of midazolam. These results point to a crucial role of the risk assessment behaviors in the development of the OTT and indicate the Cg1 as an important locus for the anxiolytic-like action of benzodiazepines in rodents.

Made available in DSpace on 2016-06-24T04:15:39Z (GMT). No. of bitstreams: 1 Texto Completo.pdf: 1087367 bytes, checksum: 37433b8a928cf0b32aadd085b4260bfe (MD5) Previous issue date: 2007-06-28 / Few studies have investigated the acute/chronic effects of physical exercises on behaviors related to anxiety in animal models and the results are quite contradictory. Those conflicts seem to result from the methodological diversity among the studies, for example, the configuration of the physical exercise program. Materials and methods. Male Wistar rats were randomly divided in 4 groups: Control, 0, 5 or 50% of the body weight. The effect of the intensity of the swimming exercise on the behavioral measurements in the tests of elevated plus-maze and open field were investigated. Results. The variance analysis revealed significant differences on the concentration of blood lactate among the groups (p < 0.01). The analyses revealed that the 50% group showed smaller stay time and entrance in the open arms of the maze compared to the Control one, and to the groups of 0% and 5% of body weight. The animals submitted to a smaller level of physical stress revealed a higher disposition - up to 54% - to stay in the open arms when compared with the Control group. Conclusions. The results suggest that the acute effects of the physical exercise result in complex and transitory changes of behavior and central neurochemistry in rats. Those changes seem to follow a charge-response ratio that depends on the intensity of the exercise. / Poucos trabalhos têm investigado os efeitos agudos/crônicos do exercício físico sobre o comportamento relacionado com a ansiedade em modelo animal e os resultados são bastante contraditórios. Esses conflitos parecem decorrentes da diversidade metodológica entre os trabalhos, por exemplo, a configuração do programa de exercício físico. Materiais e métodos. Ratos machos Wistar foram aleatoriamente divididos em 4 grupos: Controle, 0, 5 ou 50% do peso corporal. O efeito da intensidade do exercício de natação sobre medidas de comportamento nos testes de labirinto em cruz elevado e de campo aberto foi investigado. Resultados. A análise de variância revelou diferenças significativas sobre a concentração de lactato sangüíneo entre os grupos (p < 0,01). As análises revelaram que o grupo 50% apresentou menor tempo de permanência e entradas nos braços abertos do labirinto em relação ao Controle e aos grupos de 0% e 5% do peso corporal. Os animais submetidos a menor carga de estresse físico revelaram uma disposição em até 54% maior para permanecer nos braços abertos quando comparada ao Controle. Conclusões. Os resultados sugerem que os efeitos agudos do exercício físico proporcionam complexas e transitórias alterações sobre o comportamento e a neuroquímica central em ratos. Essas alterações parecem obedecer a uma relação dose-resposta dependente da intensidade do exercício.

Made available in DSpace on 2014-06-11T19:31:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-04Bitstream added on 2014-06-13T20:41:17Z : No. of bitstreams: 1 amaral_vcs_dr_arafo.pdf: 3128795 bytes, checksum: 3d66997069eddcbbbf04cf4e7e70700f (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Quando os animais são confrontados com estímulos ambientais ameaçadores como a exposição ao predador ou estímulos como altura, iluminação e estímulos nociceptivos, exibem reações de defesa coordenadas e específicas. Nas últimas décadas, observa-se um crescente interesse pela utilização de estímulos naturalísticos para o estudo das bases neurais de emoções como o medo e ansiedade. Nesse contexto, o teste de exposição ao rato (RET), um novo modelo etológico de interação presa-predador, utilizando camundongos (presa) e ratos (predador), foi desenvolvido para avaliar a expressão de diferentes comportamentos defensivos na presa. Entretanto, poucos estudos foram conduzidos com esse modelo no intuito de investigar as bases neurais das respostas defensivas de camundongos expostos ao rato. Adicionalmente, evidências da literatura destacam que o hipocampo ventral (HV) e o complexo amidalóide (CA) parecem contribuir diferencialmente na modulação de respostas defensivas frente a estímulos proximais (predador) ou potenciais. Assim, o presente estudo foi conduzido para investigar o papel do HV e do CA nas respostas defensivas de camundongos exibidas diante do predador (rato) e do contexto associado ao predador. Para tal, o presente estudo foi dividido em quatro etapas. Na primeira delas, investigamos se o estresse da exposição ao predador no RET altera a secreção de corticosterona em camundongos e determinamos a magnitude e a duração desta secreção. Na segunda etapa, avaliamos o papel do HV e do CA, através da injeção local do agonista de receptores GABAA muscimol (0,1 μg/0,1 μl), na mediação de respostas comportamentais defensivas de camundongos expostos ao RET (situação proximal) e comparamos com aquelas apresentadas durante a exposição ao labirinto em cruz elevado (LCE - situação potencial). Subsequentemente, investigamos se camundongos expostos... / When animals are confronted with environmental threatening situations such as exposure to a predator as well as to height, high illumination and nociceptive stimuli they exhibit defensive behaviors. Over the past decades there has been a growing interest by the neuroscientists in the use of naturalistic stimuli to the study of the neural systems of the emotions such as fear and anxiety. In this context, the Rat Exposure Test (RET) which is a new ethological model of prey-predator interaction using mice (prey) and rats (predator) was developed in order to evaluate the expression of different defensive behaviors in the prey. However few studies using this model have been carried out with the objective of investigating the neural systems of the defensive behaviors in mice exposed to rats. In addition, evidence in literature has shown that the ventral hippocampus (VH) and the amygdaloid complex (AC) contribute differentially in the modulation of defensive behaviors during exposure to either potential or immediate stimuli (predator). Thus, the present study was aimed at investigating the role of VH and AC in the modulation of defensive behaviors of mice when exposed to predators (rats) as well as the predatory context. The experiment comprised four parts: (i) to investigate both whether stress regarding the exposure to the predator alters the corticosterone secretion in mice and to determine the magnitude and the duration of this secretion; (ii) the role of VH and AC was evaluated through local microinjection of the GABAA receptor agonist muscimol (0,1 μg/0,1 μl) in the modulation of defensive behavioral responses of mice exposed to RET (proximal aversive situation). The responses then were compared to those presented during to the exposure to the elevated plus-maze (EPM - potential aversive situation); (iii) to investigate whether mice exposed to natural predator (rat) in RET exhibit... (Complete abstract click electronic access below)

Diversos estudos sugerem que as células-tronco da medula óssea podem ser úteis no tratamento de lesões do tecido nervoso. O presente estudo investigou se a terapia com células medulares seria capaz de modificar os efeitos comportamentais de lesões no hipocampo. Células mononucleares da medula óssea marcadas com a proteína fluorescente verde (EGFP) foram transplantadas em camundongos C57BL/6 que tiveram o hipocampo dorsal danificado por lesão eletrolítica bilateral. Os resultados da avaliação comportamental no labirinto em cruz elevado mostraram que a lesão hipocampal produziu ansiólise, quadro que foi atenuado nos animais transplantados. Na análise imuno-histoquímica do tecido cerebral, foi observada presença limitada de células EGFP+ no cérebro dos animais lesionados. Dada a não recuperação da citoarquitetura tissular, acredita-se que os benefícios observados sobre o comportamento tenham resultado de um efeito parácrino das células mononucleares, que auxiliaram na ação de mecanismos endógenos para restituição parcial das funções do hipocampo. / Several studies suggest that stem cells from bone marrow may be useful in treating lesions of the nervous tissue. This study investigated if bone marrow cell therapy would be able to modify the behavioral effects of lesions in the hippocampus. Bone marrow mononuclear cells labeled with the enhanced green fluorescent protein (EGFP) were transplanted into C57BL/6 mice which had the dorsal hippocampus damaged by bilateral electrolytic lesion. The results of the behavioral assessment in the elevated plus-maze showed that the hippocampal lesion produced anxiolysis, an effect that was attenuated in transplanted animals. Immunohistochemical analysis of brain tissue revealed, however, a limited presence of EGFP+ cells into the brains of injured animals. Given the non-recovery of the tissue cytoarchitecture, it is believed that the observed benefits on the behavior resulted from a paracrine effect of the mononuclear cells, which possibly helped in the action of endogenous mechanisms for partial reimbursement of the hippocampal functions.

Thesis (M.Sc. (Pharmacology))--North-West University, Potchefstroom Campus, 2006.

The period of early life is important for the development of individual brain function and behavior. Human studies have shown altered vulnerability to develop psychopathology and/or excessive drug intake, possibly leading to dependence, as a consequence of early life experiences. In the present thesis, maternal separation (MS), an experimental model for studies of early environmental influences, was used to investigate long-term effects on neurochemistry, voluntary ethanol intake and exploration and risk assessment behavior in rats. Rat pups were assigned to one of three different rearing conditions: daily 15 min (MS15) or 360 min (MS360) of MS and normal animal facility rearing (AFR) during the first three weeks of life. Measurements of adult endogenous opioid peptide levels, opioid- and dopamine receptor density revealed minor MS-induced effects on the opioid system whereas interesting alterations were found in dopamine receptor density. Long-term effects on voluntary ethanol intake showed distinct MS-induced alterations in male Wistar and ethanol-preferring AA (Alko, Alcohol) rats. Female Wistar rats were unaffected, indicating sex differences in the effects of MS on ethanol intake. Male MS15 rats generally had a slower acquisition phase and a low subsequent ethanol intake whereas male MS360 rats had a high ethanol intake. MS15 is therefore suggested to protect against a high voluntary ethanol intake in male rats whereas MS360 may serve as a risk factor. The recently established concentric square field test indicated alterations in risk assessment as well as an increased exploratory drive and somewhat higher risk-taking behavior in adult MS360 rats, while minor effects were seen in MS15 rats. Altogether, these results demonstrate that environmental influences during the period of early life can have long-term effects on neurochemistry and behavior. Of special interest is the finding that MS altered the inherited high ethanol intake in adult ethanol-preferring AA rats.

Posttraumatic stress disorder (PTSD) is an anxiety disorder that may result from an exposure to a severely traumatic life-event. It is characterised by a delayed onset of psychological and physical symptoms including re-experiencing the event, avoidance of reminders associated with the trauma, increased autonomic arousal and distinct memory deficits. This disorder is also characterised by a maladaptive hypothalamic-pituitary-adrenal (HPA)-axis response and altered monoamine concentrations in the hippocampus and pre-frontal cortex. The Time Dependent Sensitization (TDS) model is a putative animal model of PTSD that is based on the concept of repeated trauma, using three acute stressors (TS) of intense severity followed by a mild situational reminder (RS) on day 7 subsequent to the acute stressors. The aims of this study were to determine if the Triple Stressor (TS) induces stress and if the situational reminder (RS) is necessary for the maintenance of the stress response over time and whether these two stress responses are qualitatively and quantitively different. This was done to further validate the TDS model and to characterize the development and progression of the stress-related pathology of PTSD. Methods used were High Performance Liquid Chromatography (HPLC) with electrochemical detection (biochemical correlates) for quantifying the monoamines dopamine (DA), noradrenaline (NA) and serotonin (5-HT) concentrations in the hippocampus and pre-frontal cortex (PFC); radio immuno assay (RIA) for the determination of plasma corticosterone concentrations (neuroendocrine parameter) and the use of the Elevated Plus Maze (EPM) to detect anxiety-like behaviour (behavioural analyses). The study was subdivided into an Acute and Re-Stress study (n = 10). In the Acute Study rats were exposed to TS as the only stressor. Group 1 was sacrificed immediately after TS, Group 2 was sacrificed 3 days post TS and Group 3 on day 7 post TS. In the Re-Stress Study both TS and RS were used as stressors. Group 4 was sacrificed immediately after the situational reminder, Group 5 was sacrificed 3 days post RS and Group 6 on day 7 post RS. A group of unstressed rats were used as Control. The results of this study found corticosterone concentrations elevated immediately after the TS (p<0.05). Exposure to the RS resulted in a profound hypocortisolism (p<0.05). These results indicate a possible disturbance in the regulation of the HPA-axis, which manifests as an enhanced negative feed-back upon re-introduction of the stressful situation. Changes in MA concentrations were evident. Although no definite fixed trend is apparent in this study, it is evident that the TDS model does induce monoamine dysregulation. Hippocampal NA. DA and 5-HT concentrations were noted to be elevated on day 7 post TS (p<0.05). On day 7 post RS only hippocampal 5HT was decreased significantly (p<0.05). Behavioural analyses indicate that stress related anxiety was not sustained after the TS but 7 days after the exposure to the RS rats were most anxious (p<0.05). The results confirm that the TDS model does induce PTSD-like symptoms in rats and that the situational reminder (RS) is necessary for the maintenance of the stress response. This model may be useful in the investigation of future experimental pharmacological interventions in the management of PTSD. / Thesis (M.Sc. (Pharmacology))--North-West University, Potchefstroom Campus, 2005.

Posttraumatic stress disorder (PTSD) is an anxiety disorder that may result from an exposure to a severely traumatic life-event. It is characterised by a delayed onset of psychological and physical symptoms including re-experiencing the event, avoidance of reminders associated with the trauma, increased autonomic arousal and distinct memory deficits. This disorder is also characterised by a maladaptive hypothalamic-pituitary-adrenal (HPA)-axis response and altered monoamine concentrations in the hippocampus and pre-frontal cortex. The Time Dependent Sensitization (TDS) model is a putative animal model of PTSD that is based on the concept of repeated trauma, using three acute stressors (TS) of intense severity followed by a mild situational reminder (RS) on day 7 subsequent to the acute stressors. The aims of this study were to determine if the Triple Stressor (TS) induces stress and if the situational reminder (RS) is necessary for the maintenance of the stress response over time and whether these two stress responses are qualitatively and quantitively different. This was done to further validate the TDS model and to characterize the development and progression of the stress-related pathology of PTSD. Methods used were High Performance Liquid Chromatography (HPLC) with electrochemical detection (biochemical correlates) for quantifying the monoamines dopamine (DA), noradrenaline (NA) and serotonin (5-HT) concentrations in the hippocampus and pre-frontal cortex (PFC); radio immuno assay (RIA) for the determination of plasma corticosterone concentrations (neuroendocrine parameter) and the use of the Elevated Plus Maze (EPM) to detect anxiety-like behaviour (behavioural analyses). The study was subdivided into an Acute and Re-Stress study (n = 10). In the Acute Study rats were exposed to TS as the only stressor. Group 1 was sacrificed immediately after TS, Group 2 was sacrificed 3 days post TS and Group 3 on day 7 post TS. In the Re-Stress Study both TS and RS were used as stressors. Group 4 was sacrificed immediately after the situational reminder, Group 5 was sacrificed 3 days post RS and Group 6 on day 7 post RS. A group of unstressed rats were used as Control. The results of this study found corticosterone concentrations elevated immediately after the TS (p<0.05). Exposure to the RS resulted in a profound hypocortisolism (p<0.05). These results indicate a possible disturbance in the regulation of the HPA-axis, which manifests as an enhanced negative feed-back upon re-introduction of the stressful situation. Changes in MA concentrations were evident. Although no definite fixed trend is apparent in this study, it is evident that the TDS model does induce monoamine dysregulation. Hippocampal NA. DA and 5-HT concentrations were noted to be elevated on day 7 post TS (p<0.05). On day 7 post RS only hippocampal 5HT was decreased significantly (p<0.05). Behavioural analyses indicate that stress related anxiety was not sustained after the TS but 7 days after the exposure to the RS rats were most anxious (p<0.05). The results confirm that the TDS model does induce PTSD-like symptoms in rats and that the situational reminder (RS) is necessary for the maintenance of the stress response. This model may be useful in the investigation of future experimental pharmacological interventions in the management of PTSD. / Thesis (M.Sc. (Pharmacology))--North-West University, Potchefstroom Campus, 2005.