Introdução: A Depressão é uma condição relativamente comum, de curso crónico, recorrente, estando frequentemente associada com incapacitação funcional e comprometimento da saúde física. Entre os fatores associados, encontram-se situações de abuso e negligência, entre outros. O eixo Hipotálamo-Pituitária-Adrenal (HPA) desempenha um papel fundamental na resposta aos estímulos externos e internos, podendo desencadear episódios psiquiátricos em indivíduos predispostos. Além disso, estudos têm corroborado que alterações no funcionamento do eixo HPA estão associadas à gravidade de quadros depressivos e são indicativas de um prognóstico desfavorável. Objetivo: O objetivo deste estudo foi avaliar pacientes depressivos com presença ou ausência de estresse precoce, identificando as alterações no funcionamento do eixo HPA e a resposta terapêutica. Metodologia: A amostra foi composta por 30 sujeitos, sendo 20 pacientes depressivos em regime de semi-internação no Hospital Dia do Hospital das Clinicas da FMRP-USP e 10 controles saudáveis. Além disso, os sujeitos do estudo foram divididos em: um grupo de pacientes depressivos (n=20) e controles saudáveis (n=10); um subgrupo de pacientes respondedores (n=8) e não respondedores ao tratamento (n=8); um subgrupo de pacientes deprimidos com presença de Estresse Precoce (n=13), ausência de Estresse Precoce (n=7) e de controles saudáveis (n=10). Os pacientes foram avaliados por meio de Entrevista Clínica de acordo com os critérios diagnósticos do DSM-IV, para a confirmação do diagnóstico. Para avaliação da gravidade dos sintomas depressivos foi aplicada a Escala de Depressão de Hamilton (HAM-\'D IND. 21\'), sendo incluídos apenas pacientes com HAM-\'D IND. 21\', \'> OU =\'17. Utilizamos também a Escala de Avaliação de Depressão de Montgomery-Asberg (MADRS) para avaliação da resposta terapêutica, sendo considerados respondedores os pacientes que obtiveram uma redução da pontuação da MADRS \'> OU =\' 50% entre a admissão e 60 dias após. A presença de Estresse Precoce foi confirmada através da aplicação do Questionário Sobre Traumas na Infância (CTQ). Foram utilizados também, o Inventário de Depressão de Beck (BDI), o inventário de Ansiedade de Beck (BAI), a Escala de Ideação Suicida de Beck (BSI), a Escala de Desesperança de Beck (BHS), a Escala Hospitalar de Ansiedade e Depressão (HADS) e a Escala de Impulsividade de Barratt (BIS-11) para a avaliação dos sintomas psiquiátricos. A avaliação endócrina foi realizada através do cortisol salivar, sendo coletado às 22h, ao acordar, 30 e 60 minutos após acordar e às 8h30min na admissão e após 60 dias. Resultados: Nossos resultados demonstraram uma associação entre a gravidade dos quadros depressivos com o aumento das tentativas de suicídio, do uso abusivo de bebidas alcoólicas e da obesidade, bem como com o aumento dos sintomas de ansiedade, desesperança, impulsividade e da comorbidade com os Transtornos de Personalidade. Encontramos que além desses fatores, a resposta inadequada ao tratamento também pode ser influenciada pela história prévia de Estresse Precoce. Além disso, nossos achados indicaram que a maior gravidade dos pacientes depressivos da nossa amostra se correlacionaram com uma maior atividade do eixo HPA, e este aumento foi associado a níveis mais elevados de cortisol salivar tanto na admissão quanto 60 dias após o tratamento nos pacientes não respondedores. Evidenciamos também que este aumento da atividade do eixo HPA pode ser influenciado pelo Estresse Precoce, uma vez que os pacientes com presença EP apresentaram níveis maiores de cortisol salivar, mesmo após o tratamento. Conclusão: Com base nos resultados apresentados, nossos achados apontam para o papel etiológico do eixo HPA na depressão, estando este muitas vezes associado a situações deEP que acarretam em uma maior gravidade dos pacientes e piora da resposta terapêutica. Dessa forma, nossos dados sugarem que a avaliação do eixo HPA possa prever a recorrência da psicopatologia, servindo assim, como um potencial biomarcador na depressão destes pacientes. / Introduction: Depression is a common condition of chronic course, recurrent, and is often associated with functional disability and impaired physical health. Among the associated factors are situations of early life stress, as abuse and neglect. The Hypothalamic-Pituitary-Adrenal (HPA) axis plays a crucial role in response to external and internal stimuli, and may precipitate psychiatric episodes in predisposed individuals. Furthermore, studies have confirmed that changes in the functioning of the HPA axis are associated with the severity of depressive and are indicative of a poor prognosis. Objective: The aim of this study was to evaluate patients with depressive on presence or absence of early life stress, identifying changes in HPA axis functioning and treatment response. Methods: The sample of 30 subjects, 20 depressed patients in partial inpatient treatment in the Day Hospital of the University Hospital of the School of Medicine of Ribeirao Preto- University of Sao Paulo and 10 healthy controls. In addition, the study subjects were divided into a group of responders (n = 8) and nonresponders (n = 8), a group with presence Early Life Stress (n = 13) or absence of Early Life Stress (n = 7) and a group of healthy controls (n = 10). Patients were evaluated using Clinical Interview according to the diagnostic criteria of DSM-IV, to confirm the diagnosis. To evaluate the severity of depressive symptoms was applied to Hamilton Depression Scale (HAM-\'D IND. 21\') and included only patients with HAM-\'D IND.21\' \'> OR =\' 17. We also use the Rating Scale Montgomery-Asberg Depression (MADRS) to evaluate therapeutic response, patients were considered responders who achieved a reduction of MADRS score \'> OR =\' 50% between admission and 60 days after. The presence of Early Life Stress was confirmed by applying the Questionnaire about Childhood Trauma (CTQ). We also used the Beck Depression Inventory (BDI), the Beck Anxiety Inventory (BAI), the Scale for Suicidal Ideation Beck (BSI), the Beck Hopelessness Scale (BHS), the Hospital Anxiety Scale and Depression Scale (HADS) and the Scale Barratt Impulsiveness (BIS-11) for evaluation of psychiatric symptoms. The endocrine evaluation was performed using salivary cortisol, being collected at 22h, on awaking, 30 and 60 minutes after awaking up at 8:30 am and at baseline and after 60 days. Results: Our results demonstrated an association between the severity of depression with, attempt suicide, abuse of alcohol and obesity, as well as increased symptoms of anxiety, hopelessness, and impulsivity, personality disorders. We found that in addition to these factors, the poor response to treatment can also be influenced by the history of Early Life Stress. Moreover, our findings indicate that the greater severity of depressive patients were correlated with increased activity of the HPA axis, and this increase was associated with higher levels of salivary cortisol both at admission and 60 days after treatment in nonresponders. We evidenced also that the increased activity of the HPA axis can be influenced by Early Life Stress, since the patients with EP had higher levels of salivary cortisol, even after treatment. Conclusion: Therefore, based on the presented results, our findings suggest the etiological role of the HPA axis in depression, which itself is often associated with situations of EP that lead to greater severity of patients and worsening of therapeutic response. Thus, our data suggest that the assessment of the HPA axis can predict the recurrence of psychopathology, thereby serving as a potential biomarker for depression in these patients.

Introdução: Alterações nos eixos Hipotálamo-Hipófise-Adrenal (HHA) e Hipotálamo-Hipófise-Tireóide (HHT) estão associados a depressão. Objetivo: Avaliar a associação entre depressão e alterações nos eixos HHA, HHT e o estresse precoce (EP) em deprimidos. Metodologia: Foram avaliados 52 deprimidos e 52 voluntários com idade entre 18 e 45 anos. O diagnóstico de depressão foi baseado no DSM-IV e MINI. A gravidade da depressão foi avaliada pela HAM-D-17 e pelo IDB. Foram aplicados o CTQ buscando avaliar eventos estressantes na infância, além de questionário sócio-demográfico e clínico. Voluntários foram pareados segundo sexo, idade, IMC e submetidos aos mesmos questionários. Foram realizadas dosagem de TSH, T4 livre, anticorpos anti TPO e ATG, Cortisol plasmático, ACTH, DHEA-s, lipidograma, glicemia de jejum e cortisol salivar em 05 tempos. Resultados: Todos os deprimidos apresentaram história de EP. Houve concentrações maiores de TSH, anti TPO, anti TG, cortisol plasmático e salivar, ACTH, colesterol total, LDL, VLDL, triglicérides, AUC 8-23 e AUC0-30-60, além de concentrações menores de DHEA-s e HDL em casos do que controles, considerando a primeira e segunda coleta de dados e conforme a amostra estudada. Houve correlações entre as variáveis estudadas. Conclusão: O EP foi um dos fatores de risco para depressão. Achados desse estudo confirmam a literatura quando se compara deprimidos com controles e se relaciona depressão com os eixos HHT, HHA e o EP. Esse foi o primeiro estudo em que se comparou todas as variáveis supracitadas em pessoas CEP e SEP, gerando resultados positivos, além de revelar diferenças de gênero conforme o resultado. / Introduction: Changes in the axis hypothalamus-pituitary-adrenal (HPA) and hypothalamic-pituitary-thyroid (HPT) are associated with depression. Objective: Evaluating the association among depression and changes in the HPA, HPT axes and early stress (ES) in depressed. Methodology: A total of 52 depressed and 52 volunteers aged between 18 and 45 years were evaluated. Depression diagnosis was based on DSM-IV and MINI. The severity of depression was assessed by HAM-D-17 and BDI. The CTQ were applied for assessing stressful events in childhood, as well as socio-demographic and clinical questionnaire. Volunteers were paired by gender, age, BMI, and underwent the same questionnaires. TSH measurement was performed, free T4, anti TPO and ATG antibodies, plasma cortisol, ACTH, DHEA-s, lipid profile, fasting glucose and salivary cortisol in 05 times. Results: All depressed had history of ES. There were higher concentrations of TSH, anti TPO, anti TG, plasma and salivary cortisol, ACTH, total cholesterol, LDL, VLDL, triglycerides, AUC 8-23 and AUC0-30-60 and lower concentrations of DHEA-s and HDL in cases than controls, taking into account the first and second data collection and according to the studied sample. There were correlations between variables. Conclusion: The ES was one of the risk factors for depression. Findings of this study confirm the literature when compared depressed with controls and associated depression with HPT, HPA axes and ES. This was the first study in which we compared all the above variables in people WES and WOES, generating positive results and revealed gender differences according to result.

Introdução: Crescentes evidências indicam que o abandono e o abuso infantis são fatores de risco para transtornos psiquiátricos. Estudos realizados tanto em animais como em humanos sugerem que o estresse nas fases iniciais de desenvolvimento pode induzir alterações persistentes na capacidade do eixo HPA em responder ao estresse na vida adulta e que esse mecanismo pode levar a uma maior suscetibilidade à depressão. Esta desregulação do eixo HPA parece estar relacionada às mudanças na capacidade dos glicocorticóides circulantes em exercer seu feedback negativo na secreção dos hormônios do eixo HPA por meio da ligação aos receptores de mineralocorticóides (MR) e glicocorticóides (GR) nos tecidos do eixo HPA. Objetivo: O objetivo deste trabalho foi avaliar a resposta do eixo HPA frente aos agonistas e antagonistas dos GR e MR em pacientes depressivos com e sem estresse precoce (EP) e controles. Metodologia: Selecionamos uma amostra total de 75 sujeitos composta por um grupo de pacientes com diagnóstico de episódio depressivo atual (n=47) e um grupo de controles saudáveis (n=28). Os pacientes foram divididos em 2 grupos de acordo com o estresse precoce: um grupo de pacientes depressivos com EP (n=33) e um grupo de pacientes depressivos sem estresse precoce (n=14). Os pacientes foram avaliados por meio da Mini Entrevista Neuropsiquiátrica Internacional (MINI-Plus), para a confirmação do diagnóstico. Para avaliação da gravidade dos sintomas depressivos foi aplicada a Escala de Depressão GRID de Hamilton (GRID-HAM-D21), sendo incluídos apenas pacientes com HAM-D21>=16. Para a avaliação do estresse precoce foi aplicado o Questionário Sobre Traumas na Infância (CTQ). Utilizamos também a Escala de Avaliação de Depressão de Montgomery-Asberg (MADRS), o Inventário de Depressão de Beck (BDI-II), o Inventário de Ansiedade de Beck (BAI), a Escala de Desesperança de Beck (BHS), a Escala de Ideação Suicida de Beck (BSI), a Escala de Impulsividade de Barratt (BIS-11) e o Questionário de Qualidade de Sono de Pittsburg (PSQI), para a avaliação dos sintomas psiquiátricos. A avaliação endócrina foi controlada por placebo, cego por parte dos controles e pacientes, não randomizada, onde os efeitos da fludrocortisona (0.5 mg), da prednisolona (5 mg), da dexametasona (0.5 mg) e da espironolactona (400mg) foram avaliados através do hormônio adrenocorticotrópico (ACTH) plasmático, do cortisol plasmático e salivar, da prolactina plasmática e do sulfato de desidroepiandrosterona (DHEA-S) plasmático. A secreção de cortisol salivar e dos hormônios plasmáticos foi avaliada em todos os sujeitos, após terem tomado no dia anterior às 22h: uma cápsula de placebo, fludrocortisona, prednisolona, dexametasona e espironolactona. A secreção de cortisol salivar foi avaliada às 22h após a tomada da medicação ou do placebo, ao acordar, 30 e 60 min após acordar e às 9h (antes da coleta plasmática), para avaliação da resposta do cortisol ao acordar (CAR) e do ritmo circadiano do cortisol (RC). Foi realizado também uma coleta plasmática as 9h nos dias seguintes após os desafios para medir o cortisol plasmático, o ACTH, o DHEA-S e a prolactina. Resultados: Os pacientes depressivos apresentaram níveis basais menores de cortisol salivar, de prolactina e de DHEA-S e níveis maiores na relação cortisol/DHEA-S. Não foram encontradas diferenças entre os pacientes depressivos e os controles nos níveis basais de ACTH, de cortisol plasmático, na CAR e no RC. Os pacientes depressivos apresentaram níveis menores de ACTH e de DHEA-S após a dexametasona e a fludrocortisona e tenderam a apresentar níveis menores de cortisol salivar após a fludrocortisona. Após a espironolactona encontramos níveis menores de ACTH, de cortisol salivar e de DHEA-S e níveis maiores no índice cortisol/DHEA-S nos pacientes depressivos. Os pacientes depressivos apresentaram também níveis menores de DHEA-S após a prednisolona, porém não foram encontradas diferenças entre os grupos nos demais hormônios avaliados após a prednisolona. Não foram encontradas diferenças no cortisol plasmático e na prolactina após os desafios entre os pacientes depressivos e os controles. Com relação à avaliação do estresse precoce nas medidas hormonais, encontramos uma tendência dos pacientes com EP apresentarem níveis menores basais de prolactina e após a fludrocortisona, a prednisolona, a dexametasona e a espironolactona do que os pacientes sem EP. No entanto, não foram encontradas diferenças entre os grupos nas demais medidas hormonais basais e após os desafios avaliadas neste estudo. Conclusão: Nossos achados fornecem evidências de que existem diversas alterações nas medidas hormonais relacionadas ao funcionamento do eixo HPA e de seus receptores GR e MR nos pacientes depressivos, associado à hipocortisolemia e um aumento do feedback inibitório mediado pelos GR e MR. Sugerem também o envolvimento da prolactina no desenvolvimento de quadros depressivos com estresse precoce, porém mais estudos são necessários para elucidarmos melhor a importância dos demais hormônios do eixo HPA e dos seus receptores em quadros depressivos com estresse precoce / Introduction: There are evidences indicating that child neglect and abuse are risk factors for psychiatric disorders. Studies that had as subjects animals or human suggest that stress in early phases of development may induce persistent changes in HPA axis response to stress in adulthood, which can lead to a greater susceptibility of developing depression. These abnormalities appear to be related to changes in the ability of circulating glucocorticoids and negative feedback on the secretion of HPA hormones through binding to glucocorticoid (GR) and mineralocorticoid receptors (MR) in HPA tissue. Aim: The aim of the present study was to assess HPA response after ingestion of GR and MR agonists and antagonists by depressive patients with and without early life stress (ELS) and controls. Methods: The sample was composed by a group of patients in current depressive episode (n=47), and a healthy control group (n=28). The depressed patients were divided in 2 groups, according to the presence or absence of ELS - a group with ELS (n=33) and a group without ELS (n=14). For diagnostic assessment, MINI International Neuropsychiatric Interview (MINI-Plus) was used. To assess the intensity of depressive symptoms, GRID-Hamilton Depression Rating Scale (GRIDHAM-D21) was applied, and for being included in the patient\'s group, subjects had to score >=16 in GRID-HAM-D21. To assess ELS, Childhood Trauma Questionnaire (CTQ) was applied. Other instruments were also used in the present study to assess psychiatric symptoms: Montgomery-Åsberg Depression Rating Scale (MADRS), Beck Depression Inventory II (BDI-II), Beck Anxiety Inventory, Beck Hopelessness Scale (BHS), Beck Scale for Suicide (BSI), Barratt Impulsiveness Scale (BIS-11), and Pittsburg Sleep Quality Index (PSQI). The neuroendocrine assessment was controlled using placebo, blind to subjects, and non-randomized. The effects of fludrocortisone (0.5 mg), prednisolone (5 mg), dexamethasone (0.5 mg), and spironolactone (400mg) were assessed by measuring plasmatic adrenocorticotropic hormone (ACTH), plasmatic and salivary cortisol, plasmatic prolactin, and plasmatic dehydroepiandrosterone sulfate (DHEA-S). The secretion of all plasmatic hormones was assessed in all subjects in blood collection sample at 9AM, after they took a pill containg placebo or fludrocortisone or prednisolone or dexamethasone or spironolactone, the day before, at 10 PM. The secretion of salivary cortisol assessed the day before 10 PM (after the ingestion of the pill), upon awakening, 30 minutes and 60 minutes after awakening, and at 9AM (before plasmatic collection), for assessed the cortisol awakening response (CAR) and the cortisol circadian rhythm (CR). At 9 AM there was a blood sample collection to assess plasmatic cortisol, ACTH, DHEA-S and prolactin. Results: Depressive patients presented lower basal levels of salivar cortisol, plasmatic prolactin and DHEA-S, and higher levels in the ratio cortisol/DHEA-S. There were no differences between depressive patients and healthy controls in basal levels of ACTH, plasmatic cortisol, in CAR, and in CR. Depressive patients had lower levels of ACTH and DHEA-S after dexamethasone and fludrocortisone, and there was a tendency of having lower salivary cortisol levels after fludrocortisone. After spironolactone, lower levels of ACTH, salivary cortisol, DHEA-S were found, and higher levels in ratio cortisol/DHEA-S were found in depressive patients. These patients also presented lower levels of DHEA-S after prednisolone, although there were no differences between groups concerning the levels of other hormones assessed after prednisolone. There were no differences found in plasmatic cortisol and prolactin levels after all challenges between depressive patients and controls. Considering ELS and hormonal level assessment, there was a tendency of patients with ELS of presenting lower levels of prolactin after placebo, fludrocortisone, prednisolone, dexamethasone, and spironolactone than patients without ELS. Nevertheless, there were no differences between these groups concerning the other hormonal basal levels and after the pharmachological challenges. Conclusion: Our findings provide evidence that there are several changes in hormonal levels related to the functioning of the HPA axis and its receptors GR and MR in depressive patients associated to hypocortisolism and the increase of negative feedback MR- and GR- mediated. Our data also suggest the role of prolactin in the development of depressive disorder with ELS, however, more studies are needed to better highlight the importance of other hormones of HPA axis and its receptors in depressive disorders with ELS

Resource availability follows seasonal cycles in environmental conditions. To align physiology and behavior with prevailing environmental conditions, seasonal animals integrate cues from the environment with their internal state. One of the systems animals use to integrate those cues is the hypothalamus-pituitary-adrenal (HPA) axis and its primary effector, glucocorticoid hormones. The HPA axis has wide-ranging effects on physiology and behavior and, in the context of a glucocorticoid stress response, is known to mediate tradeoffs between immediate survival and future fitness. The HPA axis also plays an important role in facilitating predictable life-history events. Variation in HPA axis activity has been reported in all vertebrates, often coordinating seasonal reproduction and possibly also transitions between life-history stages. My dissertation research used red-sided garter snakes (Thamnophis sirtalis parietalis) to examine the role of the HPA axis in regulating seasonal life-history transitions, especially in females. In Chapter 2, I hypothesized that seasonal plasticity in stress responses is regulated, in part, by changes in the responsiveness of the adrenal glands to adrenocorticotropic hormone (ACTH). I found that glucocorticoid responses to ACTH challenge were smaller in males than in females during the spring, suggesting that reports of reduced stress responsiveness in males may reflect lower adrenal responsiveness to ACTH. The sex difference in mating season duration and consequently also in the timing of migration led me to hypothesize that sex differences in HPA axis activity could explain sex differences in the timing of migration. Furthermore, adrenal responsiveness to ACTH also varied seasonally in males, but not females, suggesting that female stress responses, which have not been studied, may not vary seasonally. In Chapter 3, I investigated potential seasonal variation in female stress responses, which have not previously been examined. In males, baseline glucocorticoids decrease over the course of the mating season resulting in significantly lower baseline levels in males that have begun to migrate. I hypothesized that a change in HPA axis activity occurs during spring and fall migration. Peak stress-induced glucocorticoid concentration occurred at an earlier sampling time in females during the spring compared to the fall. Peak stress-induced glucocorticoid concentrations also occurred at a later sampling time in migrating females than in pre-migratory females during the spring, suggesting that negative feedback regulation of the HPA axis changes as soon as females begin to migrate during the spring. Female red-sided garter snakes are biennial breeders that give birth approximately every other year implying that a female's recent reproductive history can influence whether or not she will reproduce in a given year. Body condition can be used as a proxy for recent reproductive history and can be related to baseline and stress-induced glucocorticoid concentrations. In Chapter 4, I hypothesized that hormonal and behavioral stress responses vary with body condition. Baseline glucocorticoids did not vary with body condition, but females in low body condition showed a significantly larger increase in plasma glucocorticoids in response to capture stress. Body condition, but not capture stress, influenced latency to copulate, suggesting that females are resistant to the behavioral effects of capture stress during the spring mating season. Only females in low body condition increased latency to copulate in response to injection of a physiological (15 µg) dose of exogenous CORT, while all females responded to a pharmacological (60 µg) dose, indicating that behavioral responses to exogenous glucocorticoids vary with female body condition. These data suggest that variation in body condition may be associated with differences in HPA axis sensitivity and/or glucocorticoid receptor (GR) density in the brain. I directly tested if there is a relationship among body condition, reproductive history and HPA axis activity in Chapter 5. I found that glucocorticoid stress responses and mating behavior did not vary with body condition, nor was body condition related to brain GR or reproductive condition (parturient vs post-parturient females). Only unreceptive females showed a significant stress-induced increase in glucocorticoids, suggesting that reduced stress responsiveness is associated with receptivity. Parturient females mated faster (were more proceptive) than post-parturient females. These data suggest that HPA axis activity influences reproductive "decisions" by modulating receptivity, while proceptivity is related primarily to recent reproductive history. Together, these chapters help characterize how HPA axis activity varies with season, sex, reproductive history and migration status. By systematically probing the HPA axis in a single, tractable system, I have gained insight into how changes in the HPA axis support and modulate transitions between life-history stages. These results highlight the HPA axis' important function in mediating the critical trade-offs all animals must navigate to be successful in a changing world.

Transdisciplinary research in general, and stress research in particular, requires an efficient integration of methodological knowledge of all involved academic disciplines, in order to obtain conclusions of incremental value about the investigated constructs. From a psychologist’s point of view, biochemistry and quantitative neuroendocrinology are of particular importance for the investigation of endocrine stress systems (i.e., the HPA axis, and the SNS). Despite of their fundamental role for the adequate assessment of endocrine activity, both topics are rarely covered by conventional psychological curriculae. Consequently, the transfer of the respective knowledge has to rely on other, less efficient channels of scientific exchange. The present thesis sets out to contribute to this exchange, by highlighting methodological issues that are repeatedly encountered in research on stress-related endocrine activity, and providing solutions to these issues. As outlined within this thesis, modern stress research tends to fall short of an adequate quantification of the kinetics and dynamics of bioactive cortisol. Cortisol has gained considerable popularity during the last decades, as its bioactive fraction is supposed to be reliably determinable from saliva and is therefore the most conveniently obtainable marker of HPA activity. However, a substantial fraction of salivary cortisol is metabolized to its inactivated form cortisone by the enzyme 11β-HSD2 in the parotid glands, which is likely to restrict its utility. Although the commonly used antibody-based quantification methods (i.e. immunoassays) might “involuntarily” qualify this issue to some degree (due to their inherent cross-reactivity with matrix components that are structurally-related to cortisol; e.g., cortisone), they also cause differential within-immunoassay measurement bias: Salivary cortisone has (as compared to salivary cortisol) a substantially longer half-life, which leads to an overestimation of cortisol levels the more time has passed since the onset of the prior HPA secretory episode, and thus tends to distort any inference on the kinetics of bioactive cortisol. Furthermore, absolute cortisol levels also depend on the between-immunoassay variation of antibodies. Consequently, raw signal comparisons between laboratories and studies, which are favorable as compared to effect comparisons, can hardly be performed. This finding also highlights the need for the long-sought standardization of biochemical measurement procedures. The presumably only way to circumvent both issues is to rely on quantification of ultrafiltrated blood cortisol by mass-spectrometric methods. Being partly related to biochemical considerations with research on HPA activity, a second topic arises concerning the operationalization of the construct itself: In contrast to the simple outcome measures like averaged reaction times, inclined stress researchers can only indirectly infer on the sub-processes being involved in HPA activity from longitudinally sampled hormone concentrations. HPA activity can be quantified either by (a) discrete-time, or by (b) continuous-time models. Although the former is the most popular and more convenient approach (as indicated by the overly frequent encounter of ANOVAs and trapezoidal AUC calculations in the field of psychobiological stress research), most discrete time models form rather data-driven, descriptive approaches to quantify HPA activity, that assume the existence of some endocrine resting-state (i.e., a baseline) at the first sampling point and disregard any mechanistic hormonal change occurring in between all following sampling points. Even if one ignores the fact, that such properties are unlikely to pertain to endocrine systems in general, many generic discrete time models fail to account for the specific structure of endocrine data that results from biochemical hormone measurement, as well as from the dynamics of the investigated system. More precisely speaking, cortisol time series violate homoscedasticity, residual normality, and sphericity, which need to be present in order to enable (mixed effects) GLM-based analyses. Neglecting these prerequisites may lead to inference bias unless counter-measures are taken. Such counter-measures usually involve alteration of the scale of hormone concentrations via transformation techniques. As such, a fourth-root transformation of salivary cortisol (being determined by a widely used, commercially available immunoassay) is shown to yield the optimal tradeoff for generating homoscedasticity and residual normality simultaneously. Although the violation of sphericity could be partly accounted for by several correction techniques, many modern software packages for structural equation modeling (e.g., Mplus, OpenMX, Lavaan) also offer the opportunity to easily specify more appropriate moment structures via path notation and therefore to relax the modeling assumptions of GLM approaches to the analysis of longitudinal hormone data. Proceeding from this reasoning, this thesis illustrates how one can additionally incorporate hypotheses about HPA functioning, and thus model all relevant sub-processes that give rise to HPA kinetics and dynamics. The ALT modeling framework being advocated within this thesis, is shown to serve well for this purpose: ALT modeling can recover HPA activity parameters, which are directly interpretable within a physiological framework, that is, distinct growth factors representing the amount of secreted cortisol and velocity of cortisol elimination can serve to interpret HPA reactivity and regulation in a more unambiguous way, as compared to GLM effect measures. For illustration of these advantages on a content level, cortisol elimination after stress induction was found to be elevated as compared to its known pharmacokinetics. While the mechanism behind this effect requires further investigation, its detection would obviously have been more difficult upon application of conventional GLM methods. Further extension of the ALT framework allowed to address a methodological question, which had previously been dealt with by a mere rule of thumb; what’s the optimal threshold criterion, that enables a convenient but comparably accurate classification of individuals whose HPA axis is or is not activated upon encountering a stressful situation? While a rather arbitrarily chosen baseline-to-peak threshold of 2.5 nmol/L was commonly used to identify episodes of secretory HPA activity in time series of salivary cortisol concentrations, a reanalysis of a TSST meta- dataset by means of ALT mixture modeling suggested that this 2.5 nmol/L criterion is overly conservative with modern biochemical measurement tools and should be lowered according to the precision of the utilized assay (i.e., 1.5 nmol/L). In sum, parametric ALT modeling of endocrine activity can provide a convenient alternative to the commonly utilized GLM-based approaches that enables the inference on and quantification of distinct HPA components on a theoretical foundation, and thus to bridge the gap between discrete- and continuous-time modeling frameworks. The implementation of the outlined modeling approaches by the respective statistical syntaxes and practical guidelines being derived from the comparison of cortisol assays mentioned above, are provided in the appendix of the present thesis, which will hopefully help stress researchers to directly quantify the construct they actually intend to assess.

Approximately 1 in 6 infants are born prematurely each year. Typically, these infants spend 25 days in the Neonatal Intensive Care Unit (NICU) where they experience 10-18 painful and inflammatory procedures each day. Remarkably, pre-emptive analgesics and/or anesthesia are administered less than 30% of the time. Unalleviated pain during the perinatal period is associated with permanent decreases in pain sensitivity, blunted cortisol responses and high rates of neuropsychiatric disorders. To date, the mechanism(s) by which these long-term changes in stress and pain behavior occur, and whether such alterations can be prevented by appropriate analgesia at the time of injury, remains unclear. We have previously reported in rats that inflammation experienced on the day of birth permanently upregulates central opioid tone, resulting in a significant reduction in adult pain sensitivity. However, the impact on early life pain on anxiety- and stress-related behavior and HPA axis regulation is not known. Therefore the goal of this dissertation was to determine the long-term impact of a single neonatal inflammatory pain experience on adult anxiety- and stress-related responses. Neuroanatomical changes in stress-associated neurocircuits were also examined. As the endogenous pain control system and HPA axis are in a state of exaggerated developmental plasticity early in postnatal life, and these systems work in concert to respond to noxious or aversive stimuli, this dissertation research aimed to answer the following questions: (1) Does neonatal injury produce deficits in adult stress-related behavior and alter stress-related neuroanatomy through an opioid-dependent mechanism? (2) Does neonatal injury alter receptor systems regulating the activation and termination of the stress response in adulthood? (3) Are stress- and pain-related neurotransmitters altered within the first week following early life pain? (4) Is early activation of the pain system necessary for the long-term changes in anxiety- and stress-related behavior? Together these studies demonstrate the degree, severity and preventability of the long-term deficits in stress responding associated with a single painful experience early in life. The goal of this research is to promote change in the treatment of infant pain in the NICU to reduce long-term sensory and mental health complications associated with prematurity.

Approximately 1 in 6 infants are born prematurely each year. Typically, these infants spend 25 days in the Neonatal Intensive Care Unit (NICU) where they experience 10-18 painful and inflammatory procedures each day. Remarkably, pre-emptive analgesics and/or anesthesia are administered less than 30% of the time. Unalleviated pain during the perinatal period is associated with permanent decreases in pain sensitivity, blunted cortisol responses and high rates of neuropsychiatric disorders. To date, the mechanism(s) by which these long-term changes in stress and pain behavior occur, and whether such alterations can be prevented by appropriate analgesia at the time of injury, remains unclear. We have previously reported in rats that inflammation experienced on the day of birth permanently upregulates central opioid tone, resulting in a significant reduction in adult pain sensitivity. However, the impact on early life pain on anxiety- and stress-related behavior and HPA axis regulation is not known. Therefore the goal of this dissertation was to determine the long-term impact of a single neonatal inflammatory pain experience on adult anxiety- and stress-related responses. Neuroanatomical changes in stress-associated neurocircuits were also examined. As the endogenous pain control system and HPA axis are in a state of exaggerated developmental plasticity early in postnatal life, and these systems work in concert to respond to noxious or aversive stimuli, this dissertation research aimed to answer the following questions: (1) Does neonatal injury produce deficits in adult stress-related behavior and alter stress-related neuroanatomy through an opioid-dependent mechanism? (2) Does neonatal injury alter receptor systems regulating the activation and termination of the stress response in adulthood? (3) Are stress- and pain-related neurotransmitters altered within the first week following early life pain? (4) Is early activation of the pain system necessary for the long-term changes in anxiety- and stress-related behavior? Together these studies demonstrate the degree, severity and preventability of the long-term deficits in stress responding associated with a single painful experience early in life. The goal of this research is to promote change in the treatment of infant pain in the NICU to reduce long-term sensory and mental health complications associated with prematurity.

No description available.

Teneurin C-terminal associated peptides (TCAP) are a family of bioactive peptides found on the terminal exon of the four teneurin genes. TCAP-1 is found within brain regions that modulate the activity of corticotropin-releasing factor (CRF), which is the principal neuropeptide regulator of the hypothalamic-pituitary-adrenal (HPA) axis. TCAP-1 has suppressive effects on CRF-induced anxiety behaviours in rats. However, previous studies determined that TCAP-1 does not act directly on the CRF receptors (CRFR). Thus, I postulate that TCAP-1 may act centrally to modify elements of the HPA axis. Using an immortalized mouse hippocampal cell line, I tested the hypothesis that TCAP acts either downstream of CRFR activation, or on the regulation of the glucocorticoid receptors (GCR), which modulate CRF actions. These studies indicate that TCAP-1 represents a novel peptide in the regulation of stress related systems, which acts independently of either CRF-, or glucocorticoid- mediated signal transduction and transcription.

Teneurin C-terminal associated peptides (TCAP) are a family of bioactive peptides found on the terminal exon of the four teneurin genes. TCAP-1 is found within brain regions that modulate the activity of corticotropin-releasing factor (CRF), which is the principal neuropeptide regulator of the hypothalamic-pituitary-adrenal (HPA) axis. TCAP-1 has suppressive effects on CRF-induced anxiety behaviours in rats. However, previous studies determined that TCAP-1 does not act directly on the CRF receptors (CRFR). Thus, I postulate that TCAP-1 may act centrally to modify elements of the HPA axis. Using an immortalized mouse hippocampal cell line, I tested the hypothesis that TCAP acts either downstream of CRFR activation, or on the regulation of the glucocorticoid receptors (GCR), which modulate CRF actions. These studies indicate that TCAP-1 represents a novel peptide in the regulation of stress related systems, which acts independently of either CRF-, or glucocorticoid- mediated signal transduction and transcription.