Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: This study (2 x 2 factor design) describes an investigation into the physiological interaction between the peripheral endocrine and cytokine systems after the organism has been exposed to psychological stress. An in vivo rodent model with two interventions was used: (1) mild psychological stress (immobilisation for 2 hours per day, for 4 days); (2) an antiinterleukin (IL)-6-antibody injection. Thirty-nine male Wi star rats were divided into 4 groups and given either the antibody (CA, control antibody) or stress (IP, immobilisation placebo), or both (IA, immobilisation antibody), or neither (CP, control placebo). Antibody and placebo (saline) were injected intraperitoneally. Differences between groups for the following parameters were determined in blood or metabolic tissues, viz. skeletal muscle and liver: 1) corticosterone concentrations, 2) glucocorticoid receptor (GR) binding capacity and 3) activities of metabolic enzymes, tyrosine aminotransferase (TAT) and glutamine synthetase (GS). Groups lP and lA showed a significant loss in body mass (CP vs. lP, p<O.01; CA vs. lA, p<O.001), indicating a main effect of stress. The corticosterone concentrations of only group lP were significantly elevated compared to that of group CP (CP vs. lP, p<O.01), again indicating a main effect of stress. All three intervention groups (CA, lP, lA) had decreased GR binding capacity, with group lA showing a statistically greater decrease (CP vs. CA, p<O.05; IP vs. IA, p<O.01; CP vs. IP, p<O.001; CA vs. IA, p<O.001), indicating main effects of stress and antibody treatment. In groups IP and IA increased activities of both enzymes (TAT and GS) were measured (main effect of stress), with IA again showing the greatest statistically significant increase for both enzymes. The liver tissue displayed greater sensitivity to the stress and antibody regimes. This study provides the first conclusive in vivo evidence for IL-6 modulation of glucocorticoid action in peripheral tissues in response to mild psychological stress. / AFRIKAANSE OPSOMMING: Hierdie studie (met 'n 2 X 2 faktorontwerp) beskryf 'n ondersoek oor die fisiologiese interaksie tussen die perifere endokrien- en sitokiensisteme in organismes blootgestel aan psigologiese stres. Daar word gebruik gemaak van 'n in vivo-rotmodel met twee intervensies: (1) matige psigologiese stres (immobilisering vir 2 uur per dag vir 4 dae); (2) 'n anti-interleukin (IL)-6-antiliggaam inspuiting. Nege-en-dertig manlike Wistar rotte is in vier groepe verdeel en het óf antiliggaam (CA, antiliggaam kontrole), óf stres (IP, immobilisasie placebo), óf beide stres en antiliggaam (lA, immobilisasie antiliggaam) of geen behandeling ontvang (CP, placebo kontrole). Die antiliggaam- en placebo (soutoplossing)- inspuitings is intraperitoneaal toegedien. Verskille tussen die groepe van die volgende parameters, in metaboliese weefsels (skeletspier en lewer), was bepaal: 1) kortikosteroon konsentrasies, 2) glukokortikoïed reseptor (GR) bindingskapasiteit en 3) aktiwiteite van die metaboliese ensieme, tirosien aminotransferase (TAT) en glutamien sintetase (GS). Groepe IP en IA het 'n beduidende afname in gewig getoon (CP vs. IP, p<O.01;CA vs. IA, p<O.001), wat 'n hoof-effek van stres aandui. Die kortikosteroon konsentrasies van slegs IP het beduidend toegeneem in vergelyking met CP (CP vs. IP, p<O.01),wat weereens 'n hoof-effek van stres aandui. AI drie intervensiegroepe (CA, IP, IA) het verlaagte GR bindingskapasiteit getoon, met lA wat 'n groot statistiese afname getoon het (CP vs. CA, p<O.05; IP vs. IA, p<O.01;CP vs. IP, p<O.001;CA vs. IA, p<O.001),wat hoof-effekte van beide stres en antiliggaam-behandeling aandui. In groepe IP and IA is toenames in beide ensiemaktiwiteitvlakke (TAT en GS ensieme) getoon (hoof-effek van stres), met IA wat weereens die grootste toename gewys het. Die lewer het ook verhoogde sensitiwiteit tot die stres- en antiliggaamregimente. Hierdie studie lewer die eerste daadwerklike in vivo bewyse vir IL-6 modulering van glukokortikoïedaksie in perifere weefsels na reaksie op psigologiese stres.

Stress is thought to be antithetical to play. However, this thesis shows that mild stress (e.g., social deprivation) enhances rough-and-tumble play, as opposed to other social behaviors, in adolescent rats. Social deprivation results in both higher levels of corticosterone (a stress hormone) and higher levels of play. When non-socially deprived rats were injected with ACTH (a precursor to corticosterone), the frequency of play was elevated to levels comparable to that seen when juveniles were socially deprived. Moreover, corticosterone was reduced by the opportunity to play, but not when given social contact (but no play) or solitary exercise (i.e. a running wheel). Therefore, this thesis provides evidence that play is not only enhanced by mild stress, but that it is used by animals to reduce stress. / vi, 70 leaves ; 29 cm.

Manganese-Enhanced Magnetic Resonance Imaging (MEMRI) has proven itself to be a beneficial technique in the field of Neuroscience. This thesis applies MEMRI to studies in neuroscience by first establishing the limitations concerning the use of MEMRI in live rats. Experiment 1 used an osmotic pump for manganese (Mn) delivery to the lateral ventricles for acquisition of anatomical images using MEMRI. From my knowledge, this was the first method demonstrating slow infusion of Mn to the lateral ventricles. In Experiment 2, MEMRI was used for volumetric analysis the whole brain and hippocampus of prenatally stressed rats. To my knowledge, this study was the first to investigate the effect of generational prenatal stress on the structure of a rat’s brain using MEMRI and histology. Additionally, Experiment 2 investigated the use of a subcutaneous osmotic pump to deliver Mn for MEMRI. A summary on the use of MEMRI in Neuroscience concludes this thesis, with a discussion on the methods used and related technical considerations. / xi, 84 leaves ; 29 cm

Thesis (MSCMedSc (Biomedical Sciences. Medical Physiology))--University of Stellenbosch, 2005. / Stress is considered one of the major factors involved in the pathogenesis of affective disorders, for example, direct and indirect exposure to terrorist attacks or being subjected to subtle victimization. There is a long history of development of procedures to determine anxiety responses in animals in order to find new or better treatments for patients. Prior stress exposure is known to alter the activation response to a subsequent stressor and the means of coping with stress can influence health and disease. This orchestrated process, usually referred to as the “stress response”, involves various mechanisms, which allow the body to make the necessary physical, psychological and the neuro-endocrine adjustments required to cope with the demands of a homeostatic challenge. The communication box method is a useful model to investigate the physiological changes that occur under psychological stress, since it can produce an experimental anxiety based on psychological communication between two or more animals, without the direct physical stress. In this animal model, the psychologically stressed rats are exposed to the visual, olfactory, auditory stimuli (such as struggling, vocalization, defecating, urinating and jumping) from the foot shock rat (Oishi et al., 2003). In the present study, we examined the neuro-endocrine and behavioural responses after different durations of inescapable foot shock and the subsequent effect of citalopram (10 milligram/kilogram, intraperitoneal once a day for 10 days), a selective serotonin reuptake inhibitor in reversing these responses. We have subjected rats to a number of stress paradigms (varying in duration), and assessed the effects thereof on behaviour at two different time points. Physically stressed rats were subjected to 10 unpredicted electric foot shocks (0.5 milliampere), in 10 minutes, while the psychologically stressed rats witnessed everything. The behavioural responses were assessed 5 days and 10 days after the last stress session. The rats were decapitated and corticosterone concentrations were determined one day after the open field and elevated plus-maze tests were performed. The behavioural and endocrine responses in the rats subjected to physical and psychological stress in this study showed that single stress exposure may lead to different outcomes as repetitive stress exposure and that the consequences of stress exposure develop over time and persist for an extended time period. These consequences of direct stress exposure versus indirect stress exposure show a grading in stress intensity and perception, similar to that observed in humans. In the experiment where the rats where treated with citalopram, it showed that citalopram is effective in reversing anxious-like behaviours, but not locomotor deficits. In all the animals basal plasma corticosterone concentrations were comparable and physically and psychologically stressed rats displayed a hyposensitive hypothalamic-pituitary-adrenal axis following acute restraint stress. These findings are interesting in a number of ways. It showed that our stress models propose to be useful in elucidating the complex interrelationship between an external event or stressor, and the organism experiencing it. Simultaneously it presents a promising platform for the finding of new or better treatments for patients.

Previous findings showed that mild chronic restraint stress causes motor impairments in rats. These behavioural impairments might be related to molecular changes in brain areas that regulate motor functions, such as the cerebellum. Little is known about the role of the cerebellum in stress-induced behavioural alteration. We hypothesized that alteration in animal behaviour after chronic restraint stress is due to brain-specific changes in miRNA and proteins encoding gene expression. Our results revealed that expression of three miRNAs and 39 mRNAs was changed significantly after two weeks of stress. Furthermore, we verified one putative target for one of the changed miRNAs and expression of four randomly selected genes. Changes in gene expression disappeared after two weeks of recovery from stress. These findings provide a novel insight into stress-related mechanisms of gene expression underlying altered behavioural performance. The observations bear implications for the prevention and treatment of stress-related disorders and disease. / xii, 109 leaves. : ill. ; 29 cm

Thesis (MSc (Physiological Sciences))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Bi-directional communication exists between HPA-axis activation and interleukin-6 (IL-6). However, the relative contribution of centrally versus peripherally secreted IL- 6 remains unclear, especially under psychological stress conditions. We hypothesised that the HPA response to mild psychological stress is dependent on IL- 6, both centrally and peripherally. 120 male Wistar rats were divided into four groups, depending on whether they received an anti-IL-6 antibody (Ab) (2μg/ml/kg body weight) or a placebo (sterile saline) injection and whether or not they were subjected to 1 hour of restraint stress for 1, 2 or 3 days. Rats were euthanized 24 hours after stress exposure. Plasma corticosteroid (GC) levels remained significantly increased 24 hours after a single stress exposure (control placebo (CP) versus stress placebo (SP): p < 0.05). The undetectable plasma IL-6 levels evident across all groups may be explained by the short half-life of IL-6. Plasma IL-1β levels decreased when IL-6 was blocked in unstressed animals (CP versus CAb: p < 0.05), suggesting a role for IL-6 in the maintenance of IL-1β levels under tonic physiological conditions. At tissue level, pituitary gland mass increased significantly at time point 2, independently of stress when blocking IL-6 (CAb: p < 0.05). This suggests that when normal homeostasis is threatened, immediate adaption or at least compensation may occur. It was observed that GR, IL-1β, IL-1βR, IL-6, IL-6R and GABAARα1 showed no response to stress alone in the pituitary. It is therefore more likely that resistance to adaptation exists centrally. IL-1β and IL-1βR (p < 0.05) and GABAARα1 (p < 0.005) expression increased in the CAb group in the pituitary, again suggesting a role for IL-6 under control conditions. In terms of the adrenal, blocking IL-6 resulted in decreased glandular mass at time point 1, independent of stress (CAb and SAb: p < 0.005). The up-regulation in GR expression seen in CAb and SAb (p < 0.05) may be the effect of a compensatory mechanism to increase IL-6 dependent bioactivity of GCs. The fact that expression of IL-6, IL-6R, IL-1β and IL- 1βR consistently increased in the Ab groups, and mostly in the zona fasciculata and zona reticularis, suggests that lack of local direct negative cytokine feedback occurred in response to very low plasma IL-6 levels and that this contributes more than GCs in the down-regulation of inflammatory cytokine release. In conclusion, consistent effects of the Ab were apparent in the tissues investigated, even in control conditions, suggesting that IL-6 plays a role in the maintenance of basal homeostasis, including its regulation of the response to psychological stress. We found differential regulation in terms of cytokines and GCs when comparing peripheral versus central effects of stress and Ab, as well as the levels of cytokines in the blood compartment, compared to within tissues. / AFRIKAANSE OPSOMMING: Daar bestaan twee-rigting kommunikasie tussen HPA-as aktivering en interleukin-6 (IL-6), allhoewel die relatiewe bydrae van sentraal versus perifeer afgeskeide IL-6 nog onduidelik is, veral gedurende sielkundige strestoestande. Ons hipotese is dat die HPA reaksie tot sielkundige stres afhanklik van IL-6 is, beide sentraal en in die periferie. 120 manlike Wistar rotte is in vier groepe verdeel, afhangende van of hulle ‘n anti-IL- 6 teenliggaampie (Ab) (2μg/ml/kg liggaamsgewig) of ‘n plasebo (steriele soutoplossing) inspuiting gekry het, en of hulle onderworpe was aan 1 uur van vaskeer-stres vir 1, 2 of 3 dae. Rotte is 24 uur na blootstelling aan stres aan genadedood onderwerp. Bloed kortikosteroïed (GC) vlakke het beduidend toegeneem binne 24 uur na ‘n eenmalige stres blootstelling (kontrole plasebo (CP) versus stres plasebo (SP): p < 0.05). Die onmeetbaar lae vlakke van IL-6 regoor al die groepe, kan verduidelik word na aanleiding van die kort half-leeftyd van IL-6. Bloed IL-1β vlakke het afgeneem in kontrole rotte wanneer IL-6 geblok is (CP versus CAb: p < 0.05). Dit kan beteken dat IL-6 noodsaaklik is vir die onderhoud van IL-1β vlakke gedurende basale toestande. Op weefselvlak het die hipofise massa toegeneem by tydpunt 2 toe IL-6 geblok is, onafhanklik van stres (CAb: p < 0.05). Dit dui aan dat wanneer normale homeostase bedreig word, daar onmiddelike aanpassing of kompensasie plaasvind. Dit is opvallend dat GR, IL-1β, IL-1βR, IL-6, IL-6R en GABAARα1 geen respons in terme van stres alleen in die hipofise getoon het nie. Na aanleiding daarvan is dit meer waarskynlik dat weerstand tot aanpassing sentraal bestaan. IL-1β and IL-1βR (p <0.05) en GABAARα1 (p < 0.005) uitdrukking in die hipofise het toegeneem in die CAb groep, wat weereens ‘n rol vir IL-6 onder kontrole toestande uitwys. In terme van die bynier, het die blok van IL-6 ‘n afname in massa veroorsaak by tydpunt 1, wat weer onafhanklik van stres was (CAb en SAb: p < 0.005). Die opregulering in die CAb en SAb groepe (p < 0.05), kan wees as gevolg van ‘n kompensasie meganisme om IL-6 afhanklike GC aktiwiteit te verhoog. Die feit dat die uitdrukking van IL-6, IL-6R, IL-1β and IL-1βR in die Ab groepe deurlopend verhoog was, en meeste in die zona fasciculata en zona reticularis, stel voor dat daar ‘n tekort aan plaaslike, direkte sitokien negatiewe terugvoering was, as gevolg van die merkwaardige lae bloed IL-6 vlakke en dat dit meer bydra as GCs in die afregulering van inflammatoriese sitokien vrystelling.

Thesis (PhD (Biomedical Sciences. Medical Physiology))--University of Stellenbosch, 2006. / Early life trauma leads to behavioural abnormalities later in life. These include mood and anxiety disorders such as depression and posttraumatic stress disorder (PTSD). This association may be due in part to the effects of trauma on brain development. Data from basic and clinical experiments suggest that alterations in the hippocampus may be fundamental to the development of these disorders. Here we used an animal model of early life trauma to investigate its effects on the behaviour and neurochemistry of the adult rat. Adolescent rats were subjected to time-dependent sensitization stress consisting of a triple stressor (2 hours restraint, 20 min swim stress and exposure to ether vapour) on post-natal day (PND) 28, a single re-stress on PND 35 (20 min swim stress), and a second re-stress in adulthood (PND 60, 20 min swim stress). The rationale was that the frequency of exposure to situational reminders contributes to the maintenance over time of fear-related behavioural disturbances. The effects of trauma on the hypothalamus-pituitary-adrenal-axis, hippocampal and plasma neurotrophin levels, behaviour and phosphoinositide-3 kinase (PI-3 kinase) signaling proteins were initially investigated. In addition, proteomic technologies such as protein arrays and 2D-SDS PAGE combined with liquid chromatography tandem mass spectrometry (LC-MS/MS) were employed to study trauma-induced effects on the hippocampus. Traumatized animals showed a decrease in glucocorticoid receptors in the dentate gyrus of the hippocampus and an increase in basal corticosterone levels 24 hours after adulthood re-stress. These effects were reversed by pretreatment with the serotonin selective reuptake inhibitor, escitalopram. A decrease in the neurotrophins, BDNF and NT-3 were evident 8 days, but not 24 hours after adulthood re-stress. This decrease was not accompanied by decreases in plasma neurotrophin or PI-3 kinase, protein kinase B (PKB), phosphatase and tensin homologue (PTEN), phospho-forkhead and phospho-AFX protein levels. In addition, traumatized animals showed increased rearing in both the elevated plus maze and open field. Proteomic analysis of trauma-induced changes in the hippocampus show increases in Ca2+ homeostasis / signaling proteins such as S-100B, phospho-JNK and calcineurin. Apoptotic initiator proteins, including caspase 9, -10 and -12 were increased and there was evidence of cytoskeletal protein dysregulation. Furthermore, cell cycle regulators and energy metabolism proteins were decreased. These effects indicate to a cellular state of cell cycle arrest after increased calcium influx to avoid apoptosis. Our data suggest that adolescent trauma with adulthood re-stress may affect numerous systems at different levels. These include neuroendocrine-, protein systems and behaviour, and confirmed that a systems biology approach is needed for a better understanding of the neurobiology of mental disorders.

Stress has been shown to exacerbate cell death and cognitive deficits after ischemic injury in rodents, however, little is known of the effects of stress on motor recovery. The objective of this present thesis is to examine the effects of chronic stress on skilled motor recovery after devascularization lesion in rats. It was found that pre-lesion stress induced the most behavioural impairments, while post-lesion stress exacerbated infarct volume. The effects of chronic multiple stress on skilled motor recovery after lesion was also examined. Chronic multiple stress did not modulate skilled motor recovery nor did it have any influence on infarct volume. Additionally, stress had effect on edema after devascularization lesion. The present thesis suggests that the time of exposure to chronic stress in respect to the ischemic lesion, in addition to the type of stress, will differentially affect recovery and compensation in rats. / xii, 122 leaves : ill. ; 29 cm.

Stress-related cognitive changes are still a matter of debate. In some particular neuropathological conditions such as focal ischemia, cognitive functions have been shown to be significantly impaired. These conditions, however, may be improved by some factors such as steroid hormones. The purpose of the current thesis was to assess the structural and functional effects of corticosterone-related experiences on the hippocampus before and after endothelin-1 (ET-1)-induced stroke. We found corticosterone-related experiences enhance the hippocampal recovery, and improve its function in both wet and dryland tasks after ET-1-induced focal stroke. Structural and functional effects of such experiences prior to the focal ischemia in the hippocampus, however, showed that stress, not corticosterone is a strong inhibitor for hippocampal recovery. / xii, 252 leaves : ill. ; 29 cm. --