Adaptation of anterior pituitary hormones to chronic noise stress in male rats

We have studied the effects of acute and chronic noise on serum levels of pituitary hormones in male Wistar rats. Acute noise increased serum levels of corticosterone, prolactin, and luteinizing hormone and decreased serum GH. FSH was unaffected by this stressor. Chronic noise did not modify basal levels of any hormone studied, however responsiveness of some hormones to the same stimuli was altered. Reduced corticosterone, prolactin, and GH responses to noise was observed after previous chronic exposure to this stimuli. LH response followed the same pattern although it did not reach statistical significance. It might be concluded that adaptation to a repeated stress stimulus is not confined to the pituitary-adrenal axis, however, the degree of adaptation could vary between different hormones.     

Effect of stress on a cognitive autopoietic system

A cognitive autopoietic system is a dynamic, self-generating, organized and self-organizing thing which self-regulates (by internal rearrangement) with respect to an external medium. The present model of the effect of stress on a cognitive autopoietic (ESCA) system captures the notion of how a priori cognitive structures (categories), combined with external sensations, constitute the basis for the development of cognitive structures (CS) and their architecture. The ESCA model integrates the fact that the mind–environment relation has a twofold effect: on one hand, it enables self-regulation of mind (the matching of external sensations with CS), but on the other hand, it poses a potential perturbation on the same, which may result in the breakdown of the self-regulation of mind. The architecture of the CS developed on the basis of the ESCA model is consistent with the manifestations of the effect of stress on mind behavior at different levels. The ESCA model predicts that the faculty to concatenate synthetic propositions, which enables enhanced categorical conscious cognition (ECCC) on the basis of CS, is inhibited by stress, thus reducing cognition to a mechanized heuristic categorical conscious cognition (HCCC) and/or an unconscious cognition (UC) level. The ESCA model explains the casual relation between cognition of persistent social stress and self-esteem, sensory deprivation and self-cognition, a mechanized mind state and accumulated stress, and the effect of stress activated short-term emotions on cognition. Finally, it is speculated how persistently perceived uncertainty may induce stress.     

Effect of alcohol and stress on emotion and physiological arousal

Forty-eight male normal drinkers were given a beverage to drink containing either tonic plus alcohol or tonic alone, and then were asked to perform arithmetic problems under either stressful or nonstressful conditions. Self-report measures of positive and negative affect and actual measures of physiological arousal (pulse rate and finger pulse volume) were collected at four times: baseline, ascending limb of the blood concentration BAC curve. Results indicated that (a) the stress manipulation was effective in increasing negative and actual physiological arousal, (b) subjects were more accurate in estimating the amount of alcohol they consumed under stressful than under nonstressful conditions, (c) alcohol was not effective in reducing the negative affect or physiological arousal produced by the stress, and (d) alcohol was effective in reducing negative affect and increasing positive affect under nonstressful conditions. These results support the growing body of research that suggests that alcohol produces a complex pattern of responses, one of which may be the enhancement of mood under nonstressful conditions.This research was suported in part by Grant No. AA00100 from the National Institute on Alcohol Abuse and Alcoholism, and a grant from the Vanderbilt University Research Council.     

Effect of stress on hippocampal nociceptin expression in the rat

Nociceptin/orphanin FQ (N/OFQ) peptide and its receptor are not only ubiquitously expressed in mammalian brain and spinal cord but are also abundant in limbic structures, particularly in the hippocampus. The widespread distribution of N/OFQ reflects the broad spectrum of its biological actions such as nociception, food intake, spontaneous locomotor activity, and learning and memory processes. Since the hippocampus is involved in the control of adrenocortical activity, its role in stress-related phenomena is well characterized. In male Wistar rats, we first examined the effects of acute restraint stress (120?min) on the brain immunohistochemical localization of N/OFQ. The analysis carried out on sections obtained at the onset of stress revealed enhanced expression of N/OFQ in CA1, CA3, and the dentate gyrus as well as increased plasma corticosterone concentrations. Next, we examined whether endogenous glucocorticoid hormone plays a role in the modulation of hippocampal N/OFQ expression in response to stress. To this end, rats were injected with corticosterone (1?mg/kg) or subjected to restraint stress 1 week after adrenalectomy. Two hours after corticosterone administration, plasma glucocorticoid concentrations were comparable to those observed after restraint stress, while N/OFQ expression had significantly increased in all the hippocampal subfields examined. By contrast, in adrenalectomized rats, stress did not modify protein expression. These results confirm that stress can affect N/OFQ expression and that glucocorticoids may constitute hormonal mediators of this complex interplay.     

Physiological markers of traffic-related stress during active travel

Understanding perceptions of safety and comfort (PSC) while walking or cycling is essential to accommodating and encouraging active travel, but current measures of PSC, primarily surveys, suffer from validity and reliability issues. Physiological markers of stress like electrodermal activity and heart rate variability have been proposed as alternative, objective measures of PSC. This paper presents a literature summary and conceptual framework examining the use of physiological stress markers during walking and cycling. The existing studies of active traveller stress markers report inconsistent findings and account for limited controls. We propose a comprehensive conceptual framework to describe the array of dynamic stimuli experienced during active travel, with complex appraisals and multidimensional stress responses that feedback to travel behaviour and stimuli exposure, and culminate in a set of physiological outcomes triggered by activation of the autonomic nervous system – all moderated by numerous personal and trip-related factors. The key challenge of inferring traffic-related fear or discomfort from physiological markers measured on-road is potential confounding effects of: (1) non-traffic factors that induce or modify stress responses, (2) traffic factors that induce stress responses not associated with safety or comfort, and (3) personal and environmental factors that directly influence physiological measurements outside of a stress response. No physiological stress marker has yet been shown to be reliable for on-road active travellers, particularly not for inter-subject comparisons. Physiological markers have the potential to provide high-resolution, objective information about pedestrian and cyclist PSC, but further research, particularly controlled experiments, and more precise study framing are needed to ensure validity and address moderating and confounding factors.     

Physiological changes during physical and psychological stress

Changes in urine catecholamines, blood pressure and heart rate during two physical exercise test sessions (35% VO_2max and 50% VO_2max) and one psychological stress session which involved reading under delayed auditory feedback (DAF) were compared. Increases in both the haemodynamic parameters and in the excretion of catecholamines were found in response to all three tests. The changes in adrenaline (A) did not differentiate between the test situations. Noradrenaline (NA) levels were significantly larger for physical exercise conditions and graded according to the relative workload. The ratio ΔNA/ΔA was similar for both physical tests but statistically different for the DAF session. Significant and positive correlations between haemodynamic parameters and catecholamine excretion were found only for the DAF test. These correlations and the differences in catecholamine excretion suggest different bodily responses to physical and psychological stress. These findings may have practical implications in industrial field studies.