A new test for autonomic cardiovascular and neuroendocrine responses in diabetes mellitus: evidence for early vagal dysfunction

Maternal mood and neuroendocrine programming: effects of time of exposure and sex

Adverse exposures that influence growth in prenatal and early postnatal periods are considered to influence vulnerability to chronic diseases via their effects on the neuroendocrine system. In humans, the assessment of the underlying mechanisms has been restricted. The present study aimed to investigate the effects of adverse early-life exposures, specifically maternal mood, on hypothlamic-pituitary-adrenal (HPA) axis, sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) responses to an acute physiological stressor. In addition, we conducted a preliminary examination into whether these effects varied by time of exposure and sex. One hundred and thity-nine individuals (mean age 15.12 years) were recruited from the ALSPAC (Avon Longitudinal Study of Parents and Children) birth cohort. Participants underwent the CO(2) stress test and indices of the PNS, SNS and HPA axis were measured. Pre-existing data on demographic and psychosocial factors of the mothers during pregnancy (18 and 32 weeks) and postnatally (8 weeks and 8 months) were extracted, as were participants' clinical and demographic data at birth. Increases in both pre- and postnatal anxiety and depression were associated with greater SNS reactivity to the stressor and slower recovery, as well as blunted HPA axis responses. Programming effects on the SNS appeared to be restricted to male offspring only. No consistent relationships were evident for any of the measures of pre-stress function. We have found preliminary evidence that both pre- and postnatal maternal anxiety and depression have sustained programming effects on the SNS and HPA axis. Effects on the SNS were restricted to male offspring.

Physiological and anatomical bases for sex differences in pain and nausea as presenting symptoms of acute coronary syndromes

Acute coronary syndromes (ACS) are common in both men and women. Studies show that women have longer times before diagnosis and treatment in the Emergency Department and worse outcomes than men, which may be related to the differing symptom presentations of men and women. Men are more likely to have chest pain, whereas women are more likely to have dyspnea or nausea. However, women tend to be older and more likely to have diabetes mellitus, hypertension, and peripheral neuropathies. Men and women also exhibit differences in the neural receptors and pathways involved in pain and noxious-stimuli perception. Moreover, men and women may have subtle differences in the locations and sites of their atherosclerotic lesions, all of which may affect symptom presentation. The purposes of this review are to present: (1) the physiology of two common symptoms associated with ACS, ie, pain and nausea; (2) how these symptoms differ between men and women; and (3) how different comorbidities may affect the presentation of these symptoms.

An investigation into the effects of social evaluation on cardiovascular and endocrine responses to the CO2 stress test in humans

The present study examined whether social evaluation could heighten individuals' physiological responses to the CO(2) stress test, and the hypothalamic-pituitary-adrenal (HPA) response in particular. Twenty-five healthy volunteers undertook the CO(2) test under three conditions: (i) standard CO(2) protocol, (ii) standard CO(2) protocol conducted in front of a full-length mirror (mirror) and (iii) standard CO(2) protocol conducted in front of a video camera deemed to be transmitting live images of the procedure to investigators evaluating participant performance (video). Despite counterbalancing for task order, there were significant differences in anger and depression among the conditions. Repeated measures analysis of variances (ANOVAs), controlling for these mood indices, revealed that salivary cortisol, heart rate and systolic blood pressure responses to the CO(2) test were not affected by social evaluation (i.e. mirror or video). Although the data provide no evidence that endocrine and cardiovascular responses to the CO(2) test are affected by social evaluation, the potency of the social evaluation manipulation in this study is in question. Thus, further research is warranted which includes evidence of, or instructions suggesting negative social evaluation.

Carbon dioxide-induced emotion and respiratory symptoms in healthy volunteers

A number of evidences have established that panic and respiration are closely related. Clinical studies indicated that respiratory sensations constitute a discrete cluster of panic symptoms and play a major role in the pathophysiology of panic. The aim of the present study was to explore the phenomenology of an experimental model of panic in healthy volunteers based on the hypothesis that: (1) we can isolate discrete clusters of panic symptoms, (2) respiratory symptoms represent a distinct cluster of panic symptoms, and (3) respiratory symptoms are the best predictor of the subjective feeling of panic, as defined in the DSM IV criteria.Sixty-four healthy volunteers received a double inhalation of four mixtures containing 0, 9, 17.5 and 35% CO(2,) respectively, in a double-blind, cross-over, random design. An electronic visual analog scale and the Panic Symptom List (PSL) were used to assess subjective 'fear/discomfort' and panic symptoms, respectively. Statistical analyses consisted of Spearman's correlations, a principal component factor analysis of the 13 PSL symptoms, and linear regressions analyses.The factor analysis extracted three clusters of panic symptoms: respiratory, cognitive, and neurovegetative (r(2)=0.65). Respiratory symptoms were highly related to subjective feeling of fear/discomfort specifically in the CO(2)-enriched condition. Moreover, the respiratory component was the most important predictor of the subjective feeling of 'fear/discomfort' (beta=0.54).The discrete clusters of symptoms observed in this study were similar to those elicited in panic attacks naturally occurring in patients affected by panic disorder. Consistent with the idea that respiration plays a crucial role in the pathophysiology of panic, we found that respiratory symptoms were the best predictors the subjective state defined in the DSM IV criteria for panic.

Corticosteroids and the cardiovascular response to stress: a pilot study of the 35% CO2 challenge in Addison's disease

OBJECTIVE

Glucocorticoids play an essential role in the neuroendocrine response to stress, influencing both the hypothalamic-pituitary-adrenal (HPA) axis and the sympatho-adrenomedullary (SAM) axis at several levels. In this pilot study, a clinical model of primary adrenocortical failure (Addison's disease, AD) has been used to evaluate the role of circulating glucocorticoids in both the autonomic and psychological response to stress.

DESIGN AND SUBJECTS

Five subjects with known AD underwent a randomized, double-blind, placebo-controlled investigation in which they received fixed glucocorticoid plus mineralocorticoid hormone replacement or placebo for 48 h prior to a 35% CO2 challenge.

MEASUREMENT

Psychological responses immediately before and after CO2 exposure were assessed by questionnaire. Systolic blood pressure (SBP) and heart rate were measured automatically at 1-min intervals for 5 min before and 5 min after the CO2 exposure.

RESULTS

While on hormone replacement, all subjects had an identical response to CO2 to that recorded in normal volunteers (initial bradycardia, an increase in blood pressure and subjective feelings of anxiety). On no replacement, however, the bradycardia and anxiety responses were not significantly altered, but the pressor response was markedly attenuated (+15.6 +/- 5 mmHg on replacement compared with +4.2 +/- 3.3 mmHg off replacement; P = 0.043).

CONCLUSIONS

These data provide further evidence that the CO2-induced bradycardia is a direct--presumably parasympathetic--response to CO2 independent of the pressor effect, and that the pressor response itself is dependent on the presence of the circulating corticosteroid.

The four-dimensional stress test: psychological, sympathetic-adrenal-medullary, parasympathetic and hypothalamic-pituitary-adrenal responses following inhalation of 35% CO2

BACKGROUND

Hypercapnia is a threat to homeostasis and results in neuroendocrine, autonomic and anxiogenic responses. The inhalation of carbon dioxide (CO2) may, therefore, provide a good paradigm for exploring the pathways by which stress can lead to increased susceptibility to ill-health through physiological and psychological stress reactivity. The current study was designed, therefore, to assess the psychological and physiological responses to the inhalation of CO2.

METHODS

Healthy participants (N = 24) inhaled a single vital capacity breath of a mixture of CO2 (35%) and oxygen (65%). Blood pressure and heart rate were recorded for 5 min before and after the test and blood and saliva samples were taken immediately before and 2, 10, 20 and 30 min post-inhalation for the measurement of noradrenaline, salivary and serum cortisol and salivary alpha amylase. In addition, psychosomatic symptoms were recorded immediately before and after the test. The same protocol was repeated 4-6 weeks later at the same time of day.

RESULTS

A single inhalation of CO2 increased blood pressure, noradrenaline, salivary alpha amylase and psychosomatic symptoms, but decreased heart rate at both testing sessions. Analyses of salivary cortisol data revealed that 70% of the sample could be reliably classified as either responders (i.e. demonstrated a post-CO2 cortisol increase) or non-responders (i.e. responded with a decrease or no change in cortisol following CO2) at both test sessions. Responders also perceived the test to be more aversive than non-responders.

CONCLUSIONS

Inhalation of 35% CO2 reliably stimulated the key mechanisms involved in the human stress response. The inter-individual differences in the reactivity of the hypothalamic-pituitary-adrenal axis were also related to differences in the perception of the test.

Neuroendocrine and behavioural responses to CO2 inhalation in central versus peripheral autonomic failure

Multiple system atrophy (MSA) and pure autonomic failure (PAF) represent distinct pathological models of autonomic failure in humans. We have investigated the neuroendocrine, behavioural and autonomic cardiovascular responses to the 35% CO2 challenge. Nine patients with MSA, nine with PAF and five control subjects received a single breath of 35% CO2. Peripheral autonomic failure (i.e., PAF) was associated with significantly lower resting noradrenaline levels. All groups demonstrated a significant pressor response to CO2. In controls, the mean pressor response was +60.2 mm Hg, which was significantly smaller in both the PAF (+26.8 mm Hg, P < 0.01) and MSA (+18.3 mm Hg, P < 0.001) patients. In addition, the onset of the response was significantly delayed in both MSA (140.2 s) and PAF (154.2 s) patients compared with controls (32.4 s, P = 0.04 and P = 0.03, respectively). Noradrenaline levels increased only in controls. Central autonomic impairment (i.e., MSA) was associated with lower cortisol release (+8.8% in MSA compared with +35.2% in control and +23.7% in PAF) and fewer somatic symptoms of emotional arousal. Both MSA and PAF exhibit marked sympathetic autonomic impairment, however, residual (albeit differing) sympathetic pathways can still maintain a partial cardiovascular response. A central autonomic lesion, however, also appears to be associated with blunting of both cortisol and emotional responses to this stress paradigm.