Cardiac responses associated with "yoked-chair" shock avoidance in squirrel monkeys

An essay on the circulation as behavior

Most conceptual models of the organization of the cardiovascular system begin with the premise that the nervous system regulates the metabolic and nonmetabolic reflex adjustments of the circulation. These models assume that all the neurally mediated responses of the circulation are reactive, i.e., reflexes elicited by adequate stimuli. This target article suggests that the responses of the circulation are conditional in three senses. First, as Sherrington argued, reflexes are conditional in that they never operate in a vacuum but in a context together with other reflexes. Guided by functional utility, they interact rather than add. Second, as Pavlov argued, stimuli acquire meanings as a result of experience. This notion of stimulus effect plus the Sherringtonian notion of conditionality suggest that association is one of the ways stimuli eliciting cardiovascular reflexes acquire their meanings and thus their relative strengths. Finally, as Skinner and others have argued, operants are responses that act upon the environment to obtain consequences – that is, stimuli. As operants, cardiovascular responses fulfill a major biological need, functioning proactively. The cardiovascular response is an integral component of the animal's behavior regardless of whether it is an elicited reflex or the eliciting stimulus acquired its properties as a result of the genetic inheritance of the animal or through experience, or the cardiovascular response is emitted in anticipation of an environmental consequence. The main theses of this essay are: (1) behavior is an integrated set of responses and the circulation is one of the response systems comprising behavior; (2) behavior is, in part, determined by its functional significance within a context; (3) the contextual factors operative at the time of the behavior have a major role in determining which of the set of possible responses will determine the final act, that is, which behavior will be the effective response and which other behaviors will be concomitants.

Experimental studies of psychophysiological factors in sudden cardiac death

Earlier research in the field of sudden cardiac death is reviewed. Such studies have largely oriented towards the provocation of myocardial injury and asystole in normal animals. However, such investigations constitute an inadequate model to describe the clinical appearance of sudden death, where underlying coronary disease is often present and the precipitating event is usually ventricular fibrillation rather than asystole. This report describes a series of studies designed to investigate the processes underlying cardiac vulnerability and the influence upon it of various psychological stresses. It is concluded that the primary mediator of ventricular vulnerability is the sympathetic nervous system. The efferent vagus appears to exert some protective influence against arrhythmias due to adrenergic stimulation. An appropriate clinical strategy for the treatment of malignant arrhythmias would therefore involve attempts to decrease cardiac sympathetic drive whilst at the same time enhancing vagal tone. Treatments are described which aim to bring this situation about by the use of clonidine, morphine sulphate, l-tryptophan and tyrosine. The use of neurochemical agents in this context appears promising.

Hopelessness is associated with decreased heart rate variability during championship chess games

OBJECTIVE

Clinical observations suggest that negative affects such as helplessness/hopelessness (HE/HO) may induce autonomic duration; affects were assessed for every move after reconstruction of the games. In all games compiled, 18 situation of intense confidence/optimism and 20 of intense helplessness/hopelessness were observed.

RESULTS

Intense affects of HE/HO were associated with decreasing HF-HRV (Fisher exact test, p =.003), increasing "nervousness" (p =.0005), decreasing "optimism" (p =.0005), and decreasing "calmness" (p =.0005).

CONCLUSIONS

Investigation of championship chess game players with an ELO strength > or = 2300 in a natural field setting revealed increasing HE/HO being associated with reduced HF-HRV suggestive of vagal withdrawal. Thus, our data may help link negative mood states, autonomic nervous system disturbances, and cardiac events.

Clinical application of noradrenaline spillover methodology: delineation of regional human sympathetic nervous responses

The proportionality which in general exists between rates of sympathetic nerve firing and the overflow of noradrenaline into the venous drainage of an organ provides the experimental justification for the use of measurements of noradrenaline in plasma as a biochemical measure of sympathetic nervous function. Static measurements of noradrenaline plasma concentration have several limitations. One is the confounding influence of noradrenaline plasma clearance on plasma concentration. Other drawbacks include the distortion arising from antecubital venous sampling (this represents but one venous drainage, that of the forearm), and the inability to detect regional differentiation of sympathetic responses. Clinical regional noradrenaline spillover measurements, performed with infusions of radiolabelled noradrenaline and sampling from centrally placed catheters, and derived from regional isotope dilution, overcome these deficiencies. The strength of the methodology is that sympathetic nervous function may be studied in the internal organs not accessible to nerve recording with microneurography. Examples of the regionalization of human sympathetic responses disclosed include the preferential activation of the cardiac sympathetic outflow with mental stress, cigarette smoking, aerobic exercise, cardiac failure, coronary insufficiency, essential hypertension and in ventricular arrhythmias, and the preferential stimulation or inhibition of the renal sympathetic nerves with low salt diets and mental stress, and with exercise training, respectively. By application of the same principles, regional release of the sympathetic cotransmitters neuropeptide Y and adrenaline can be studied in humans. Cotransmitter release, however, is detected only with some difficulty. In restricted circumstances we find evidence of regional cotransmitter release to plasma, such as the release of neuropeptide Y from the heart at the very high rates of sympathetic nerve firing occurring with aerobic exercise, and cardiac adrenaline release also with exercise and after loading of the neuronal adrenaline pool by intravenous infusion of adrenaline.

Adverse effects on rat cardiac function ex vivo after repeated administration of the benzodiazepine partial inverse agonist, FG7142

1. The Langendorff preparation was used to investigate functional changes in rat heart one week after the last of a course of repeated injections of the benzodiazepine inverse agonist, FG7142 (20 mg kg-1 i.p; three times weekly for five weeks). 2. Under these conditions, FG7142 caused a statistically significant reduction in both cardiac basal tension and the inotropic effect of noradrenaline at doses giving 50 and 100% of the maximum response. 3. Basal heart rate, basal coronary perfusion pressure and the effects of noradrenaline ex vivo on these parameters were all unaffected by repeated administration of FG7142. 4. FG7142 had no intrinsic effects on cardiac function when administered in vitro. 5. We discuss mechanisms which could underlie the effects of FG7142 on cardiac tension ex vivo and consider the possibility that this action may be related to the anxiogenic or proconvulsant actions of this drug.

Review of autonomic dysfunction, cardiac arrhythmias, and epileptogenic activity

Similarities in autonomic dysfunction associated with arrhythmias and death in animal models for digitalis toxicity, myocardial infarction, psychotropic toxicity, and epileptogenic activity are reviewed. When intravenous (IV) pentylenetetrazol was given to anesthetized cats, autonomic dysfunction was associated with both interictal and ictal epileptogenic activity. The autonomic dysfunction was manifested by the fact that autonomic cardiac nerves did not always respond in a predictable manner to changes in blood pressure, the development of a marked increase in variability in mean autonomic cardiac nerve discharge, and the appearance of a very large increase in the variability of the discharge rate of parasympathetic nerves first and then secondly in sympathetic discharge. The altered autonomic cardiac nerve discharge was associated with interictal epileptogenic activity and arrhythmia, which may contribute to sudden unexplained death in patients with epilepsy. Since phenobarbital (20 mg/kg, IV 60 min prior to pentylenetetrazol) exhibited anticonvulsant, but not antiarrhythmic and neural depressant activity, phenobarbital does not appear to be the ideal agent to prevent the autonomic dysfunction associated with epileptogenic activity in this animal model.

Psychoactive agents, seizure production, and sudden death in epilepsy

Major tranquilizers as well as antidepressant agents have been associated with clinical seizures in patients administered these agents. The incidence of such seizures is generally low when these drugs are administered in therapeutic doses. However, administration of large doses of these agents has been associated with many cases of convulsion production. The effects that these drugs have on animal models of epilepsy have been examined. It appears that the phenothiazines act as convulsant agents at lower doses, whereas, at higher doses, they act as anticonvulsant drugs. Antidepressants, on the other hand, appear to exert an anticonvulsant effect at low doses and convulsant effects at high doses. The mechanism by which these agents alter the seizure threshold is not yet known. Clinically, drugs of lower seizure production potential should be substituted for those drugs with greater potential in treating epileptic patients for psychiatric ailments. The problem of sudden death in epileptic patients is one that must be confronted. Sudden death has most frequently been attributed to autonomic dysfunction and cardiac arrhythmia in these patients. The contribution of stress in sudden death production also must be taken into account. In addition, some psychoactive agents have been associated with sudden death as well as cardiac arrhythmia and seizure production. Thus, in light of the possible additivity of the factors involved in the production of sudden death, the administration of a psychoactive agent to an epileptic patient should be approached with caution. Those agents that do not alter cardiac rhythm or seizure threshold should be administered if a psychoactive agent is deemed necessary for the management of psychiatric illness in the epileptic patient.

Psychosocial predictors of sudden death: a review and critique

Research and selected case studies concerning psychosocial prediction of sudden death are evaluated under three categories: sudden cardiac, sudden infant and sudden traumatic death. The psychosocial predictors reviewed include novelty-pre-exposure, control-helplessness, restraint, Type A behavior, life change, bereavement, denial, social support and contact, voodoo, psychiatric illness, mother infant separation, submission-defeat, housing, handling and environmental enrichment. Four of these predictors, controllability-helplessness, pre-exposure-novelty, depressive affect and physical restraint are repeatedly cited in both human and animal studies and their importance is critically evaluated. Methodological and substantive recommendations for future research are made and a discussion of possible mechanisms is presented.

Hypertension: psychological aspects and diagnostic impact in a clinical trial

The widespread acceptance of evidence that even mildly raised blood pressure is associated with an increased risk of cardiovascular morbidity has led to the setting up of screening programmes and treatment trials for hypertension in several countries. In order to allay anxieties about adverse psychological consequences of their own treatment trial of mild to moderate hypertension in a population of 35-64 year old adults of both sexes, the Medical Research Council supported a special psychiatric study in the pilot phase of the trial. This case-controlled study demonstrated that there was no increase in psychiatric morbidity after diagnosis (labelling) of hypertension nor during one year on the trial. There was, in fact, a fall in such morbidity for trial entrants, related to a greater rate of improvement for those subjects who displayed morbidity and not to any alteration in the incidence of new morbidity. The improvement in psychological state was not associated with any of the antihypertensive drug regimes, nor was it an artefact of selection; rather it appeared to be a beneficial effect of regular clinic attendance. The results of this study are presented and discussed in the context of current research into the psychological aspects of hypertension.

Stress, predisposition and the onset of serious disease: implications about psychosomatic etiology

Based on the author's own work and a review of the literature, the hypothesis is made that potentially lethal disease does not usually occur in healthy animals or people but does so when covert or overt disease exists or when a predisposition for disease exists. The author supports this hypothesis in his assessment of the human literature on sudden death. Further support for the hypothesis is presented from 2 animal models being studied in his laboratory--stress-induced heart failure in the cardiomyopathic hamster and stress-induced sensitization of digitalis-toxic ventricular arrhythmias. This analysis suggests a different view from the classical one of what a psychosomatic disease might be.

Plasma Catecholamine and corticosterone as well as brain catecholamine changes during coping in rats exposed to stressful footshock

Rats received 60 minutes of footshock that was escapable (coping group) or inescapable (non-coping group). Plasma taken by jugular catheter showed that non-coping rats, compared with coping rats, had significantly higher peak norepinephrine (NE) and epinephrine (E) concentrations and significantly longer elevation of these catecholamines after footshock. Similarly, plasma corticosterone levels remained elevated significantly longer after footshock in non-coping rats. In brain, hypothalamic NE concentrations were lower in non-coping rats compared with coping controls, and this difference remained for at least 30 minutes after shock. A fall in hippocampal NE concentration was seen only in coping rats once they learned to terminate shock. Our data indicate that neurochemical changes can be separated into changes due to the aversive nature of the stimulus and the ability to cope with a stressor. The inability to cope augments plasma catecholamine increases in response to a stressor and prolongs their return to baseline values. The latter is also true for corticosterone levels. The decrease in hippocampal NE in coping and the decrease in hypothalamic NE in non-coping rats is not due to footshock by itself but to the ability of the rat to terminate this stressor. No strong correlation between central and peripheral catecholamine changes became apparent except a possible negative correlation between hypothalamic NE and peripheral NE and E levels.

Psychosocial and behavioral influences in the pathogenesis of acquired cardiovascular disease

When taken together, studies relating psychosocial and behavioral factors to cardiovascular disease phenomena provide justification for the conclusion that such factors are importantly involved. We would emphasize the need to study and evaluate the interaction of environmental and biological factors in both laboratory studies of pathogenesis as well as in clinical studies of management. Indeed, upon careful scrutiny, even the accepted "nonbehavioral" risk factors such as hypercholesterolemia, hypertension, cigarette smoking, obesity, and sedentary lifestyles are each composite manifestations rather than single pathogens whose identities are powerfully impregnanted and bolstered by varieties of behavioral and psychosocial underpinnings. In view of the awesome impact of contemporary cardiovascular disease, both in terms of its increasing socioeconomic importance and its biologic devastation, we can not long afford comprehensive public health programs without increased and improved attention to psychosocial and behavioral influences in the pathogenesis of acquired cardiovascular disease.

Human stress cardiomyopathy. Myocardial lesions in victims of homicidal assaults without internal injuries

In order to clarify the relationship between stress and sudden death, we reviewed homicidal assaults that occurred in Cuyahoga County, Ohio (metropolitan Cleveland), over the preceding 30 years. Specifically, attention was focused on the autopsy and investigative findings relating to victims who died as a direct result of physical assault without sustaining internal injuries. Fifteen such victims were identified, and 11 of them showed cardiac changes (myofibrillar degeneration) consistent with "stress cardiomyopathy," comparable to lesions described in stressed animal experiments. Age matched and cardiac disease matched control subjects showed little or no evidence of such changes. Two victims survived for a time in the hospital, suffered arrhythmias throughout the hospital course, and had the described cardiac lesions at autopsy. We interpret our data as being strongly supportive of the theory of catecholamine mediation of these myocardial changes in man and of the lethal potential of stress through its effect on the heart.

Neural and psychologic mechanisms and the problem of sudden cardiac death

Brain stimulation can provoke a variety of arrhythmias and lower the ventricular vulnerable threshold. In the animal with acute myocardial ischemia such stimuli suffice to provoke ventricular fibrillation. Vagal neural traffic or adrenal catecholamines are not the conduits for this brain-heart linkage. Accompanying increases in heart rate or blood pressure are not prerequisites for the changes in cardiac excitability. Increased sympathetic activity, whether induced by neural or neurohumoral action, predisposes the heart to ventricular fibrillation. Protection can be achieved with surgical and pharmacologic denervation or reflex reduction in sympathetic tone. With acute myocardial ischemia, augmented sympathetic activity accounts for the early surge of ectopic activity frequently precipitating ventricular fibrillation. Asymmetries in sympathetic neural discharge may also contribute to the genesis of serious arrhythmias. The vagus nerve, through its muscarinic action, exerts an indirect effect on cardiac vulnerability, the consequence of annulment of concomitant adrenergic influence, rather than of any direct cholinergic action on the ventricles. There exist anatomic, physiologic as well as molecular bases for such interactions. Available experimental evidence indicates that environmental stresses of diverse types can injure the heart, lower the threshold of cardiac vulnerability to ventricular fibrillation and, in the animal with coronary occlusion, provoke potentially malignant ventricular arrhythmias. Available evidence indicates that in man, as in the experimental animal, administration of catecholamines can induce ventricular arrhythmia, whereas vagal activity exerts an opposite effect. Furthermore, in certain subjects diverse stresses and various psychologic states provoke ventricular ectopic activity.