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J M Koolhaas

Publications and source records attributed to J M Koolhaas.

At least 109 records · Page 6Linked to original sources
PubMed1991

Central amygdala lesions affect behavioral and autonomic balance during stress in rats.

The effects of a bilateral electrolytical lesion of the CEA on the behavioral and sympathetically induced cardiac response in the shock-probe/defensive-burying test have been analyzed in male Wistar rats. Lesions in the CEA failed to affect defensive burying and accompanying tachycardiac response as compared to sham-lesioned controls during the presentation of the electrified shock probe (unconditioned test). However, CEA lesioning attenuated the bradycardiac response and the immobility behavior during the late part of the test. Retention of this behavior one day after the exposure to the probe (conditioned test) was attenuated by the lesion. However, when the lesion was placed after the unconditioned test situation, retention of the burying was not affected, but the animals failed to show immobility behavior. These results, in agreement with former studies, suggest that the CEA is involved particularly in the organization and/or expression of the passive component of the behavior and the parasympathetic outflow during stress. The active component, i.e., burying behavior, and the accompanying tachycardiac response remains unaffected unless the acquisition of the stress response took place with damaged CEA.

Amygdala↗
PubMed1991

Endotoxin treatment of pregnant rats affects sexual behavior of the male offspring.

The offspring of endotoxin-infused pregnant rats (0.2 micrograms endotoxin, 53.3 min, day 18 of pregnancy) did not exhibit different behavior in the Hebb-Williams-type maze test, but the males showed aberrations in the sexual behavior test. Because endotoxin did not cross the placental barrier, it was concluded that the effect reflects abnormal brain development, caused by endotoxin-induced placental malfunction, notably impaired oxygen transport.

Animals↗
PubMed1991

Effects of neonatal administration of vasopressin on cardiac and behavioral responses to emotional stress in adult male rats.

Arginine-8-vasopressin (AVP) was administered subcutaneously on postnatal days 3-7 in a high (10 micrograms/100 g b.wt.) or a low dose (1 microgram/100 g b.wt.) to male Wistar rats. Control pups were untreated or saline injected. Behavioral observations in a complex maze after maturation indicated that neonatal administration of AVP increases exploratory behavior in this novel environment in a dose-dependent way. Cardiac monitoring during the conditioned emotional stress of fear of inescapable electric footshock showed that only the high dose of AVP attenuates the bradycardiac stress response. The analysis of cardiac responses also suggested an adult hyposensitivity to AVP in rats treated neonatally with AVP. In addition, the low dose of neonatal AVP was impairing the retention of a passive avoidance behavior. The data indicate that the neonatal administration of AVP exerts long-term effects upon the behavioral adaptation to novelty and memory processes related to emotional stress. That neonatal AVP is less effective in influencing adult vagally mediated cardiac stress responses suggests differences in the developmental sensitivity ("critical periods") of the central vasopressinergic systems involved in the regulation of behavior and autonomic functioning.

Animals↗
PubMed1991

Stress and differential alterations in immune system functions: conclusions from social stress studies in animals.

Psychosocial factors are implicated in the development, in the course of, and in the recovery from disease. The immune system may be a mediator of the disease. Studies with animal models using social interactions in rodents suggest that short- and long-term social stress does not invariably suppress immune system functions. The magnitude and direction of changes in diverse compartments of the immune system are highly correlated to the social position of the animal. Furthermore, genetic, developmental, and adult experience may predetermine the animal's coping strategy both in terms of behaviour and neuroendocrinology, and hence in immunology as well. It is argued that disease processes should be considered as a function of baseline immunological state.

Adaptation, Psychological↗
PubMed1990

Differential effect of lesioning of the central amygdala on the bradycardiac and behavioral response of the rat in relation to conditioned social and solitary stress.

The central nucleus of the amygdala (CEA) is considered to be involved in stress-dependent regulation of autonomic functions. In the present study the effects of a bilateral electrolytic lesion of the CEA on the cardiac response and on the duration of immobility behavior in two conditioned stress situations have been analysed in Wistar rats. Fear of a previously received electric footshock elicited in almost all animals a profound early bradycardia and a marked immobility behavior in comparison to non-stressed freely moving controls. Lesioning of the CEA completely abolished the bradycardiac response. Immobility behavior was slightly diminished. The conditioned fear of a dominant rat following social defeat was accompanied by a bradycardiac response in about 50% of the rats. This bradycardiac response was not accompanied by significant immobility behavior. The rest of the defeated rats--i.e. cardiac 'non-responders'--displayed an early increase in immobility behavior. The CEA lesion abolished again the bradycardiac response, but the immobility behavior remained unchanged. In the cardiac 'non-responders' CEA lesion failed to affect immobility behavior, and the heart rate also remained unchanged. These results suggest that the CEA is involved in the organization of conditioned parasympathetic responses independent of the nature of stress. In contrast, the role of this nucleus in the organization of the immobility behavior seems to depend on the nature of stress and other, probably individual characteristics of the rats' behavior.

Amygdala↗
PubMed1990

The central amygdala is involved in the conditioned but not in the meal-induced cephalic insulin response in the rat.

The central nucleus of the amygdala (CEA) is considered to be involved in the regulation of autonomic correlates of fear. Its involvement in the control of autonomic functions other than elicited by fear has received little attention. The effects of a bilateral electrolytical lesion of the CEA on feeding related insulin responses have been analyzed in male Wistar rats. The cephalic phase of the insulin response is a vagally mediated elevation of plasma insulin concentration during the first minute after meal onset, before any increase in plasma glucose can be noticed. This response can also be entrained to environmental stimuli. The insulin response elicited under these conditions is due to conditioning. CEA lesioning abolished the conditioned insulin response but not the early insulin elevation during the presentation of food. The CEA lesion failed to affect plasma glucose levels in both the meal-induced and conditioned test situations. To our knowledge this is the first study that shows that the CEA is also involved in the organization of conditioned metabolic endocrine responses.

Amygdala↗
PubMed1990

Anxiolytics and stress-induced behavioural and cardiac responses: a study of diazepam and ipsapirone (TVX Q 7821).

The present study has been designed to investigate the effects of the 5-HT1A receptor agonist, ipsapirone (TVX Q 7821), a representative of a novel class of anxiolytics, and the classical benzodiazepine anxiolytic, diazepam, on cardiac and behavioural responses in an emotional stress situation. The emotional stress of fear of punishment, induced by training male Wistar rats in an inhibitory avoidance situation, was followed by a bradycardiac response relative to similarly trained, but non-punished, freely moving rats. The behavioural response of stressed rats was immobility in the dark compartment in which an electric footshock (0.6 mA a.c. for 3 s) had been administered as punishment a day earlier. Diazepam administered i.p. in doses of 2.5 mg/kg and 7.5 mg/kg caused a decrease in the interbeat interval (IBI) in shocked and non-shocked rats whereas ipsapirone administered i.p. in doses of 2.5 and 12.5 mg/kg decreased the IBI in shocked rats only. Ipsapirone diminished the duration of immobility in both shocked and non-shocked animals whereas diazepam decreased immobility in shocked rats only. These results suggest a differential effect of the two anxiolytics on the behavioural and cardiac responses to an emotional stress situation. It is suggested that ipsapirone has an anxiolytic-like effect and 'anti-stress' action that is clearly reflected in the cardiac physiology in an anxiety-inducing situation.

Animals↗
PubMed1990

Behavioral and neuroendocrine response to psychosocial stress in male rats: the effects of the 5-HT 1A agonist ipsapirone.

The effect of the 5-HT 1A agonist ipsapirone on the behavior, plasma catecholamine, and corticosterone levels was studied in male Wistar rats during the psychosocial stress of confrontation with a confined dominant opponent 24 hr after defeat. The effect of the drug was also studied during a predefeat confrontation with the confined (would-be dominant) rat. Blood samples were withdrawn via a permanent heart catheter. The drug (5 mg/kg, ip) or vehicle was given 30 min before transportation to the experimental room. Ipsapirone had no major effects on the plasma hormone concentrations and had no influence upon the behavioral response to the confined rat. At the postdefeat test ipsapirone led to a significant increase of immobility, whereas both rearing and time spent sniffing the cage were diminished. Postdefeat psychosocial stress resulted in an increase of the hormone, particularly catecholamine levels. These responses were further elevated by the drug. The presence of high corticosterone levels in the home cage after postdefeat ipsapirone treatment leads to the hypothesis that postsynaptic 5-HT 1A receptor hypersensitivity develops after the social stress of defeat.

Agonistic Behavior↗
PubMed1990

Behavioural physiology of serotonergic and steroid-like anxiolytics as antistress drugs.

Pharmacological studies are useful tools to understand the neurobiological basis of behavioural and physiological stress mechanisms. Ipsapirone, a 5-HT1A autoreceptor agonist is a representative of novel anxiolytics without the disadvantages of benzodiazepam-like drugs. Behavioural, physiological and neuroendocrine studies in the rat are reviewed which were aimed to investigate the antistress properties of ipsapirone during reexposure to various conditioned emotional stress situations. It is demonstrated that in certain situations, probably due to a stress-induced sensitisation of postsynaptic 5-HT1A receptors, anxiolytic doses of the drug may show prostress (anxiogenic) behavioural and neuroendocrine effects. Furthermore, brain corticosteroid receptors, probably interacting with the serotonergic transmission, are involved in anxiogenic/prostress processes. In this respect antagonists of the brain mineralocorticoid-like (type I) receptors may be important antistress drugs of the future.

Animals↗
PubMed1989

Behavioral and cardiac responses to a sudden change in environmental stimuli: effect of forced shift in food intake.

In order to test the possibility of a change in stress susceptibility induced by a forced change in activity rhythm, during control weeks food availability was restricted to the dark period only (fa-D) and to the light period only during the test week (fa-L). Stress susceptibility was measured on the basis of the decrease in heart rate (bradycardia) and an increase in freezing behavior in response to a sudden reduction in background noise. A significant increase in bradycardia both in magnitude and duration was observed during fa-L conditions as compared to the control fa-D condition. Also the duration of freezing behavior was increased during the fa-L condition. These results support the hypothesis that forced changes in circadian activities affect stress susceptibility. The significance of this finding for the incidence of stress pathologies is discussed.

Activity Cycles↗
PubMed1988

A coherent pattern among social behavior, blood pressure, corticosterone and catecholamine measures in individual male rats.

Behavioral and physiological responses of 18 chronically cannulated male TMD-S3 rats were assessed during various social interactions with conspecifics, both with and without the possibility for physical contact (social vs. psychosocial stimulation). Response magnitudes (behavior, blood pressure, plasma catecholamines) depend upon both the social environmental requirements (offense, defense, psychosocial stimulus following defense) and individual characteristics. The more competitive males generally reacted with higher responses of blood pressure and catecholamines than more passive rats. In addition, these competitive males had higher baseline levels of noradrenaline. The present experiment shows that male rats differ in the individual sympathetic tone and reactivity in relation to their behavior in a social environment.

Animals↗
PubMed1988

The propensity for schedule-induced polydipsia is related to differences in conditioned avoidance behaviour and in defense reactions in a defeat test.

In line with previous research showing that animals predisposed to develop schedule-induced polydipsia when submitted to intermittent distribution of food show differential behavioural and neurochemical characteristics, the present experiments investigated the nature of defense reactions to aversive situations in rats that do or do not develop schedule-induced polydipsia. It was found that rats that engage in excessive drinking during intermittent feeding display more rapid active avoidance learning in a 2-way shuttle-box and show less freezing when confronted with an aggressive resident male in a defeat test than those that do not develop schedule-induced polydipsia. These results are consistent with the hypothesis that individual differences in the propensity to exhibit oral consummatory activities in conditions of mild stress are related to the ability to shift behavioural programmes in response to external stimulation.

Aggression↗
PubMed1988

Aggression and adaptation to the light-dark cycle: role of intrinsic and extrinsic control.

In wild house mice, the hypothesis that in the organization of behavior the relative contribution of intrinsic factors is more important in aggressive males, while that of extrinsic factors is more important in nonaggressive individuals was confirmed using the circadian rhythmicity of activity. The faster rate of reentrainment and the suppression of activity during a subjective night and during adaptation to the new LD cycle in the nonaggressive males indicate that their circadian rhythmicity of activity is to a large extent determined by the Zeitgeber, an extrinsic factor. The slower reentrainment rate, the lack of response to a subjective night and the normal activity level seen during reentrainment in the aggressive mice suggest strong control by the pacemaker, an intrinsic factor. Tau differences between the aggressive and nonaggressive mice provide some evidence that the pacemaker of nonaggressive males is fairly labile and is easily influenced by external factors, whereas the pacemaker of aggressive animals is rather stable.

Acclimatization↗
PubMed1987

Medial amygdala lesions in male rats reduce aggressive behavior: interference with experience.

The medial nucleus of the amygdala (am) has been implicated in a variety of social behaviors. The present experiment will test the hypothesis that the effect of am lesions on intermale aggressive behavior is due to interference with social learning processes. Small electrolytic lesions of the am had no significant effect in socially naive male rats. A marked reduction of aggressive behavior was observed in animals that were lesioned after experience with four aggressive interactions. Repeated testing suggests that these lesioned animals are unable to adapt their aggressive behavior on the basis of previous victory experience. The results are discussed in terms of social learning and memory processes in relation to the afferent and efferent connections of the am.

Aggression↗
PubMed1986

Social stress induced pressure breathing and consequent blood pressure oscillation.

A large amplitude blood pressure oscillation occurs during social defeat in a territorial fight between male rats, and during the application of a psychosocial stimulus associated with this defeat. Synchronous recording of blood pressure, intrathoracic pressure and diaphragm activity shows that the blood pressure oscillation coincides with a typical respiratory pattern called 'pressure breathing', during which a strongly positive intrathoracic pressure with expiration can be observed. The expiration was relatively prolonged and accompanied by a rise in blood pressure and a decrease in heart frequency. These alterations outlast the applied social respectively psychosocial stimulations. The results of this study suggest that behaviorally induced pressure breathing is of importance to attentional processes during social stimulation. The contribution to the development of hypertension is discussed.

Aggression↗
PubMed1985

The cortico-medial amygdala in the central nervous system organization of agonistic behavior.

Previous studies suggested that the corticomedial amygdala is involved in agonistic behavior by affecting social learning processes. The present study shows that deficits in the avoidance of a dominant male rat conditioned by defeat were only observed after bilateral lesions restricted to the medial amygdala and not after destroying the cortical portion. These results are related to the specific afferent and efferent connections of the medial amygdala with other brain structures involved in the control of agonistic behavior. Within the corticomedial amygdala the medial amygdaloid nucleus was found to be a major recipient of afferents from the accessory olfactory bulb, but also a source of efferent projections to the ventrolateral aspects of the ventromedial hypothalamic nucleus and the ventral premammillary nucleus. A strong reciprocity exists in the connections between ventromedial hypothalamus and premammillary nuclei with the medial amygdala. The connections between the ventromedial hypothalamic and dorsal premammillary nucleus with the midbrain periaqueductal grey suggest an important role for the periaqueductal gray in the descending output in the anatomical substrate for agonistic behavior.

Aggression↗
PubMed1985

Acute and conditioned blood pressure changes in relation to social and psychosocial stimuli in rats.

The naturally occurring tendency to compete with other rats for territorial space has been used to study individual behavior characteristics and blood pressure reactivity to social stimuli in adult male TMD-S3 rats. The competitive characteristics of the individual rats are consistent in two different social situations (victory and defeat). Blood pressure responses during the victory of home territory rats over intruders was more pronounced in the more competitive animals. In addition to defeat by a trained fighter rat, the experimentals were also psychosocially stimulated by the fighter while it was confined in a small wire mesh cage. The blood pressure response to this event was enhanced by the prior defeat of the test animal by the one now confined to the small cage. This response was more pronounced in competitive rats. This approach has potential as an animal model of etiological processes in socially induced hypertension.

Aggression↗