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At least 397 records · Page 22Linked to original sources
PubMed1990

[Central nervous system control for maximal alertness in danger].

A survey is given of the various "emotional" neuro-hormonal response patterns, organised at the limbic-hypothalamic level of the brain and specialised in dealing with the multiplicity of challenging environmental stimuli that all organisms, including man, have to cope with. Typically they involve all three efferent links of body control--i e, the somatomotor system, governing behaviour, the visceromotor (autonomic nervous) system, adjusting inner organs to suit behavioural response, and the hormonal system, adjusting metabolism, nutritional depots and water-electrolyte balance, again to provide optimal support for behavioural response. Special emphasis is put on the visceromotor and hormonal adjustment of the cardiovascular system, affecting blood pressure, cardiac output and blood flow distribution, particularly in stressful situations, where such responses as the "defence reaction", the "defeat reaction" and the "playing-dead reaction", are virtually the same in all species. It is discussed how in humans such age-old response patterns are also elicited by a variety of artificial or symbolic challenges typical of hectic modern society; and how, if provoked too often or too long, they may constitute crucial determinants of such serious cardiovascular disorders as hypertension and atherosclerosis. In this context, the defence and defeat reactions would seem to be particularly relevant, and the importance is stressed of animal studies of such complex systemic adjustments, for the understanding and hence future prevention of certain particularly serious disorders common in modern society.

Animals↗
PubMedDate not supplied

[The behavioral characteristics of rats induced by partial degeneration of the hippocampal cholinergic neurons].

The effects of intraventricular administration of ethylcholine aziridinium ion (AF64A) were studied in male Wistar rats. Bilateral injections of AF64A (3 nm/3 mcl) reduced the reactions to biological alarm signal and produced a decrease in the open-field activity 3 weeks after this lesion. The lesioned rats also displayed deficit in retention of a passive avoidance task.

Animals↗
PubMed2005

Functional interaction between nucleus tractus solitarius NK1 and 5-HT3 receptors in the inhibition of baroreflex in rats.

OBJECTIVE: Previous data showed that in the nucleus tractus solitarius (NTS), 5-HT(3) receptors are critically involved in the inhibition of cardiac baroreceptor reflex response occurring during the defense reaction. Since stimulation of NTS NK(1) receptors has been found to inhibit the baroreflex bradycardia, we examined in this study whether this reflex response is inhibited during the defense reaction via an interaction between NK(1) and 5-HT(3) receptors. METHODS: For this purpose, we analyzed in urethane-anaesthetized rats the effects of intra-NTS GR205171, a selective NK(1) receptor antagonist, on the baroreflex bradycardia inhibition observed either during the defense reaction triggered by electrical stimulation of the dorsal periaqueductal grey matter (dPAG) or after NTS 5-HT(3) receptor activation. RESULTS: Intra-NTS GR205171, reversed, in dose-dependent manner, the inhibitory effect of dPAG stimulation on baroreflex bradycardia. This reversion was of 49% when both sinus carotid and aortic baroreceptors were stimulated by phenylephrine, and of 84% when aortic depressor nerve was stimulated. Similarly, intra-NTS GR205171 reversed partially or almost totally the inhibitory effect of local microinjections of phenylbiguanide, a 5-HT(3) receptor agonist, on baroreflex bradycardia induced either by phenylephrine administration or aortic nerve stimulation, respectively. CONCLUSION: These results strongly suggest that NK(1) receptors contribute downstream to the 5-HT(3) receptor-mediated inhibition of the aortic but not carotid cardiac baroreflex response occurring during the defense reaction, therefore implying that baroreceptor afferent inputs may be differentially modulated depending on their origin. This differentiation may be useful for a better understanding of baroreflex dysfunction in disease-induced conditions.

Animals↗
PubMed2000

Dendritic cell activation by danger and antigen-specific T-cell signalling.

Recent transplantation, animal and in vitro studies suggest a dependence of some immune reactions on tissue damage. Although many factors involved in enhancing immune responses through tissue damage have yet to be identified, recent data suggests that one of the targets of these cellular stress factors is the bone marrow derived dendritic cell (DC). DC are potent initiators of primary immune responses and hold the key to immune reactions through their ability to sense changes in their local environment and respond appropriately to induce T-cell immunity, or possibly tolerance. In the lymph node, DC are also influenced by antigen-specific signalling from T cells, which may extend and amplify DC antigen presenting capabilities, especially for the stimulation of cytotoxic responses. It now appears that both tissue damage and antigen-specific T-cell derived signals act together on the DC to promote the appropriate immune reaction to antigen. Thus DC antigen presenting behaviour is not only dependent on the context of antigen encounter in the periphery, but also on the availability of antigen-specific T cells and their T-cell receptor specificities.

Dendritic Cells↗
PubMedDate not supplied

[Effect of haloperidol on development of amnesia in aggressive and submissive mice].

The effect of haloperidol on the passive avoidance habit retrieval upon amnesia was studied in C57BL/6J mice with aggressive and submissive behavioral stereotypes formed under agonist confrontation conditions. In the control (untreated) group, the efficacy of the amnesic action of detention in the dangerous compartment on the learning day was reduced for the aggressive stereotype as compared to the submissive one. In the aggressive mice, the administration of haloperidol (0.5 mg/kg) one hour before learning deteriorated the conditional reaction retrieval between 2nd and 13th days of test. In the submissive mice, the administration of haloperidol produced a prolonged antiamnesic effect. Thus, the effect of haloperidol on the violated memory trace reproduction depends on the individual behavioral state.

Aggression↗
PubMedDate not supplied

[The dynamics of the defensive and feeding conditioned reactions of the edible snail during long-term sensitization].

During the long-term sensitization in a snail there occurs an enhancement of a defensive reaction and a significant decrease of food intake. Defensive conditioning is facilitated and feeding conditioning deteriorated. The results give evidence that a formation of the state of the long-term sensitization is accompanied by a generation of a dominant defense focus.

Animals↗
PubMedDate not supplied

[Is pain-induced aggression actually a defensive form of that behavior?].

25-minute testing of aggressive reactions in constant pairs of male rats, elicited by electric shocks shows that electro-pain aggression of rats is not a homogeneous process, but consists of three successive stages: orienting-investigatory activity and attempts to get out of the chamber; defensive aggression; establishing of relations of domination-subordination and attacking aggression. Division in attacking rats and defending themselves, occurs mainly at final stages of testing (15-25 min); in some pairs reactions of attacking aggression are accomplished by the same rats. It is supposed that rats pain aggression is not a purely defensive form of this behaviour, but a modification of intermale aggression caused by specificity of laboratory conditions.

Aggression↗
PubMed1983

The opioid/nonopioid nature of stress-induced analgesia and learned helplessness.

Exposure to a variety of stressors produces a subsequent analgesic reaction. This stress-induced analgesia (SIA) is sometimes opioid in nature (reversed by opiate antagonists and cross-tolerant with morphine) and sometimes nonopioid. Both 30 min of intermittent footshock and 60-80 five-sec tailshocks have been shown to produce opioid SIA, whereas 3 min of continuous footshock and 5-40 tailshocks produce nonopioid SIA. We report that both of the opioid SIA procedures produce a learned helplessness effect as assessed by shuttlebox escape acquisition and an analgesia that is reinstatable 24 hr. later. The nonopioid procedures produce neither a learned helplessness effect nor a reinstatable analgesia. It is argued that these data implicate the learning of uncontrollability in the activation of opioid systems.

Analgesia↗
PubMed1985

Predictors of dominance in male Betta splendens.

The formation of dominance/subordinancy relations in pairs of male Siamese fighting fish was examined in six experiments. Dominant animals typically were those fish that built the largest nests and that attacked an image of a live, displaying male most intensely prior to combat. However, pretest performance on an operant task and reaction to an animal's own mirror image were not useful predictors of subsequent dominance. These findings are consistent with the suggestion that domesticated Bettas have a territorial social strategy that includes both nest-building and fighting behaviors.

Aggression↗
PubMed1983

Neuroeffector mechanisms of the defense reaction in the rat.

Electrical stimulation of the dorsal periaqueductal gray matter (DPAG) eliciting flight behavior in awake rats caused an increase in arterial blood pressure (BP), heart rate (HR) and respiration in rats anesthetized with urethane. The hypertension was markedly reduced by 5 mg/kg of intravenously injected hexamethonium or bretylium, virtually abolished by 5 mg/kg of phentolamine and partially antagonized by 0.1 mg/kg of the alpha 1-adrenoceptor blocker, prazosin. The tachycardia induced by DPAG stimulation was partially antagonized by hexamethonium or bretylium and abolished by propranolol (5 mg/kg, IV) or practolol (5 mg/kg, IV), but not affected by N-butylscopolamine (10 mg/kg, IV). Phentolamine increased basal HR and abolished the tachycardic response caused by either brain stimulation or intravenous noradrenaline. Prazosin moderately decreased the response to noradrenaline, but did not affect basal HR or the tachycardia induced by brain stimulation. The increase in respiratory amplitude occurring during brain stimulation was abolished by phentolamine as well as by prazosin, while the increase in respiratory rate was moderately reduced by phentolamine and propranolol. These results demonstrate that the cardiovascular component of the defense reaction of the rat is almost entirely due to a sharp increase in sympathetic tone. They also suggest that the hyperventilation induced by aversive brain stimulation is modulated by central and peripheral adrenergic mechanisms.

Animals↗
PubMed1982

Systems of reinforcement and drug dependence.

Experimental data are presented in support of the hypothesis on the role of positive and negative reinforcing systems in the mechanism of drug dependence. Drugs with abuse potential (DAP) may change the manner of response to negative emotional stimuli, activate positive emotional reactions in animals, and possess primary reinforcing properties. Reward and punishment systems respond sensitively to withdrawal from DAP or antagonist administration. Catecholaminergic and peptidergic processes are of importance in the mechanisms of the emotionally positive action of DAP.

Amphetamines↗
PubMed1996

Forced swimming behavior is not related to the corticosterone levels achieved in the test: a study with four inbred rat strains.

The behavior of four inbred strains of rats in the holeboard and the forced swimming tests, and its relationship with a physiological index of stress (serum corticosterone) were studied in adult male rats. The strains were: Fisher 344 (FIS), Lewis (LEW), Spontaneously hypertensive (SHR), and Wistar-Kyoto (WKY). In the holeboard, SHR rats were the most active and WKY the less active, the other strains showing intermediate levels of activity. During the first exposure to forced swimming WKY were far more passive than the other three strains and the same was observed during the second exposure. When corticosterone levels after this second exposure to water was determined, LEW rats showed lower values than the other three strains. Therefore, no apparent relationship between behavior and stress-induced corticosterone secretion exists. Although a single point measurement of only on physiological index of stress has important limitations, the present data do not give support to a strong relationship between the behavior of the animals in the forced swimming test and emotional reactivity to stress. It is therefore possible that forced swimming behavior might not be mainly a panic-like reaction, but the result of the tendency of the animals to adopt passive strategies in inescapable situations. Although more studies are needed to firmly establish this assumption, WKY rats might be, at least potentially, a useful model of depressive-like behavior.

Animals↗
PubMed1979

Membrane potential changes during chemokinesis in Paramecium.

Intracellular recordings show that (i) paramecia hyperpolarize slightly in attractants and depolarize in repellents that depend on the avoiding reaction (an abrupt change of swimming direction), and (ii) paramecia more strongly hyperpolarize in repellents and more strongly depolarize in attractants that depend on changes of swimming velocity. These membrane potential changes are in agreement with a hypothesis of membrane potential control of chemokinesis in Paramecium.

Animals↗
PubMed1982

Estrogen and haloperidol-induced versus handling-related catalepsy in male rats.

A single injection of 17 beta-estradiol valerate produces, 6-7 days later, potentiation of neuroleptic catalepsy. Multiple behavioral measures demonstrate that this effect occurs with an acute dose of haloperidol of 0.25 mg/kg IP. An even lower dose of haloperidol (0.10 mg/kg), which fails to make control rats cataleptic, produces catalepsy in estrogen-treated animals. Thus, estrogen lowers the threshold of haloperidol-induced catalepsy. Repeated testing alone induces cataleptic reactions in control rats. Estrogen suppresses such handling-related catalepsy in animals that subsequently show potentiation of catalepsy at a dose of haloperidol (0.10 mg/kg), which has virtually no effect on control rats. Thus, in these behavioral paradigms, estrogen by itself does not produce cataleptic effects, and estrogen-induced potentiation of haloperidol catalepsy is not merely additive to an antecedent, neuroleptic-like effect of this hormone. We interpret our results in terms of (1) the relationship of cataleptic reactions in normal rats to drug-induced cataleptic states; (2) the possible relevance of our behavioral results to basal ganglia disorders; and (3) the relationship of neuroleptic catalepsy to striatal DA receptors and their modulation by estrogen.

Animals↗
PubMedDate not supplied

[Can the function of the extirpated amygdaloid complex be compensated for by the transplantation of embryonic nerve tissue?].

In 20 white rats bilateral coagulation of the amygdalar complex was produced; on the fifth day to one half of them transplantation was performed by introducing stereotaxically on the left side 0.2-0.5 mm3 of the brain embryonal tissue from the corresponding area of the amygdala of 20-days embryo; in control saline was administered. After two months the rats were sacrificed to determine the activity of antiradical defense by superoxide dismutase (SOD) and the level of lipids peroxide oxidation (LPO) in the cerebral cortex. The transplantation decreased LPO even more and increased SOD as compared to amygdalectomy, e. i. caused still greater deviations from the norm (in this meaning--paradoxal effect), what apparently corresponds to intensification of adaptative-compensatory processes caused by amygdalectomy. The transplantation did not reverse the rats behaviour to the initial one and did not eliminate memory defect in the test of conditioned reaction of passive avoidance (like pyrazetam); it had different direction influence on "drinking under current" in conflict situation, only in particular cases approaching it to the norm.

Adaptation, Physiological↗
PubMed1989

Cardiovascular change in response to prolonged defense area stimulation in freely moving rats.

The mean blood pressure and heart rate of freely moving rats were directly recorded over a 1-min period of electrical stimulation of the periaqueductal gray with intensities that induced freezing behavior, intense flight or no behavioral changes. Blood pressure and heart rate increased only when flight was induced and only during the first 15 s of stimulation. These cardiovascular changes suggest that homeostatic mechanisms act during the defense reaction and are markedly inhibited only at the beginning of the stimuli that induce the flight response, this inhibition quickly undergoing attenuation. These data do not suggest that activation of defense area, per se, contributes to the development of primary hypertension.

Animals↗
PubMed2002

Dual 5-HT mechanisms in basolateral and central nuclei of amygdala in the regulation of the defensive behavior induced by electrical stimulation of the inferior colliculus.

Regulatory mechanisms in the basolateral nucleus of the amygdala (BLA) serves as a filter for unconditioned and conditioned aversive information that ascend to higher structures from the brainstem whereas the central nucleus (CeA) is the main output for the resultant defense reaction. We have shown that neural substrates in the inferior colliculus are activated by threatening stimuli of acoustic nature and have important functional links with the amygdala. In this work, we examined the influence of lesions with 5,7-dihydroxytryptamine (5,7-DHT) of these nuclei of amygdala on the aversive responses induced by electrical stimulation of the inferior colliculus. Thus, rats were implanted with an electrode in the CeA of the inferior colliculus for the determination of the thresholds of alertness, freezing and escape responses. Each rat also bore a cannula implanted in the BLA or CeA for injection of 5,7-DHT (8.0 microg/0.8 microl) or its vehicle. The data obtained show that CeA lesions increase the thresholds of aversive responses whereas BLA lesions decrease the thresholds of these responses. From this evidence it is suggested that defensive behavior induced by activation of the neural substrates of aversion in the inferior colliculus seems to depend on the integrity of the amygdala. BLA regulates the input and CeA functions as the output for these aversive states generated at brainstem level. It is likely that aversive information ascending from the inferior colliculus may receive either inhibitory or excitatory influences of 5-HT mechanisms in the BLA or CeA, respectively.

5,7-Dihydroxytryptamine↗
PubMed1986

A search for brain stem cell groups integrating the defence reaction in the rat.

The defence areas of the rat brain stem have been extensively explored using electrical and chemical stimulation in an attempt to locate the regions containing the perikarya of neurones which may initiate or integrate the visceral and behavioural components of the defence reaction. In rats anaesthetized with alphaxalone-alphadolone, a cannula electrode was used to compare the responses to electrical stimuli with those evoked by microinjection of the excitatory amino acid D,L-homocysteic acid (DLH), at the same site. A total of 128 sites throughout the brain stem was studied in 75 rats. The pattern of visceral and somatic changes characteristic of the defence reaction, viz. increases in arterial blood pressure and heart rate, vasodilatation in hind-limb muscles and vasoconstriction in the kidney, hyperpnoea and tachypnoea, exophthalmos, mydriasis, twitching of the vibrissae and retroflexion of the tail, was evoked by electrical stimulation within well-defined regions of the brain stem, from the anterior hypothalamus to the pons. Microinjection of DLH into the same regions could evoke the full defence reaction, as defined above, but only from the dorsomedial periaqueductal grey matter. Three other regions were defined from which almost all the autonomic components of the defence reaction were evoked, except that blood pressure fell. These were located: immediately dorsal to the optic chiasma, in the medial tuberal region of the hypothalamus and in the lateral pontine tegmentum. In conscious rats with implanted guide cannulae, darting and flight responses were evoked by microinjections of DLH into the periaqueductal grey matter but not from the hypothalamus or tegmentum. Brisk locomotion followed injections of DLH into the region overlying the optic chiasma. It is concluded that the brain stem neurones involved in integrating the somatic and visceral components of the defence reaction are concentrated within the four regions defined above. Whereas neurones in the periaqueductal grey matter can initiate the fully integrated defence reaction, those concentrated in the three other areas cannot be shown to do so. Of these three cell groups, the suprachiasmatic neurones seem to be closer in function to the periaqueductal group than are the neurones in the tuberal hypothalamus and pontine tegmentum.

Anesthesia, General↗