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PubMedDate not supplied

[The role of the lateral and medial hypothalamus in reproducing a motor reaction as the signal during the acquisition of classical conditioned reflexes].

In experiments on three dogs there was shown that testing electrostimulation of the lateral hypothalamus reproduced the motor reaction which is a signal stimulus at elaboration of classic alimentary conditioned reflexes (CRs) and did not reproduce it at elaboration of classic defensive CR. Testing electrostimulation of medial parts of the hypothalamus reproduced, as LH electrostimulation the "signal" motor reaction, but in less percentage of cases, during elaboration of classic alimentary CRs and did not reproduce it at elaboration of classic defensive CRs. The reproduction of the signal motor reaction at LH electrostimulation is connected with activation of backward conditioned connection from motivation structures of the hypothalamus to representation of the signal stimulus in the motor cortex.

Animals↗
PubMed1990

[The neuronal mechanisms of the defensive reaction to stimulation of the cutaneous nerve in the freshwater snail].

The whole body withdrawal reaction of freshwater snail Planorbarius corneus consists of two phases. In the first phase the shell is rapidly moved down to cover the head, in the second one the body is slowly retracted into the shell. The columellar muscle is involved in this behaviour. Motoneurons of the columellar muscle are identified in the cerebral, parietal and pedal ganglia. In the preparation of the central nervous system connected with the columellar muscle it is demonstrated that stimulation of the lip nerve evoked a biphasic motoneuron excitation responsible for two phases of the muscle contraction. A similar biphasic excitation of the motoneurons could arise spontaneously. This implies that the whole body withdrawal reaction is, at least partly, a fixed act generated by a central mechanism (a central program) which is triggered by a sensory stimulus. The central mechanism of the withdrawal reaction could be also activated by a depolarization of some columellar motoneurons. This suggests that the central mechanism received a feedback from the motoneurons.

Animals↗
PubMed1988

Substantia nigra pars reticulata modulates spontaneous and goal-directed behaviour of rat.

Spontaneous and active avoidance behaviour was compared pre- and postoperatively on 11 six month old male hooded rats of the Long-Evans strain. Seven of them with small bilateral symmetric lesions only in the ventromedial part of substantia nigra pars reticulata (SNR) were characterized by a strong decrease of exploratory parameters except rearings, without differences of ambulatory activity in the open field (OF) test. The SNR group showed a significant retention loss, increased reaction times and run durations in three variants of preoperatively consolidated Y-maze performance and weakened brightness discrimination. They were unable to relearn the tasks and to reduce errors to the preoperative level which was zero. Postoperative acquisition of a new active avoidance stereotype in the jump test box was impossible. They ignored the hanging rod in this box and did not find the escape possibility. Prevailing flexor tonus of trunk and forelegs after SNR lesions was no sufficient reason for these changes, because inborn and automated programs were far less concerned than learnt or operative programs and the accuracy of goal-directed behaviour.

Animals↗
PubMed2002

Role of benzodiazepine and serotonergic mechanisms in conditioned freezing and antinociception using electrical stimulation of the dorsal periaqueductal gray as unconditioned stimulus in rats.

RATIONALE: The dorsal periaqueductal gray matter (dPAG) has been implicated in the modulation of defensive behavior. Electrical stimulation of this structure can be used as an unconditioned stimulus to produce a conditioned fear reaction expressed by freezing, antinociception, and autonomic responses. OBJECTIVES: This study investigated the influence of benzodiazepine, serotonergic, and opioid mechanisms on these conditioned responses. METHODS: Animals implanted with an electrode and a guide cannula into the dPAG were submitted to two conditioning sessions. Each session consisted of ten pairings of the light in a distinctive chamber (CS) with the electrical stimulation of this structure at the escape threshold. On the next day, each animal was exposed only to the CS (testing) and the duration of freezing, number of rearing and grooming episodes were recorded for 5 min. Before and after the testing session, animals were submitted to the tail-flick test. Fifteen minutes before the exposure to the CS, animals received injections into the dPAG of midazolam (a positive modulator of benzodiazepine sites), alpha-methyl-5-hydroxytryptamine (alpha-Me-5-HT; an agonist of 5-HT(2) receptors), naltrexone (an opioid antagonist), or vehicle. RESULTS: Conditioning with dPAG electrical stimulation caused significant increases in the time of freezing and conditioned antinociception. Injections of midazolam into the dPAG significantly inhibited freezing behavior and antinociception due to conditioning. Injections of alpha-Me-5-HT inhibited the effects of conditioning on freezing without affecting conditioned antinociception. Injections of naltrexone (13 nmol/0.2 micro l) did not change any of the conditioned responses studied. CONCLUSIONS: (1) Conditioned freezing and antinociception are modulated by benzodiazepine mechanisms into dPAG. (2) 5-HT(2) receptors seem to regulate conditioned freezing behavior. However, conditioned antinociception was not affected by 13 nmol naltrexone. (3) Opioid mechanisms do not seem to be involved in the conditioned responses using electrical stimulation of the dPAG as unconditioned stimulus. Further studies with other opioid and 5-HT(2) receptor antagonists are still needed to confirm the conclusions drawn from the present work.

Animals↗
PubMed1983

Amphetamine: differential effects on defensive flight and motor behavior in the rat.

As in previous research, hooded rats treated with an acute high dose of d-amphetamine sulfate (5 mg/kg free base) showed a dramatic defensive flight reaction to a novel stimulus (mechanical robot) that did not elicit flight from saline controls. Both the defense response and stereotypy behavior (repetitive movements and oral, licking chewing) were assessed at eight time periods after injection: 1, 15, 30, 45, 75, 105, 135, and 165 min. The defense response peaked early (15-30 min) after injection and showed a significant decline by 75 min, with no reemergence as stereotypy subsided. Stereotypy peaked later (45 min) and did not decline until 105 min. Tests in the absence of the robot provided a control for motor effects of the drug. Whereas stereotypy occurred in both Robot and No Robot conditions, the defense response occurred only in the Robot condition. These results were thought to provide further evidence that the effects of amphetamine on defensive flight could not be attributed to purely motor reactions. Thus, amphetamine-induced defensive flight may be an appropriate pharmacological model of affective psychosis. As such, it may be helpful in establishing differential pharmacological profiles for affective versus motor potencies of potential antipsychotic compounds.

Animals↗
PubMedDate not supplied

[Increasing selectivity of defense behavior during development of pied flycatcher nestlings].

The development of defense reaction was studied in the wildlife and experimentally in 7 broods of altricial pied flycatcher (Ficedula hypoleuca) nestlings. Field studies demonstrated that passive-defense response first appeared on the 4th day of the nest life. It developed from the cessation of begging in young relatively satiated nestlings to characteristic freezing response independent of the level of feeding motivation in older nestlings. Older nestlings also acquire the defense reaction in response to novel visual stimuli. The efficiency of the natural stimulus for defense behavior (species-specific alarm call) nongradually changes during the nest life attaining the 100% level only on the 11th posthatching day. During the initial phase of defense behavior development, the reaction can be induced by different rhythmically organized stimuli. Later it becomes considerably more selective and other rhythmic and acoustic signals become much less effective than the alarm call.

Acoustic Stimulation↗
PubMedDate not supplied

[Characteristics of the pharmacological action of piracetam].

As concerns most generally accepted characteristics adopted in pharmacological studies of psychotropic drugs pyracetam is little active, has no effect on the EEG of the cortex and subcortical structures of the brain. At the same time, in a number of tests this drug displayed a well-marked influence on the central nervous system. It restrains convulsive activity provoked by application to the cerebral cortex of strychnine and penicillin solutions, reduces EEG disturbances produced by barbiturates poisoning and acute hypoxia of the brain. Pyracetam also facilitates the process of teaching in rats, improves the execution of a developed conditioned avoidance reaction, protects rats against manifestations of retrograde amnesia induced by an electric shock, applied after development of the conditioned reflex of passive avoidance.

Animals↗
PubMedDate not supplied

[The effect of a deficiency of the hormones of the peripheral endocrine glands on behavioral, learning and memory processes].

A comparative study of the effects of thyroid, adrenal, and gonadal deficit on capability for learning, retention of memory traces, and behavior was carried out in male rats under conditions of hormonal disbalance produced by extirpation of the endocrine glands. Behavior of animals was tested during the active and passive avoidance learning and in the open field. It was found out that the extirpation of the peripheral endocrine glands impairs learning and reproduction of the acquired reaction and alters the behavior. The results suggest that corticosteroid hormones take part in learning and behavior. Gonadal and thyroid hormones appear to exert a modulating influence on the higher nervous activity.

Adrenal Cortex Hormones↗
PubMedDate not supplied

[Effect of the microiontophoretic application of acetylcholine on the formation of conditioned reactions in motor cortex neurons].

In alert rabbits the activity of the motor cortex neurones was recorded with simultaneous application of acetylcholine to them in the process of defensive conditioning. Conditioned reorganization, mainly of activation type, were found in 60% of neurones. In most cases conditionally reacting cells were sensitive to acetylcholine. Ionophoretic application of the transmitter promoted the formation of conditioned neuronal responses and increased them in comparison with conditioned reactions evoked in absence of acetylcholine. It is supposed that the influence of acetylcholine on conditioned cellular process is realized due to its action on the state of excitability of the cortical neurones.

Acetylcholine↗
PubMed1987

[Primary and secondary motor responses to the presentation of an unexpected stimulus (a startle stimulus) in freely moving cats].

Mechano- and electromyographical motor responses evoked by unexpected acoustic and somesthetic stimuli were studied in freely-moving cats. The responses were presented by different combination of three types of reflex activity-startle reflex (SR, primary responses), orienting reflex (OR) and avoidance reaction (secondary responses). Dependence between SR and OR parameters was established. Data suggest an important role of SR in the development of secondary motor responses to unexpected stimuli.

Acoustic Stimulation↗
PubMed2005

Organization of electrically and chemically evoked defensive behaviors within the deeper collicular layers as compared to the periaqueductal gray matter of the rat.

Stimulation of the periaqueductal gray matter (PAG) and the deeper layers of superior colliculus (SC) produces both freezing (tense immobility) and flight (trotting, galloping and jumping) behaviors along with exophthalmus (fully opened bulging eyes) and, less often, micturition and defecation. The topography of these behaviors within the distinct layers of SC remains unclear. Therefore, this study compared the defensive repertoire of intermediate (ILSC) and deep (DLSC) layers of SC to those of dorsolateral periaqueductal gray matter (DLPAG) and lateral periaqueductal gray matter (LPAG) [Neuroscience 125 (2004) 71]. Electrical stimulation was carried out through intensity- (0-70 microA) and frequency-varying (0-130 Hz) pulses. Chemical stimulation employed a slow microinfusion of N-methyl-d-aspartic acid (NMDA, 0-2.3 nmol, 0.5 nmol/min). Probability curves of intensity-, frequency- and NMDA-evoked behaviors, as well as the unbiased estimates of median stimuli, were obtained by threshold logistic analysis. Compared with the PAG, the most important differences were the lack of frequency-evoked jumping in both layers of SC and the lack of NMDA-evoked galloping in the ILSC. Moreover, although galloping and jumping were also elicited by NMDA stimulation of DLSC, effective doses were about three times higher than those of DLPAG, suggesting the spreading of the injectate to the latter structure. In contrast, exophthalmus, immobility and trotting were evoked throughout the tectum structures. However, whatever the response and kind of stimulus, the lowest thresholds were always found in the DLPAG and the highest ones in the ILSC. Besides, neither the appetitive, nor the offensive, muricide or male reproductive behaviors were produced by any kind of stimulus in the presence of appropriate targets. Accordingly, the present data suggest that the deeper layers of SC are most likely involved in the increased attentiveness (exophthalmus, immobility) or restlessness (trotting) behaviors that herald a full-blown flight reaction (galloping, jumping) mediated in the PAG.

Aggression↗
PubMedDate not supplied

[Behavioral reactions to stimulation of the emotiogenic zones of the brain in the rats with different individual experience].

Emotional reactions evoked by electric stimulation of the hypothalamus and amygdala were studied in white outbred rats, grown either in conditions of isolation or in community. The method of self-stimulation in shuttle box was used. The values of self-stimulation reaction were significantly lower and those of avoidance reactions were higher in animals bred in isolation. Their food-procuring behaviour disappeared faster at stimulation of the negative emotiogenic zones. The observed differences are due to plastic reorganization of the brain reinforcing systems.

Amygdala↗
PubMed1990

Hyper-running activity originating from the hypothalamus is blocked by GABA.

Our previous study showed that injection of the hydrogel of a water-absorbent polymer (WAPGEL) into the ventromedial nucleus of the hypothalamus (VMH) induced stereotyped long-lasting running activity without association of any aggressive reactions, and suggested that swelling of the polymer at the site of injection affected the inhibitory neuron system, resulting in the expression of running activity. In the present study, we injected WAPGEL impregnated with different doses of GABA. By this treatment, the expression of running activity was inhibited in a dose-dependent manner. Contrarily, microinjection of a GABA-A receptor blocker, bicuculline methiodide (BM), released the running reaction in a dose-dependent manner with similar features to that induced by WAPGEL. It is suggested that the running-related neurons in the VMH are inhibited by GABA when the animals are at rest.

Aggression↗
PubMed1994

Defensive reactions evoked by activation of NMDA receptors in distinct sites of the inferior colliculus.

The inferior colliculus (IC) is primarily involved in conveying auditory information to higher cortical structures. Recently we have shown that this structure may also be part of a brain system commanding defensive behaviour. There is evidence that the neural substrates responsible for defensive behaviour in the inferior colliculus are regulated by GABAergic, serotonergic and opioid mechanisms and that these substrates may also be depressed by benzodiazepines as part of their anxiolytic action. Here we present evidence for the involvement of excitatory amino acids in the IC in the expression of defensive reactions. Microinjections of NMDA (5-40 nmol)--an excitatory amino acid--into the ventrolateral division of the central nucleus of the IC of rats placed inside a circular arena induced aversive reactions, characterized by running, rearing, and jumping. This hyperactivity was interspersed by immobility states which often progressed to convulsive seizures. These reactions were inhibited by the NMDA specific antagonist AP7 previously microinjected into the IC. It is suggested that NMDA receptor mediated mechanisms are called into play during the display of the defensive behaviour.

Animals↗
PubMed1986

Pyridoxal 5'-phosphate-dependent histidine decarboxylase. Inactivation by alpha-fluoromethylhistidine and comparative sequences at the inhibitor- and coenzyme-binding sites.

Pyridoxal phosphate-dependent histidine decarboxylase from Morganella morganii AM-15 was inactivated by (S)-alpha-fluoromethylhistidine by a pseudo first-order reaction, with KI and k inact values of 0.1 mM and 32.2 min-1, respectively, and was most efficient at pH 6.5-7.0. Both L-histidine and the competitive inhibitor, L-histidine methyl ester, protected against inactivation. The apoenzyme was not inactivated. These findings indicate that inhibition is a mechanism-based process. Under optimal conditions a single molecule of alpha-fluoromethylhistidine inactivates one enzyme subunit, indicating that no escaping side reaction occurs during the inactivation process. The bound inactivator is not released by dialysis of the native protein but is released upon denaturation by heat or urea. This released product was not fully characterized, but it contains the tritium of ring-labeled alpha-fluoromethyl-[3H]histidine, exhibits the spectral properties of a 3-hydroxypyridine derivative, and does not yield any amino acids on hydrolysis. The label was much more stable following borohydride reduction of the inactivated protein, and a tryptic peptide containing the modified residue was isolated. Sequencing of this peptide and the corresponding peptide from the native enzyme revealed that the inactivator binds to a serine residue of the holoenzyme. Two P-pyridoxyl peptides from tryptic or CNBr digests of the NaBH4-reduced enzyme were also isolated. Sequence and compositional data obtained with these peptides showed that the serine residue to which the inhibitor binds is not near the lysine residue that binds pyridoxal-P in the primary sequence of the protein, although the two residues must be near one another in the three-dimensional structure to account for these results. A speculative mechanism for inactivation, consistent with the experimental findings, is presented.

Amino Acid Sequence↗
PubMed1988

A rapidly acquired one-way conditioned avoidance procedure in rats as a primary screening test for antipsychotics: influence of shock intensity on avoidance performance.

Antipsychotics selectively disrupt relatively weak responses maintained by conditioned stimuli compared with stronger responses maintained by unconditioned stimuli. The present study describes an easily taught and rapidly acquired (within one 15-trial session) one-way conditioned avoidance procedure for rats suitable for screening of drugs for potential antipsychotic activity. This was achieved by using an easily acquired response (running, part of the species-specific defense reaction repertoire), a clearly discriminated conditioned stimulus and determination of the appropriate strength of the unconditioned stimulus (i.e. shock level) for this procedure. Behavior acquired under these described conditions resulted in stable performance over long retest periods. By using either a low or high intensity of shock level under which the animals were trained and tested, the difference between the dose of haloperidol and chlorpromazine able to disrupt avoidance and that which disrupted escape response rates was increased. This effect was also observed for morphine, which inhibited both avoidance and escape responses at similar dose levels only under low shock conditions. At a high shock condition morphine more selectively inhibited avoidance responding. Diazepam did not affect avoidance behavior under the conditions described here.

Animals↗
PubMed1990

Flight and immobility evoked by excitatory amino acid microinjection within distinct parts of the subtentorial midbrain periaqueductal gray of the cat.

Unilateral microinjections of the excitatory amino acid, D,L-homocysteic acid (DLH) made in the lateral and ventrolateral parts of the subtentorial (A 1.0-P 1.5) midbrain periaqueductal gray (PAG) of the freely moving cat evoked two distinct patterns of coordinated somatic changes. When DLH injection (80 nmol) was made within the lateral part of the subtentorial PAG it evoked a flight reaction, characterized by strong locomotion (running) and multiple jumps. This flight reaction was quite distinct from the defensive threat display previously described following DLH microinjection in the lateral part of the pretentorial PAG. When DLH injection (80 nmol) was made in the subtentorial PAG region, ventrolateral to the aqueduct, it elicited a cessation of both spontaneous locomotion and general movements (e.g. licking, scratching, grooming, head and limb movements), a reaction termed immobility. The subtentorial PAG regions from which flight and immobility were evoked are seemingly identical to the lateral and ventrolateral subtentorial PAG regions in which hypertensive and hypotensive reactions have been evoked previously by DLH microinjection. The present results together with our previous studies suggest that: (1) the lateral PAG of the cat contains at least two, topographically separable neuronal pools, which mediate different types of defense reactions (i.e. threat display--lateral part of the pretentorial PAG; flight reaction--lateral part of the subtentorial PAG); and (2) excitation of neurons in the ventrolateral PAG alters autonomic and somatic functions, but in a direction opposite to that of lateral PAG neurons, namely decreased somatomotor activity and hypotension.

Animals↗
PubMed2005

Role of nitric oxide in brain regions related to defensive reactions.

Nitric oxide synthase (NOS) positive neurons are located in most brain areas related to defensive reactions, including the dorsolateral periaqueductal grey (dlPAG). NOS inhibitors injected into this structure induce anxiolytic-like responses whereas NO donors promote flight reactions. Intra-dlPAG administration of carboxy-PTIO, a NO scavenger, or ODQ, a soluble guanylate cyclase inhibitor, produced anxiolytic-like effects on rats exposed to the elevated plus-maze (EPM). A double-staining experiment using NADPHd histochemistry and c-Fos immunohistochemistry in rats exposed to a cat or to the EPM showed increased activation of NO producing neurons in the dlPAG, paraventricular and lateral nuclei of hypothalamus and dorsal raphe nucleus. Cat exposure also increased activation of NOS neurons in the medial amygdala, dorsal pre-mammillary nucleus and bed nucleus of stria terminalis. Local infusion into the dlPAG of a glutamate NMDA-receptor antagonist (AP7) or a benzodiazepine agonist (midazolam) completely prevented the flight reactions induced by intra-dlPAG administration of SIN-1, a NO donor. The responses were also inhibited by the 5-HT2A/C agonist DOI but not by a 5-HT1A agonist. These results suggest a modulatory role for NO on brain areas related to defensive reactions, probably by interacting with glutamate, serotonin and/or GABA-mediated neurotransmission.

2-Amino-5-phosphonovalerate↗