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  • 1
    Electronic Resource
    Electronic Resource
    Longitudinal neuronal organization of defensive reactions in the midbrain periaqueductal gray region of the rat (1992)
    Springer
    Experimental brain research 90 (1992), S. 307-318 
    Details
    ISSN: 1432-1106
    Keywords: Periaqueductal gray matter ; Defensive behavior ; Excitatory amino acids ; Freezing ; Hypertensive reaction ; Ultrasonic vocalization ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In a previous study we investigated the intraspecific defensive reactions evoked by excitation of neurons in the intermediate third of the midbrain periaqueductal gray matter (PAG) of the rat. Experiments revealed that activation of neurons in this region of the PAG mediated: (i) backward defensive behavior, characterized by upright postures and backward movements, and (ii) reactive immobility (“freezing”), in which the rat remained immobile, but reacted with backward defensive behavior to investigative, non-aggressive contact initiated by the partner. In the present study, we aimed to extend our understanding of PAG mediation of defensive behavior by observing: (i) in a non-aggressive social interaction test, the behavioral effects of microinjections of low doses of kainic acid (40 pmol in 200 nl) made in the caudal third of the PAG; and (ii) the behavioral and cardiovascular effects of microinjections of d, l-homocysteic acid (5–10 nmol in 50–100 nl) made in the PAG of the unanesthetized decerebrate rat. Kainic acid injections into the area lateral to the midbrain aqueduct in the caudal third of the PAG evoked: (i) forward avoidance behavior, characterized by forward locomotion and occasional hop/jumps; (ii) reactive immobility (“freezing”), in which the rat remained immobile, but reacted with forward avoidance behavior to investigative, non-aggressive contact initiated by the partner; and (iii) 22–28 kHz ultrasonic vocalizations. These injections also evoked a dramatic increase in defensive responsiveness to tactile stimuli on the half of the body contralateral, but not ipsilateral, to the site of injection. Electroencephalographic measurements indicated that none of these effects were secondary to seizure activity. In the decerebrate rat, d, l-homocysteic acid injections in the caudal third of the PAG evoked forward running movements along with increased blood pressure and heart rate, the strongest effects being evoked from the region lateral to the midbrain aqueduct. More rostrally, sites in the intermediate PAG evoked backward “defensive” movements, which were also associated with increased blood pressure and heart rate. These data, along with those from our previous study in the rat indicate that: (i) defensive reactions are integrated within a longitudinal neuronal column which spans the caudal two thirds of the lateral PAG; (ii) the lateral PAG “defensive behavior” column contains two distinct populations of neurons, one within the intermediate lateral PAG which integrates defensive behavior characterized by facing towards and backing away from a “threatening” stimulus, and a second in the caudal lateral PAG which integrates defensive behavior characterized by forward avoidance behavior; and (iii) neurons within the lateral PAG couple strong cardiovascular changes with each distinctive defensive behavior pattern. The emerging view from this and recent studies of this midbrain region in other species, suggests that similar rostrocaudal differences within a longitudinally oriented lateral PAG neuronal column represent a fundamental principle underlying the PAG organization of defensive behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227243
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  • 2
    Electronic Resource
    Electronic Resource
    Quiescence and hyporeactivity evoked by activation of cell bodies in the ventrolateral midbrain periaqueductal gray of the rat (1994)
    Springer
    Experimental brain research 99 (1994), S. 75-83 
    Details
    ISSN: 1432-1106
    Keywords: Periaqueductal gray ; Stress ; Defense Passive coping behavior ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Much evidence suggests that the midbrain periaqueductal gray region (PAG) plays a pivotal role in mediating an animal's responses to threatening, stressful, or painful stimuli. Active defensive reactions, hypertension, tachycardia and tachypnea are coordinated by a longitudinally oriented column of cells, found lateral to the midbrain aqueduct, in the caudal two-thirds of the PAG. In contrast, microinjections of excitatory amino acid (EAA) made in the ventrolateral region of the PAG in anesthetized or isolated animals evoke hypotension, bradycardia, and behavioral arrest. The aim of the present study was to examine further the effects of activation of neurons in the ventrolateral PAG. By injecting into this region low doses (40 pmol) of kainic acid (KA), a long-acting EAA, it was possible to observe a freely moving rat's behavior in a social situation (i.e., paired with a weight-matched, untreated partner). Such injected rats become quiescent, i.e., there was a cessation of all ongoing spontaneous activity. These rats were also hyporeactive: the investigative approaches of the partner failed to evoke orientation, startle reactions, or vocalization. Electroencephalographic measurements indicated that the effects of injections of KA in the ventrolateral PAG were not secondary to seizure activity. In addition to the quiescence and hyporeactivity reported here, and the hypotension and bradycardia reported previously, the ventrolateral PAG is a part of the brain from which analgesia has been readily evoked by electrical stimulation, or microinjections of either EAA or morphine. As a reaction to “deep” or “inescapable” pain, chronic injury, or defeat, animals often reduce their somatomotor activity, become more solitary, and are generally much less responsive to their environment. These data, and those from other recent studies, suggest that neurons in the ventrolateral PAG may play an important role in integrating such a passive behavioral response of which quiescence and hyporeactivity are the major components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00241413
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  • 3
    Electronic Resource
    Electronic Resource
    Opposite effects of agonist and inverse agonist ligands of benzodiazepine receptor on self-defensive and submissive postures in the rat (1991)
    Springer
    Psychopharmacology 103 (1991), S. 56-61 
    Details
    ISSN: 1432-2072
    Keywords: Benzodiazepine ; Defense ; Submission ; Ethopharmacology ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of benzodiazepine receptor ligands on different types of defensive behaviours were examined in intruder male rats confronted with offensive residents. Chronic administration, via a subcutaneous silastic pellet, of a full agonist (diazepam) for 15 days increased self-defensive postures as well as social and non-social behaviour whereas submissive postures and flight were reduced. Acute administration of a partial agonist (ZK 91296) resulted in a similar increase in self-defensive postures and a decrease of submissive and non-social elements. Acute administration of a partial inverse agonist (FG 7142) reduced defensive postures and social behaviour whereas submissive postures were increased. These results show that activation of benzodiazepine receptors by full or partial agonists increased self-defensive responses to attacks by a conspecific, while decreasing submissive postures. On the contrary, “inverse activation” of these receptors by an inverse agonist increased submissive postures while decreasing self-defensive responses. These data suggest that benzodiazepine receptors are involved in the control of the animal's strategy to respond to an attack of another rat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02244074
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Opposite effects of pentylenetetrazol on self-defensive and submissive postures in the rat (1992)
    Springer
    Psychopharmacology 107 (1992), S. 457-460 
    Details
    ISSN: 1432-2072
    Keywords: Defense ; Submission ; Flight ; Ethopharmacology ; Pentylenetetrazol ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In a previous work, using the resident-intruder situation, we have shown that a benzodiazepine inverse agonist could exert a “fear-promoting” effect, in decreasing self-defensive behaviours while increasing submissive postures. To further test this hypothesis, the effects of pentylenetetrazol on different forms of defensive behaviour were examined in male intruder rats confronted with offensive residents. Administration of pentylenetetrazol (10 and 20 mg/kg, IP) increased submissive postures such as immobility and on-the-back, but reduced self-defensive postures. Other active behaviours were not reduced, thus excluding a non-specific behavioural suppression. These results suggest that self-defensive and submissive behaviours can be dissociated and that anxiogenic compounds are more likely to increase submissive behaviours than self-defensive ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245176
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    22–28 Khz ultrasonic vocalizations associated with defensive reactions in male rats do not result from fear or aversion (1993)
    Springer
    Psychopharmacology 111 (1993), S. 190-194 
    Details
    ISSN: 1432-2072
    Keywords: Ultrasonic vocalizations ; Defense ; Pain ; Fear ; Aversion ; Social interactions ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study was carried out to determine whether 22–28 kHz vocalizations emitted during intermale interactions in adult rats were related with a state of fear, aversion or resulted from painful stimulation. Vocalizations in the 22–28 kHz range were measured in male rats during non-aggressive and aggressive social interactions; when given foot shock with a partner; during non-aggressive social interactions after an injection of (i) acetic acid (1%, IP); (ii) pentylenetetrazol (20–30 mg/kg, IP) and (iii) lithium chloride (63.8 mg/kg, IP). Ultrasonic vocalizations were consistantly detected in all rats while the animals displayed defensive or submissive postures when tested as intruders confronted with offensive residents or when administered foot shocks. Only occasional vocalizations were emitted, even in the presence of a partner, when the animals had received other painful or aversive treatments. These data support the hypothesis that 22–28 kHz vocalizations during intermale interactions are associated with defensive postures and are not the consequence of a state of fear or aversion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02245522
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    Paper (German National Licenses)
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