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R Bandler

Publications and source records attributed to R Bandler.

At least 19 recordsLinked to original sources
PubMed1994

Quiescence and hyporeactivity evoked by activation of cell bodies in the ventrolateral midbrain periaqueductal gray of the rat.

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.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Columnar organization in the midbrain periaqueductal gray: modules for emotional expression?

Independent discoveries in several laboratories suggest that the midbrain periaqueductal gray (PAG), the cell-dense region surrounding the midbrain aqueduct, contains a previously unsuspected degree of anatomical and functional organization. This organization takes the form of longitudinal columns of afferent inputs, output neurons and intrinsic interneurons. Recent evidence suggests: that the important functions that are classically associated with the PAG--defensive reactions, analgesia and autonomic regulation--are integrated by overlapping longitudinal columns of neurons; and that different classes of threatening or nociceptive stimuli trigger distinct co-ordinated patterns of skeletal, autonomic and antinociceptive adjustments by selectively targeting specific PAG columnar circuits. These findings call for a fundamental revision in our concept of the organization of the PAG, and a recognition of the special roles played by different longitudinal PAG columns in co-ordinating distinct strategies for coping with different types of stress, threat and pain.

Animals↗
PubMed1994

Convergence of deep somatic and visceral nociceptive information onto a discrete ventrolateral midbrain periaqueductal gray region.

Pain arising from deep structures (muscles, joints, viscera) is the type of pain of most clinical relevance and also the type of pain about whose central representation we have the least knowledge. In contrast to cutaneous pain which evokes defensive behaviours, hypertension and tachycardia, the physiological reactions to most deep pain (especially if persistent) usually include quiescence, hypotension, bradycardia and decreased reactivity to the environment. Excitation of neurons within a discrete ventrolateral midbrain periaqueductal gray region evokes a reaction seemingly identical to that evoked by pain arising from deep structures. We report here, using the technique of the noxious stimulus-evoked expression of the immediate-early gene, c-fos, that neurons within this same ventrolateral periaqueductal gray region are selectively activated by a range of deep somatic and visceral nociceptive manipulations. Thus we have identified a specific brain region that both receives convergent, deep somatic and visceral nociceptive input, and which mediates the behavioural and physiological reactions characteristic of most deep pain.

Animals↗
PubMed1994

Brain stem integration of vocalization: role of the midbrain periaqueductal gray.

1. The contribution of the midbrain periaqueductal gray (PAG) to the central regulation of vocalization was investigated by analyzing the electromyographic (EMG) changes in respiratory, laryngeal, and oral muscles evoked by microinjection of D,L-homocysteic acid (DLH) in the PAG of unanesthetized, precollicular decerebrate cats. Moderate to large (6-40 nmol) doses of DLH evoked natural-sounding vocalization as well as increases in inspiratory depth and respiratory rate. 2. Two basic types of vocalization were evoked, each associated with a distinct and characteristic pattern of respiratory, laryngeal and oral EMG changes. Type A vocalization (voiced sounds such as howl/mew/growl) was characterized by excitation of the cricothyroid (CT) and thyro-arytenoid (TA) muscles, and inhibition of the posterior crico-arytenoid (PCA) muscle, whereas type B vocalization (unvoiced hiss sounds) was characterized by excitation of the PCA and TA muscles and no significant activation of the CT muscle. In addition, stronger expiratory (external oblique, internal oblique, internal intercostal) EMG increases were associated with type A responses, and larger increases in genioglossus and digastric muscle activity were associated with type B responses. 3. Microinjections of small doses of DLH (300 pmol-3 nmol), also evoked patterned changes in muscle activity (usually without audible vocalization) that, although of lower amplitude, were identical to those evoked by injections of moderate to large DLH doses. In no such experiments (175 sites) were individual muscles activated by small dose injections of DLH into the PAG. Further, type A vocalization/muscle patterns were evoked from PAG sites caudal to those at which type B vocalization/muscle patterns were evoked. 4. Considered together these results indicate: that the PAG contains topographically separable groups of neurons that coordinate laryngeal, respiratory, and oral muscle patterns characteristic of two fundamental types of vocalization and that the underlying PAG organization takes the form of a representation of muscle patterns, rather than individual muscles. 5. The patterns of EMG activity evoked by excitation of PAG neurons were strikingly similar to previously reported patterns of EMG activity characteristic of major phonatory categories in higher species, including humans (e.g., vowel phonation, voiceless consonant phonation). These findings raise the possibility that the sound production circuitry of the PAG could well be utilized by cortical and subcortical "language structures" to coordinate basic respiratory and laryngeal motor patterns that are necessary for speech.

Animals↗
PubMed1993

Expression of c-Fos-like immunoreactivity in the caudal medulla and upper cervical spinal cord following stimulation of the superior sagittal sinus in the cat.

Migraine is an episodic vascular headache with a well-recognized clinical picture but a poorly understood pathogenesis. Stimulation of a pain-sensitive trigeminally innervated intracranial structure, the superior sagittal sinus (SSS), was undertaken to map the higher-order neurons potentially involved in the processing of vascular head pain. The animals were prepared for stimulation by exposure of the sinus and then maintained under alpha-chloralose anaesthesia for 24 h before SSS stimulation, perfusion and immunohistochemical processing for the detection of Fos protein. Examination of the medulla and upper cervical cord revealed marked increases in Fos-like immunoreactivity in laminae I and IIo of the trigeminal nucleus caudalis and the dorsal horn of the upper cervical spinal cord. In addition, Fos-like immunoreactivity was observed in lamina X of the upper cervical spinal cord, in the commissural and medial nuclei of the solitary tract and in the nucleus retroambigualis. The use of immunohistochemical detection of Fos has allowed visualization of several populations of neurons likely to be involved in the central neural processing of vascular headache syndromes, particularly migraine.

Animals↗
PubMed1993

Deep and superficial noxious stimulation increases Fos-like immunoreactivity in different regions of the midbrain periaqueductal grey of the rat.

UNLABELLED: We have reported that the lateral region of the caudal third of the midbrain periaqueductal grey (PAG), which mediates flight and hypertension, receives inputs from lamina I and IIo and the lateral cervical nucleus (LCN) of the upper cervical spinal cord (UCC); whereas the ventrolateral PAG region, which mediates hypotension, quiescence and immobility, is targeted by cells in laminae VII, VIII and X. In the UCC the cells of laminae VII and VIII receive a significant afferent input from the deep neck muscles, whereas cells of laminae I and IIo and the LCN receive a large input from cutaneous nociceptors. Thus we investigated the hypothesis that nociceptive activation of the deep neck muscles would activate the spinal-ventrolateral PAG projection, whereas cutaneous nociceptive stimulation would activate the spinal-lateral PAG projection, by examining the expression of Fos protein. We found that deep noxious stimulation led to Fos-positive cells predominantly in the ventrolateral PAG and superficial noxious stimulation led to Fos-positive cells predominantly in the lateral PAG. THE RESULTS: (i) indicate that the UCC afferent regulation of the PAG arises from topographically separable and functionally dissociable populations of neurons and (ii) raise the possibility that the ventrolateral and lateral PAG play important but different roles in mediating the distinctive affective, emotional and autonomic responses evoked by pain arising from deep or superficial structures.

Animals↗
PubMed1993

Pulmonary and upper airway afferent influences on the motor pattern of vocalization evoked by excitation of the midbrain periaqueductal gray of the cat.

It has been established previously that natural-sounding vocalization is evoked by excitation of the midbrain periaqueductal gray (PAG). It is not known, however, whether the motor output for such vocalization is invariant, or whether it is influenced by afferent discharge. We have investigated, in the unanesthetized precollicular decerebrate cat, the patterns of upper airway and respiratory EMG activity evoked by microinjection into the PAG of the excitatory amino acid D,L-homocysteic acid (6 to 40 nmol in 30-200 nl), under conditions of varied pulmonary and upper airway afferent input. The PAG-evoked pattern in the control state consisted of a 1- to 2-min sequence of episodic vocalizations (hiss or howl-like) with expiratory (vocalization) durations of generally less than 2 s, separated by one or more inspirations. During such PAG-evoked vocalization, a significant prolongation of the expiratory duration and an extended discharge in laryngeal, intercostal and abdominal muscles was evoked by the application of warm, humidified static air pressures (5-30 cm H2O) either: (i) to the lungs and tracheo-bronchial tree via a tracheostomy, or (ii) as an airflow through the upper airways in an expiratory direction. In contrast, if the development of the usual vocalization-related air pressures (5-45 cm H2O) in the lungs and airways was prevented by opening a tracheal cannula to the atmosphere, shortened respiratory durations (inspiratory and expiratory) occurred. The effects evoked by static pressure inflations of the lungs could be blocked by bilateral vagotomy or reversibly blocked by unilateral vagotomy combined with vagal cooling sufficient to abolish Hering-Breuer reflexes. These results indicate that the motor pattern for vocalization evoked by excitation of PAG is exquisitely sensitive to pulmonary and upper airway afferent input.

Air Pressure↗
PubMed1992

Vocalization and marked pressor effect evoked from the region of the nucleus retroambigualis in the caudal ventrolateral medulla of the cat.

It is well established that the nucleus retroambigualis (NRA) of the cat contains a population of expiratory-related neurons. We report here that in the unanesthetized, decerebrate cat, microinjections of 300-900 pmol of D,L-homocysteic acid within the NRA evoked excitation of laryngeal as well as expiratory muscles, and often pressor responses. Moreover, vocalizations, which did not sound like normal feline vocalizations (i.e., hiss, howl, mew, growl), were evoked from a restricted region of the NRA, 1-3 mm caudal to the obex. The results indicate that in addition to its role in expiration: (i) the NRA plays an important role in the control of laryngeal muscles and the production of vocalization; and (ii) that neurons in the NRA region can modulate arterial pressure.

Animals↗
PubMed1992

Anatomical evidence for segregated input from the upper cervical spinal cord to functionally distinct regions of the periaqueductal gray region of the cat.

In the cat, the caudal third of the midbrain periaqueductal gray region (PAG) mediates two distinct behavioral and cardiovascular patterns: (i) flight and hypertension from the lateral PAG and (ii) immobility and hypotension from the ventrolateral PAG. The afferent input from the upper cervical spinal cord (UCC) to these functionally distinct PAG regions was investigated using retrograde tracing techniques. The following results were obtained: (i) following tracer injections into the lateral PAG large numbers of labelled cells were found in lamina I and the lateral cervical nucleus; (ii) following tracer injections into the ventrolateral PAG large numbers of labelled cells were found in the ventral horn; (iii) both PAG regions received substantial projections from UCC cells in laminae IV and V, however, no double labelled cells were observed. Thus, functionally distinct regions of the caudal PAG are targeted by quite separate and discrete UCC neural populations. These anatomical differences likely reflect functionally distinct UCC afferent regulation of the functionally opposite PAG regions.

Animals↗
PubMed1992

Longitudinal neuronal organization of defensive reactions in the midbrain periaqueductal gray region of the rat.

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.(ABSTRACT TRUNCATED AT 400 WORDS)

Aggression↗
PubMed1991

Viscerotopic organization of neurons subserving hypotensive reactions within the midbrain periaqueductal grey: a correlative functional and anatomical study.

Microinjection of the excitatory amino acid D,L-homocysteic acid (40 nmol, in 200 nl) made into the ventrolateral part of the caudal half (A2.5-P1.5) of the midbrain periaqueductal gray (PAG) of the decerebrate cat evoked a hypotensive reaction associated with a slowing of the heart and a decrease in either external iliac or renal vascular resistance. The decrease in iliac vascular resistance was elicited from the pretentorial portion (A2.5-A0.6) of the PAG hypotensive area, whereas the decrease in renal vascular resistance was elicited from the subtentorial portion (A0.6-P1.5). Anatomical experiments using the method of retrograde transport of rhodamine-labelled microspheres or wheat germ agglutinin-horseradish peroxidase demonstrated topographically organized projections from the ventrolateral PAG to the subretrofacial (SRF) pressor nucleus in the rostral ventrolateral medulla. The pretentorial part of the ventrolateral PAG projected mainly to the caudal part of the SRF nucleus, which preferentially controls iliac vascular resistance. The subtentorial part of the ventrolateral PAG projected mainly to the rostral part of the SRF nucleus, which preferentially controls renal vascular resistance. Taken together, these findings suggest: (i) that neurons within the ventrolateral PAG are viscerotopically organized; and (ii) that their hypotensive function may be mediated by an inhibition of SRF pressor neurons. The results are discussed in relation to the recently described PAG hypertensive area which also is viscerotopically organized and projects to the SRF nucleus.

Amino Acids↗
PubMed1991

Control of extracranial and hindlimb blood flow by the midbrain periaqueductal grey of the cat.

Microinjections of D,L homocysteic acid (DLH, 40 nmoles) made in the lateral PAG of the unanesthetized and paralyzed decerebrate cat evoked distinct patterns of extracranial and hindlimb blood flow. One pattern, evoked from the pretentorial part of the lateral PAG (A3.3-A2.5), consisted of an extracranial vasodilation associated with an iliac vasoconstriction. Another pattern, evoked from the subtentorial part of the lateral PAG (P0.2-P0.9), consisted of an extracranial vasoconstriction associated with an iliac vasodilation. Both patterns were associated with increased arterial blood pressure. These results indicate (i) that the PAG contains neurons regulating head and hindlimb vasculature, and (ii) that these neurons are viscerotopically organized, in the sense that different representations of the head and hindlimb are found at different rostrocaudal levels. The significance of the results is discussed in the context of our previous findings that different kinds of defense reactions are evoked from these same pretentorial and subtentorial PAG regions.

Animals↗
PubMed1991

Neurobiological evidence for epilepsy-induced interictal disturbances.

It is not in the best interest of persons with epilepsy to deny the possibility that seizures could cause enduring behavioral disturbances. Rather, it is essential to pursue clinical and animal investigations in order to identify any such changes that might occur and to elucidate their mechanisms. Many testable hypotheses can be developed from existing evidence. Antiepileptic medication may produce interictal behavioral disturbances in patients with epilepsy by indirect mechanisms. Some aberrant behaviors could be due to medication-induced systemic disorders, neuroendocrine dysfunction, or REM deficit, whereas depression following successful treatment with drugs, as well as with surgery, may be related more specifically to cessation of seizures. The underlying neuropathological process also induces neurological and mental deficits, but it is not always possible to differentiate those behavioral disturbances due to destructive effects of the lesion from those due to recurrent epileptic seizures. Behavioral disturbances are associated more frequently with epileptogenic lesions in limbic structures than with those elsewhere in the brain, but a relationship between hemispheric lateralization of the epileptogenic lesion and specific interictal behavioral symptoms remains controversial. When considering the effects of seizures per se on interictal behavior, it is important to realize that some "interictal" behavioral disturbances may actually be ictal events. Prolonged affective, autonomic, and psychic disturbances can occur in clear consciousness with unilateral limbic seizures that are not associated with scalp EEG changes. When epilepsy is acquired as a result of cerebral damage, the epileptogenic process takes time to develop before spontaneous seizures appear. It is more reasonable to assume that this progressive process continues than to postulate that it stops completely at the time the first seizure occurs. Epilepsy-induced protective homeostatic mechanisms that act to terminate ictal events, prevent ictal spread, and maintain the interictal state may also disrupt interictal function. Furthermore, seizures could indirectly influence interictal behavior as a result of their effects on neuroendocrine function and sleep. Because of confounding biological factors, it is difficult to document the association of any epilepsy disorder, by itself, with progressive behavioral disturbances in humans. Secondary epileptogenesis, protective homeostatic mechanisms, and epilepsy-induced disturbances in development can be readily demonstrated, however, in experimental animal models. In experimental animals, endogenous opoids are released during seizures and mediate some postictal behaviors. A physiological dependency on high levels of endogenous opioids released during seizures could produce depression as a withdrawal symptom interictally or when seizures no longer occur as a result of successful therapy. Experimental animal models of depression exist to test hypotheses concerning pro- and antidepressant effects of epileptogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)

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↗
PubMed1989

Viscerotopic control of regional vascular beds by discrete groups of neurons within the midbrain periaqueductal gray.

It is well established that a group of bulbospinal neurons within the rostral ventrolateral medulla plays a crucial role in the tonic and phasic control of arterial pressure. In the cat, these neurons are confined to a discrete region which has been termed the subretrofacial (SRF) nucleus. Recent evidence suggests that this nucleus is viscerotopically organized with respect to its control over different vascular beds. These observations raise the question as to whether functionally different subgroups of SRF pressor neurons receive inputs from supramedullary cell groups that also exert a specific control over particular vascular beds. To answer this question retrogradely transported tracers (i.e. rhodamine or fluorescein-labelled microspheres, wheat germ agglutinin-horseradish peroxidase) were injected into physiologically identified sites within the rostral or caudal parts of the SRF nucleus of the cat. Separate groups of neurons in the midbrain periaqueductal gray region (PAG) were found to project specifically to subgroups of cells within the rostral and caudal parts of the SRF nucleus. These findings, together with the results of recent functional studies of the PAG suggest that these distinct projections from the PAG to the SRF nucleus are involved in the expression of different patterns of emotionally coupled cardiovascular responses.

Animals↗
PubMed1989

Characterization of pretentorial periaqueductal gray matter neurons mediating intraspecific defensive behaviors in the rat by microinjections of kainic acid.

Unilateral microinjections of 40 pmol of kainic acid (KA; in 0.2 microliter) within the periaqueductal gray matter (PAG) evoked intraspecific defensive postures (defensive uprights, defensive alterting, defensive sideways, backing) in rats confronted with a conspecific. These reactions, which lasted for up to 30 min, were seemingly identical to the rat's natural defensive reaction to attacks by a conspecific although they were evoked by the investigatory approach, rather than the attack, of another rat. Histological analysis revealed that the strongest defensive reactions were evoked from sites within a restricted part of the pretentorial periaqueductal gray matter. Lower doses of KA induced fewer (20 pmol) or non-significant increases (4 pmol) in defensive reactions. Higher doses (100 and 200 pmol) increased the percentage of defensive behavior and also induced oriented jumps out of the test cage. In tests with a conspecific, defensive reactions were elicited most frequently when investigation by the partner was localized to the side of the body contralateral to the injection site. This was confirmed in a sensory reactivity test in which tactile stimulation by the experimenter elicited most defensive reactions when applied on the side of the body contralateral to the injection side. This test also revealed a somatotopic gradient in the animal's reaction: tactile stimulation of the contralateral head and the forelimb evoked the strongest reactions, whereas no responses were observed upon tactile stimulation of the contralateral flank or hindlimb. Measurement of electroencephalographic activity at the cortical, hippocampal, amygdala and PAG levels indicated that the evoked defensive reactions were not secondary to epileptogenic effects. Finally, quantitative analysis of an autoradiographic study found that [3H]KA diffused within a diameter of 1.0-1.2 mm around the cannula tip. Taken together, these results indicate the existence of a population of neurons within a restricted part of the pretentorial PAG of the rat, the excitation of which produces defensive responses and demonstrate that these defensive reactions have a socially adaptive value.

Animals↗
PubMed1989

Somatic and autonomic integration in the midbrain of the unanesthetized decerebrate cat: a distinctive pattern evoked by excitation of neurones in the subtentorial portion of the midbrain periaqueductal grey.

Microinjections of the excitant amino acid D,L-homocysteic acid (DLH) made in a restricted part of the subtentorial (P0.2-P0.9) midbrain periaqueductal grey (PAG) of the unanesthetized decerebrate cat evoked a distinctive pattern of coordinated somatic and autonomic changes which was characterized by strenuous hindlimb movement and a concomitant vasodilation in the hindlimb vascular bed. The vasodilation was not secondary to movement as it could still be evoked in the paralyzed preparation. The autonomic changes also included pupillary dilation, increases in arterial pressure and heart rate, and vasoconstriction in renal and mesenteric vascular beds. This evoked response is quite different from that elicited by DLH microinjections made in a restricted part of the pretentorial PAG of the unanesthetized cat (Carrive et al., Neurosci. Lett., 81 (1987) 273-278). This latter response is characterized by a threat display which includes strong facial and vocal changes, but no strenuous hindlimb movement, and skeletal muscle vasoconstriction. The present results together with our previous research suggest that two distinct sets of neurons located in different midbrain PAG regions mediate coordinated patterns of somatic and autonomic change characteristics of different aspects of defensive behavior.

Action Potentials↗