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At least 19 recordsLinked to original sources

PubMed1978

Generation of scratching. I. Activity of spinal interneurons during scratching.

1. In decerebrate, curarized cats, stimulation of the cervical spinal cord evoked fictitious scratching (9), i.e., periodical activity of the hindlimb motoneurons with a discharge pattern typical of actual scratching (cycle duration about 250 ms, flexor phase about 200 ms, extensor phase about 50 ms). During fictitious scratching, extra-cellular records were obtained from 182 spinal neurons located in different regions of the gray matter cross section (except for the motor nuclei), from segments L4 and L5. 2. The firing rate of 73% of neurons was rhythmically modulated in relation with the scratch cycle. Most of the modulated neurons fired in bursts and were silent between bursts. They were located mainly in Rexed's (22) layer VII. 3. Burst onsets ("switchings on" of the neurons) were distributed rather evenly throughout the scratch cycle except for a small maximum at the very beginning of the cycle (the cycle was assumed to start with the termination of the extensor phase). Burst terminations ("switchings off") in the overwhelming majority of the neurons were distributed over the last-third part of the cycle. As a result, those neurons which began to fire earlier in the cycle usually had longer bursts, compared to the neurons which began to fire later. Besides, since there were very few switchings off in the first half of the cycle, the number of simultaneously active neurons increased during the first half of the cycle, reached the maximum somewhat later than the middle of the cycle, and considerably decreased by the end of the cycle. 4. With more intensive scratching, the firing rate in the bursts considerably increased in all neurons tested, while the duration of the scratch cycle changed only slightly. 5. A correlation between the burst position in the cycle and the behavior during the latent period of scratching (when stimulation of the cervical spinal cord had already been started but rhythmical oscillations had not yet appeared) was found in many neurons. Most of the neurons which began to fire at the beginning of the scratch cycle and had long bursts were tonically activated during the latent period. On the contrary, most of the neurons which fired in short bursts at the end of the cycle were either inhibited or not affected during this period. 6. A correlation betwen the burst position in the cycle and the frequency pattern was found in many neurons. In most of the neurons which began to fire in the first half of the cycle (except for the very beginning), the discharge rate increased in the course of the burst. In the remaining neurons, the discharge rate changed only slightly during the burst. 7. Hypotheses concerning organization of the spinal mechanism of scratching are discussed.

Animals↗

PubMed1978

Messages conveyed by spinocerebellar pathways during scratching in the cat. II. Activity of neurons of the ventral spinocerebellar tract.

(1) The activity of neurons of the ventral spinocerebellar tract (VSCT) during scratching was studied in thalamic and decapitate cats. The neurons were identified antidromically either by stimulation of the hindlimb area in the anterior lobe of the cerebellum (in thalamic cats) or by stimulation of the contralateral ventrolateral funiculus of the spinal cord (in decapitate cats). The scratch reflex was elicited by stimulation of either the pinna (in thalamic cats) or the cervical spinal cord (in decapitate cats). In most experiments, animals were immobilized and the activity of VSCT neurons was recorded during fictitious scratching. (2) During both actual and fictitious scratching, the discharge of VSCT neurons was rhythmically modulated in relation with the scratch cycle: neurons fired in bursts separated with periods of silence. Phases of activity of different neurons were unevenly distributed over the scratch cycle: most neurons fired within the limits of the flexor phase of the cycle. (3) The firing pattern of VSCT neurons during fictitious scratching was similar to that during actual scratching. Therefore, rhythmical burst firing of VSCT neurons is determined mainly by central mechanisms and not by a rhythmical sensory input. (4) The firing pattern of VSCT neurons in decapitate cats was similar to that in thalamic cats. Therefore, rhythmical burst firing of VSCT neurons is determined mainly by the central spinal mechanism and not by supraspinal motor centers. (5) The VSCT neurons which fired in long bursts during the greater part of the flexor phase were usually activated during the latent period of scratching, while those firing later in the cycle were usually either inhibited or not affected during this period. (6) The antidromic response in most VSCT neurons could be evoked from a large number of points in the hindlimb area of the cerebellar anterior lobe, both in the vermis and in the pars intermedia. Due to such extensive branching of axons, each point of the cortex receives signals from neurons firing in different phases of the cycle. But axons of VSCT neurons firing in long bursts during the greater part of the flexor phase terminate more extensively in the pars intermedia, while axons of neurons firing later in the cycle terminate more extensively in the vermis. (7) The functioning of the VSCT is essentially similar to that of the spino-reticulocerebellar pathway (SRCP). Both pathways convey messages about activity of the central spinal mechanism generating the motor output pattern of scratching, but the VSCT is active mainly in the flexor phase of the scratch cycle and the SRCP in the extensor one. A hypothesis is advanced that these pathways monitor activity of different groups of spinal interneurons.

Animals↗

PubMed1978

Messages conveyed by spinocerebellar pathways during scratching in the cat. I. Activity of neurons of the lateral reticular nucleus.

(1) Signals transmitted to the cerebellum by the spino-reticulocerebellar pathway (SRCP) during scratching were studied. For this purpose, the activity of neurons of the lateral reticular nucleus (LRN), which are the last-order neurons of the SRCP, was recorded during scratching in thalamic cats. Scratching was evoked by stimulation of the pinna. LRN neurons were identified antidromically by stimulation of the hindlimb area in the cerebellar anterior lobe. In most experiments, animals were immobilized with Flaxedil, and stimulation of the pinna resulted in fictitious scratching, i.e., in periodical reciprocal activity of flexor and extensor motoneurons typical of actual scratching. (2) During both actual and fictitious scratching, the discharge frequency of LRN neurons was rhythmically modulated in relation with the scratch cycle. Most LRN neurons fired in short high-frequency bursts of spikes which coincided (completely or partly) with the extensor phase of the cycle. In this respect the SRCP differs from the ventral spinocerebellar tract (VSCT) which is maximally active in the flexor phase of the cycle. (3) The firing pattern of LRN neurons during fictitious scratching was similar to that during actual scratching. Therefore, the rhythmical burst firing of LRN neurons is determined mainly by the central mechanisms and not by the rhythmical sensory input. (4) Rhythmical modulation of LRN neurons disappeared after transection of the ipsilateral lateral funiculus of the spinal cord in which spinoreticular fibers are located. On the other hand, considerable reduction of rhythmical activity in descending brainstem-spinal pathways after contralateral hemisection of the spinal cord did not affect the discharge pattern of LRN neurons. These two facts indicate that the SRCP conveys mainly messages about activity of the central spinal mechanisms, and that influences of supraspinal motor centers.on LRN neurons and on spinoreticular neurons are of minor importance. (5) Axonal terminations of LRN neurons are distributed rather evenly over the hindlimb area in the anterior lobe of the cerebellum. Therefore, messages about the events, which happen within the spinal cord in the vicinity of the extensor phase of the cycle, arrive at every point of the hindlimb area.

Animals↗

PubMed1992

Glutamate antagonists applied to midbody spinal cord segments reduce the excitability of the fictive rostral scratch reflex in the turtle.

Glutamate antagonists applied to the cutaneous-processing region of the rostral scratch circuit in turtles reduced the excitability of the rostral scratch reflex. Segments D3-D6 (D3 = 3rd postcervical) of the midbody spinal cord receive cutaneous afferents from the rostral scratch receptive field and perform the initial integration of this cutaneous sensory input. These cutaneous-processing segments are located anterior to the rostral scratch motor pattern generator that resides mainly in segments D7-D10 located in and near the hindlimb enlargement. We prepared 1 or 2 of the midbody segments for bath application of glutamate antagonists in preparations with a complete transection of the spinal cord anterior to segment D3. Each preparation was immobilized by neuromuscular blockade and fictive scratch motor output was recorded from hindlimb muscle nerves. Application of the NMDA N-methyl-D-aspartate) antagonist APV (D-2-amino-5-phosphonovaleric acid, 50 microM) to a midbody segment significantly reduced the motor burst frequency of rostral scratch responses evoked by 3-Hz electrical stimulation of a site in that segment's dermatome. These data suggest that NMDA receptors contribute to cutaneous processing in the rostral scratch circuit. Application of APV to a midbody segment also reduced the magnitude of temporal summation in the scratch circuit in response to electrical stimuli delivered to the shell at 4- to 5-s intervals. Temporal summation was monitored at the level of hindlimb motor output as well as at the level of unit activity from 'long-afterdischarge' neurons in the midbody segments. Our observations are consistent with the hypothesis that NMDA receptors contribute to the prolonged activation of 'long-afterdischarge' neurons and the multisecond storage of excitation in the scratch reflex pathway.

2-Amino-5-phosphonovalerate↗

PubMed1978

Messages conveyed by descending tracts during scratching in the cat. I. Activity of vestibulospinal neurons.

(1) The activity of vestibulospinal (VS) neurons giving axons to the lumbosacral spinal cord was recorded during scratching in thalamic and decerebrate cats. The most part of the experiments was carried out on curarized cats, in which fictitious scratching13, i.e. rhythmical activity of motoneurons typical of actual scratching, was evoked. (2) During both actual and fictitious scratching, the discharge frequency of many VS neurons was rhythmically modulated in relation to the scratch cycle. Most modulated neurons were maximally active in the extensor phase of the cycle. (3) The firing pattern of VS neurons during fictitious scratching was similar to that during actual scratching. Therefore, rhythmical modulation of VS neurons is determined mainly by central mechanisms and not be a rhythmical sensory input. (4) In decerebellate cats, rhythmical modulation was not found during either actual or fictitious scratching. (5) Transection of the ventral spinocerebellar tract (VSCT) resulted in considerable reduction of rhythmical modulation of VS neurons during fictitious scratching, while transection of the spino-reticulocerebellar pathway (SRCP) resulted in just a small decrease of modulation. Therefore, of the two pathways (VSCT and SRCP) transmitting messages about intraspinal processes to the cerebellum during scratching6,7, the VSCT is of major importance for modulating VS neurons.

Animals↗

PubMed1975

On the role of central program and afferent inflow in the control of scratching movements in the cat.

Rhythmical scratching movements of the hindlimb were evoked in decerebrate and decapitate cats by stimulation of C1-C2 segments of the spinal cord. Movements of the limb and electrical activity of its muscles were recorded. All muscles were divided into two groups according to their activity. Muscles of the first group supported the limb in a propriate position; they were active during most of the cycle and relaxed during small intervals when muscles of the second group contracted. A deafferented limb was also capable of rhythmical scratching movements with approximately the same cycle duration. However, after deafferentation, the mean position of the limb changed and the amplitude of oscillations increased. This is due mainly to decreased activity of the first group muscles. In curarized preparations, stimulation of C1-C2 segments evoked a rhythmical process within the lumbosacral spinal cord ('fictive' scratching) with a cycle duration nearly the same as in normal scratching. Electrical activity of the muscle nerves during 'fictive' scratching resembled that of corresponding muscles during normal movements. 'Fictive' scratching could be easily elicited provided that the limb was put in a position similar to that of normal scratching.

Animals↗

PubMed1978

Messages conveyed by descending tracts during scratching in the cat. II. Activity of rubrospinal neurons.

(1) The activity of rubrospinal (RS) neurons giving axons to the lumbosacral spinal cord was recorded during actual and fictitious8 scratching in thalamic cats. (2) During both actual and fictitious scratching, the discharge frequency of many RS neurons was rhythmically modulated. Different neurons were active in different parts of the scratch cycle, but most neurons were active in the flexor phase. (3) The discharge frequency within the bursts during fictitious scratching was, on the average, equal to that during actual scratching. Immobilization usually resulted only in a small displacement of the burst position in the scratch cycle. Therefore, rhythmical modulation of RS neurons is determined mainly by central mechanisms and not by a rhythmical sensory input. (4) In decerebellate cats, the overwhelming majority of RS neurons had no rhythmical modulation. Very weak modulation was found only in a few neurons. (5) Transection of the ventral spinocerebellar tract (VSCT) resulted in considerable reduction or complete cessation of rhythmical modulation in RS neurons during fictitious scratching. On the contrary, transection of the spino-reticulocerebellar pathway (SRCP) resulted in just a small decrease of modulation. Therefore, of the two pathways (the VSCT and SRCP) transmitting messages about intraspinal processes to the cerebellum during scratching2,3, the VSCT is of major importance for modulating RS neurons.

Animals↗

PubMed1978

Generation of scratching. II. Nonregular regimes of generation.

1. The activity of muscle nerves and that of spinal interneurons from the L4 and L5 segments was recorded during fictitious scratching (5), which was evoked in decerebrate curarized cats by stimulation of the cervical spinal cord. In some experiments, rhythmical generation was disturbed by stimulation of the fifth lumbar dorsal root (DL5). 2. Excluding the very beginning of scratching, rhythmical generation was usually rather regular: fluctuations of the cycle duration were less than +/-5%. But changes in the stimulation strength, in the stimulating electrode position, and in the hindlimb position led to changes of the generation regime. In different regimes, the mean value of the cycle duration could differ by 20-30%. No correlation was found between mean durations of flexor and extensor phases for different regimes. 3. Rhythmical generation was possible only if the hindlimb was put to "scratch posture," i.e., deflected forward. Generation immediately stopped when the limb was deflected backward, and immediately started when it was returned to scratch posture. 4. In some experiments, stimulation of the cervical spinal cord first resulted in generation of slow oscillations with the temporal pattern typical of stepping (cycle duration about 500 ms, flexor and extensor phases being almost equal to each other). Then, during 5-20 cycles, gradual transition to a normal scratch cycle (about 250 ms) occurred mainly due to considerable shortening (5-10 times) of the extensor phase. In some experiments, considerable spontaneous variations of the flexor phase were observed, while the extensor phase was constant. 5. A single stimulus applied to DL5 considerably affected the cycle duration. Repetitive DL5 stimulation,with a rhythm close to that of scratching, resulted in synchronization of the spinal generator by the stimuli. 6. Spinal interneurons recorded during transition from slow oscillations to a normal scratch cycle only slightly changed phases of their activity in relation to the activity of motoneurons. 7. A hypothesis is advanced that generation of different kinds of limb movements is produced by one and the same central spinal mechanism which can operate in different regimes. The role of sensory input for operation of this mechanism is discussed.

Afferent Pathways↗

PubMed1992

Effects of central administration of opioids on facial scratching in monkeys.

Epidural and intrathecal administration of opioids to humans can produce facial pruritus and scratching that is naloxone reversible. It has been proposed that opioids may act at the level of the medulla to produce facial pruritus and associated scratching behavior. We investigated the effects of mu, delta and kappa opioid-receptor agonists microinjected unilaterally into the medullary dorsal horn (MDH) on facial scratching in cynomolgus monkeys. The selective mu opioid-receptor agonist, DAMGO (3.1-25.0 ng) produced large dose-dependent, naloxone-reversible increases in facial scratches. The selective delta opioid-receptor agonist, DPDPE (1.0-5.0 micrograms) and the selective kappa opioid-receptor agonist, U-50,488H (0.1-5.0 micrograms) did not produce significant increases in facial scratching behavior. We conclude that the MDH is a site where DAMGO, a mu opioid-receptor agonist, can act to produce facial scratching in monkeys, and that the MDH is likely the site where centrally administered opioids act to produce facial pruritus in humans.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed1992

Peripheral 5-carboxamidotryptamine induces hindlimb scratching by stimulating 5-HT1A receptors in rats.

Treatment of rats with 5-carboxamidotryptamine (5-CT) or 5-methoxy-tryptamine (5-MeOT) induces a hindlimb scratch response. These compounds have high affinity for 5-HT1A and 5-HT1D receptors. The selective 5-HT1A receptor agonist N,N-dipropyl-5-CT (DP-5-CT) also induced hindlimb scratching while the selective 5-HT1D receptor agonist, sumatriptan, did not. 5-CT-induced hindlimb scratching was inhibited dose-dependently by several 5-HT1A antagonists (BMY 7378, NAN-190, MDL 73005EF and pindobind-5-HT1A) as well as the non-selective 5-HT antagonist, methiothepin. Pretreatment of rats with the serotonin (5-HT) synthesis inhibitor, p-chlorophenylalanine (PCPA) or the 5-HT depleting agent, reserpine, markedly attenuated 5-CT-induced hindlimb scratching. These data suggest that hindlimb scratching induced by 5-HT agonists may not be centrally mediated but rather may be mediated by a neuronal 5-HT1A receptor localized outside the blood-brain barrier.

5-Methoxytryptamine↗

PubMed1977

[Activity of propriospinal neurons in cats during the scratch reflex].

In the thalamic cats immobilized with flaxedil, the tactile stimulation of the pinna evoked fictitious scratching, i.e. rhythmical activity of the hindlimb motoneurons with a pattern of discharge typical of the actual scratching. Activity of propriospinal neurons from the segments C1--C2 and Th4--Th7 was recorded during such scratching. The neurons were identified by the antidromic response to L1 stimulation. Most neurons did not respond to the pinna stimulation, but some neurons did. They were tonically active during fictitious scratching. The neurons from cervical segments responded also to some other peripheral stimuli, but neurons from thoracic segments did not. Their activity could be inhibited by stimulation of the contralateral pinna. A role of propriospinal neurons in the activation of the spinal mechanisms of scratching is discussed.

Animals↗

PubMed1978

Oculoglandular disease of parinaud. A manifestation of cat-scratch disease.

Among patients with cat-scratch disease, the oculoglandular form is the most common unusual manifestation. This condition, seen in 14 of 585 patients with the infection encountered in a private pediatric practice over a span of 23 years, belongs in the syndrome of the oculoglandular disease of Parinaud. Most of the 14 patients described were only mildly ill and had but little discomfort. All patients recovered without residuals. Diagnosis is based on four criteria: exposure to a cat, usually an immature one; the presence of a localized granuloma of the eye; the presence of preauricular lymphadenopathy; and a positive skin test to cat-scratch antigen of known potency. Several unusual features, never before described, of oculoglandular disease due to cat-scratch disease are submitted.

Adolescent↗

PubMed1975

Cat-scratch disease skin test. Studies of specificity and histopathologic features.

Microscopical examination of biopsy specimens from cat-scratch skin test sites, performed in patients with cat-scratch disease (CSD), sarcoidosis, tuberculosis, and other granulomatous diseases, showed noncaseating granulomatous dermal inflammation in 11 of 12 patients with CSD and in some patients with sarcoidosis or tuberculosis. Biopsy of cat-scratch skin test sites may be a useful ancillary procedure in diagnosing CSD if other granulomatous diseases are excluded.

Adolescent↗

PubMed1992

Multiple scattered granulomatous skin lesions in cat scratch disease.

We report a patient with cat scratch disease who presented with multiple scattered nodular lesions on the legs. Examination of skin biopsy specimens revealed a granulomatous pattern. In our opinion, this is a previously undescribed secondary cutaneous reaction of cat scratch disease. The pathogenesis of this reaction is unclear but some data suggest that the eruption might be caused by a hematogenous spread of cat scratch disease bacteria to the skin. Pathogenetic relationships with so-called bacillary angiomatosis, recently described in patients with acquired immunodeficiency syndrome, are reviewed here.

Cat-Scratch Disease↗

PubMed1977

Cat scratch disease: report of case and discussion.

A case of cat scratch disease with a submental mass as the initial symptom has been presented. The disease should be considered in the evaluation of swellings and masses of the cervicofacial region. However, because of the benign course of cat scratch disease, other more serious disease processes must be ruled out before establishing the diagnosis of cat scratch disease.

Adult↗

PubMed1992

Induction of fos expression by activity in the spinal rhythm generator for scratching.

Fos expression was evaluated immunohistochemically in L7-S1 spinal segments after inducing fictive scratching in paralysed, unanaesthetized, decerebrate cats. The activity was induced by cutaneous stimulation of the pinna on one side and recorded from peripheral nerves. A cumulative duration of scratching of 60 to 90 min was effective in inducing fos expression. Most Fos-positive neurones were found in the dorsolateral part of the ventral horn and in the intermediate region of the spinal cord on the scratching side. In sham-operated animals the finding of Fos-positive neurones in these areas was very rare.

Animals↗

PubMed1975

Emotions and skin (II)-the conditioning of scratch responses in cases of lichen simplex.

Lichen simplex is generally regarded as a condition initiated and perpetuated by scratching and emotional tension. It was felt that the scratching might partly be a conditional response to itching and other signals, and that feelings of guilt, anxiety and hostility would be prominent features in these patients. Conditioning experiments designed to establish scratch responses to an itch stimulus (UCS) and a tone (CS) showed that lichen simplex patients conditioned more readily and extinguished more slowly than controls. These finding were more marked when the itch stimulus was applied to affected as compared with normal skin. It was not possible to distinguish differences in the psychological tests between patients and controls. The possible significance of these findings is discussed.

Adolescent↗

PubMed1979

Effects of trimeprazine and trimipramine on nocturnal scratching in patients with atopic eczema.

Twelve men with severe and long-standing atopic eczema were admitted to a double-blind trial to establish the effects of trimeprazine tartrate, trimipramine maleate, and placebo on nocturnal scratching. Neither of the drugs altered the likelihood of a scratching bout beginning in wakefulness or in any stage of sleep. However, both drugs, especially trimipramine, made sleep less broken, and the reduced time spent in stage 1 of sleep accounted for a modest reduction in the overall amount of scratching during the night.

Adult↗