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Biomedical subjects

J C Roy

Publications and source records attributed to J C Roy.

At least 19 recordsLinked to original sources
PubMed1998

Opioid peptide involvement in the bulbar inhibition of electrodermal activity in the cat.

By analogy with supraspinal and spinal inhibitory controls of pain, it was hypothesized that an opioid mechanism could be involved in the bulbar inhibitory control of the electrodermal activity. This activity was evoked as skin potential responses on the footpads of 13 cats by the central tegmental field stimulation (control responses) and inhibited by the simultaneous stimulation of bulbar reticular formation (experimental responses). Then, naloxone, an opioid peptide antagonist, was injected intravenously or intrathecally and its effects were analyzed on both control and experimental responses. Intravenous injections of naloxone increased significantly the amplitude of experimental responses from 6 to 12 min after the injection and had no effect on the amplitude of control responses. Intrathecal injections of naloxone induced significant increases of amplitude of experimental responses from 6 to 42 min after the injection. These results showed that a spinal opioid peptide link could be involved in bulbar inhibition mechanisms of electrodermal activity.

Animals↗
PubMed1996

Corticospinal collaterals to medullary cardiovascular nuclei in the rat: an anterograde and a retrograde double-labeling study.

There is little evidence allowing the hypothesis of the existence of direct pathways from the sensorimotor cortex (SMC) to main cardiovascular medullary nuclei: the dorsal motor nucleus of the vagus (DMV), the nucleus of the solitary tract (NTS) and the rostral ventrolateral medulla (RVLM). The purpose of this study was to identify in the rat direct SMC-NTS/DMV and-RVLM projections descending through the pyramidal tract (PT) and corticospinal neurones projecting to spinal somatic centers and sending collaterals to the NTS/DMV and the RVLM. The first group of animals (N = 15) received injections of anterograde tracers into the SMC: wheat germ agglutinin conjugated to horseradish peroxydase (WGA-HRP) or rhodamine-conjugated dextran (DR). In the second group (n = 35), retrograde tracers were injected: fluorogold (FG) into the NTS/DMV or into the RVLM and DR into the lateral thoracic cord (Th2-Th4). Anterograde transport of WGA-HRP and DR allowed corticofugal fibers to be followed inside the PT ipsilaterally to the site of cortical injection and showed bilateral labeled projections to the NTS/DMV and RVLM. After retrograde transport, bilateral FG or DR labeled cells were distributed in the SMC, mainly in the medial (AGm) and lateral (AGl) agranular cortex. After spinal and bulbar injections, double-labeled cells were distributed in same cortical areas. After injections in RVLM, 49% of labeled cells showed a double-labeling in the frontal cortex (rostral AGm and premotor cortex) while only 24% were observed in the posterior SMC (caudal AGl). On the contrary, when injections were done in NTS/DMV, double-labeled neurons were respectively of 11% in the frontal cortex and 4% in the posterior SMC. In the present work it was shown that the SMC sent direct projections to bulbar cardiovascular nuclei by means of fibers descending through the PT and corticospinal collaterals. The hypothesis which may be drawn from this study is that cortical motor areas probably program cardiovascular adjustments, preparatory or concomitant to the control of striate muscles.

Animals↗
PubMed1995

Fronto-parietal control of electrodermal activity in the cat.

The aim of this work was to investigate the direct involvement of the fronto-parietal cortex in the control of spinal autonomic centers eliciting electrodermal activity (EDA). This autonomic response, linked with the activity of sweat glands, was recorded as skin potential responses (SPRs) from forepaws in the cat. Animals were paralyzed by gallamine and SPRs were obtained under halothane anaesthesia. For each animal, a transection of the medulla sparing only pyramidal tracts was carried out. SPRs were elicited by direct electrical stimulation of pericruciate and posterior parietal cortical areas before and after such a transection. Results showed that in intact preparations, stimulation of the pericruciate cortex evoked SPRs at lower thresholds than the posterior parietal cortex. After the bulbar transection, only the stimulation of pericruciate areas still elicited SPRs at low intensities. Results are interpreted as indicating that fronto-parietal control of EDA is probably mediated by a double descending system: one involving corticoreticulospinal pathways and a direct corticospinal one. We hypothesized that the somatic motor cortex initiates descending programs to autonomic centers at bulbar and spinal levels, and that these centers are involved in autonomic adjustments to somatomotor movements.

Anesthesia↗
PubMed1993

Sensorimotor cortex projections to the ventrolateral and the dorsomedial medulla oblongata in the rat.

After small pressure injections of Fluorogold (FG), and Dextran-tetramethylrodamine (DR) into the dorsal motor nucleus of the vagus/nucleus of the solitary tract (DMV/NTS) and the rostral ventrolateral medulla (RVLM), respectively, retrograde FG-labelled cells were found mainly in the sensorimotor cortex; retrograde DR-labelled cells were located in the same cortical areas and in the prefrontal cortex. Double-labelled cells were also found in the sensorimotor cortical areas. These results provide evidence of direct projections from the sensorimotor cortex to the DMV/NTS and RVLM and suggest that somatic cortical areas directly control cardiovascular output during sensory and somatic processes.

Animals↗
PubMed1993

Bilateral electrodermal activity during sleep and waking in the cat.

Electrodermal activity (EDA) was recorded as skin potential responses (SPRs), on the hindpaws of cats during waking and sleep. SPRs recorded on both paws showed an overall parallelism during all stages of vigilance. SPRs on both paws significantly decreased in amplitude and in frequency from wakefulness to sleep. Most SPRs were synchronous but showed bilateral differences larger than 0.1 mV. However, this asymmetry did not show any significant variation as a function of sleep stages. Electrical stimulation of the reticular central tegmental field at levels below the thresholds for behavioral and cortical arousal thresholds evoked SPRs during wakefulness and all stages of sleep. Bilateral differences between evoked SPR amplitudes did not show significant variations as a function of the stages of vigilance. Moreover, the bilateral asymmetry of the evoked SPRs was significantly lower than that of the spontaneous SPRs. These results are discussed in relation to the variations in bilateral EDA recorded in humans during waking and sleep; the influence of central and peripheral factors on EDA laterality is also discussed.

Animals↗
PubMed1992

Anxiety, emotion and cerebral blood flow.

Regional cerebral blood flow was measured by the xenon inhalation technique using a DSPECT system, during neutral and emotional auditory stimulations. Subjects were 10 high and 10 low trait anxiety, right-handed females. State anxiety was retrospectively assessed. Results indicated a lower rCBF in the high trait or state anxiety subjects who presented also a global rCBF asymmetry in the right > left direction. Additionally, the emotional content of the stimuli interacted significantly with the side of the brain in the thalamic area.

Adult↗
PubMed1992

Convergence of visceral and somatic inputs onto subnucleus reticularis dorsalis neurones in the rat medulla.

1. In anaesthetized rats, recordings were made within the medullary subnucleus reticularis dorsalis (SRD) from neurones that exhibited convergence of nociceptive inputs from the entire surface of the body. Neurones with total nociceptive convergence responded to supramaximal percutaneous electrical stimuli (2 ms duration) with early and late peaks due to the activation of A delta and C fibres, respectively, no matter which part of the body was stimulated. Neurones with partial nociceptive convergence responded to identical stimuli with an A delta peak of activation regardless of which part of the body was stimulated and with a C peak of activation from some, mainly contralateral, parts of the body. The characteristics of the responses of these neurones to graded colo-rectal distension (< or = 100 mmHg) were analysed. 2. The majority of neurones with total nociceptive convergence (n = 13 out of 16) responded to colo-rectal distension by increasing their firing rates. Although these neurones were virtually unresponsive to the lowest pressure employed (12.5 mmHg), they increased their discharges monotonically for distensions in the 26-100 mmHg range and these responses were sometimes followed by after-discharges. One of these neurones, which exhibited a high level of spontaneous activity, was inhibited during colo-rectal distension. None of the neurones with partial nociceptive convergence recorded (n = 10) ever changed its firing rate during increases of intracolonic pressure up to 100 mmHg. 3. It is concluded that neurones with total nociceptive convergence give monotonic stimulus-response relationships for colo-rectal distensions. Thus, neurones with total nociceptive convergence can encode the strength of visceral stimuli, probably within the noxious range, just as they have previously been shown to do for thermal and mechanical cutaneous stimuli. Together with previous electrophysiological and neuroanatomical findings, this study provides further evidence for the convergence of noxious inputs onto single SRD neurones. 4. It is suggested that neurones with total nociceptive convergence could be a link in spino-bulbospinal loops involved in autonomic reactions to strong visceral stimulation. In addition, SRD neurones could be an important supraspinal relay in the mechanisms of visceral pain.

Action Potentials↗
PubMed1991

Instrumental conditioning of skin potential responses in curarized cats: non specific effects of a punishment procedure.

This study evaluates the effects of a punishment paradigm upon electrodermal activity (EDA) in curarized cats. In ten experimental subjects, any skin potential response (SPR) exceeding threshold value was punished by an electric shock. Ten control subjects received an electric shock or an electric stimulation of the mesencephalic reticular formation unrelated to the EDA. The results show that: a) No significant modifications of EDA occurred in subjects characterized by low initial activity; b) The frequency of SPR significantly decreased in high activity subjects used both for the experiments and the controls. Therefore, this diminution, in experimental subjects, cannot be due to a learning process. Neither can it be related to level of curarization or to rate of artificial ventilation. It is suggested that this effect results from a non-specific cortical inhibitory mechanism acting on the reticular activating system. The results obtained in three decorticated cats submitted to a punishment procedure are in accordance with such an hypothesis. Consequently the existence of operant autonomic learning remains unproven.

Analysis of Variance↗
PubMed1989

The ontogeny of spontaneous skin potential responses in kittens.

The evolution of frequency and amplitude of spontaneous skin potential responses (SPRs) was studied in kittens from birth to 30 days. Results showed that: i) at birth, electrodermal activity is very low, and significantly lower than in adults; ii) the evolution of electrodermal activity is rapid, the adult level being reached by the end of the third week. Frequency and amplitude evolve at approximately the same rate; iii) SPRs recorded on the forepaw were significantly more frequent and larger than those for the hindpaw up to 13 days; iv) changes in electrodermal activity as a function of sleep and waking showed that sleep is characterized by a moderate decrease of SPR amplitude and by a pronounced decrease in SPR frequency. The results are discussed in terms of maturation of the central nervous system.

Aging↗
PubMed1987

Isolation of polymorphic DNA fragments from human chromosome 4.

We have identified and characterized 40 DNA probes detecting restriction fragment length polymorphism (RFLP) on human chromosome 4. Single copy human clones were isolated from a bacteriophage library enriched for chromosome 4 sequences. Each clone was hybridized to somatic cell hybrid DNAs for verification of its species and chromosomal origin and for regional localization. Sequences specific for chromosome 4 were tested for their ability to detect RFLPs in human DNA and their potential utility as genetic markers was assessed. Approximately 263,000 base pairs or 0.13% of the chromosome was screened for sequence variation. The estimate of heterozygosity calculated from this large body of data, H = 0.0021, indicates that the degree of sequence variation on chromosome 4 is comparable to other autosomes. The characterization of these 40 markers has tripled the number of polymorphic loci available for linkage studies on chromosome 4, making it feasible to begin construction of a detailed linkage map that will span the entire chromosome.

Animals↗
PubMed1987

DNA linkage analysis in Von Recklinghausen neurofibromatosis.

We have used DNA linkage analysis in 11 families with Von Recklinghausen neurofibromatosis (VRNF) in order to search for the chromosomal localisation of the defective gene causing this serious neurological disorder. Three groups of polymorphic DNA markers were used: (1) markers for chromosome 22, because of possible allelic genetic heterogeneity between VRNF and bilateral acoustic neurofibromatosis; (2) markers near the centromere of chromosome 4, since there was preliminary evidence for linkage between the VRNF gene and Gc; and (3) oncogenes and growth factors as possible candidate genes for VRNF. Our data exclude close linkage between any of these markers and the gene for VRNF.

DNA↗
PubMed1986

Influence of skin temperature on latency and amplitude of skin potential responses in the cat.

The effect of skin temperature changes on skin potential response (SPR) amplitude and latency was examined in the cat. SPRs were elicited either by stimulating the reticular formation or the distal end of the median nerve. At room temperature, the latency due to the neuroglandular transmission and to the peripheral effector accounts for about half of the total latency of SPR evoked by reticular stimulation. This latency increases to several seconds at low skin temperatures (approximately 10 degrees C), decreases with temperature, and is minimal (300 msec) at high temperatures (over 40 degrees C). SPR amplitude increases with skin temperature, reaches a maximal value (usually around 30 degrees C) and then decreases at higher temperatures. The decrease of latency at higher temperatures confirms results previously obtained in humans. However, the mechanisms of amplitude decrease for high temperatures remain unclear.

Animals↗
PubMed1986

Sex differences in latencies of bilateral electrodermal responses.

The present study examined sex differences in the latencies of bilateral electrodermal responses to stimuli presented in monocular vision. The stimuli were spatial-emotional, verbal-emotional, spatial-neutral and verbal-neutral slides, presented for either 35 ms or 1 s. Subjects were 15 males and 15 females. Bilateral latencies were not influenced by type of stimulus or by right/left hemisphere stimulation, which is in keeping with the most recent findings of bilateral electrodermal activity studies. However, females gave a faster right hand than left hand response and appeared to be more lateralized than males. Males showed shorter latencies on the left hand than on the right. These results confirm the importance of gender in experiments using the bilateral recordings of electrodermal activity.

Adolescent↗
PubMed1985

Metallic elements in crude and milled chrysotile asbestos from Quebec.

Crude and milled fibers from different asbestos mines in Quebec have been analyzed for their metallic content. Crude fibers present a few metal concentrations that are characteristic for each mine. Manganese and iron can be used as discriminators, zinc and cobalt are constantly present in minute quantities, and calcium is virtually absent from crude fibers. Milled fibers are enriched in metals by factors ranging from 1.3 to greater than 15. Chromium and nickel concentrations are many times higher than in crude fibers and iron content is increased by more than 100%. Total metal content in milled fibers is mainly due to nonchrysotile material.

Asbestos↗
PubMed1985

A stereotaxic headholder for Psittacidae.

A stereotaxic headholder suitable for lovebirds is described. In addition to modified ear bars, the head is fixed by means of a clamp gripping the depressions of the lacrimal bones.

Animals↗
PubMed1985

Methodological problems in bilateral electrodermal research.

Since the beginning of the 1970's, bilaterally recorded electrodermal activity (EDA) has generated a significant amount of research. It has been used in studies of hemispheric asymmetry, as well as in psychiatry as an indicator of left and right hemisphere activity. However an examination of the various studies which have utilized this technique does not show an overall consensus, and the results, as well as their interpretations, are often contradictory. These difficulties can partially be explained in terms of problems of methodology and interpretation. The aim of this paper is to review the methodological considerations, which have been grouped into 3 categories: stimulus specificity; the selection of subjects; and the measurement and interpretation of EDA.

Brain↗
PubMed1984

Pyramidal control of skin potential responses in the cat.

Pyramidal command of Skin Potential Response (SPR) was investigated in 20 cats paralyzed by gallamine and under a halothane anaesthetic. For each animal, a transection of the medulla sparing only the pyramidal tract was carried out. The pyramidal tract and Mesencephalic Reticular Formation (MRF) were stimulated before and after the transection. Results taken before transection show that the SPR can be elicited from stimulation of the pyramidal tract and the MRF. After transection, stereotaxic stimulations of the pyramidal tract still evoked the SPR even after aspiration of the medullary tissue posterior to the section and overlying the pyramids. Control reticular stimulations with higher stimulus intensities failed to evoked the SPR. These results show that stimulation of the pyramidal tract can elicit the SPR independently of reticulospinal neurons. It is hypothesized that a group of corticospinal fibers could transmit volleys having autonomic activity on preganglionic autonomic neurons of the intermediate zone of the grey matter.

Animals↗