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Biomedical subjects

A Limoge

Publications and source records attributed to A Limoge.

At least 19 recordsLinked to original sources
PubMed1999

[Electricity in pain management].

UNLABELLED: AVAILABLE TECHNIQUES: For more than thirty years there has been a revival of electrotherapy in the treatment of pain. Analgesia by electrical current is now based on transcutaneous or percutaneous nerve stimulation, deep stimulation, posterior spinal cords stimulation, and transcutaneous cranial stimulation. EFFICACY: It is now scientifically proven that electrostimulation of certain peripheral fibers and of different structures of the central nervous system plays an undeniable role in filtration and control of painful messages. However, precise indications are a prerequisite. Transcutaneous electrical nerve stimulation is only effective if it acts on neurogenic pain, only if the nerve pathways to be stimulated are superficial, and only if the conduction pathways between the area of stimulation and the superior centers are intact. Neurosurgical electrostimulation techniques should only be proposed after failure of simple therapies. INDICATIONS: For acute pain, electrostimulation of certain intracerebral structures and transcutaneous cranial electrostimulation may be indicated. Clinicians have a multitude of electrostimulators at their disposal but generally, the parameters recommended for their use have no serious scientific basis. The selected electrical neurostimulator must provide effective nerve stimulation without causing lesions. Electrostimulation could be considered as an adjunct to medicinal treatment for pain relief.

Analgesia↗
PubMed1999

Automated sleep staging systems in rats.

One of the major inconveniences encountered in sleep studies is the time consuming labor involved in equating visual analysis of physiological recordings (EEG, EMG, EOG, ...) to an appropriate state of vigilance. The explosion of computer technology is responsible for the emergence of several automated sleep-wake staging systems to supplement human analysis. Conversely to human sleep analysis, rat sleep is characterized by the absence of consensus about numerous elements constituting the sleep-wake staging systems used to build a hypnogram (recording position, length of epoch, number and definition of the vigilance state discriminated, ...). If justified, the choices of the parameters involved by each system generally result from various viewpoints (physiology, mathematics, electronics, ...). The diversity generated by the liberty offered the investigator in building a system excludes any rigorous comparison between systems. Nevertheless, this variety can also be viewed as a representative of the effervescence of research in the field of sleep, and as a catalyst for new ideas.

Animals↗
PubMed1999

Transcranial electrical stimulation (Limoge's currents) potentiates the inhibition of righting reflex induced by droperidol in rats.

The effects of transcranial electrical stimulation (TCES) on droperidol-treated rats were evaluated using the righting reflex latency (RRL) test. TCES (high frequency (HF)-166 kHz, intermittent-100 Hz current) delivered through three electrodes (a negative electrode placed between the eyebrows and positive electrodes located in the retro-mastoid region) was shown to potentiate the inhibition of righting reflex induced by droperidol. This potentiation was found to depend on the dose of the drug, the characteristics of the current delivered and the duration of stimulation. We also observed that TCES-induced potentiation of inhibition of righting reflex produced by droperidol injection was not reversed: (i) after naltrexone administration, (ii) when measures were performed on p-chlorophenylalanine (pCPA)-treated animals. These results suggest that, under the experimental conditions: (i) TCES does not interact with opioid endogenous to potentiate droperidol effects, (ii) the effect of TCES on dopaminergic system prevails against TCES action on serotonergic system. Though these findings enlarge the comprehension of TCES effects on the central nervous system, further investigations are necessary to elucidate TCES mechanisms.

Animals↗
PubMed1999

Transcutaneous cranial electrical stimulation (TCES): a review 1998.

The Transcutaneous Cranial Electrical Stimulation (TCES) technique appeared at the beginning of the 1960s and is aimed to act at the level of the central nervous system. The current, composed of high frequency pulses interrupted with a repetitive low frequency, is delivered through three electrodes (a negative electrode placed between the eyebrows while two positive electrodes are located in the retro-mastoid region). Due to the characteristics of the current delivered, shortcomings encountered with previous electrical stimulation techniques are avoided. The main property of TCES is to potentiate some drug effects, especially opiates and neuroleptics, during anesthetic clinical procedures. This potentiation effect permits drastic reduction of pharmacological anesthetic agent and reduces post-operative complications. Animal studies performed with TCES demonstrated that this stimulation releases 5-hydroxy-indol-acetic acid and enkephalins. Despite numerous clinical and animal studies performed with this technique for several decades, TCES mechanisms are not completely elucidated but results obtained without undesirable effect are encouraging signs to continue investigations of this particular technique.

Animals↗
PubMed1999

Sleep impairments in rats implanted with morphine pellets.

Morphine pellets (2 x 75 mg) were subcutaneously implanted in rats and vigilance states (wakefulness, slow wave sleep and paradoxical sleep) were observed during ten days. Significant impairment of each vigilance state distribution appeared during the first days of morphine dependence. Although waking and slow wave sleep were not affected during the last days, paradoxical sleep duration was reduced during dependence. Nevertheless, the sleep-wake circadian rhythm was not abolished. These results suggest that the sleep process is affected differently in its components (slow wave sleep and paradoxical sleep) during morphine dependence.

Animals↗
PubMed1998

Review of neural network applications in sleep research.

To find a better automated sleep-wake staging system for human analyses of numerous polygraphic records is an interesting challenge in sleep research. Over the last few decades, many automated systems have been developed but none are universally applicable. Improvements in computer technology coupled with artificial neural networks based systems (connectionist models) are responsible for new data processing approaches. Despite extensive use of connectionist models in biological data processing, in the past, the field of sleep research appeared to have neglected this approach. Only a few sleep-wake staging systems based on neural network technology have been developed. This paper reviews the current use of artificial neural networks in sleep research. Following a brief presentation of neural network technology, each of the existing system is described and attention drawn to the heterogeneity of the different processing approaches in sleep research. The high performances observed with systems based on neural networks highlight the need to integrate these tools into the field of sleep research.

Animals↗
PubMed1998

Continuous quantitative monitoring of spontaneous opiate withdrawal: locomotor activity and sleep disorders.

The time course of drug abstinence is not readily amenable to examination using intermittent observations, because abstinence is known to interfere with circadian rhythms of general activity. Accordingly, we propose a model for continuous assessment of spontaneous withdrawal without any intervention by the investigator. This model is based on the automatic recording of locomotor activity. Experiments were performed in rectangular activity cages equipped with two infrared photoelectric cells. In a parallel experiment, to confirm the locomotor activity effects, continuous monitoring of EEG activities was achieved from two cortical and one reference electrodes. Morphine dependence was induced by intraperitoneal injections of increasing doses of morphine twice daily for 10 days (from 5 up to 90 mg/kg). Behavioral and EEG activities were recorded for 8 to 10 days following the last injection of morphine. Although control rats displayed a typical locomotor activity pattern characterized by nocturnal hyperactivity that was markedly reduced during the light phase, opiate abstinent rats developed a constant motor activity during the first 3 or 4 postinjection days and that was associated with a drastic reduction of overall rapid eye movement sleep (REM) and non-REM sleep and with an increase of waking (W). Although morphine-abstinent rats slowly resumed a normal circadian cycle after the fourth day in terms of horizontal activity, REMS, NREMS and W, long-term effects were revealed by the permanent motor instability recorded during both the light and the dark phases when the total amount of photocell counts was considered, and by the perturbation of the circadian rhythm of the ratio of REM sleep to total sleep time. Automatic continuous recording of total motor behavior appears to be a useful index with which to follow, over an extended period of time, the acute and long-term consequences of opiate abstinence. Therefore, long-term withdrawal-induced changes in activity could be a suitable model for the validation of antiabstinence therapies.

Analgesics, Opioid↗
PubMed1997

Potentiation of fentanyl suppression of the jaw-opening reflex by transcranial electrical stimulation.

Stinus et al. [L. Stinus, M. Auriacombe, J. Tignol, A. Limoge, M. Le Moal, Transcranial electrical stimulation with high frequency intermittent current (Limoge's) potentiates opiate-induced analgesia: blind studies, Pain, 42 (1990) 351-363.] observed that transcranial electrical stimulation (TCES) with high-frequency intermittent current potentiated opiate-induced analgesia using the tail-flick test. In unanesthetized, chronic preparations, electrical stimulation (0.5 Hz) of the lower incisor pulp of rats elicits a short-(6 ms) and a long-latency (12-18 ms) jaw-opening reflex (JOR) without any evidence of aversive behavior [J. Azerad, F. Fuentes, I. Lendais, A. Limoge, B. Pollin, Methods for selective tooth pulp stimulation in acute and chronic preparations in rats, J. Physiol., 406 (1988) 3P.]. Fentanyl increases thresholds of both reflexes and transiently suppresses the long-latency JOR. We then decided to look at the influence of TCES on both drug-induced mean of maximal threshold variation (MMTV) and duration of JOR suppression period. These parameters have been investigated in 43 Wistar rats with or without TCES administered for 3 h before the drug injection and throughout the testing period. TCES alone has no effect. In contrast, it significantly increases the duration of the reflex suppression period (149 +/- 5% vs. control, P < 0.001) while fentanyl-increased reflex thresholds remain unchanged. The fentanyl-induced JOR suppression period returns to the control values 2 days later. When a second 3-h TCES session is delivered 2 or 4 days after the first TCES session, a similar increase of this suppression period is observed. Moreover, 2 days after a second TCES session, an increase of the duration of the fentanyl-induced JOR suppression period is systematically observed. In contrast, a 6-h TCES session never induces such effects. These results confirm a potentiating effect of TCES on opioid action and demonstrate the value of repeated TCES sessions.

Analgesics, Opioid↗
PubMed1997

Comparison between conventional and neural network classifiers for rat sleep-wake stage discrimination.

This article describes an approach to selecting the most efficient classifier for rat sleep staging (waking, REM sleep and NREM sleep) discrimination. Three conventional (bayesian, linear, and euclidean) and two neural network (multilayer perceptrons integrating or not integrating contextual information) classifiers were compared. For each classifier, performances were presented in the form of a statistical concordance matrix comparing classifier results versus human expert results on 6 24-hour records (1 record per animal). Comparison between classifiers was based on the estimation and accuracy of global agreements. Interest was also focused on REM sleep state discrimination. The results show that neural network classifiers are appropriate tools to be integrated in an automatic rat sleep-wake stage system. The approach presented should help scientists in choosing a method of data classification.

Animals↗
PubMed1996

Adult rat vigilance states discrimination by artificial neural networks using a single EEG channel.

Two multilayer neural networks were designed to discriminate vigilance states (waking, paradoxical sleep, and non-REM sleep) in the rat using a single parieto-occipital EEG derivation. After filtering (bandwidth 3.18-25 Hz) and digitization at 512 HZ, the EEG signal was segmented into eight second epochs. Five variables (three statistical, two temporal) were extracted from each epoch. The first network computed an epoch by epoch classification, while the second network also utilized contextual information from contiguous epochs. A specific postprocessing procedure was developed to enhance the vigilance state discrimination of the neural networks designed and especially paradoxical sleep state estimation. The classifications made by the networks (with or without the postprocessing procedure) for six rats were compared to these made by two human experts using EMG and EEG informations on 63,000 epochs. High rates of agreement (> 90%) between humans and neural networks classifications were obtained. In view of its development possibilities and its applicability to other signals, this method could prove of value in biomedical research.

Animals↗
PubMed1996

Transcutaneous cranial electrical stimulation (Limoge's currents) decreases early buprenorphine analgesic requirements after abdominal surgery.

Transcutaneous cranial electrical stimulation with Limoge's currents (TCES) consists of high frequency, low intensity currents which decreased anesthetic requirements during elective surgery. This action is likely to be mediated by the release of central endogenous opioids. In the present study, we hypothesized that TCES applied intraoperatively may decrease early postoperative narcotic requirements. Thirty-nine ASA physical status I and II patients undergoing elective abdominal surgery were enrolled in this prospective, randomized, double-blind, placebo-controlled study. Just before induction of anesthesia, patients were connected to the electrical stimulator and randomly allocated to be either stimulated (TCES group, n = 20) or not (control group, n = 19) during surgery. The managing anesthesiologist was unaware of which group the patient was assigned. Postoperatively, patients were given a patient-controlled analgesia (PCA) device delivering buprenorphine for the first four postoperative hours. The recorded variables included postoperative buprenorphine requirements, pain scores (0-10 visual analog scale [VAS]), sedation (0-4 scale), and intraoperative isoflurane requirements. Patients were comparable with respect to age, sex ratio, weight, duration of surgery, intraoperative hemodynamics, fentanyl requirements, and time from skin closure to tracheal extubation. Buprenorphine requirements were significantly reduced in the TCES group versus the control group (2.36 vs 3.43 micrograms.kg-1.h-1; P = 0.002). Intraoperative isoflurane anesthetic requirements, as well as hourly postoperative scores for pain and sedation, were the same for the two groups. These data indicate that TCES reduces narcotic requirements for early postoperative analgesia. This technique might have potential to facilitate early postoperative analgesia in patients undergoing elective abdominal surgery.

Abdomen↗
PubMed1994

Real-time sleep-wake scoring in the rat using a single EEG channel.

A new method of analysis of sleep in the rat based on the electrocorticogram (ECoG) is described. Three states, awake (W), nonrapid eye movement (NREM) and rapid eye movement (REM) sleep are automatically classified by the system. After amplification of the ECoG over a restricted bandwidth (3.18-25 Hz) and sampling at 512 Hz, the data are processed in 8-second epochs by a microcomputer, which generates three statistical and two harmonic variables. Each 8-second epoch is thus compressed into five numerical values occupying 10 bytes of memory. Epochs for each state of vigilance are identified by an expert observer to produce three reference models. The program classifies each epoch into the appropriate state by the least quadratic distance. The system was validated by comparing the results with a visual analysis of polygraph recordings. The agreement between the program and the two independent scorers for 24-hour tracings of six rats was 83% for REM sleep, 96% for W and 97% for NREM sleep.

Animals↗
PubMed1992

Transcranial electrical stimulation with Limoge's currents decreases halothane requirements in rats. Evidence for the involvement of endogenous opioids.

Transcutaneous cranial electrical stimulation with Limoge's currents has been shown to facilitate anesthesia/analgesia in surgical patients. However, the neurobiologic substrate of this effect remains unknown. The present study was designed to analyze the influence of transcranial electrical stimulation (TCES) on halothane requirements in rats and the contribution of the central endogenous opioid, alpha 2-adrenergic and 5-hydroxytryptamine (5-HT1 and 5-HT2) serotonergic systems to this effect. The influence of TCES on the MAC of halothane (MACH) and its reversibility by a subcutaneous 2 mg/kg naloxone injection were first determined in 20 rats using a randomized blinded protocol. MACH was decreased markedly in stimulated animals (TCES, n = 10) in comparison with sham-operated nonstimulated rats (controls, n = 10): MACH = 0.60 +/- 0.15, mean +/- SD, versus 1.07 +/- 0.05 vol%, P less than 0.001. In TCES animals, naloxone administration restored MACH values to the levels of controls but failed to affect MACH in controls. The influence of the duration of TCES applied prior to MACH determination was further investigated in 30 animals. The magnitude of MACH reduction was significantly increased with the cumulative duration of stimulation. For each duration of stimulation tested, administration of a 5-micrograms intracerebroventricular (icv) dose of the enkephalinase inhibitor thiorphan significantly enhanced TCES effects (P less than 0.05). Finally, the icv administration of a 15-micrograms naloxone dose appeared to reverse completely the MACH reduction elicited by TCES (n = 8, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1992

[Analgesic effect of transcutaneous cranial electrostimulation in patients treated by Nd:YAG laser for cancer of the rectum. A double-blind randomized trial].

The aim of this double blind cross-over randomized trial was to assess if transcutaneous cranial electrical stimulation by Limoge current could decrease the dose of fentanyl required in patients with rectal cancer treated by Nd:YAG laser. Fifty patients, 29 women, 21 men, 78 +/- 10 years old (range: 53-96 years), were treated by 2 laser sessions with an interval of 48 hours between each session. Active and sham electrostimulation were given in random order for the 2 laser sessions. The major end point was the quantity of fentanyl injected when the score of pain was greater than or equal to 5 according to a visual analgesic scale. Age, sex, body weight, tumor location and length, tumor circumferential extent and luminal patency, duration of laser session, amount of energy delivered per session (watt-seconds), and number of patients with deep sedation did not differ between the 2 groups. There was no interaction between the order of treatments and the treatments. The mean quantity of fentanyl was 29 micrograms and 42 micrograms when sham electrostimulation was given. There was a decrease of 31 percent in the quantity of fentanyl with active electrostimulation (P less than 0.05). Results were not affected either by the treatment order nor by tumor location. There were no side effects in either group.

Aged↗
PubMed1989

[Effect of transcranial electrical stimulation on sleep in rats].

Transcranial electrical stimulation with high frequency intermittent current (Limoge's current) was delivered to normal rats and to PCPA-treated rats with impaired sleep. Electrocorticogram was continuously recorded for quantifying the stage of the sleep-waking cycle. The current did not affect the sleep pattern of normal rats whereas the number of paradoxical sleep episodes increased in insomniac animals. The increased duration of paradoxical sleep in PCPA-treated rats favored the recovery of sleep in this group. The stimulation increased the brain serotonin turnover, which could possibly contribute to its hypnogenic action.

Animals↗