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Biomedical subjects

D Albe-Fessard

Publications and source records attributed to D Albe-Fessard.

At least 19 recordsLinked to original sources
PubMed1991

Neurones with epileptiform discharge in the central nervous system and chronic pain. Experimental and clinical investigations.

Epileptiform discharge was recorded from neurons in the thalamic nuclei of chronic pain patients during stereotactic surgery. Hyperactive neurons showed regular firing of 3-5 trains of epileptic-like group discharges with a frequency of 4 to 5 Hz. As described by Lombard et al. (1979), we operated on the dorsal root unilaterally, sectioning C5 to Thl in male Wistar rats. One to three months after the operation, hyperactive neurons were examined in the contra-lateral thalamic nuclei (VP, zona incerta), and lemniscus medialis. The firing patterns and distribution of hyperactive neurons in these animals was very similar to those of humans. The hyperactive neuron was unaffected by electrical stimulation of the nucleus raphe dorsalis (NRD) and locus ceruleus (LC). Administration of phenytoin and diazepam reduced the firing. However, no effect was seen with valproic acid. During spreading depression of the sensorimotor cortex, a remarkable reduction was seen on the firing of thalamic hyperactive neurons. This suggested that hyperactive neurons of the thalamic nuclei received facilitory effects from the sensorimotor cortex with little influence from adrenergic or serotoenergic systems.

Animals↗
PubMed1991

Spontaneous neuronal hyperactivity in the medial and intralaminar thalamic nuclei of patients with deafferentation pain.

Electrical activity was recorded from single cells in the thalamus of 10 patients with chronic pain associated with deafferentation. Under local anesthesia, these patients underwent either electrode implantation or thalamotomy for treatment of their pain. In eight of the 10 patients, single units were identified as discharging spontaneously in high-frequency, often rhythmic, bursts. The discharges were of two types: short bursts comprised of two to six spikes with a burst frequency of one to four per second; and long trains of 30 to 80 spikes of similar frequency. Reconstruction of electrode trajectories indicated that recordings were made from the region corresponding to the lateral aspect of the mediodorsal thalamic nucleus, the central lateral nucleus, a small part of the central median nucleus, and the parafascicular nucleus. In the eight patients in whom spontaneous neuronal burst activity was exhibited, it was impossible to study activity evoked by natural cutaneous stimulation due to the continuous spontaneous neuronal discharges. Both animal and human studies have suggested that pain related to deafferentation is accompanied by spontaneous hyperactivity in the dorsal horn of the spinal cord and in the ventral posterior thalamic nuclei. The authors present evidence of spontaneous neuronal hyperactivity in the intralaminar thalamic nuclei of patients with pain related to deafferentation. The findings suggest that spontaneous neuronal discharge in patients with pain related to deafferentation is more widespread in the central nervous system than has been previously appreciated. The results have important implications for the surgical treatment of chronic pain.

Afferent Pathways↗
PubMed1990

The influence of striatum on the substantia nigra: a study using the spreading depression technique.

Effects of changes in striatal neurone activity on substantia nigra (SN) unit activity were studied in rats. Striatal changes were produced by the spreading depression (STSD) induced by perfusing the head of striatum with 0.06 M KCl via a push-pull cannula. In the medial part (caudate) striatal neurones are silent, with the arrival of STSD they exhibit a brief excitation coinciding with the onset of a slow wave of depolarisation in the extracellular steady potential. In the lateral part (putamen) striatal neurones are active, they undergo an arrest of their spontaneous activity for about 1 minute following the brief excitation. Antidromic activation of SN reticulata (SNr) neurones was attempted from the superior colliculus (SC). The majority of the 54 SNr neurones (96%) exhibited changes in firing rate during STSD. Ten neurones underwent brief single or repetitive changes of the same duration as the brief striatal excitation. Eight presented an initial brief change of activity followed by a longer duration inverse change in firing rate. Eighteen exhibited multiple brief changes followed by or superimposed on a long lasting decrease of firing rate and 50% of them were nigrotectal neurones. Sixteen neurones presented long duration biphasic changes in firing rate. Two SNr neurones and the 12 substantia nigra compacta (SNc) neurones studied were unaffected. Some neurones received both inhibitory and facilitatory striatal controls. In total thirty-nine neurones were inhibited and 47 facilitated, the origin of these effects from caudate and putamen are discussed. The excitatory action may be due to either a direct excitatory pathway or to a relayed effect of the inhibitory GABAergic pathway.

Action Potentials↗
PubMed1989

Pain from renal/ureteral calculosis: evaluation of sensory thresholds in the lumbar area.

Patients with unilateral renal/ureteral calculosis who had suffered a few painful attacks were examined. In the pain-free period, muscular, subcutaneous and cutaneous sensory thresholds to electrical stimulation were measured in the lumbar region (metamer L1) on both sides: (1) pain thresholds were lower on the affected side with respect to both the contralateral side and control thresholds recorded in normal subjects; (2) the greatest decrease in threshold was in the muscle (even the sensation of sustained contraction was no longer detectable), followed by subcutaneous tissue, and the smallest decrease was in the skin.

Adult↗
PubMed1989

A stereotaxic apparatus for the study of the central nervous structures in the pig.

An apparatus has been developed derived from the Horsley-Clarke principle. Specific requirement was to use large breeds of pigs from weaning to adult age (5 to 120 kg). The pig auditory canals are oblique; the measurement of the corresponding angles was achieved by means of two interconnected barrels, used afterwards to fix the ear-bars. The wide variability of the skull morphology led to the systematic use of ventriculography with a liquid of contrast. Consequently the pieces allowing the head fixation in the stereotaxic apparatus were designed to avoid any shadow on the brain area. As it was not always possible to localize the commissura anterior, the anterior border of the recessus preopticus was chosen to determine, together with the commissura posterior, the reference horizontal plane. The antero-posterior coordinates were counted from the anterior border of the commissura posterior. The methodology, which has been tested in a wide range of pigs, is discussed in relation with the methods used for other animal species.

Animals↗
PubMed1989

Antibiotics and morphinomimetic injections prevent automutilation behavior in rats after dorsal rhizotomy.

Unilateral section of dorsal roots C5 to T1 were performed in rats, and the automutilation behavior was measured by the extent of the limb lesions expressed in arbitrary units. Changes in the scores of automutilation were studied after the injection of four substances: a morphinomimetic (pethidine) and three antibiotics, chloramphenicol, amoxicillin, and doxycycline. Effects were tested on groups of at least eight rats that were compared with another group of eight animals operated on in the same way but injected with distilled water. The animals of the group treated with pethidine performed significantly less autotomy than did the animals in the control group. The same effect was found when the animals were injected with chloramphenicol and amoxicillin. On the contrary, doxycycline was found less efficacious. These results are discussed using the hypothesis of autotomy caused by an abnormal painful sensation felt in the deafferented forelimb.

Amoxicillin↗
PubMed1989

Evoked potentials from the human thalamus: correlation with microstimulation and single unit recording.

During stereotactic surgery, intrathalamic single unit recordings and summated evoked potentials (Th-SEP), evoked by percutaneous electrical median nerve stimulation and intrathalamic microstimulation, were done using the same microelectrode at the same site. Potentials evoked by natural and electrical stimulation were compared. The format of Th-SEP varied in anteroposterior, mediolateral and dorsoventral directions in the ventrocaudal nucleus (Vc). The positive response peak latency was shortest from the caudal part of Vc and longest from the anterior part of Vc.

Electric Stimulation↗
PubMed1988

Muscular hyperalgesia and hypoalgesia after stimulation of the ureter in rats.

Vocalization electric thresholds were measured bilaterally in muscles of the lower back and in the tail after electrical stimulation of the left ureter in rats implanted with electrodes. 'Painful' stimulation immediately produced a hyperalgesia lasting about half an hour in the left lower back muscles and tail, followed by a 10 min hypoalgesia limited to the back muscles. No modification or only a delayed hypoalgesia appeared in the right muscle. Strong but 'non-painful' stimulation produced no effect or gave rise to an immediate hypoalgesia in the left muscle. Weak non-painful stimulation produced a delayed hypoalgesia in the tail.

Animals↗
PubMed1988

[Interactions between basic and clinical research. 2 examples drawn from a personal experience].

Basic research helps to understand clinical knowledge which in turn leads to new fundamental research. Two examples are taken from the studies of the anomalies existing in the brain of patients suffering from Parkinson disease or deafferentation Pain. The researches performed to solve these two problems for the past 40 years (in particular by the author's working group) are replaced in the international context. In Man the precision of stereotaxic technique was improved by using the organisation of the somato-sensory thalamic projection described in animals by the physiologists. In the thalamus of Parkinsonian patients, the presence of cells bursting at tremor frequency led to search for the relations existing between the striato-nigral system and the motor thalamus. In the patients suffering from deafferentation Pain, a special role is attributed to the medial thalamus, whose characteristics were formerly studied in animals. The origin of the deafferentation Pain is nowadays studied in an animal model of this disease.

Animals↗
PubMed1986

Changes in substantia nigra pars reticulata activity following lesions of the substantia nigra pars compacta.

Single unit activity of substantia nigra reticulata (SNr) neurons was recorded in normal rats and bilaterally in rats subjected to a unilateral 6-hydroxydopamine lesion of the substantia nigra compacta 2-4 weeks previously. Lesions were assessed by rotational behaviour to apomorphine. In normal rats the majority of neurons (63%) showed a regular firing pattern. Following lesion the percentage of these cells was similar in the SNr contralateral to the lesion but decreased on the lesioned side to 26%, whereas bursting activity developed (37% vs 5% in normal rats). The mean firing rate of reticulata neurons was slightly increased after lesion, but not statistically significant.

Action Potentials↗
PubMed1986

Cortifugal influences on dorsal column nuclei: an electrophysiological study in the rat using the cortical spreading depression technique.

The sign and duration of corticofugal effects on the extracellularly recorded spontaneous activity of cuneate and gracile neurons were examined by means of the cortical spreading depression technique (CSD). Among the 40 units studied 22 showed changes in their spontaneous firing rate during the passage of a CSD. Changes were of either short (5-20 s) or long (greater than 20-140 s) duration. Increases and decreases in activity, as well as sequences of both types of alteration were observed. Short duration changes were more frequent and much more pronounced than those of long duration. From their time course and intensity the short duration effects seem to be related to the brief high frequency cortical neuron discharge that precedes the cortical silence due to CSD, whereas the long lasting effects seem related to the cortical block. It is concluded that the most important corticofugal effects on gracile and cuneate neurons are phasic in nature and the sensorimotor cortical regions were found to be responsible for these influences.

Animals↗
PubMed1986

Comparison in man of short latency averaged evoked potentials recorded in thalamic and scalp hand zones of representation.

Recordings were performed in the thalamus of 13 patients suffering from either abnormal movements or intractable pain, with the aim of delimiting the region to be destroyed or stimulated in order to diminish the syndrome. In 11 of these patients averaged evoked potentials were recorded simultaneously from the scalp and specific thalamus (VP) hand area levels following median nerve stimulation. These recordings were done during the operation or afterwards when an electrode was left in place for a program of stimulation. The latencies of onsets and peaks on the scalp 'P15' were compared with those of the VP wave; a clear correspondence was found. Moreover, when increased stimulation was used, both waves began to develop in parallel. Thus in the contralateral 'P15' a component exists due to the field produced by the thalamic response. To explain the presence of an ipsilateral scalp 'P15' wave, we propose that a second wave having the same latency and a slightly shorter peak exists on the scalp due to a field produced by a brain-stem response. This double origin of 'P15' is also shown by the different changes which the ipsilateral and contralateral waves present during changes in alertness. The scalp 'N18-N20' is also composed of at least 2 components. The first peak appears on the scalp with a latency shorter than that of the negativity which develops in the thalamus. The N wave, moreover, increases in latency with rapid stimulus repetition. We propose with others that 'N18' is a cortical event reflecting the arrival of the thalamo-cortical volley. The second component, 'N20,' has a peak latency closely correlated to that of the thalamic negativity. This component was present alone in 'N' when rapid stimulation (greater than 4/sec) was used, which did not change the thalamic response. It must be a field produced by the thalamic negativity.

Electrodes↗