Non-operative management of a pathological malaria splenic rupture A case report

Malaria continues to be a major health problem in many parts of the world especially in the endemic countries. Though, because of the international travelling, any physician everywhere should know this disease and its complications such as splenic rupture which is rare but life threatening. We report the case of an expatriate Tunisian man who had been working in Togo and who had consulted in Tunisia for an acute abdominal pain. Explorations concluded to a splenic rupture, a rare complication of malaria. Our attitude was conservative based on ressuscitation with monitoring and watchful waiting. The evolution was favorable marked by a significant regression of the splenic hematoma 5 months after hospital discharge. KEY WORDS: Haematoma, Malaria, Splenic rupture, Sub capsular.

Right hepatic artery pseudoaneurysm post laparoscopic cholecystectomy A case report

Right hepatic artery pseudoaneurysm following laparoscopic cholecystectomy is rare, but its rupture is common. It carries a high mortality rate if not successfully timely managed. In laparoscopic era, surgeons and physicians in general must be aware of this entity and its therapy. Conservative management is not recommended due to the propensity to rupture. Treatment consists on reconstructive surgery or ligation, but coil embolization is the treatment of choice nowadays and should be done without delay. KEY WORDS: Cholecystectomy, Embolization, Laparoscopy, Pseudoaneurysm rupture, Right hepatic artery.

The Performance Measurement Frameworks in Healthcare: Scopus Study

Object:

The purpose of this article is to analyse and compare the frameworks of performance measurement in primary health care in the world. The objective is to determine whether the frameworks of performance measurement in primary health care have an influence on the performance of health centres.

Method:

We conducted a systematic review of the literature to: (a) identify a conceptual framework for measuring quality management systems; and (b) assess the effects of the conceptual framework on quality improvement and quality of care outcomes. We chose frameworks highly cited in the literature and analysed and compared these frameworks.

Results:

Eight dimensions were identified for assessing performance in primary health care facilities (PHCFs) in more than 50% frameworks: effectiveness, safety, accessibility, equity, efficiency, acceptability, patient-centredness and timeliness.

Conclusion:

Even if the links are not established within the framework of a scientific research, quality approaches are generally recognised as an essential tool to help establishments improve their quality of care and the safety of their patients. Until now, the evaluation of the quality of care in the 'PHCF' is not yet in place, a blatant need for performance measurement tools, relevant information, coherence between the operational and strategic levels, integration of organizational objectives in the measurement of performance in order to direct the structures towards a true management by quality.

Factors related to the dangerousness of psychiatric inpatients

Introduction

Mental illness may explain some acting outs, but it does not necessarily lead to a dangerous attitude.

Objectives

Describe the socio-demographic, clinical and therapeutic characteristics of patients considered dangerous and to identify the determinants of psychiatric dangerousness.

Methods

We carried out a descriptive and analytical cross-sectional study during six months including patients hospitalized in the psychiatric department at the University Hospital of Mahdia. The data was collected using a 47-item pre-established questionnaire. The assessment of general psychopathology was carried out using the Brief Psychiatric Rating Scale (BPRS) and that of dangerousness using the Historical Clinical Risk-20 scale (HCR-20).

Results

We have collected 143 patients. The average age was 35 years. The majority of patients were single (70.6%). More than half of the population had addictive behaviors (60.1%). Personal psychiatric and criminal histories were present in 81.1% and 11.9% of cases respectively. More than three-quarters of patients (81.8%) were hospitalized without their consent. Hetero-aggressiveness was the main reason for hospitalization (67.8%). The diagnosis was schizophrenia and bipolar disorder type 2 in 21% of cases for each. The evaluation of psychiatric dangerousness by the HCR-20 scale revealed a mean score of 20.6 with an HCR-20 > 20 in 58.7% of cases indicating a high risk of violence. Factors contributing to violent or criminal behavior in psychiatric inpatients were marital status, presence of personal psychiatric history, presence of criminal history and hospitalization modalities.

Conclusions

The results of our study were generally consistent with the data in the literature.

Influence of weather and air pollution on the occurrence of idiopathic pulmonary embolism in the region of Sousse (Tunisia)

Pulmonary embolism (PE) is the most serious manifestation of thromboembolic conditions. Its incidence varies considerably between countries, suggesting its interaction with the external environment. To analyze the influence of climate and air pollution on the occurrence of idiopathic PE in the region of Sousse (Tunisia). A total of 142 patients with idiopathic PE at two academic hospitals in Sousse (Tunisia) were enrolled in the study over a 7-year period. An analysis of two time series (environmental data and PE cases) was performed. Climatic data were collected from the National Institute of Meteorology. Air pollution data were obtained from the modeling platform of the National Agency for Protection of the Environment. The year 2015 was marked by the occurrence of the highest number of cases (24.6%). A statistically significant decrease in PE risk of 41.9% was observed during the summer with an OR of 0.59 (95% CI [0.36-0.94] and p = 0.026), compared with other seasons. Poisson GLM regression showed a significant increased risk of PE of 3.3% for each 1 °C temperature drop. After multiple binary logistic regression, the elevation of PM₁₀ concentration was independently associated with an increased risk of PE (p < 10^-3, OR 79.55, 95% CI [42.28-149.6]). Some environmental parameters may predispose to the onset of idiopathic PE. Understanding their accurate influence may have preventive and curative implications.

Residence time distribution studies using radiotracers in a lab-scale distillation column: Experiments and modeling

The radiotracer's residence time distribution (RTD) is an important study of the performance of industrial process reactors.The application of radiotracers is the method used to diagnose the functioning of packed distillation columns. This paper presents the results of an experiment carried out using the Technitium-99 (Mo⁹⁹) radiotracer to determine the RTD in a laboratory-scale packed distillation column.The concentration of the radiotracer is monitored using eight scintillation detectors.The obtained data is treated for background correction, radioactive decay correction, starting point correction, filtering, and data extrapolation. After this preprocessing, two mathematical models are investigated on this data using International Atomic Energy Agency (IAEA) RTD software. The parameters of each model are optimized in oder to calculate the value of the RTD, and to determine the model which gives the best match with the experimental data. The appropriate model is than selected. Consequenly the one with the best match, is used to deduce the crucial parameter RTD in this experiment.

Assessment of the operating room efficiency by the real time of room occupancy

BACKGROUND

The operating room is the most cost consuming area of hospitals. However, it still suffers from a non-optimized organization.

AIM

To evaluate the performance of our operating rooms by the real room occupancy time (RROT), to identify the main causes of its alteration and to analyze the problem of deprogramming.

METHODS

This is an observational and descriptive study conducted in two operating rooms in Sahloul teaching Hospital during August 2016. For the two studied rooms, a pre-established data sheet was filled during the days of scheduled activity. Collected parameters were  total RROT,  different periods of RROT, room occupancy rate, room overflow rate, incidence and causes of non-compliance with the surgical program and causes of RROT alteration.

RESULTS

  The mean start time of the activity was 41.93 min/day. The mean overflow time was 11.51 min/day. The RROT was 246.56 min/day, corresponding to an average occupancy rate of 68.49%. On average 1.86 acts were performed per room and per morning with a total of 86 interventions. The deprogramming problem was noted in 38 cases. Its main causes were the overshoot of the vacation time offered to surgeons (36.84%), the emergencies (18.42%) and the non-respect of the anesthesia instructions (15.78%).

CONCLUSION

The occupancy rate in our structures is relatively acceptable but should not hide the need to optimize the use of available resources. Corrective actions focusing primarily on delayed start-up and periodic reassessments are essential.

Intravenous lidocaine as adjuvant to general anesthesia in renal surgery

The role of intraoperative intravenous lidocaine infusion has been previously evaluated for pain relief, inflammatory response, and post-operative recovery, particularly in abdominal surgery. The present study is a randomized double-blinded trial in which we evaluated whether IV lidocaine infusion reduces isoflurane requirement, intraoperative remifentanil consumption and time to post-operative recovery in non-laparoscopic renal surgery. Sixty patients scheduled to undergo elective non-laparoscopic renal surgery under general anesthesia were enrolled to receive either systemic lidocaine infusion (group L: bolus 1.5 mg/kg followed by a continuous infusion at the rate of 2 mg/kg/hr until skin closure) or normal saline (0.9% NaCl solution) (Group C). The depth of anesthesia was monitored using the Bispectral Index Scale (BIS), which is based on measurement of the patient’s cerebral electrical activity. Primary outcome of the study was End-tidal of isoflurane concentration (Et-Iso) at BIS values of 40–60. Secondary outcomes include remifentanil consumption during the operation and time to extubation. Et-Iso was significantly lower in group L than in group C (0.63% ± 0.10% vs 0.92% ± 0.11%, p < 10^–3). Mean remifentanil consumption of was significantly lower in group L than in group C (0.13 ± 0.04 µg/kg/min vs 0.18 ± 0.04 µg/kg/min, p < 10^–3). Thus, IV lidocaine infusion permits a reduction of 31% in isoflurane concentration requirement and 27% in the intraoperative remifentanil need. In addition, recovery from anesthesia and extubation time was shorter in group L (5.8 ± 1.8 min vs 7.9 ± 2.0 min, p < 10^–3). By reducing significantly isoflurane and remifentanil requirements during renal surgery, intravenous lidocaine could provide effective strategy to limit volatile agent and intraoperative opioids consumption especially in low and middle income countries.

Effects of music therapy under general anesthesia in patients undergoing abdominal surgery

BACKGROUND

Music therapy, an innovative approach that has proven effectiveness in many medical conditions, seems beneficial also in managing surgical patients. The aim of this study is to evaluate its effects, under general anesthesia, on perioperative patient satisfaction, stress, pain, and awareness.

METHODS

This is a prospective, randomized, double-blind study conducted in the operating theatre of visceral surgery at Sahloul Teaching Hospital over a period of 4 months. Patients aged more than 18 undergoing a scheduled surgery under general anesthesia were included. Patients undergoing urgent surgery or presenting hearing or cognitive disorders were excluded. Before induction, patients wore headphones linked to an MP3 player. They were randomly allocated into 2 groups: Group M (with music during surgery) and group C (without music). Hemodynamic parameters, quality of arousal, pain experienced, patient's satisfaction, and awareness incidence during anesthesia were recorded.

RESULTS

One hundred and forty patients were included and allocated into 2 groups that were comparable in demographic characteristics, surgical intervention type and anesthesia duration. Comparison of these two groups regarding the hemodynamic profile found more stability in group M for systolic arterial blood pressure. A calm recovery was more often noted in group M (77.1% versus 44%, p < 10^-3). The average Visual Analog Scale (VAS) score was lower in the intervention group (33.8 ± 13.63 versus 45.1 ± 16.2; p < 10^-3). The satisfaction rate was significantly higher among the experimental group (81.4% versus 51.4%; p < 10^-3). The incidence of intraoperative awareness was higher in group C (8 cases versus 3 cases) but the difference was not statistically significant.

CONCLUSION

Music therapy is a non-pharmacological, inexpensive, and non-invasive technique that can significantly enhance patient satisfaction and decrease patients' embarrassing experiences related to perioperative stress, pain, and awareness.

Prévalence du burnout en milieu d'anesthésie réanimation dans le centre tunisien

Introduction

l'épuisement professionnel serait particulièrement préoccupant en milieu d'anesthésie réanimation. En plus de ses répercussions socio-économiques, il altère la qualité des soins prodigués et le pronostic des malades. Notre but est d'évaluer sa prévalence chez le personnel d'anesthésie-réanimation dans le centre tunisien.

Méthodes

il s'agit d'une enquête multicentrique transversale réalisée au sein des services d'anesthésie-réanimation dans les sept centres hospitalo-universitaires du centre tunisien et portant sur tout le personnel médical et paramédical consentant. L'instrument de mesure utilisé est le Maslach burnout Inventory.

Résultats

deux cent quatre-vingt-trois personnes ont participé à l'étude (72,19%). L'âge moyen était de 40,2 ± 9,38 ans avec une prédominance féminine. L'analyse de l'échelle de Maslach a révélé que 94,71% des participants étaient concernés par le burnout. Les scores moyens d'épuisement émotionnel, de dépersonnalisation et d'accomplissement professionnel étaient respectivement de 28,65 ± 11,92; 8,62 ± 6.65 et 34,58 ± 8,07. Un niveau élevé à modéré de burnout a été trouvé respectivement dans 13,3% et 26,2% des cas. Un niveau bas a été trouvé dans 55,21% des cas. Les répercussions du burnout sont dominées par les conduites additives (52,65%) et les idées suicidaires (4,59%).

Conclusion

le burnout apparaît de plus en plus comme une réalité palpable chez le personnel d'anesthésie réanimation. Ses conséquences sont graves aussi bien sur le plan individuel que social.

Founder effect and estimation of the age of the c.892C>T (p.Arg298Cys) mutation in LMNA associated to Charcot-Marie-Tooth subtype CMT2B1 in families from North Western Africa

CMT2B1, an axonal subtype (MIM 605588) of the Charcot-Marie-Tooth disease, is an autosomal recessive motor and sensory neuropathy characterized by progressive muscular and sensory loss in the distal extremities with chronic distal weakness. The genetic defect associated with the disease is, to date, a unique homozygous missense mutation, p.Arg298Cys (c.892C>T), in the LMNA gene. So far, this mutation has only been found in affected individuals originating from a restricted region of North Western Africa (northwest of Algeria and east of Morocco), strongly suggesting a founder effect. In order to address this hypothesis, genotyping of both STRs and intragenic SNPs was performed at the LMNA locus, at chromosome 1q21.2-q21.3, in 42 individuals affected with CMT2B1 from 25 Algerian families. Our results indicate that the affected individuals share a common ancestral haplotype in a region of about 1.0 Mb (1 cM) and that the most recent common ancestor would have lived about 800-900 years ago (95% confidence interval: 550 to 1300 years).

Dégradation photochimique d'herbicides chlorophenoxyalcanoïques en milieux aqueux

La dégradation photochimique de cinq herbicides appartenant à la famille des chlorophénoxyalcanoïques a été étudiée en solution aqueuse par irradiation à 254 nm selon trois systèmes : UV seul, UV/H2O2 et UV/H2O2/ FeIII (photo-Fenton). Le procédé photochimique semble constituer une alternative prometteuse aux méthodes existantes de traitement chimique des eaux polluées; en effet il permet de détruire photochimiquement l'herbicide initial et d'obtenir, dans les conditions opératoires initiales, sa minéralisation complète en CO2 et H2O. Il s'agit d'un procédé d'oxydation avancé, utilisant comme agent oxydant, des radicaux OH. produits in situ photochimiquement. L'évolution de la composition chimique des solutions d'herbicides étudiés a été suivie par chromatographie liquide à haute performance (CLHP). La minéralisation a été évaluée par mesure de la demande chimique en oxygène (DCO) et par le dosage des ions chlorures libérés. La cinétique de photodégradation, la nature et l'évolution des produits formés ainsi que le rendement du procédé ont été déterminés.

Effects of intraperitoneally administered vitamin E and selenium on calcium oxalate renal stone formation: experimental study in rat

Forty-eight Wistar rats were treated for 3 weeks with water containing 0.7% ethylene-glycol and divided into four groups. The first group, used as control, has received sodium chloride at 1 ml/100 g BW daily. The second group was intraperitoneally injected with selenium at 10 micrograms/d per 100 g BW as NaSeO3 for 3 weeks. The third group was intraperitoneally administered with 15 mg Vit E/d per 100 g BW as alpha-tocopherol acetate for 3 weeks. The last group was simultaneously administered vitamin E and Se at the same doses and periods as the precedent groups. One day before the end of the treatment, each animal was placed in a metabolic cage for collection of 24 h urine samples and determination of urinary creatinin, urea, calcium, magnesium, phosphate and oxalate levels. Immediately thereafter, all the rats were anesthetized and aortic blood was collected to determine the same parameters as in urine. The kidneys were also removed to determine calcium oxalate deposits, dry weight and to conduct a histological examination. Our results showed decreased ionic product and increased magnesium fractional reabsorption in the group receiving only selenium and in the group receiving selenium in combination with vitamin E, in comparison with the control animals. In view of the knowledge concerning the same protective action of Vit E and selenium, regardless of tubular membrane alteration, the absence of any inhibitory effect of Vit E on calcium oxalate formation suggests that selenium, like other minerals, could be stuck onto the crystal surface and would inhibit induction of new crystals, growth and aggregation.

The phenotypic manifestations of autosomal recessive axonal Charcot-Marie-Tooth due to a mutation in Lamin A/C gene

Charcot-Marie-Tooth disease constitutes a genetically heterogeneous group of hereditary motor and sensory peripheral neuropathies. The axonal type of Charcot-Marie-Tooth is designated type 2. Six loci for autosomal dominant and three for recessive Charcot-Marie-Tooth type 2 have been reported so far. In this study we report the phenotype of autosomal recessive axonal Charcot-Marie-Tooth type 2 due to a recently-described mutation (c.892C>T-p.R298C) in a gene encoding Lamin A/C nuclear envelope proteins and the first gene in which a mutation leads to autosomal recessive Charcot-Marie-Tooth type 2. We have explored eight patients from four Algerian families. The onset is usually in the second decade and the course is rapid, involving upper limbs and proximal muscles, leading to a severe condition in less than 4 years. Many different mutations in Lamin A/C have been identified as causing variable phenotypes, such as limb girdle muscular dystrophy type 1B, autosomal dominant and recessive Emery-Dreyfuss muscular dystrophy, dilated cardiomyopathy with atrioventricular conduction defect, and Dunnigan-type familial partial lipodystrophy should prompt us to fully investigate the skeletal and cardiac muscles in patients affected with autosomal recessive Charcot-Marie-Tooth type 2 carrying a mutation in LMNA.

[Septic arthritis of posterior lumbar facet joint]

Septic arthritis of the posterior lumbar joints is extremely rare. The clinical picture of this unusual site of infection can easily lead to confusion with spondylodiscitis which is more common. We report a case of a 50-year-old woman with Staphylococcus aureus septic arthritis of the left L5-S1 lumbar facet joint. CT scan was helpful to establish the diagnosis and to guide the percutaneous needle biopsy.

[Absence of litholytic effects of zinc sulfate and copper sulfate in experimental lithiasis in rats]

Seventy two male Wistar-strain rats were fed lithogenic diet with ethylene-glycol within three weeks. At the end of this treatment, six rats were killed in order to determine the oxalate and calcium concentrations in renal tissue. Remained rats was randomly divided in four series, each series consisting of three groups. In first series (T), the animals were treated with distilled water; in the second (D1Zn), the animals were treated intramuscularly with the zinc at the rate of 24 micrograms per 100 grams of body weight and per day; in the third (D2Zn), 240 micrograms of zinc were administrated to animals and in the last series (D2Cu), the animals were treated at the same dose as the previous series, but with the copper. The groups which making up each series were killed successively at the 5th, 10th and 15th day after ending treatment with ethyleneglycol in order to determine urinary pH, percentage of water in renal tissue, uremia and concentrations of oxalate and calcium in renal tissue. Then, the comparisons of means were carried out, at each time, between different treated groups and reference group which was treated with distilled water. Litholytic effect was found in all series, including that which had been treated with distilled water. However, compared to reference animals, no acceleration of litholytic process was induced by zinc or copper. The high doses used in these experimentations proved therefore that calcium oxalate calculi were insoluble by zinc and copper.

Severe childhood autosomal recessive muscular dystrophy with the deficiency of the 50 kDa dystrophin-associated glycoprotein maps to chromosome 13q12

We have recently demonstrated the specific deficiency for the 50 kDa dystrophin-associated glycoprotein (50DAG) in Algerian patients afflicted with severe childhood autosomal recessive muscular dystrophy with DMD-like phenotype (SCARMD). A similar disease affecting Tunisian patients was linked to chromosome 13q but the status of the 50DAG was not investigated. Here we show by linkage analysis of Algerian families that the genetic defect which leads, either directly or indirectly, to the deficiency of the 50DAG in skeletal muscle is localized to the proximal part of chromosome 13q. We have not found any evidence of genetic heterogeneity among the thirteen families studied. It remains to be demonstrated whether the 50DAG gene maps at 13q12, and to determine if it is mutated in this disease.

Neurons at the origin of the medial component of the bulbopontine spinoreticular tract in the rat: an anatomical study using horseradish peroxidase retrograde transport

An anatomical technique based on the retrograde transport of horseradish peroxidase (HRP) was used to investigate the projections of spinal cord neurons to the reticular formations in the rat. Both large and restricted injections were staggered all along the bulbar and pontine levels, involving the nucleus gigantocellularis, the nuclei reticularis pontis, pars oralis and caudalis and in some cases the nucleus raphé magnus. Labeled cells were constantly encountered in the reticular part of the neck of the dorsal horn throughout the whole length of the cord, mainly contralateral to the central core of the injection site. This area was taken as the equivalent of lamina V in the cat. Other labeled cells were observed in the medial parts of the intermediate and ventral horns, in areas considered similar to laminae VII and VIII in the cat. The two most rostral cervical segments were characterized by an additional bilateral projection originating from the dorsolateral part of ventral horns. Thus, this study is a clear confirmation that the bulbopontine reticular formations constitute a target for various somatosensory inputs originating in spinal cord. It demonstrates that the medial spinoreticular tract (mSRT) differs from the other main ascending tracts by the absence of projections from (1) superficial layers and nucleus of the dorsolateral funiculus contrary to the spinomesencephalic tract; (2) ventromedial zone of the lumbar dorsal horn unlike the spinothalamic tract; (3) the neck of the dorsal horn in its medial portion contrary to the spinoreticular component reaching the lateral reticular nucleus; and (4) central cervical nucleus and Clarke's columns, unlike the spinocerebellar tracts. The difficulty in demonstrating retrograde labeling from discrete injections could result from the fact that mSRT neurons have sparsely ramified collaterals on their terminal zones.

The origin of the spinomesencephalic tract in the rat: an anatomical study using the retrograde transport of horseradish peroxidase

An anatomical technique based on the retrograde transport of horseradish peroxidase (HRP) was used to investigate the projections of spinal cord neurons to the mesencephalic tegmentum in the rat. Restricted unilateral injections were confined to central grey, cuneiformis areas, and superior colliculus. Injections into all these loci produced labeling in similar spinal areas. Only quantitative differences were noted. In the spinal grey matter, numerous labeled cells were regularly encountered in the marginal zone, the lateral part of the neck of the dorsal horn, and the dorsal grey commissure. Projections from the marginal zone and neck of the dorsal horn were predominantly contralateral. In the white matter, a pronounced bilateral labeling was observed in the nucleus of the dorsolateral funiculus, thus confirming our previous electrophysiological findings (Menétrey et al., '80). This distribution of labeled cells was commonly observed throughout the whole length of the cord. Additional sites of projecting cells have also been identified at the most rostral levels (obex, C1, C2). They mostly derived from spinal extensions of the dorsal column nuclei and lateral cervical nucleus contralaterally; from the lateral ventral horns bilaterally and from the nucleus commissuralis ipsilaterally. This study is thus a clear confirmation that the mesencephalic tegmentum constitutes a target for various somatosensory inputs originating from spinal cord, dorsal column nuclei, and lateral cervical nucleus. Moreover, from these results together with those obtained for the spinothalamic tract in the rat, it appears that marginal and dorsolateral funiculus neurons preferentially project to the mesencephalic tegmentum. The importance of marginal zone projections underlines the involvement of the spinomesencephalic tract in pain mechanisms.

Diffuse noxious inhibitory controls (DNIC) in the rat with or without pCPA pretreatment

Diffuse Noxious Inhibitory Controls (DNIC) were investigated in anaesthetized intact rats, with or without p-chlorophenylalanine (pCPA) pretreatment. Dorsal horn convergent neurones responding to both noxious and non-noxious stimuli applied to their excitatory receptive field located on the distal part of the hindlimb, were recorded in the lumbar spinal cord. These cells received A alpha and C fibre inputs as shown by electrical stimulation of their receptive field. In control animals, the evoked responses to C fibre inputs could be strongly inhibited by various noxious stimuli applied to widespread areas of the body: the inhibitory effects induced by intraperitoneal administration of bradykinin, pinch applied to the tail or muzzle and noxious heat applied to the tail were of 77%, 87%, 83% and 61% respectively. Long-lasting post-effects were seen in most cases after cessation of the application of the conditioning stimulus. Pretreatment with pCPA (300 mg/kg, i.p., 3 days) resulted in a strong reduction of DNIC. The inhibitory effects induced by intraperitoneal administration of bradykinin, pinch applied to the tail or muzzle and noxious heat applied to the tail were reduced by 47%, 63%, 87% and 63%, respectively. The post-effects were also reduced both in terms of magnitude and duration. These results strongly suggest that serotonergic pathways partially involved in DNIC. They are discussed with reference to the descending control systems, originating from the caudal raphé, which modulate the transmission and/or the integration of nociceptive messages at the spinal level. The possible involvement of DNIC and 5-HT mechanisms to the hypo-algesic phenomena induced by hyper-stimulation is also suggested.

Nucleus raphe magnus modulation of response of rat dorsal horn neurons to unmyelinated fiber inputs: partial involvement of serotonergic pathways

1. In the rat under N2O-halothane anesthesia, stimulation of the nucleus raphe magnus (NRM) with stimulus parameters similar to those used to obtain analgesia in freely moving animals strongly inhibits the responses of dorsal horn convergent neurons due to A-delta- and C-afferents. 2. Responses to noxious radiant heat were also depressed, and pronounced post-effects were frequently observed. 3. Comparison between coupled sites of stimulation in NRM and in adjacent bulbar reticular formation (BRF) on responses to C-fibers revealed the preeminent effects of NRM; these were systematically encountered (93% of neurons), much more pronounced, and of longer duration. 4. The latency of these inhibitory effects (around 20 ms) suggests the participation of myelinated axons in such descending action and, consequently, we question the involvement of unmyelinated serotonergic fibers. 5. However, descending inhibitory influences from NRM on responses to C-fibers are reduced after 5-hydroxytryptamine (5-HT) depletion by p-chlorophenylalinine (pCPA), thus demonstrating the implication of both serotonergic and nonserotonergic pathways. 6. In addition, after pCPA pretreatment, long-lasting and sustained excitatory effects from NRM were observed in 35% of convergent neurons; their possible origin is discussed.

Location and properties of dorsal horn neurons at origin of spinoreticular tract in lumbar enlargement of the rat

1. Spinoreticular tract neurons at the rat lumbar cord level were identified by antidromic activation following stimulation at mainly pontine and mesencephalic levels. These units, which were found in the dorsal half of the cord, could be separated into two groups according to their spinal location, electrophysiological properties, and their central projections. 2. Units in the dorsolateral funiculus nucleus projected mainly to the cuneiformis area and adjacent structures with frequent bilateral projections. They had the slowest conduction velocities, sometimes in the unmyelinated range. Generally, they were driven only by stimulation of subcutaneous and/or deep structures. 3. Neurons located in the dorsal horn mainly projected contralaterally to pontine and mesencephalic levels. their conduction velocities and the electrophysiological properties were identical to those observed for the rat spinothalamic tract (22). Almost all (86%) had clear cutaneous sensitivity and generally large receptive fields: 40% responded to nonnoxious and noxious mechanical cutaneous stimuli and frequently to noxious radiant heat, 26% were exclusively excited by light tactile stimuli, and 20% required noxious cutaneous mechanical stimulation for activation. There was a good correlation between responses to natural and transcutaneous electrical stimulation: units driven by noxious mechanical stimuli received A-delta- and/or C-fiber inputs. The remaining units (14%) had more complex receptive fields associated with both excitatory and inhibitory inputs originating from a single peripheral area. 4. The functional heterogeneity of the rat spinoreticular tract is reminiscent of that demonstrated for the rat and monkey spinothalamic tracts. Similarly, the rat spinoreticular neurons are under the influence of descending inhibitory controls originating from the nucleus raphe magnus and bulbar reticular formation. 5. Responses of the rat spinoreticular tract neurons are consistent with the involvement of this pathway in the transmission of messages of both innocuous and noxious origins.

[Role of serotonin in the diffuse inhibitory controls induced by nociceptive stimulation]

In the anaesthetized Rat, the entire population of dorsal horn convergent neurones is differentially affected by a noxious stimulus: while exciting the segmental pool, it strongly inhibits the remaining population. The inhibitory effects, which involve supraspinal mechanisms, are reduced to a great extent in parachlorophenylalanine pretreated animals. The role of raphé-spinal serotonergic pathways in nociception is discussed.

The influence of naloxone on the C fiber response of dorsal horn neurons and their inhibitory control by raphe magnus stimulation

In intact rats anesthetized with chloralose, the effects of naloxone were studied on the responses of spinal cord dorsal horn neurons to C fiber stimulation and upon the inhibition induced on these responses by stimulation of the nucleus raphé magnus (NRM). (1) A mean 44% facilitatory effect on responses to C fibers was observed for 12/19 units. (2) A mean 30% reduction of the inhibitory effects of NRM was found for 14/29 units. (3) However there is no clear relationship between these facilitatory effects and the diminution of the efficiency of NRM stimulation. These results demonstrate a facilitatory effect of naloxone upon the transmission of noxious messages at the spinal level and confirm that opiate endogenous substances are implicated in the inhibitory mechanisms activated by stimulation of NRM.

Responses of spinal cord dorsal horn neurones to non-noxious and noxious cutaneous temperature changes in the spinal rat

(1) Lumbar dorsal horn units characterized by their mechanical cutaneous sensitivities were tested for their responses to temperature changes of the skin in the decerebrate spinal rats. (a) Class 1 units (i.e. driven by non-noxious mechanical stimuli) were rarely thermally sensitive. (b) Nearly all class 2 units (i.e. driven by both non-noxious and noxious mechanical stimuli) and 4 of the 5 class 3 units (i.e. driven by noxious mechanical stimuli) were sensitive to temperature changes. (2) According to their thermal response threshold and their response range, these units were divided into 3 groups. (a) Warming units whose response threshold and maximum response were below 42.5 degrees C. Such units were rarely encountered. (b) Warming/noxious heat units whose response threshold was below 42.5 degrees C but with a maximum response above this temperature. They represented approximatively one-third of the radiant heat-sensitive units. (c) Noxious heat units whose response threshold was above 42.5 degrees C and maximum discharge several degrees above it. Approximately 50% of units activated by radiant heat belonged to this group. (3) Responses to radiant heat stimulation were frequently affected by a first noxious heat application. It consisted: --in a threshold decrease and/or an increase of their cellular discharge for a same temperature range. Only observed for warming/noxious heat units and noxious heat units, this sensitization phenomenon predminantly affected noxious heat units. --in a decrease of cellular discharge for a same temperature range. This desensitization phenomenon was observed for the 3 groups of units driven by radiant heat but mainly for warming units. (4) Supramaximal transcutaneous electrical stimulation revealed that nearly all the thermally sensitive units received A delta and/or C inputs. These units were largely distributed throughout the dorsal horn (laminae I, IV and V). Ten of the 12 lamina I units responded to noxious thermal stimuli. (5) These data indicate that an increase in skin temperature is coded at the level of the rat spinal cord dorsal horn by both an increase in discharge of low threshold temperature sensitive units and a progressive recruitment of high threshold units.