Inhibitory control of nociceptive responses of trigeminal spinal nucleus cells by somatosensory corticofugal projection in rat.

The caudal division of the trigeminal spinal nucleus (Sp5C) is an important brainstem relay station of orofacial pain transmission. The aim of the present study was to examine the effect of cortical electrical stimulation on nociceptive responses in Sp5C neurons. Extracellular recordings were performed in the Sp5C nucleus by tungsten microelectrodes in urethane-anesthetized Sprague-Dawley rats. Nociceptive stimulation was produced by application of capsaicin cream on the whisker pad or by constriction of the infraorbital nerve. Capsaicin application evoked a long-lasting increase in the spontaneous firing rate from 1.4±0.2 to 3.4±0.6 spikes/s. Non-noxious tactile responses from stimuli delivered to the receptive field (RF) center decreased 5 min. after capsaicin application (from 2.3±0.1 to 1.6±0.1 spikes/stimulus) while responses from the whisker located at the RF periphery increased (from 1.3±0.2 to 2.0±0.1 spikes/stimulus under capsaicin). Electrical train stimulation of the primary (S1) or secondary (S2) somatosensory cortical areas reduced the increase in the firing rate evoked by capsaicin. Also, S1, but not S2, cortical stimulation reduced the increase in non-noxious tactile responses from the RF periphery. Inhibitory cortical effects were mediated by the activation of GABAergic and glycinergic neurons because they were blocked by bicuculline or strychnine. The S1 and S2 cortical stimulation also inhibited Sp5C neurons in animals with constriction of the infraorbital nerve. Consequently, the corticofugal projection from S1 and S2 cortical areas modulates nociceptive responses of Sp5C neurons and may control the transmission of nociceptive sensory stimulus.

Aspectos básicos en la práctica actual de la medicina clínica en el trópico (I). Enfermedades parasitarias / Basic features in the current practice of clinical medicine in the tropics (I). Parasitic diseases

En los últimos años, cada vez más médicos desean pasar parte de su formación médica en centros sanitarios de países en vías de desarrollo. Cuando se trabaja en estos centros destaca la importancia de las habilidades clínicas ante la limitación de recursos diagnósticos. Se van a encontrar numerosas enfermedades parasitarias, destacando el paludismo y las geohelmintiasis. En este trabajo se presentan nociones básicas de epidemiología, clínica, diagnóstico y tratamiento de las principales enfermedades parasitarias que pueden encontrarse en un centro sanitario rural del trópico(AU)

In recent years an increasing number of physicians want to spend part of their medical training in health facilities in developing countries. Working in these areas requires good clinical skills, particularly where diagnostic resources are limited. Trainees will attend patients with many different parasitic diseases such as malaria and soil transmitted helminthic infections. The aim of this work is to provide basic concepts of epidemiology, clinical characteristics, diagnosis and treatment of the principal parasitic diseases that could occur in a rural health post in the tropics(AU)

[Basic features in the current practice of clinical medicine in the tropics (I). Parasitic diseases]. / Aspectos básicos en la práctica actual de la medicina clínica en el trópico (I). Enfermedades parasitarias.

In recent years an increasing number of physicians want to spend part of their medical training in health facilities in developing countries. Working in these areas requires good clinical skills, particularly where diagnostic resources are limited. Trainees will attend patients with many different parasitic diseases such as malaria and soil transmitted helminthic infections. The aim of this work is to provide basic concepts of epidemiology, clinical characteristics, diagnosis and treatment of the principal parasitic diseases that could occur in a rural health post in the tropics.

Glial reactivity after antipsychotic treatment. An experimental study in rats and its implications for psychiatry.

INTRODUCTION: The importance of the glial cells in the function of the nervous system and in its pathology has been the object of multiple studies in the last years. Specifically, their role in the action of the antipsychotics is debated. Our study has analyzed glial reactivity in rats treated with antipsychotics. METHODOLOGY: In a first ultrastructural study of the arcuate nucleus of the hypothalamus, the animals were treated with chlorpromazine for 40 days, and were sacrificed at the end of the treatment, after 20 days of rest without treatment. In another series of studies, with the light microscope and immunohistochemistry we evaluated the immunoreactivity of the glial fibrillary acidic protein (GFAP) in six regions of the central nervous system of rats treated with typical and atypical antipsychotics. RESULTS: With the electron microscope, the animals treated with chlorpromazine showed a significant reduction of the axosomatic synapses on the neurons of the hypothalamic arcuate nucleus and an increase of glial presence, as noted by the greater amount of astrocyte processes. The mentioned modifications were reversible, tending to normalize in a group of animals sacrificed 20 days after completion of the treatment. In the immunohistochemical study, the glial reaction was important in the territory of the nucleus accumbens with all the antipsychotics, moderate in the cingulate cortex, although only with atypical antipsychotics, and scarcely significant in the rest of the regions. CONCLUSIONS: Our results confirm that the glial cells are targets of the antipsychotic action, and this will allow us to better understand the action of these drugs and the role of the glial cells in the normal function of the nervous system and in the mental disease.

Reactividad glial tras el tratamiemto con antipsicóticos. Estudio experimental en ratas e implicaciones para la psiquiatría / Glial reactivity after antipsychotic treatment. An experimental study in rats and its implications for psychiatry

Introducción. La importancia de las células gliales en la función del sistema nervioso y en su patología ha sido objeto de múltiples estudios en los últimos años. Concretamente se debate su papel en la acción de los antipsicóticos. Nuestro estudio analiza la reactividad glial en ratas tratadas con antipsicóticos. Metodología. En un primer estudio ultraestructural del núcleo arcuato del hipotálamo, los animales fueron tratados con clorpromacina durante 40 días, sacrificándose al final del tratamiento y tras 20 días de descanso. En otra serie de estudios, con el microscopio de luz y con técnicas inmunohistoquímicas valoramos la reacción a la proteína glial fibrilar ácida (GFAP) en seis regiones del sistema nervioso central de ratas tratadas con antipsicóticos típicos y atípicos. Resultados. Con el microscopio electrónico, las ratas tratadas mostraron una reducción significativa de las sinapsis axosomáticas sobre las neuronas del núcleo arcuato del hipotálamo, así como un incremento de la presencia glial evidenciable por la mayor cantidad de laminillas de astrocitos. Las modificaciones mencionadas son reversibles, tendiendo a normalizarse en los animales sacrificados a los 20 días de finalizado el tratamiento. En el estudio inmunohistoquímico la reacción astrocitaria fue muy importante en el territorio del núcleo accumbens con todos los antipsicóticos, moderada en la corteza cingular, aunque sólo con los atípicos, y discreta en el resto de las regiones. Conclusiones. Nuestros resultados confirman que las células gliales son diana de los antipsicóticos, lo que ha de contribuir a entender mejor la acción de estos fármacos y el papel de las células gliales en el normal funcionamiento del sistema nervioso y en la enfermedad mental (AU)

Introduction. The importance of the glial cells in the function of the nervous system and in its pathology has been the object of multiple studies in the last years. Specifically, their role in the action of the antipsychoticsis debated. Our study has analyzed glial reactivity in rats treated with antipsychotics. Methodology. In a first ultrastructural study of the arcuate nucleus of the hypothalamus, the animals were treated with chlorpromazine for 40 days, and were sacrificed at the end of the treatment, after 20 days of rest without treatment. In another series of studies, with the light microscope and immunohistochemistry we evaluated the immunoreactivity of the glial fibrillary acidic protein (GFAP) in six regions of the central nervous system ofrats treated with typical and atypical antipsychotics. Results. With the electron microscope, the animals treated with chlorpromazine showed a significant reduction of the axosomatic synapses on the neurons of the hypothalamic arcuate nucleus and an increase of glial presence, as noted by the greater amount of astrocyte processes. The mentioned modifications were reversible, tending to normalize in a group of animals sacrificed 20 days after completion of the treatment. In the immunohistochemical study, the glial reaction was important in the territory of the nucleus accumbens with all the antipsychotics, moderate in the cingulate cortex, although only with atypical antipsychotics, and scarcely significant in the rest of the regions. Conclusions. Our results confirm that the glial cells are targets of the antipsychotic action, and this will allow us to better understand the action of these drugs and the role of the glial cells in the normal function of the nervous system and in the mental disease (AU)

Characteristics of louse-borne relapsing fever in Ethiopian children and adults.

Louse-borne relapsing fever (LBRF) is endemic in Ethiopia. The epidemiological and clinical aspects of LBRF and the differences between the infection in children and that in adults were investigated in a rural hospital in Ethiopia. During the 5-year study (1997-2002), 197 patients had a confirmed diagnosis of LBRF. Most (62.1%) of the cases were children under 15 years of age. The adult cases (i.e. those aged > or =15 years) were far more likely to present with headache (76.9% v. 40%; P <0.001), musculo-skeletal pains (61.5% v. 30.5%; P <0.001), dizziness (64% v. 39%; P =0.002) and bleeding (16.9% v. 3.8%; P =0.005) than the paediatric. The overall level of case fatality was 6.4%. Death appeared to be significantly associated with adulthood (P =0.01), delay in consultation (P =0.026) and the presence of vomiting (P =0.023). LBRF is clearly still a public-health problem in Ethiopia, where the clinical manifestations of the disease differ according to the age of the case.

Corticofugal action on somatosensory response properties of rat nucleus gracilis cells.

Single unit recordings were performed in the nucleus gracilis (Gr) of anesthetized rats to study the influences of the sensorimotor corticofugal projections on sensory responses of those cells. The effects of electrical stimulation of contralateral primary sensory cortex were studied in two conditions: when the receptive fields of the stimulated cortical area and the gracilis cells overlapped (matched) or when they were completely different (unmatched). Cortical stimulation at low intensities (<50 microA) evoked spike firing only in gracilis neurons with matched receptive fields. When the receptive fields were unmatched, the intensity of the stimulation had to be increased above 50 microA to elicit spike firing. To study the corticofugal actions on the responses of Gr neurons, the onset of peripheral stimulation was likened to a single cortical shock in the sensorimotor cortex. When receptive fields matched, cortical stimulation facilitated the cellular responses to the natural sensory stimulation of their RF in most of the Gr neurons (86%). In the unmatched receptive fields, cortical stimulation could either inhibit (66.7%), facilitate (20.8%) or did not modify (12.5%) the sensory response at all. Trains of cortical shocks during sensory stimulation demonstrated that the facilitatory and inhibitory effects on Gr neurons outlasted the period of stimulation by 30-60 s. Results indicate that the sensorimotor cortex exercises a very precise control of sensory transmission throughout the Gr nucleus and suggest that the corticofugal projection may play an important role in the plasticity of the sensorimotor system.