Administration of pilocarpine causes epilepsy in rats if status epilepticus (SE) is induced at an early age. To determine in detail the electrophysiological patterns of the epileptogenic activity in these animals, 46 Wistar rats, 7-17 days old, were subjected to SE induced by pilocarpine and electro-oscillograms from the cortex, hippocampus, amygdala, thalamus and hypothalamus, as well as head, rostrum and vibrissa, eye, ear and forelimb movements, were recorded 120 days later. Six control animals of the same age range did not show any signs of epilepsy. In all the rats subjected to SE, iterative spike-wave complexes (8.1 ± 0.5 Hz in frequency, 18.9 ± 9.1 s in duration) were recorded from the frontal cortex during absence fits. However, similar spike-wave discharges were always found also in the hippocampus and, less frequently, in the amygdala and in thalamic nuclei. Repetitive or single spikes were also detected in these same central structures. Clonic movements and single jerks were recorded from all the rats, either concomitantly with or independently of the spike-wave complexes and spikes. We conclude that rats made epileptic with pilocarpine develop absence seizures also occurring during paradoxical sleep, showing the characteristic spike-wave bursts in neocortical areas and also in the hippocampus. This is in contrast to the well-accepted statement that one of the main characteristics of absence-like fits in the rat is that spike-wave discharges are never recorded from the hippocampal fields.

This article is a transcription of an electronic symposium held on February 5, 2001 by the Brazilian Society of Neuroscience and Behavior (SBNeC) during which eight specialists involved in clinical and experimental research on sleep and dreaming exposed their personal experience and theoretical points of view concerning these highly polemic subjects. Unlike most other bodily functions, sleep and dreaming cannot, so far, be defined in terms of definitive functions that play an ascribable role in maintaining the organism as a whole. Such difficulties appear quite clearly all along the discussions. In this symposium, concepts on sleep function range from a protective behavior to an essential function for maturation of the nervous system. Kleitman's hypothesis [Journal of Nervous and Mental Disease (1974), 159: 293-294] was discussed, according to which the basal state is not the wakeful state but sleep, from which we awake to eat, to protect ourselves, to procreate, etc. Dreams, on the other hand, were widely discussed, being considered either as an important step in consolidation of learning or simply the conscious identification of functional patterns derived from the configuration of released or revoked memorized information.

This article is an edited transcription of a virtual symposium promoted by the Brazilian Society of Neuroscience and Behavior (SBNeC). Although the dynamics of sensory and motor representations have been one of the most studied features of the central nervous system, the actual mechanisms of brain plasticity that underlie the dynamic nature of sensory and motor maps are not entirely unraveled. Our discussion began with the notion that the processing of sensory information depends on many different cortical areas. Some of them are arranged topographically and others have non-topographic (analytical) properties. Besides a sensory component, every cortical area has an efferent output that can be mapped and can influence motor behavior. Although new behaviors might be related to modifications of the sensory or motor representations in a given cortical area, they can also be the result of the acquired ability to make new associations between specific sensory cues and certain movements, a type of learning known as conditioning motor learning. Many types of learning are directly related to the emotional or cognitive context in which a new behavior is acquired. This has been demonstrated by paradigms in which the receptive field properties of cortical neurons are modified when an animal is engaged in a given discrimination task or when a triggering feature is paired with an aversive stimulus. The role of the cholinergic input from the nucleus basalis to the neocortex was also highlighted as one important component of the circuits responsible for the context-dependent changes that can be induced in cortical maps.

Foram determinados os perigos e os pontos críticos de controle (PCC) associados a preparações de almôndegas e kibes em uma cozinha hospitalar, baseados em fluxogramas de preparo e análises microbiológicas de amostras coletadas ao longo da preparação. As análises microbiológicas incluíram a contagem de microrganismos mesófilos, psicrotróficos, bolores e leveduras, C. perfringens, estafilococos coagulase positiva, bactérias do grupo B. cereus, número mais provável de coliformes totais e fecais e pesquisa de Salmonella. Foram medidos o tempo e a temperatura em todas as etapas da preparação. Para a determinação dos PCCs foi utilizada uma árvore decisória. Foram detectados os seguintes perigos: a contaminação da carne e vegetais crus, a multiplicação dos microrganismos durante a etapa de manipulação da carne, a falta de higiene dos utensílios equipamentos, a sobrevivência de microrganismos ao processo de cocção. A cocção e a manutenção à quente foram considerados PCCs. Os resultados indicam a importância da implantação de um programa de treinamento de nutricionistas e cozinheiros e de um sistema de monitoramento dos PCCs, assim como de medidas para a prevenção de doenças de origem alimentar.

Hazards and critical control points (CCP) associated with meat balls and kibbe preparations in a hospital kitchen were determined using flow diagrams and microbiological testing of samples collected along the production line. Microbiological testing included counts of mesophilic and psicrothrophic microorganisms, yeasts and molds, total and fecal coliforms, C. perfringens, coagulase positive staphylococci, bacteria of the B. cereus group and detection of Salmonella. Time/temperature binomial was measured in all steps of preparation. A decision tree was used to help in the determination of CCPs. The detected hazards were: contamination of raw meat and vegetables, multiplication of the microorganisms during meat manipulation, poor hygiene of utensils and equipment, and survival of microorganisms to the cooking process. Cooking and hot-holding were considered CCPs. The results stress the importance of the implementation of a training program for nutricionists and foodhandlers and the monitoring of CCPs and other measures to prevent foodborne diseases.

Theta rhythm in many brain structures characterizes wakefulness and desynchronized sleep in most subprimate mammalian brains. In close relation to behaviors, theta frequency and voltage undergo a fine modulation which may involve mobilization of dorsal raphe nucleus efferent pathways. In the present study we analyzed frequency modulation (through instantaneous frequency variation) of theta waves occurring in three cortical areas, in hippocampal CA1 and in the dorsal raphe nucleus of Wistar rats during normal wakefulness and after injection of the 5-HT1a receptor agonist 8-OH-DPAT into the dorsal raphe. We demonstrated that in attentive states the variation of theta frequency among the above structures is highly congruent, whereas after 8-OH-DPAT injection, although regular signals are present, the variation is much more complex and shows no relation to behaviors. Such functional uncoupling after blockade demonstrates the influence of dorsal raphe nucleus efferent serotoninergic fibers on the organization of alertness, as evaluated by electro-oscillographic analysis.

Foram obtidos potenciais evocados transcalosos por aplicação de pulsos quadrados de 1 ms, 5 c/s e intensidade variável e registro sobre a corticalidade de gatos anestesiados com quetamina. Os locais de estimulação e registro eram selecionados através de mapa cartesiano de grande parte do neocórtex. Além das bem conhecidas projeções calosas, foram discriminadas áreas posteriores cuja estimulação evocava potenciais de baixa amplitude em sua área homóloga e potenciais de grande amplitude em regiões mais anteriores, ipsi- e contralateralmente. Esta conexão transcalosa em forma de 'L' pode estar envolvida em processos corticais complexos e é compatível aos bons resultados obtidos por calosotomias parciais anteriores em pacientes com epilepsia multifocal e bissincronia frontal.

Transcallosal potentials evoked by electrical stimulation with rectangular pulses of 1 ms, 5 c/s and variable intensity were recorded from the cortical surface in cats anesthetized with ketamine hydrochloride. Sites of stimulation and recording were selected by means of a cartesian map of most of the neocortex. In addition to the well known transcallosal projection pattern it was found that stimulation of a restricted posterior area evokes low voltage potentials over the contralateral symmetric area while high voltage potentials are recorded from a few sites located at the ipsilateral anterior cortex and from the area symmetric as to the latter. This L-shaped transcallosal connection may be involved in complex cortical processes and is compatible with effective results of partial anterior callosotomies in patients with multifocal epilepsy and frontal bisynchronism.

Em dez gatos anestesiados com cetamina (Ketalar) o neocórtex foi exposto e pulsos retangulares (1 ms, 0,5Hz e intensidade variável) foram aplicados a pontos discretos de um lado enquanto se registravam os potenciais evocados no outro lado. As posições de estimulação e registro eram determinadas em mapa cartesiano que abrangia quase todo o neocórtex. Os potenciais foram analisados quanto aos seus componentes, voltagem e latência. A difusão passiva, potenciais eletrotônicos e os efeitos do incremento da frequência de estimulação sobre os vários componentes foram analisados. Os resultados mostram a presença de grandes potenciais evocados transcalosos em algumas regiões, com incremento de sua amplitude no sentido caudo-rostral, sendo máximos em áreas anteromediais do giro suprasilviano. Confirmando estudos anatômicos, em algumas regiões do córtex soma-tomotor e visual foram registrados potenciais bastante reduzidos ou ausentes. A estimulação de algumas áreas posteriores causava o aparecimento de pequenos potenciais em sua área homóloga contralateral ao mesmo tempo em que grandes potenciais eram registrados em áreas anteriores ipsi- e contralateralmente, constituindo uma conexão em L ainda não descrita. É possível que tal conexão esteja implicada em alguns tipos de epilepsia e possa explicar em parte a eficácia de calosotomias parciais para seu tratamento.

In ten adult cats anesthetized with ketamine hydrochloride the neocortex was exposed and rectangular pulses (1msec, 0.5 Hz and variable intensity) were applied to discrete points of one side and transcallosal evoked potentials were recorded from the other. The stimulation and recording positions were determined on a cartesian map of most of the exposable neocortical areas and the potentials were analysed as to their components, voltage and latency. Passive spread and electrotonic potentials and the effects of increasing frequency were also analysed. The results showed large transcallosal potentials in some areas and an increase of potentials in the caudorostral direction, attaining the highest values in anteromedial areas of the suprasylvian gyrus. Confirming anatomical studies, a few silent spots were found in the motor and somesthetic cortex and in restricted posterior regions of the visual cortex, where small or zero voltages occurred. While causing weak contralateral potentials, stimulation of some posterior sites provoked high voltage potentials in anterior regions of the side being stimulated and in the corresponding area of the opposite site. These posterior sites are. poorly interconnected by the corpus callosum. The L-shaped indirect connection described in this work may be involved in some types of epilepsy and may explain the effectiveness of partial callosotomy in their treatment.

Para este trabalho foram utilizados 18 ratos albinos da raça Wistar com lesões eletrolíticas crônicas da formação reticular mesencefálica, sendo 11 unilaterais e 7 bilaterais. Todas as lesões foram suficientemente amplas para interromper completamente o sistema ativador ascendente de uma ou de ambas as metades do mesencéfalo. Aumento da sincronização do eletrocorticograma provocado pelo sono espontâneo foi observado mesmo nos animais com lesão bilateral; este fato fala a favor da existência de mecanismos ativadores corticais situados acima do nível mesencefálico, que são deprimidos durante o sono. Progressivamente observa-se recuperação da atividade elétrica cortical dessincronizada e da atividade motora (comportamentos de alerta e de vigília), tanto nos animais com lesão unilateral como nos com bilateral. Nos primeiros, contudo, a recuperação é mais precoce e rápida. O sono fisiológico se desenvolve com todas as suas fases normais a partir do 4.° ou 5.° dias depois da lesão. A atividade dessincronizada do neocórtex observada durante a fase paradoxal do sono independe de qualquer estrutura em particular existente no tegmento do mesencéfalo.

This study was performed on 18 albino rats subjected to either unilateral (11) or bilateral (7) electrolytic destruction of the midbrain reticular formation. In all preparations a complete unilateral or bilateral interruption of the ascending activating system was achieved. The electrocorticographic pattern of synchronized sleep ocurred in both unilaterally and bilaterally lesioned rats. This was found as soon as the animal recovered from the surgical trauma, when slow waves still predominated. Such finding support the hypothesis that activating systems other than the midbrain reticular activating system exist whose functional block during sleep furthers the synchronization of the cortical electrical activity. An increasing recovery of desynchronization and motor activity as a function of time was shown by all rats. However, recovery occurred earlier and more quickly in the animal with unilateral lesions. Physiological sleep evolved with all its phases by the fourth or fifth day after the lesion was made. It seems that desynchronization of the paradoxical phase of sleed does not involve any particular struture arising from and/or passing through the midbrain tegmentum.

Para êste estudo foram empregados 35 ratos da raça Wistar em preparação aguda (24 com lesão bilateral e 11 com lesão unilateral) da formação reticular mesencefálica e 18 preparações crônicas. O método empregado na obtenção das preparações foi descrito em trabalho anterior12. O objetivo desta série de experiências foi o de verificar de que maneira o pentobarbital interfere sobre as características da atividade elétrica cortical após lesão da formação reticular mesencefálica. Para tal, em animais preparados agudamente, foram feitas lesões progressivamente mais extensas e o barbitúrico injetado por via intravenosa em doses crescentes. A fim de testar a integridade do sistema reticular ativador ascendente, além de estímulos dolorosos intensos, aplicávamos pulsos de 5 a 10 V, 100 Hz, e 0,1 ms à formação reticular mesencefálica situada abaixo da região lesada. A ausência de reação de alerta cortical (dessincronização) nos assegurava que tal sistema havia sido lesado completamente. Nas preparações crônicas o pentobarbital era injetado por via intraperitoneal. Dessas experiências concluimos o seguinte: 1. Aumento da sincronização do eletrocorticograma nos animais com lesões parciais ou totais da formação reticular mesencefálica. 2. Depressão acentuada e precoce da atividade elétrica cerebral nos ratos com lesão muito extensa (comprometendo também a porção ventrobasal do tálamo). 3. Isocronismo da atividade elétrica cortical nos dois hemisférios cerebrais. 4. O pentobarbital parece agir tanto sobre os sistemas ativadores como sobre o sincronizador do eletrocorticograma. As doses pequenas deprimem os primeiros, liberando o segundo, enquanto que as maiores bloqueiam também este último. Sòmente doses muito mais altas é que fazem desaparecer totalmente a atividade do córtex cerebral, que se mostra, portanto, mais resistente à ação da droga.

This study was performed on 35 albino rats prepared for acut and 18 for chronic experiments. The midbrain reticular formation was electrolytically destroyed on both sides in 24 animals, and in 11 on one side. The interruption of the reticular activating system was checked by strong nociceptive and electrical stimulation below the lesioned area. In acute preparations pentobarbital was given by intravenous injection in increasing doses, and in chronic experiments by intraperitoneal injections. The barbiturate always augmented synchronization of the electrocorticogram but induced an early depression of the electrical activity in rats with bilateral extensive lesions. After barbiturate administration the electro-corticogram of both hemispheres tended to became more isochronized. Pentobarbital seems to depress the activating systems in small doses, thus liberating the synchronizing systems, whereas larger doses block also the latter. Only very large doses depress the cortical activity.

No presente estudo foram utilizados 73 ratos em preparações agudas e crônicas, nas quais lesamos a formação reticular mesencefálica com corrente contínua (3,5 a 4,0 mA durante 5 a 10 segundos). O eletródio ativo era implantado estereotàxicamente segundo as coordenadas de König e Klippel. As lesões eram feitas parcial ou totalmente, uni ou bilateralmente, e em todos os animais procedeu-se ao controle histológico das áreas lesadas, usando-se o método de Weil. O registro da atividade elétrica cortical foi feito com polígrafo Beckman de 4 canais, utilizando-se derivações bipolares curtas (1mm) com eletródios esféricos de platina. As experiências permitiram as seguintes conclusões: 1 — As características eletrofisiológicas dos fusos que ocorrem após lesões da formação reticular mesencefálica são muito semelhantes às dos fusos espontâneos e barbitúricos, inclusive quanto à projeção cortical. Quanto à duração dos potenciais que os constituem, contudo, notamos que a faixa de variação era mais centuada (20 a 80 ms), o que pode ser atribuído à maior complexidade dos potenciais do cérebro isolado, possivelmente pela falta de ação cronadora da formação reticular sobre o sistema sincronizador talâmico. 2 — Os mecanismos envolvidos na gênese dos fusos do sono barbitúrico ou espontâneo e os do cérebro isolado são, pelo menos em parte, dependentes do bloqueio da formação reticular mesencefálica. 3 — A formação reticular mesencefálica ativa preferencialmente o hemisfério cerebral homolateral; o contingente cruzado talvez seja mobilizado somente quando estímulos alertantes intensos atingem o tegmento mesencefálico. 4 — Além da formação reticular mesencefálica deve haver outros mecanismos ativadores corticais, visto que, em preparações agudas de cérebro isolado, observamos: a) surtos de curta duração de atividade dessincronizada; b) oscilações freqüentes do ECoG durante o registro, denotando fases de maior ou menor sincronização do traçado; c) ondas teta nas áreas límbicas (talvez evidenciando alerta) registradas simultâneamente com fusos em áreas neocorticais.

Seventy three rats were prepared for acute and chronic experiments. The midbrain reticular formation was electrolitically destroyed (3,5 — 4,0 mA and 5 — 10 sec) by means of an active electrode estereotactically guided according with the atlas of König an Klippel. The procedure was destined to provoke parcial, total, unilateral and bilateral lesions in different preparations. The ECoG was recorded with a 4-channel Beckman polygraph. Short bipolar leads were used in all experiments. 1. Spindling wich occurred after the operation was similar to spindling found in phisiological sleep and in barbiturate narcosis as well. Similarity was striking as to the electrophysiological properties and cortical projections. However, the duration of the individual potentials dispersed much more than in the above mentioned conditions (20 — 80 msec), wich may be related to the higlher complexity exhibited by the spindles which appear on the ECoG after destruction of the reticular formation of the midbrain, possibly due to lack of reticular timing of the thalamic synchronizing system activity, since spindling was more regular when circumscribed lesions of the midbrain were made. 2. The mechanisms involved in production of spindles during spontaneous and barbiturate sleep and after lesioning of the midbrain reticular formation are at least partially dependent upon reticular blocking. 3. The midbrain reticular formation activates mainly the ipsilateral hemisphere. The crossed component of the activating system is, probably, brought in action only when arousing stimuli are very strong. 4. Besides midbrain reticular formation other cortical activating mechanisms certainly play a role in arousing, since, in acute preparations, simultaneously with neocortical spindling, we frequently recorded: a) short-lasting periods of desynchronization of the ECoG; b) synchronization of the ECoG is not steady but waxes and wanes in time; c) theta waves, wich are associated with limbic arousal, are recorded on the cortical limbic areas.