Neuroethologic differences in sleep deprivation induced by the single- and multiple-platform methods

It has been proposed that the multiple-platform method (MP) for desynchronized sleep (DS) deprivation eliminates the stress induced by social isolation and by the restriction of locomotion in the single-platform (SP) method. MP, however, induces a higher increase in plasma corticosterone and ACTH levels than SP. Since deprivation is of heuristic value to identify the functional role of this state of sleep, the objective of the present study was to determine the behavioral differences exhibited by rats during sleep deprivation induced by these two methods. All behavioral patterns exhibited by a group of 7 albino male Wistar rats submitted to 4 days of sleep deprivation by the MP method (15 platforms, spaced 150 mm apart) and by 7 other rats submitted to sleep deprivation by the SP method were recorded in order to elaborate an ethogram. The behavioral patterns were quantitated in 10 replications by naive observers using other groups of 7 rats each submitted to the same deprivation schedule. Each quantification session lasted 35 min and the behavioral patterns presented by each rat over a period of 5 min were counted. The results obtained were: a) rats submitted to the MP method changed platforms at a mean rate of 2.62 ± 1.17 platforms h-1 animal-1; b) the number of episodes of noninteractive waking patterns for the MP animals was significantly higher than that for SP animals (1077 vs 768); c) additional episodes of waking patterns (26.9 ± 18.9 episodes/session) were promoted by social interaction in MP animals; d) the cumulative number of sleep episodes observed in the MP test (311) was significantly lower (chi-square test, 1 d.f., P<0.05) than that observed in the SP test (534); e) rats submitted to the MP test did not show the well-known increase in ambulatory activity observed after the end of the SP test; f) comparison of 6 MP and 6 SP rats showed a significantly shorter latency to the onset of DS in MP rats (7.8 ± 4.3 and 29.0 ± 25.0 min, respectively; Student t-test, P<0.05). We conclude that the social interaction occurring in the MP test generates additional stress since it increases the time of forced wakefulness and reduces the time of rest promoted by synchronized sleep.Universidade Federal de São Paulo (UNIFESP)Universidade Estadual PaulistaUNIFESPSciEL

REVERSIBLE CARDIAC ARREST INDUCED BY STARTLING STIMULI IN THE ANTARCTIC FISH Notothenia neglecta

Estímulos de alarme induzem inibição temporária dos batimentos cardíacos em muitos animais. Como essa proprieade, denominada parada (arrest) cardíaca reversível não vem sendo estudada sistematicamente em peixes, os presente trabalho investigou a sua ocorrência em peixes antárticos que evoluíram independentemente de outros grupos de teleósteos. Alterações do ritmo cardíaco em resposta a diferentes estímulos foram monitoradas por registro eletrocardiográfico em 15 espécimes de Notothenia neglecta (400-700 g) mantidas em uma câmara experimental com água do mar aerada e temperatura controlada. Vibrações repentinas da câmara, a aproximação do observador e outros estímulos de alerta provocavam no animal paradas cardíacas algumas vezes por um ou mais batimentos, mas a resposta mais comum era somente de uma parada curta do batimento cardíaco após estímulo. Aumento da temperatura até 11ºC eleva o ritmo (rate) cardíaco sem abolir a resposta contudo. Hipóxia moderada facilita a parada cardíaca. Inibição cardíaca pronunciada com algum batimento isolado foi observada quando os animais eram manuseados ou quando a água da câmara era removida. Administração de atropina (1 mg/kg) bloqueia a parada cardíaca induzida por tais procedimentos. Conclui-se, então, que a parada cardíaca reversível é provavelmente uma propriedade comum de muitos peixes que se desenvolveu antes da sua adaptação ao ambiente antártico. Abstract Startling stimuli induce temporary inhibition of heart beats in many animals. Since such property, named reversible cardiac arrest, has not been systematically studied in fishes, the present work investigated its occurrence in an Antarctic fish that evolved independently from other teleost groups. Heart rate changes in response to different stimuli were monitored by conventional electrocardiographic recording in 15 Notothenia neglecta (400-700 grams), maintained in an experimental chamber with aerated sea water and controlled temperature. Sudden vibration of the chamber, observer approximation and other alerting stimuli evoked cardiac arrest sometimes for one or more beats, but the most common response was only a short delay of the beat after the stimulus. Increase in temperature up to 11ºC raised heart rate but did not abolish the response. Moderate hypoxia facilitated cardiac arrest. Pronounced cardiac inhibition with some isolated beats was observed when the animals were handled or when the water of the chamber was removed. Atropine (1mg/kg) administration blocked the cardiac arrest induced by such procedures. It is concluded that reversible cardiac arrest is probably a common property of many fishes and developed before the adaptation to the Antarctic environment

Temperature-dependent tonic contraction of smooth muscle in Antarctic fishes Notothenia neglecta and Chaenocephalus aceratus - Role of calcium ions and responses to acetylcholine

The isolated intestinal smooth muscle of Antarctic fishes Notothenia neglecta and the icefish Chaenocephalus aceratus displayed a sustained tonic contraction depending upon the temperature of the nutritive bath. The contraction was maximal at 2℃, relaxing proportionally with rise of the temperature, from 2℃ to 18℃. The contractile responses to acetylcholine gradually increased in proportion to the rise of temperature. By chelating calcium ions, EDTA caused a reversible relaxation of the contracted muscle at 2.0℃. This effect was eliminated by washing out the drug from the muscle nutritive bath. Similar results were found with the administration of verapamil, a calcium channel blocker. However, after this drug, tonic contraction was not restored by washout. Such contraction was partially inhibited by the muscarinic blocking drug atropine. Results show that the tonic contraction is an active response, dependent on the entry of calcium into the cell and mediated by cholinergic receptors. The temperature-related tonic contraction is not a general event in poikilotherm animals, since it did not occur in the Bufo marinus intestinal smooth muscle, in similar experiments carried out as a control, in a tropical environment. The responsiveness of the smooth muscle to acetylcholine appeared to increase with temperature, suggesting lack of adaptation of the organ to low Antarctic temperature

Ressignificação existencial do pretérito e longevidade humana

Nowadays there are more than 300 hypotheses to explain ageing characteristics, function and mechanisms, possibly due to the large and increasing number of old people in the world. Though having a social function attributed to elders, transformations - under way currently in society - have imposed a discard culture, including old people. This is an authentic exclusion that is frequently associated with sadness, depression and death in its group, contradicting the alleged idea that older people increase life-time (as has been observed in recent years). This manuscript has the aim of determining environmental aspects involved with longevity; it thus uses "grounded theory", a technique of qualitative research method, operating on data provided by elderly former railroad workers. It was observed that former railroad worker's social representations convey to a central category: desolation from perceiving life and environmental annihilation due to continuous State and Society negligence to promote and preserve good things - that existed in the past. We can also observe that, in a parallel way, by hyper valorizing past things, they recognize their existence as part of an epic process that promoted the São Paulo state countryside economic and social development, with an existential meaning to the past, which suggests to be a strong defense mechanism that contributes to longevity. This finding can be included in the hypothesis that the function of longevity would be to preserve a social contingent with knowledge about a way of life that was successful because it was socially advantageous.Existem, atualmente, mais de 300 hipóteses relativas à caracterização, função e mecanismos do envelhecimento, possivelmente devido ao aumento de idosos no mundo. Embora se avente uma função social à velhice humana, as transformações da sociedade impuseram uma cultura de descarte, incluindo pessoas como os idosos. Tal exclusão, que se associa à tristeza, depressão e morte desse grupo, é contraditória ao aumento do tempo de vida dos idosos constatado atualmente. O presente trabalho tentou determinar os aspectos ambientais envolvidos na longevidade usando uma técnica de metodologia qualitativa denominada grounded theory (ou teoria fundamentada nos dados) em dados fornecidos por ex-ferroviários longevos. Constatou-se que as representações dos ex-ferroviários confluem para a categoria central: desolação pelo aniquilamento da vida e do ambiente, no presente, devido à continuada negligência do Estado e da Sociedade na promoção e preservação das coisas boas para a vida que havia no passado. Observou-se ainda que, paralelamente à hipervalorização genérica das coisas do passado, há constatação recente de que suas existências fizeram parte da epopeia que promoveu o desenvolvimento econômico e social do interior paulista e possibilitou uma ressignificação existencial do passado, sugerindo ser um potente mecanismo de defesa que culmina em longevidade. Tal achado se insere na hipótese de que a função da longevidade seria a de preservar um contingente social com conhecimentos de um modo de vida que deu certo por ser socialmente vantajoso

Compensatory rebound of body movements during sleep, after asphyxia in neonatal rats Resposta compensatória dos movimentos corporais do sono após a asfixia em ratos recém-nascidos

PURPOSE: The usefulness of body movements that occur during sleep when assessing perinatal asphyxia and predicting its long-term consequences is contradictory. This study investigated whether neonatal rats manifest these movements in compensatory rebound after asphyxia, and if these alterations play an important role in its pathogenesis. METHODS: Eight neonatal rats (aged 6-48h) were implanted with small EMG and EKG electrodes and sleep movements were recorded over a 30-minute control period. Recordings were continued during asphyxia caused by the enclosure of the animal in a polyvinyl sheet for 60 minutes, followed by a 30-minute recovery period. RESULTS: Heart rate was lowered to bradycardic level during asphyxia causing behavioral agitation and increased waking time during the initial phase (30 minutes). Sleep-related movements were also significantly reduced from 12.5 &plusmn; 0.5 (median &plusmn; SE/2min) to 9.0 &plusmn; 0.44 in the final half of the period (Anova, p<0.05). Movement frequency increased in the recovery period to 15.0 &plusmn; 0.49 (Anova, p<0.05). CONCLUSION: These data show that newborn rats present compensatory rebound of body movements during sleep which may help in the diagnosis of asphyxia and other problems related to sleep parameters.<br>OBJETIVO: A utilidade dos movimentos corporais (MC) que ocorrem durante o sono para diagnosticar e predizer as conseqüências, em longo prazo, da asfixia perinatal é contraditório. Este estudo investigou se ratos recém-nascidos (RN) manifestam MC em resposta compensatória à asfixia, e se estas alterações podem ter alguma importância na sua patogênese. MÉTODOS: Oito ratos RN (6-48h de vida) foram submetidos à implantação de pequenos eletrodos para registros da eletromiografia e eletrocardiografia. Os MC e a freqüência cardíaca (FC) foram registrados durante períodos de 30 min: fase controle (F1), fases de asfixia (F2; F3) e fase de recuperação pós-asfixia (F4). A asfixia foi promovida pelo envolvimento completo do animal com uma lâmina de polivinil. RESULTADOS: A FC diminuiu progressivamente durante F2 e F3 até a bradicardia. Em F2 houve grande agitação dos animais e aumento dos períodos de vigília. Em F3 houve redução significante dos MC de 12,5 &plusmn; 0,5 (Md &plusmn; SE/2min) para 9,0 &plusmn; 0,44 (P<0,05). A freqüência dos MC aumentou em F4 para 15,0 &plusmn; 0,49. CONCLUSÃO: Estes dados mostram que ratos RN com asfixia apresentam MC compensatórios durante o sono que podem ajudar no diagnóstico desta afecção e de outros problemas relacionados aos parâmetros do sono

Abolição da imobilidade de defesa induzida pela estimulação aversiva em ratos (Rattus norvegicus albinus) (Mammalia, Rodentia) com lesão do núcleo mediano da rafe

Behavior is an evolutionary product and, at least, some disorders may affect different species throught homologous etiological mechanisms. The present study evaluated the compulsive nature of the locomotor hyperactivity observed in rats with electrolytic lesion of the median raphe nucleus, a possible behavioral inhibition system postulated by the ethologists. The number of crossings of the median line of a wiremesh cage was counted during 10 minutes in lesioned (n=6) and controls (n=7) rats (baseline period). They were submitted during 30s to footshocks and crossings were counted again. The number of crossings was higher in lesioned animals and did not reduce significantly after the aversive stimulation. Control animals showed long lasting behavioral freezing after shocks that resulted in significantly lower rates of crossings. It is concluded that such lesioned rats may be a valuable paradigm for studies on repetitive behavior disorders

O segredo da longevidade segundo as percepções dos próprios longevos The secret of longevity in the perception of the old-aged

Estudos apontam fatores que podem aumentar a longevidade; no entanto, muitas questões pertinentes a este tema ainda não foram elucidadas. Percepções do próprio longevo a respeito dos fatores contribuintes para longevidade são importantes, permitindo levantamento de cada fator e suas interações com demais variáveis que promovem a longevidade. O presente artigo relata dados da investigação sobre "o segredo da longevidade", segundo percepções dos próprios longevos, analisados pelo referencial metodológico da grounded theory. Foram entrevistados trinta ferroviários longevos do município de Botucatu (SP). A análise das falas dos longevos possibilitou determinar que a percepção dos fatores se aglutina em torno de categorias progressivamente abrangentes que culminam na representação coletiva de que a longevidade é dependente do embate entre fatores prejudiciais que aniquilam a vida e fatores saudáveis que geram e preservam a vida, sobre o qual a falta de controle social e do Estado torna pessimista a visão do futuro.<br>Many studies point to factors capable of increasing longevity but many questions regarding this subject were still not elucidated. The perceptions of the old aged themselves with respect to factors that contribute to longevity are important, allowing to identify each factor and its interactions with other variables promoting longevity. This article presents the results of an investigation about "the secret of longevity", according to old-aged themselves, analyzed through grounded theory. Thirty old-aged men, former railroad workers, were interviewed in the city of Botucatu (SP). The analysis of their discourse led to the conclusion that the perception of the factors can be grouped around progressively inclusive categories that culminate in the collective representation that longevity depends on the balance between negative life-destroying factors and healthy, life-generating and life-preserving factors. The lack of social and state control over these factors is generating a pessimistic view for the future