Selection of environmental temperature by the yellow scorpion Tityus serrulatus Lutz & Mello, 1922 (Scorpiones, Buthidae)

The preferred temperature of the yellow scorpion Tityus serrulatus was investigated since its dispersion is a matter of concern. Adult T. serrulatus, weighing 1.24 + 0.20 g (mean + sd) and with a standard length of 59.3 + 2.5 mm, were used. A metallic corridor (120 cm long, 5 cm large and 10 cm high) with thermal gradient ranging from 0°C to 40°C was used. Tityus serrulatus chose and stayed in temperatures ranging from 14°C to 38°C when safe conditions were offered (dark and thigmotactic stimuli). The number of animals that remained in the 11°C-20°C, 21°C-30°C, and 31°C-40°C temperature zones were 8, 8, and 9, respectively. The chi-square test (degree of freedom = 2) showed that differences were not significant (p>0.05). Some animals moved to lower temperature areas (less than 8°C) when the corridor was completely illuminated and thigmotactic stimuli were absent, which led the animals to present a torpor state. It is concluded that T. serrulatus does not select a specific environmental temperature. Associated with the capacity of temporally surviving at low temperatures, this species seems to be highly adaptable to different thermal zones.

The compulsive-like aspect of the head dipping emission in rats with chronic electrolytic lesion in the area of the median raphe nucleus

Head dipping (HD) is a behavioral pattern considered to have a risk assessment or an exploratory role and is used as a complementary parameter to evaluate anxiety in experimental animals. Since rats with electrolytic lesion in the area of the median raphe nucleus displayed high frequencies of HD in a previous study, the present investigation was undertaken to confirm this observation and to determine its anxiety-related origin. HD episodes were counted in adult male Wistar rats (270-350 g) with electrolytic lesion (N = 11) and sham-lesioned controls (N = 12). When HD was measured for 60 min on an elevated open platform, lesioned rats emitted 13 times more HD than controls (264.7 ± 93.3 vs 20.3 ± 7.6 episodes), with the difference being statistically significant (P < 0.05). HD counts during 10-min sessions held 7, 14, 21, 27, and 63 days after lesion showed significantly higher means (range: 28.14 ± 5.38 to 62.85 ± 9.48) compared to sham-lesioned controls (range: 7.37 ± 1.13 to 8.5 ± 1.45). Normal rats stepped down into their home cages when the vertical distance between them and the cage was short (16 cm), and the step-down latencies increased with increasing depths (36.7 ± 7.92 to 185.87 ± 35.44 s). Lesioned rats showed a similar behavior when facing the shortest depth, but had a significantly increased number (23.28 ± 2.35 episodes) and latency (300 ± 0.00 s) of HD compared to normal rats (9.25 ± 1.37 episodes and 185.87 ± 35.44 s) when facing the greatest depth (30 cm). This suggests that HD may be a depth-measuring behavior related to risk assessment.

Fighting by sleep-deprived rats as a possible manifestation of panic: effects of sodium lactate

Increased fighting is an effect of desynchronized sleep deprivation (DSD) in rats, and recently this behavior has been suggested to be spontaneous panic and equivalent to panic disorder. In the present study we tested this hypothesis by evaluating the effect of sodium lactate on this aggressiveness, because this substance is recognized to induce spontaneous panic attacks in patients. A total of 186 male albino Wistar rats, 250-350 g, 90-120 days of age, were submitted to DSD (multiple platform method) for 0, 4, or 5 days. At the end of the deprivation period the rats were divided into subgroups respectively injected intraperitoneally with 1.86, 2.98 and 3.72 g/kg of 1 M sodium lactate, or 1.86 and 3.72 g/kg of 2 M sodium lactate. The control animals were submitted to the same procedures but received equivalent injections of sodium chloride. Regardless of DSD time, sleep-deprived animals that received sodium lactate presented a significantly higher mean number of fights (0.13 + or - 0.02 fights/min) and a longer mean time spent in confrontation (2.43 + or - 0.66 s/min) than the controls (0.01 + or - 0.006 fights/min and 0.12 + or - 0.07 s/min, respectively; P<0.01, Student t-test). For the sodium lactate group, concentration of the solution and time of deprivation increased the number of fights, with the mean number of fights and mean duration of fighting episodes being greater with the 2.98 g/kg dose using 1 M lactate concentration. These results support the hypothesis that fighting induced by DSD is probably a spontaneous panic manifestation. However, additional investigations are necessary in order to accept this as a promising animal model for studies on panic disorder

Electrolocation-communication discharges of the fish Gymnotus carapo L. (Gymnotidae: Gymnotiformes) during behavioral sleep

Technical problems have hampered the study of sleep in teleosts. The electrical discharges of Gymnotus carapo L. (Gymnotidae: Gymnotiformes) were monitored to evaluate their ease and reliability as parameters to study sleep. The discharges were detected by electrodes immersed in a glass aquarium and were recorded on a conventional polygraph. G. carapo showed conspicuous signs of behavioral sleep. During these periods, opercular beat rates were counted, electric discharges recorded, and the "sharp discharge increase" (SDI) of the orienting reflex was investigated. All 20 animals monitored maintained electrical discharges during behavioral sleep. The discharge frequencies during sleep (50.3 Ý 10.4 Hz) were not significantly different from those observed when the fish was awake and inactive (57.2 Ý 12.1 Hz) (Wilcoxon matched-pairs signed-ranks test, P>0.05). However, the SDI, which was prevalent in the awake fish, was not observed during periods of behavioral sleep. Additional observations showed that the species had cannibalistic habits. When presented with electrical discharges from a conspecific, the sleeping fish showed an initial decrease or pause in discharge frequency, while the awake fish did not have this response. We conclude that the electrical discharges of G. carapo were not conspicuous indicators of behavioral sleep. Discharges may have been maintained during sleep for sensory purposes, i.e., conspecific detection and avoidance of cannibalistic attacks

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 6MP and 6SP 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; Studentt-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.

Food deprivation and hypothermia in desynchronized sleep-deprived rats

Reports of the effect of desynchronized sleep (DS) deprivation on body temperature (Tb) of rats in the literature are contradictory. Since conspicuous body weight loss is common in such deprivation, the effect of food plus DS deprivation on Tb of adult male Wistar rats was studied. DS deprivation carried out by the small platform method with food ad libitum (N = 8) induced hyperthermia (Tb above 38.5 degrees Celsius) in 1 to 3 rats daily until the 8th day, when a case of discrete hypothermia (Tb below 36.9 degrees Celsius) appeared. Food deprivation alone started to induce hypothermia on the third day in one (20 percent) out of five rats. Fasting imposed from the 5th to the 8th day of DS deprivation (N = 12) caused hypothermia in 33 percent and 67 percent of the animals on the second and third day of starvation, respectively. DS compensatory manifestations in 6 starved rats intensified (N = 2) or precipitated (N = 2) hypothermia after the end of sleep deprivation. It is concluded that the hypothermia is not a primary effect of DS deprivation, and this state of sleep seems to have its particular functional role which is independent of thermoregulation.

Neocortical spindling during wakefulness in the rat

Neocortical spindling that frequently occurs in rats during wakefulness was studied to evaluate the hypotheses that spindle bursts are either the electrophysiological manifestation of a short-lasting sleep episode that briefly interrupts wakefulness (due to an urge to sleep) or a short decrease of the vigilance level. In order to evaluate sleep need, the latency to the onset of natural sleep, the percentual composition of the sleep-waskefulness cycles, and the durations and intervals of desynchronized sleep episodes were determined in six male Wistar rats weighing 250-350 g and having chronically implanted electrodes for frontal electrocorticogram and cervical electromyogram. These animals were selected on the basis of spindling manifestation during wakefulness. The occurrence of spindling during a period of repeated painful tail-pinching was subsequently measured to determine the vigilance level in the same animals. Two rats were also studied during forced immobilization for the same purpose. Sleep parameters were found to be normal in all rats studied, thus exluding the hypothesis that spindling in wakefulness is a manifestation of a high sleep need...

Recovery facilitation of malathion-intoxicated freshwater fish by exposure to hypertonic environment

The possibility of recovery in a hypertonic environment (10-40%NaCl) was investigated in the freshwater fish Oreochromis niloticus acutely intoxicated with the pesticide Malathion (40 ml/l. Survival was significantly higher in 15 g/l NaCl, with a shorter time required to reover posture and swimming, although 20% of revovered animals died on subsequent days.Exposure to a hypertonic environment plus pesticide did not protect the animals. Fish explosed to air until they became unresponsive recovered faster in freshwater than in a hupertnic environment. It os concluded that a hypertonic environmnet only facilitates recovery and that although osmotic mechanisms may explain the results, other possibilities reamin to be investigated

Hiperatividade motora e ulceras gastricas induzidas pela lesao dos nucleos da rafe de ratos. / Motor hiperactivity and gastric ulcers induced by raphe nuclei lesions in rats

A correlacao entre os niveis de atividade locomotora de ratos submetidos a lesao dos nucleos mediano e dorsal da rafe e os parametros de ulceracao gastrica observada nestes animais foi estudada, testando-se hipotese da exacerbacao do comportamento locomotor ser o fator primordial da patologia gastrica, como sugerem os dados da literatura.A ausencia de uma correlacao significativa demostra que a atividade locomotora nao tem papel preponderante no desenvolvimento das ulceras nos animais submetidos a lesao.Discute-se o possivel envolvimento de um mecanismo dopaminergico central comum responsavel pelas ulceras gastricas induzidas pela lesao e as observadas como decorrencia da atividade locomotora

Ulceras gastricas induzidas pela lesao dos nucleos da rafe no rato. / Gastric ulcers induced by raphe nuclei lesion in rats

O primeiro objetivo do presente artigo e fazer uma breve revisao dos diferentes dados experimentais obtidos ate agora a respeito das ulceras gastricas que ocorrem na parte glandular do estomago de ratos apos a lesao dos nucleos mediano e dorsal da rafe. O segundo objetivo e tentar elaborar um esquema conceptual mais global que oriente a investigacao futura. A destruicao de um dos sistemas cerebrais implicados na genese dos estados de sono, com liberacao dos sistemas de vigilia, parece levar a concepcao de que o estresse e uma condicao de hipervirgilia do organismo.Por outro lado, e possivel aventarse a hipotese de que as ulceras gastricas decorrem da nao efetivacao completa de uma resposta biologica adaptativa a situacao de estresse