Neuronal excitability level transition induced by electrical stimulation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Correlation between the fighting rates of REM sleep-deprived rats and susceptibility to the 'wild running' of audiogenic seizures

Sleep-deprived rats exhibit defensive fighting as well as explosive flights very similar to the wild-running of audiogenic seizures. In order to determine why sleep deprivation is a common factor that facilitates both panic and convulsive manifestations, the present study was undertaken to investigate whether rats that display sleep deprivation-induced fighting (SDIF) are the same as those that are susceptible to audiogenic wild-running (WR). Twenty-eight male adult Wistar rats were divided into two groups assigned to two e-sleep deprivation for 5 days and had their SDIF evaluated in social experimental schemes. In the first, 18 subjects were submitted to REM grouping. After 1 week for recovery, their susceptibility to WR was tested in an acoustic stimulation trial ( 104 dB, 200 Hz, 60 S). Rats that did not present WR received a lactate infusion and were tested again by acoustic stimulation 40 min later. In the second experimental scheme, 10 subjects were initially evaluated for WR susceptibility and the number of SDIF was recorded in social grouping after I week. Three categories of WR-susceptibility were determined: WR-sensitive rats, intermediate WR-sensitive rats and WR-insensitive rats. T'he number of SDIF in each category was significantly different and there was a high positive correlation (r=0.89; Spearman test) between the number of SDIF and the level of WR-susceptibility. We conclude that the reasons why sleep deprivation exerts facilitatory effects on both panic and convulsive manifestations are due to overlappings of neural pathways responsible for both behavioral patterns and for the property of sleep deprivation to increase neuronal excitability. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Equine poisoning by coffee husk (Coffea arabica L.)

Background: In Brazil, coffee (Coffea arabica) husks are reused in several ways due to their abundance, including as stall bedding. However, field veterinarians have reported that horses become intoxicated after ingesting the coffee husks that are used as bedding. The objective of this study was to evaluate whether coffee husk consumption causes intoxication in horses.Results: Six horses fed coast cross hay ad libitum were given access to coffee husks and excitability, restlessness, involuntary muscle tremors, chewing movements and constant tremors of the lips and tongue, excessive sweating and increased respiration and heart rates were the most evident clinical signs. Caffeine levels were measured in the plasma and urine of these horses on two occasions: immediately before the coffee husks were made available to the animals (T0) and at the time of the clinical presentation of intoxication, 56 h after the animals started to consume the husks (T56). The concentrations of caffeine in the plasma (p < 0.001) and urine (p < 0.001) of these animals were significantly greater at T56 than at T0.Conclusions: It was concluded that consumption of coffee husks was toxic to horses due to the high levels of caffeine present in their composition. Therefore, coffee husks pose a risk when used as bedding or as feed for horses.

Potentiation of panic-like behaviors of the rat by subconvulsive doses of strychnine

The present study was carried out to determine possible panicogenic effects of strychnine administered in subconvulsive doses to rats. Two experiments were conducted to assess two major features of panic in animal models: panic-related flight (through the observation of wild running [WR]) and defensive fights. In the first one, 20 adult male Wistar rats were injected with six different doses of strychnine ranging from 0.5 to 4.0 mg/kg. After 15 min of free observation, the animals were submitted to high-intensity acoustic stimulation and the incidence of WR was recorded. Higher doses of strychnine (above 2.5 mg/kg) easily evoked seizures, but lower doses raised the incidence of WR in a dose-dependent manner. The most effective dose for WR (1.5 mg/kg) was used in the second experiment, in which we investigated the effects of strychnine on sleep-deprivation-induced fights (SDIFs) that have defensive characteristics. For this purpose, 40 subjects were submitted to 5 days of REM-sleep deprivation by the single-platform method and were then assigned into two groups, i.e., strychnine vs. control. After the injections, the animals were observed in social groupings for SDIF recordings over a period of 60 min. The strychnine-treated groups had more SDIF than the control groups (P<.05, Mann-Whitney U test). We conclude that the high level of neural excitability promoted by partial blockade of the glycinergic system can contribute to the manifestation of panic reactions. (C) 2003 Elsevier B.V. All rights reserved.

Toward an Explanation of the Genesis of Ketamine-Induced Perceptual Distortions and Hallucinatory States

The NMDA receptor (NMDAR) channel has been proposed to function as a coincidence-detection mechanism for afferent and reentrant signals, supporting conscious perception, learning, and memory formation. In this paper we discuss the genesis of distorted perceptual states induced by subanesthetic doses of ketamine, a well-known NMDA antagonist. NMDAR blockage has been suggested to perturb perceptual processing in sensory cortex, and also to decrease GABAergic inhibition in limbic areas (leading to an increase in dopamine excitability). We propose that perceptual distortions and hallucinations induced by ketamine blocking of NMDARs are generated by alternative signaling pathways, which include increase of excitability in frontal areas, and glutamate binding to AMPA in sensory cortex prompting Ca++ entry through voltage-dependent calcium channels (VDCCs). This mechanism supports the thesis that glutamate binding to AMPA and NMDARs at sensory cortex mediates most normal perception, while binding to AMPA and activating VDCCs mediates some types of altered perceptual states. We suggest that Ca++ metabolic activity in neurons at associative and sensory cortices is an important factor in the generation of both kinds of perceptual consciousness.

Bioprospecção e caracterização químico-funcional de compostos orgânicos da baixas massas molecularesde venenos das vespas sociais: Agelaia pallipes pallipes, Agelaia vicina e Polybia paulista (Hymenoptera - Vespidae)

Pós-graduação em Ciências Biológicas (Biologia Celular e Molecular) - IBRC

Avaliação toxicológica da Ipomoea asarifolia (salsa) em ratos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Intoxicação experimental por Ipomoea asarifolia em ovinos: achados clínicos, laboratoriais e anatomopatológicos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeitos do tramadol isolado ou associado à xilazina em equinos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Wolf presence in the ranch of origin: Impacts on temperament and physiological responses of beef cattle following a simulated wolf encounter

This experiment evaluated temperament, vaginal temperature, and plasma cortisol in beef cows from wolf-naive and wolf-experienced origins that were subjected to a simulated wolf encounter. Multiparous, pregnant, nonlactating Angus-crossbreed cows from the Eastern Oregon Agricultural Research Center located near Burns, OR (CON; n = 50), and from a commercial operation near Council, ID (WLF; n = 50), were used. To date, grey wolves are not present around Burns, OR, and thus CON were naive to wolves. Conversely, wolves are present around Council, ID, and WLF cows were selected from a herd that had experienced multiple confirmed wolf-predation episodes from 2008 to 2012. Following a 50-d commingling and adaptation period, CON and WLF cows were ranked by temperament, BW, and BCS and allocated to 5 groups (d 0; 10 CON and 10 WLF cows/group). Groups were individually subjected to the experimental procedures on d 2 (n = 3) and d 3 (n = 2). Before the simulated wolf encounter, cow temperament was assessed and blood samples and vaginal temperatures (using intravaginal data loggers) were collected (presimulation assessments). Cows were then sorted by origin, moved to 2 adjacent drylot pens (10 WLF and 10 CON cows/pen), and subjected to a simulated wolf encounter event for 20 min, which consisted of 1) cotton plugs saturated with wolf urine attached to the drylot fence, 2) continuous reproduction of wolf howls, and 3) 3 leashed dogs that were walked along the fence perimeter. Thereafter, WLF and CON cows were commingled and returned to the handling facility for postsimulation assessments, which were conducted immediately after exposure to wolf-urine-saturated cotton plugs, wolf howl reproduction, and 20-s exposure to the 3 dogs while being restrained in a squeeze chute. Chute score, temperament score, and plasma cortisol concentration increased (P <= 0.01) from pre- to postsimulation assessment in WLF but did not change in CON cows (P >= 0.19). Exit velocity decreased (P = 0.01) from pre-to postsimulation assessment in CON but did not change (P = 0.79) in WLF cows. In addition, WLF cows had a greater (P = 0.03) increase in temperature from pre-to postsimulation assessments compared with CON cows. In conclusion, the simulated wolf encounter increased excitability and fear-related physiological stress responses in cows that originated from a wolf-experienced herd but not in cows that originated from a wolf-naive herd.

Cardiovascular responses to injections of angiotensin II or carbachol into the rostral ventrolateral medulla in rats with AV3V lesions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Atividade espontânea e estimulação do inseto (T. molitor)

The heart of the insect is essentially myogenic, in others words, electrical activity and spontaneous contractions are generated by their muscle cells. However, the nature of pacemaker activity is not yet fully elucidated. One aspect that deserves attention, beyond the pacemaker activity, is the amplitude of heart contractions of the insect. For this, it is necessary that the heart to be stimulated electrically to the frequency to be controlled. In the present work, it was developed a method of stimulation (preparation and instrumentation). The contractile activity of the heart of the insect remained regular when stimulated at frequencies lightly above the spontaneous frequency. To characterize excitability of the preparation the intensity-duration curve was determined

Ritmo sinoventricular secundário a hipercalemia em gatos com obstrução uretral: breve descrição de três casos

Hyperkalemia is a common electrolyte imbalance in cats with obstructive feline lower urinary tract disease (FLUTD). The effects of serum potassium elevation in heart rhythm are serious and potentially lethal. The clinical manifestations reflect changes in the excitability of the cell membrane. Increased potassium levels lead to a reduction of the resting membrane potential of heart muscle cells, making them less excitable and resulting in cardiac arrhythmias. The sinoventricular rhythm with atrial arrest is among the types of arrhythmias caused by hyperkalemia. The purpose of this report was to highlight the importance of electrocardiographic monitoring for the early detection of potentially lethal arrhythmias in cats with obstructive FLUTD. We hereby describe the occurrence of three cases treated at the Small Animal Clinic of FMVZ/Unesp, Botucatu Campus.