Establishing a safe anesthesia concentration window for Nile tilapia (Oreochromis niloticus) (Linnaeus 1758) by monitoring cardiac activity in eugenol immersion baths.

Nile tilapia, Oreochromis niloticus, is the most cultivated fish species in the world, due to its low cost, high growth rate, environmental adaptability, and resistance to disease and stress. Anesthetics for fish become necessary in management because they minimize mortality during transport and maintenance of ponds, one of the most used anesthetics is clove oil, which has eugenol as the major substance, representing 90-95 % of clove oil. The present study evaluates the effect of eugenol on cardiac activity in Oreochromis niloticus specimens and relates it to behavioral data to determine a concentration window for safe anesthesia. For the comportamental analysis, was used five treatments (50, 75, 100, 125, and 150 µL·L-1) were evaluated and for the eletrocardiographic test was used seven groups (Control, Vehicle, 50, 75, 100, 125, and 150 µL·L-1), n = 9/treatment, totaling 108 animals. Behavioral and electrocardiographic tests were performed on all treatments during induction and recovery. The results of the behavioral tests demonstrated the reversibility of the effects with recovery of the posture reflex, varying according to the concentration. The ECG results showed a slow recovery because, at concentrations above 100 µL·L-1, there was no full reversibility of the cardiac effects in the observed experiment time, which could cause greater changes in the tilapia hemodynamics, which led us to identify a window for safe anesthesia. Eugenol is an effective anesthetic in Nile tilapia juveniles when used in concentrations ranging from 50 to 100 µL·L-1, if there is a need for anesthetic deepening, doses above 100 µL·L-1, however, the animals must be monitored due to hemodynamic changes.

Behavioral, electrocorticographic and electrocardiologic changes in Colossoma macropomum (Tambaqui) in the effect of cunaniol.

The Clibadium spp. is a shrub of occurrence in the Amazon, popularly known as Cunambi. The compounds in the leaves demonstrate ichthyotoxic properties, and its major substance, cunaniol, is a powerful central nervous system stimulant with proconvulsant activity. Few current studies relate behavioral changes to the electrophysiological profile of fish poisoning. This study aimed to describe the behavioral, electromyographic, electroencephalographic, electrocardiographic, and seizure control characteristics of anticonvulsant drugs in Colossoma macropomum submitted to cunaniol intoxication during bathing containing 0.3 µg/L cunaniol. The behavioral test showed rapid evolution presenting excitability and spasms, which were confirmed by the analysis of Electroencephalogram (EEG), Electromyogram (EMG), and changes in cardiac function detected in the ECG. Cunaniol-induced excitability control was evaluated using three anticonvulsant agents: Phenytoin, Phenobarbital, and Diazepam. While phenytoin was not effective in seizure control, diazepam proved to be the most efficient. These results demonstrate the susceptibility of Colossoma macropomum to cunaniol poisoning, given that the central nervous system and electrocardiographic changes were considered severe.

Electroencephalographic Response in Juvenile Tambaqui, Colossoma macropomum, Exposed to Short-Term Anaesthetic Baths with Geraniol and Citronellol.

The aim of this study was to evaluate the level of neuronal depression in juvenile tambaqui, Colossoma macropomum, exposed to geraniol (GRL) and citronellol (CTL) in immersion baths. A total of 36 juveniles weighing 35.2 ± 9.4 g were used, organised into six experimental groups: I-control (clean water); II-ethanol (water containing the highest volume of ethanol used in the anaesthetic pre-dilution); III-GRL induction (70 µL·L-1); IV-CTL induction (90 µL·L-1); V-GRL recovery; VI-CTL recovery. Electroencephalographic (EEG) recordings were performed for 300 s in each group. EEG tracings of the control and ethanol groups showed regular and similar activity. Upon exposure to the anaesthetics, irregularities were observed in the tracings showing neuronal excitability and increased amplitudes, mainly in the case of CTL. Overall, GRL-exposed fish showed depression of the central nervous system with low and regular tracings throughout induction, presenting a gradual recovery and stable tracings, which were consistent with an adequate general anaesthetic effect. On the other hand, fish exposed to CTL showed altered EEG activity during induction, that could be considered incompatible with an appropriate anaesthetic effect and smooth recovery, presenting high and irregular EEG tracing amplitudes.

Cardiac response in tambaqui Colossoma macropomum anaesthetised with Piper divaricatum essential oil.

The aim of this study was to evaluate the electrocardiographic responses of Colossoma macropomum exposed to short-term baths using the essential oil of Piper divaricatum (EOPD) as an anaesthetic-like agent in different doses (40, 60, and 80 µL L-1). Cardiac responses throughout and after exposure to EOPD were monitored and evaluated through mean heart rate (HR), duration and amplitude of the QRS complex (ventricular depolarization), and Q-T (ventricular contraction) and R-R (time between two successive QRS complexes) wave intervals. Across all doses, there was a marked depression of the HR, mainly at 80 µL L-1 EOPD. Mean amplitudes recorded for the QRS complex and Q-T interval at 40 µL L-1 EOPD were indistinguishable from the control, which could reinforce this concentration as sufficient and safe to promote fast anaesthesia without affecting cardiac function. Recovery from bradycardia, duration of the R-R interval, and QRS complex were similar at 60 and 80 µL L-1 EOPD; however, the Q-T interval at 80 µL L-1 EOPD revealed a more pronounced cardiac depression in relation to the controls and fish exposed to 60 µL L-1 EOPD. Thus, we conclude that 40 µL L-1 EOPD should suffice to induce fast, deep, and safe anaesthesia in tambaqui juveniles, whereas the concentration of 80 µL L-1 led to a greater depression of the cardiac function, albeit showing effect reversibility.

Caffeine intoxication: Behavioral and electrocorticographic patterns in Wistar rats.

Caffeine is a psychoactive substance used worldwide. The present study analyzes the seizure-related behavior and electrocorticographic (ECoG) patterns observed in rats following of a toxic dose of caffeine (150 mg/kg; intraperitoneal). Sixty-three rats were divided into three experiments: 1-Behavior's Description associated with caffeine-induced convulsion; 2- Comparison of the electrocorticographic patterns induced by caffeine and pentylenetetrazole, and 3- Assessment of the electrocorticographic response to antiepileptic drugs (diazepam, phenytoin, and phenobarbital). The behavioral analysis demonstrated tonic-clonic seizures with a loss of postural reflex and a latency of 365.8 s after the caffeine's administration. Caffeine-induced changes in the ECoG were consistent with the development of seizures with rapid evolution and burst potential consistent with the behavioral patterns observed during the caffeine-induced seizure. The ECoG of the brainwaves varied significantly between the seizures caused by caffeine and pentylenetetrazole. The predominant brain forces observed during the seizures were beta-band oscillations. The caffeine-induced seizures were resistant to attempted control with phenytoin and phenobarbital, but responded well to diazepam, which is consistent with a study of Pilocarpine, which showed that diazepam has anticonvulsant effects. These findings are important for the development of effective treatments for caffeine intoxication, in particular for individuals with a low seizure threshold.

Evaluation of cardiotoxicity in Amazonian fish Bryconops caudomaculatus by acute exposure to aluminium in an acidic environment.

Aluminium (Al) is soluble in acidic waters and may become toxic to organisms. In this study, the acute effects of two Al concentrations were evaluated in the Amazonian fish Bryconops caudomaculatus. Antioxidant responses and lipid damage were assessed in gills, liver and muscle, along with the electrocardiography (ECG) and characterization of cardiac complex and wave intervals. Fish were essayed as follows: two control groups at neutral and acidic pH and two exposure groups at acidic pH (0.3 mg/L and 3.0 mg/L Al). Water samples were collected at 0h, 24h and 48h, for chloride (Cl-), fluoride (F-) and sulphate (SO42-) ion analyses, while total Al was quantified in muscle. Concentrations of Cl- and SO42- were constant over time whereas F- was not detected. Total Al concentrations in water and muscle were concentration-dependent. Antioxidant responses, total antioxidant capacity against peroxyl radicals (ACAP) and glutathione S-transferase were not triggered in fish tissues exposed to 0.3 mg/L Al; however, fish exposed to 3.0 mg/L Al presented increased and reduced ACAP in gills and liver, respectively. No changes in lipoperoxidation levels occurred among groups. Fish exposed to 0.3 mg/L Al showed prolonged intervals in ECG as a reflection of low heart rate (HR), with sinus bradycardia. Moreover, there was a marked prolongation of the PQ interval (time between the atrial activity and the start of ventricular activity), indicating interference on the cardiac cell automaticity. Fish exposed to the highest concentration of Al showed reduced wave intervals as a consequence of increased HR, with sinus arrhythmia, while ECG tracings did not present P waves (atrial contraction), indicating an atrioventricular blockade. In conclusion, 48h exposure sufficed to cause cardiotoxicity in B. caudomaculatus at either Al concentration. However, as oxidative stress was not observed, such cardiac alterations seem to be reversible under the experimental conditions established herein.

Oxidative stress and antioxidant responses in juvenile Brazilian flounder Paralichthys orbignyanus exposed to sublethal levels of nitrite.

This study evaluated the effects of short-term exposure to sublethal levels of nitrite on oxidative stress parameters and histology of juvenile Brazilian flounder Paralichthys orbignyanus. An assessment of fish recovery was also performed. Fish were exposed to 0.08 (control), 5.72, 10.43, and 15.27 NO2-N mg L-1 for 10 days followed by the same recovery time. Gill, liver, and muscle samples were collected after 1, 5, and 10 days of exposure and after recovery for the measurement of antioxidant capacity against peroxyl radicals (ACAP), glutathione-S-transferase (GST) activity, content of non-protein (NPSH) and protein thiols (PSH), and lipid peroxidation levels by thiobarbituric acid-reactive substances (TBARS) content. Nitrite exposure induced alterations which compromised the overall antioxidant system (reduced ACAP and GST activity) and enhanced oxidative damage in lipids and proteins. Increases in GST activity and NPSH and PSH contents were also demonstrated. The recovery period allowed for resumption of basal levels for all (treatment 5.72 NO2-N mg L-1) or some of the evaluated parameters (other treatments). In conclusion, exposure to nitrite concentrations from 5.72 to 15.27 NO2-N mg L-1 induced oxidative stress and antioxidant responses in juvenile Brazilian flounder. The 10-day recovery period was sufficient for a complete resumption of basal physiological condition of fish exposed to concentrations of up to 5.72 NO2-N mg L-1.

Haematological assessment of four amazonian ornamental armoured catfish (Teleostei, Loricariidae) / Avaliação hematológica em quatro acaris ornamentais amazônicos (Teleostei, Loricariidae)

The aim of this study was to characterize the haematological profile of four Amazonian ornamentalfreshwater armoured catfish: acari-bola (Peckoltia oligospila - L06), acari-pleco (Cochliodon sp. - L145), acari-canoa(Lasiancistrus saetiger - L323) and acari-assacu (Pseudocanthicus spinosus - L160). The highest blood glucose levels(72.47 ± 28.7 mg dL-1) and erythrocyte counts (0.51 ± 0.2 x 106 cel. μL-1) were recorded for acari-canoa. Theacari-bola and acari-pleco presented similar concentrations of total plasma protein (TPP) (7.96 ± 1.8 and 7.93 ±1.8 g dL-1, respectively) against lower TPP concentrations observed in acari-canoa (4.87 ± 1.5 g dL-1) and acariassacu(6.55 ± 1.5 g dL-1). The acari-assacu had lower total haemoglobin concentration (5.88 ± 1.7 g dL-1) andhaematocrit (12.66 ± 4.6%). No interspecific differences were observed in mean corpuscular volume (MCV) andmean corpuscular haemoglobin concentration (MCHC). The acari-pleco and acari-assacu presented the highestcounts for neutrophils (4142.42 ± 3280.1 cel. μL-1) and thrombocytes (4778.33 ± 1224.8 cel. μL-1), respectively.The haematological profiles were similar to those reported in the literature for freshwater fish and the interspecificdifferences observed were discussed.

O objetivo deste estudo foi caracterizar os perfis hematológicos de quatro espécies de acarisornamentais da região amazônica: acari-bola (Peckoltia oligospila - L06), acari-pleco (Cochliodon sp. - L145), acaricanoa(Lasiancistrus saetiger - L323) e acari-assacu (Pseudocanthicus spinosus - L160). Os maiores níveis de glicose(72,47 ± 28,7 mg dL-1) e contagem de eritrócitos (0,51 ± 0,2 x 106 cel. μL-1) foram encontrados no acari-canoa. Oacari-bola e acari-pleco apresentaram concentrações semelhantes de proteína plasmática total (PPT) (7,96 ± 1,8 e7,93 ± 1,8 g dL-1, respectivamente) em oposição às menores concentrações de PPT no acari-canoa (4,87 ±1,5 g dL-1) e acari-assacu (6,55 ± 1,5 g dL-1). Essa última espécie apresentou menor concentração total dehemoglobina (5,88 ± 1,7 g dL-1) e hematócrito (12,66 ± 4,6%). Não foram observadas diferenças significativasentre as quatro espécies nos parâmetros volume corpuscular médio (VCM) e concentração de hemoglobinacorpuscular média (CHCM). O acari-pleco e o acari-assacu apresentaram os maiores valores de neutrófilos(4142,42 ± 3280,1 cel. μL-1) e de trombócitos (4778,33 ± 1224,8 cel. μL-1), respectivamente. Os perfishematológicos foram semelhantes aos relatados na literatura para peixes de água doce e as diferençasinterespecíficas observadas foram discutidas.

Clove oil induces anaesthesia and blunts muscle contraction power in three Amazon fish species.

Clove oil is used as an anaesthetic for many species of fish worldwide; however, relatively few studies have assessed its effectiveness on Amazon fish species and no compelling evidence has ever been reported on the relaxant properties of this oil for skeletal muscle of fish. Thus, the objective of this study was to evaluate the latencies to deep anaesthesia and recovery, along with the myorelaxant effect of clove oil on three Amazon fish species: cardinal tetra, Paracheirodon axelrodi, banded cichlid, Heros severus and angelfish, Pterophyllum scalare, submitted to short-term anaesthetic baths. Fish were assayed in three groups of 60 fish each and individually anaesthetized in a completely randomized design with six clove oil concentrations using 10 fish/species/concentration. Electromyographic recordings from dorsal muscle were performed during stages of induction and recovery in which nine fish/species/stage were used. Deep anaesthesia was attained for all concentrations tested, and no mortalities were observed throughout the experiments and after a 48-h observation period. Concentration of 90 µL L-1 and above promoted fast deep anaesthesia (< 3 min) and calm recovery in angelfish and cardinal tetra, whereas the concentration of 60 µL L-1 sufficed to quickly anaesthetize banded cichlid. Times to full recovery were not significantly contrasting among species and occurred within appropriate time threshold (< 5 min). Clove oil exerted a conspicuous depression of muscle contraction power, and therefore can be effectively used as a muscle relaxant agent for P. scalare, P. axelrodi, H. severus and potentially, for other fish species.