It’s Tea Time: Interference of Ayahuasca Brew on Discriminative Learning in Zebrafish

Ayahuasca is a psychoactive brew traditionally used in shamanistic and vegetalistic rituals and has recently received lot of attention due to potential cognitive benefits. Ayahuasca effects are caused by the synergistic interaction of β-carbolines (harmine, harmaline and tetrahydroarmine) contained in Banisteriopsis caapi stalks combined with the N,N-dimethyltryptamine (DMT) from Psychotria viridis leaves, a potent agonist to serotonin (5-HT) receptors. The present study approaches the effects of chronic and acute exposure to two Ayahuasca concentrations (0.1 and 0.5 ml/L) on the cognitive ability to discriminate objects in a one-trial learning task in zebrafish. Based on the combination of concentrations and exposure regimens, we divided adult zebrafish in five treatment groups: acute 0.1 and 0.5 ml/L, chronic 0.1 and 0.5 ml/L, and control 0.0 (n = 20 for each group). Then we tested them in a memory task of object discrimination. Acute Ayahuasca exposed groups performed similarly to the control group, however chronically treated fish (13 days) presented both impaired discriminative performance and locomotor alterations. Overall, these results indicate that Ayahuasca is a potent psychoactive drug that, in chronic exposure, negatively affects mnemonic parameters in zebrafish. In single exposure it does not affects cognitive performance, but the higher concentration (0.5) affected locomotion. Moreover, we reinforce the importance of the zebrafish for behavioral pharmacological studies of drug screening, in special to psychedelic drug research

Frequência do canibalismo em diferentes fases de crescimento de matrinxã, Brycon amazonicus (Spix & Agassiz, 1829)

O canibalismo pode ser definido como uma interação agressiva predatória intraespecífica que resulta em consumo total ou parcial de coespecíficos. Esse comportamento agressivo é exibido por várias espécies de peixes, torna-se um fator limitante em criação intensiva devido à diminuição da taxa de sobrevivência em cativeiro. Assim, o objetivo deste projeto é descrever o desenvolvimento do comportamento agressivo e do canibalismo em diferentes estágios de crescimento em matrinxã, Brycon amazonicus. Para isso, análises comportamentais serão realizadas em 12, 24, 36 horas (fase larval), 48, 60 e 72 horas (fase juvenil) após a eclosão (n=8 / cada). Para cada tratamento experimental, cinco indivíduos serão aclimatados por 10 minutos e, em seguida, será feito o registro do comportamento (60 minutos). A taxa de locomoção será quantificada pela porcentagem de tempo que o animal se locomove (movimento retilíneo ou circular) durante cada observação. Já o comportamento agressivo será estimado pela freqüência de perseguição e mordida por minuto. Após esse período, os espécimes (40 indivíduos / tratamento) serão fixados em formalina 4% para posteriores medidas biométricas (peso corporal e comprimento total). Ao final de cada tratamento experimental também será verificada a taxa de sobrevivência. Assim, os resultados fornecerão informações etológicas básicas que poderão ser utilizadas para prover melhorias em métodos de larvicultura e, consequentemente, aumentar a eficiência da produção comercial dessa espécie.FAPEA

Frequência do canibalismo em diferentes fases de crescimento de matrinxã, Brycon amazonicus (Spix & Agassiz, 1829)

O canibalismo pode ser definido como uma interação agressiva predatória intraespecífica que pode resultar em consumo total ou parcial de coespecíficos. Esse comportamento agressivo é exibido por várias espécies de peixes, torna-se um fator limitante em criação intensiva devido à diminuição da taxa de sobrevivência em cativeiro. Assim, o objetivo deste projeto é descrever o comportamento agressivo e avaliar a taxa de sobrevivência em diferentes estágios de crescimento de matrinxã, Brycon amazonicus. Para isso, serão realizados dois experimentos. Experimento I: análises comportamentais serão realizadas em 12, 24, 36 horas (fase larval), 48, 60 e 72 horas (fase juvenil) após a eclosão (n=10 / cada). Para cada tratamento experimental, três indivíduos serão aclimatados por 10 minutos e, em seguida, será feito o registro do comportamento (20 minutos). A taxa de locomoção será quantificada pela porcentagem de tempo que o animal se locomove (movimento retilíneo ou circular) durante cada observação. Já o comportamento agressivo será descrito e quantificado com base nas unidades comportamentais observadas. Após esse período, os espécimes (30 indivíduos / tratamento) serão fixados em formalina 4% para posteriores medidas biométricas (peso corporal e comprimento total). Experimento II: será comparada a taxa de sobrevivência dos peixes durante os seis períodos de observação (n=5), conforme descrito no experimento I. Os ovos fertilizados serão mantidos em incubadoras cilíndricas de 35 litros, com a água em regime de renovação constante e densidade de 1g de ovos por litro de água. A taxa de fertilização será medida 12 horas após a última dose de indução hormonal e a taxa de eclosão será observada 5 horas após a fertilização. Em cada cinco horas antes da observação, 100 larvas serão transferidas para recipientes (bandejas de polipropileno) de 50 x 30 cm e, em cada período, será verificada a taxa de sobrevivência das larvas expressa em porcentagem. Assim, os resultados fornecerão informações etológicas básicas que poderão ser utilizadas para prover melhorias em métodos de larvicultura e, consequentemente, aumentar a eficiência da produção comercial dessa espécie.FAPEA

Embryonic ethanol exposure on zebrafish early development

Abstract Introduction Embryonic exposure to ethanol leads to a condition of physical, behavioral, and cognitive deficiencies named fetal alcohol spectrum disorders (FASD). The most severe variations are in fetal alcohol syndrome (FAS), which is easier to diagnose and not studied in animal models. On the other side, the pFAS (partial fetal alcohol syndrome) includes cases of alcohol‐related congenital disabilities and neurodevelopmental disorder with an inconclusive diagnosis. In recent years, the zebrafish has become a valuable model to study FASD and its variations. Methods This study characterizes the zebrafish embryonic and larval development after low and moderate ethanol concentration exposure. Fish eggs were exposed to 0.0%, 0.25%, 0.5%, and 1.0% ethanol at 24 hr postfertilization, and embryonic development was observed every 8 hr up to 120 hpf. It evaluated movements, phenotypic abnormalities, hatching, cardiac function and heartbeat frequency, larvae length at 120 hpf, and the apoptotic cells' fluorescence stained with acridine orange. Results Embryonic exposure to 0.5% and 1% ethanol presented reduced body size, decreased heartbeat rate, higher numbers of apoptotic cells, and hatching time differences. Conclusions Our results suggest any ethanol exposure during embryogenesis can be harmful and reinforces zebrafish as a suitable model for fetal alcohol spectrum disorders (FASD)

Sleep deprivation impairs cognitive performance in zebrafish: A matter of fact?

The zebrafish (Danio rerio) has become a valuable model organism for behavioral studies examining learning and memory. Its diurnal circadian rhythm and characterized sleep-like state make it comparable to mammals, features that have contributed to establishing this small vertebrate as a translational model for sleep research. Despite sleep being an evolutionarily conserved behavior, its mechanisms and functions are still debated. Sleep deprivation is commonly associated with decreased attention, reduced responsiveness to external stimuli, altered locomotor activity and impaired performance on cognitive tasks. In the current study, we examined the effects of partial and total sleep deprivation on zebrafish learning performance in an active avoidance conditioning paradigm. In addition, we examined the effects of two drugs known to alter sleep (alcohol and melatonin) on learning performance in sleep deprived animals. Our results suggest that although partial sleep deprivation did not alter learning performance, total sleep deprivation was found to significantly impair behavioral responses to the electric shock as well as avoidance learning. However, when sleep deprived fish were treated with alcohol the night before the learning task, learning performance was similar to the control group. In contrast, melatonin treatment did not alter learning performance in sleep deprived animals. We conclude that the zebrafish is a sensitive tool for investigating the effects of sleep deprivation on cognitive performance and may be a useful model for dissecting the mechanisms underlying learning and memory

Good night, sleep tight: The effects of sleep deprivation on spatial associative learning in zebrafish

Learning and memory are vital to an animal's survival, and numerous factors can disrupt cognitive performance. Sleep is an evolutionarily conserved physiological process known to be important for the consolidation of learning and memory. The zebrafish has emerged as a powerful model organism sharing organizational and functional characteristics with other vertebrates, providing great translational relevance. In our study, we used a simple spatial associative learning task to quantify the effects of sleep deprivation (partial vs. total) on learning performance in zebrafish, using an animated conspecific shoal image as a reward. Control animals maintained on a regular light:dark cycle were able to acquire the association between the unconditioned and conditioned stimulus, reinforcing zebrafish as a valid and reliable model for appetitive conditioning tasks. Notably, sleep deprivation did not alter the perception of and response to the conspecific image. In contrast, although partial sleep deprivation did not impair cognitive performance, total sleep deprivation significantly impaired performance on the associative learning task. Our results suggest that sleep is important for learning and memory, and that the effects of sleep deprivation on these processes can be investigated in zebrafish

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Individual differences in response to alcohol exposure in zebrafish (<i>Danio rerio</i>) - Fig 1

<p><b>Schematic overview of the (a) emergence tank and (b) exploration/sociability tank.</b> Tanks measured 40 x 25 x 20 cm (15L). For the emergence tank, an opaque glass wall with a 2 cm guillotine door allowed the fish to swim from the black to white compartment; all the surrounding walls were completely covered with opaque self-adhesive plastic films (white or black). Transparent walls divided the exploration/sociability tank into 5 chambers; the first chamber contained the ‘starting box’, and the fifth chamber ended in the ‘shoal tank’. Chambers 1, 2 and 3 were considered pathway areas. Chambers 4 and 5 were considered shoal areas, since these two chambers were bordering the stimulus tank.</p

Time zebrafish spent in each area of the tank (mean + SEM) during the exploration/sociability test.

<p>Different lowercase letters indicate statistical significance between pathways areas (bold and shy groups: two-way ANOVA, p< 0.05). Different capital letters indicate statistical significance among shoal areas (bold and shy groups: two-way ANOVA, p<0.05. Asterisk indicates a statistical difference between pathway and shoal areas, in the same alcohol treatment (p<0.05).</p

Comparison between bold and shy experimental groups following alcohol exposure.

<p>Bars indicates zebrafish locomotor behavior (mean + SEM) for 10 min in the test tank: (a) Average swimming speed, (b) Maximum swimming speed, (c) Total distance traveled, and (d) Total time spent immobile. Average speed and total distance traveled were not statistically significant between treatments. Different letters indicate statistical significance between alcohol treatments (two-ay ANOVA, p<0.05).</p