Investigation on the mancozeb toxicity in adult zebrafish (Danio rerio).

Agriculture has gained increasing importance in response to the continuous growth of the world population and constant need for food. To avoid production losses, farmers commonly use pesticides. Mancozeb is a fungicide used in agriculture as this compound is effective in combating fungi that harm crops. However, this fungicide may also produce damage to non-target organisms present in soil and water. Therefore, this study aimed to investigate the influence of exposure to mancozeb on survival rate, locomotor activity, behavior, and oxidative status utilizing adult zebrafish (Danio rerio) as a model following exposure to environmentally relevant concentrations of this pesticide. The experimental groups were negative control, positive control, and mancozeb (0.3; 1.02; 3.47; 11.8 or 40 µg/L). Zebrafish were exposed to the respective treatments for 96 hr. Exposure to mancozeb did not markedly alter survival rate and oxidative status of Danio rerio. At a concentration of 11.8 µg/L, the fungicide initiated changes in locomotor pattern of the animals. The results obtained suggest that the presence of mancozeb in the environment might produce locomotor alterations in adult zebrafish, which subsequently disrupt the animals' innate defense mechanisms. In nature, this effect attributed to mancozeb on non-target organisms might result in adverse population impacts and ecological imbalance.

Recycled polyvinyl chloride microplastics: investigation of environmentally relevant concentrations on toxicity in adult zebrafish.

Recycled polyvinyl chloride (PVC) microplastics have been detected in the aquatic environment. These recycled microparticles contain chemicals that are released into the environment reaching different organisms. Although the problem of the presence of recycled PVC microparticles in the environment is evident, the toxicological consequences of this contaminant to exposed organisms remains to be better determined. The aim of this study was to investigate the toxicity attributed to exposure to environmentally relevant concentrations of recycled PVC microplastics in adult zebrafish (Danio rerio). The experimental groups were: negative control, vehicle control, positive control, and recycled microplastics (20 ± 5 µm) at 5, 10 or 20 µg/L. Zebrafish (D. rerio) were exposed to respective treatments for 96 hr. Locomotion and oxidative status parameters were measured and mortality recorded. The positive control group presented increased mortality rates and decreased locomotor activity. Animals from the vehicle group did not show marked differences. Finally, no significant disturbances were found in survival rate, locomotion pattern and oxidative status of animals exposed to recycled PVC microparticles at 5, 10 or 20 µg/L. Taken together our results suggest that recycled PVC microplastics in this particle size range do not appear to exert harmful effects on exposed adult D. rerio. However, these results need to be carefully observed due to limitations including size of particle and duration of exposure parameters that might affect ecological consequences. It is suggested that additional studies applying other particles sizes and chronic exposure are needed to more comprehensively verify the toxicity of the contaminant investigated here.

Evaluation of Resveratrol and Piceatannol Anticonvulsant Potential in Adult Zebrafish (Danio rerio).

Epilepsy is a common neurological disorder which affects 50 million people worldwide. Patients with epilepsy may present cognitive deficits and psychological impairment. Currently, 30% of patients fail to respond to any available antiseizure drug, and a significant number of patients do not well tolerate the offered treatments. Then, it is necessary to find out alternatives for controlling epileptic seizures. Studies have shown that despite its neuroprotective effects, resveratrol shows poor anticonvulsant properties. Resveratrol analog, piceatannol, possesses higher biological activity than resveratrol and could be an alternative to control seizure. Thus, the present study investigated the effects of resveratrol and piceatannol in pentylenetetrazole-induced seizures in adult zebrafish (Danio rerio). Only the experimental positive control (diazepam) showed anticonvulsant effect in this study. In addition, no behavioral changes were observed 24 h after seizure occurrence. Finally, the expression of genes related to neuronal activity (c-fos), neurogenesis (p70S6Ka and p70S6Kb), inflammatory response (interleukin 1ß), and cell apoptosis (caspase-3) did not change by pentylenetetrazole-induced seizures. Therefore, we failed to observe any anticonvulsant and neuroprotective potential of resveratrol and piceatannol in adult zebrafish. However, resveratrol and piceatannol benefits in epilepsy are not discharged, and more studies are necessary.

Micronized Resveratrol Shows Anticonvulsant Properties in Pentylenetetrazole-Induced Seizure Model in Adult Zebrafish.

Epilepsy affects 50 million people around the world, and the patients experience cognitive, psychological and social consequences. Despite the considerable quantity of antiepileptic drugs available, 30% of patients still suffer in seizure. Therefore, the advance in therapeutic alternatives is mandatory. Resveratrol has been attracting the attention of many researchers because of its pharmacological potential. However, despite its neuroprotective and anti-epileptic effects, clinical resveratrol use is impaired by its low bioavailability. Here, we applied the supercritical fluid micronization technology (SEDS) to overcome this deficit, and investigated the anticonvulsant potential of micronized resveratrol in a PTZ-induced seizure model in adult zebrafish (Danio rerio). SEDS permits obtaining significantly reduced particle size with a fine size distribution in comparison with the starting material. It can improve the pharmacotherapeutic efficacy. Our data showed that micronized resveratrol decreased the occurrence of the tonic-clonic seizure stage and slowed the development of the seizures in a similar manner of diazepam. Non-processed resveratrol was not able to protect the animals. Furthermore, diazepam decreased the locomotion and exploratory behavior. Differently from diazepam, the micronized resveratrol did not induce behavioral adverse events. In addition, our data showed that the PTZ-induced seizures increased the c-fos transcript levels following the neural excitability. However, the increase in c-fos levels was prevented by micronized resveratrol. In conclusion, our results demonstrate that the micronized resveratrol shows anticonvulsant effect, like the classical antiepileptic drug diazepam in a PTZ-induced seizure model. Excitingly, different from diazepam, micronized resveratrol did not provoke behavioral adverse events.

Investigation on the Anticonvulsant Potential of Luteolin and Micronized Luteolin in Adult Zebrafish (Danio rerio).

Epilepsy affects around 50 million people worldwide, and an important number of patients (30%) fail to respond to any available antiepileptic drug. Previous studies have shown that luteolin presents a promising potential as an anticonvulsant. On the other hand, different studies showed that luteolin does not promote anticonvulsant effects. Therefore, there is a lack of consensus about the use of luteolin for seizure control. Luteolin low bioavailability could be a limiting factor to obtain better results. Attractively, micronization technology has been applied to improve flavonoids bioavailability. Thus, the present study aimed to investigate the effects of luteolin on its raw form and micronized luteolin in a PTZ-induced seizure model in adult zebrafish (Danio rerio). Our results demonstrate that luteolin and micronized luteolin did not block PTZ-induced seizures in adult zebrafish. Also, luteolin and micronized luteolin did not provoke behavioral changes. Finally, our results show that 24 h after seizure occurrence, no changes were detected for p70S6Kb, interleukin 1ß, and caspase-3 transcript levels. Altogether, we failed to observe an anticonvulsant potential of luteolin in adult zebrafish, even in its micronized form. However, we recommend new studies to investigate luteolin benefits in epilepsy.

Erythromycin in the aquatic environment: deleterious effects on the initial development of zebrafish.

Due to the large volume of erythromycin continuously reaching waterbodies and its high persistence, this antibiotic drug has been detected in the aquatic environment at elevated concentrations. Although the problem of the presence of erythromycin in the environment is evident due to its influence in development of antimicrobial resistance, the toxicological consequences on non-target organisms remain to be determined. There are no apparent data on the impact of environmentally relevant concentrations of erythromycin on developing fish. Data on toxic effects during development are essential for evaluation of environmental risk to organisms. Therefore, the aim of this study was to investigate the effects of exposure to erythromycin on certain parameters including hatchability, survival rate, heart rate, and behavior in developing zebrafish. Zebrafish were exposed to a range of environmentally relevant concentrations of antibiotic (0.001, 0.01, 0.1, 1 µg/L) and one concentration 10-fold higher (10 µg/L). Exposure to erythromycin at 0.1 µg/L delayed hatching and decreased survival rate. Exposure to all tested concentrations increased heart rate. Further, exposure to erythromycin at 1 or 10 µg/L enhanced swimming activity. Our results indicated that erythromycin present in the aquatic environment might lead to disabling consequences in developing fish organisms and subsequently may result in ecological imbalance in the natural environment.

Hyperglycemia alters E-NTPDases, ecto-5'-nucleotidase, and ectosolic and cytosolic adenosine deaminase activities and expression from encephala of adult zebrafish (Danio rerio).

Hyperglycemia is the main feature for the diagnosis of diabetes mellitus (DM). Some studies have demonstrated the relationship between DM and dysfunction on neurotransmission systems, such as the purinergic system. In this study, we evaluated the extracellular nucleotide hydrolysis and adenosine deamination activities from encephalic membranes of hyperglycemic zebrafish. A significant decrease in ATP, ADP, and AMP hydrolyses was observed at 111-mM glucose-treated group, which returned to normal levels after 7 days of glucose withdrawal. A significant increase in ecto-adenosine deaminase activity was observed in 111-mM glucose group, which remain elevated after 7 days of glucose withdrawal. The soluble-adenosine deaminase activity was significantly increased just after 7 days of glucose withdrawal. We also evaluated the gene expressions of ecto-nucleoside triphosphate diphosphohydrolases (E-NTPDases), ecto-5'-nucleotidase, ADA, and adenosine receptors from encephala of adult zebrafish. The entpd 2a.1, entpd 2a.2, entpd 3, and entpd 8 mRNA levels from encephala of adult zebrafish were decreased in 111-mM glucose-treated and glucose withdrawal groups. The gene expressions of adenosine receptors (adora 1 , adora 2aa , adora 2ab , and adora 2b ) were decreased in 111-mM glucose-treated and glucose withdrawal groups. The gene expression of ADA (ada 2a.1) was decreased in glucose withdrawal group. Maltodextrin, used as a control, did not affect the expression of adenosine receptors, ADA and E-NTPDases 2, 3, and 8, while the expression of ecto-5'-nucleotidase was slightly increased and the E-NTPDases 1 decreased. These findings demonstrated that hyperglycemia might affect the ecto-nucleotidase and adenosine deaminase activities and gene expression in zebrafish, probably through a mechanism involving the osmotic effect, suggesting that the modifications caused on purinergic system may also contribute to the diabetes-induced progressive cognitive impairment.

Genotoxic potential and physicochemical parameters of Sinos River, southern Brazil.

The present study aimed to evaluate the physicochemical parameters and the genotoxic potential of water samples collected in the upper, middle, and lower courses of the Sinos River, southern Brazil. The comet assay was performed in the peripheral blood of fish Hyphessobrycon luetkenii exposed under laboratory conditions to water samples collected in summer and winter in three sampling sites of Sinos River. Water quality analysis demonstrated values above those described in Brazilian legislation in Parobé and Sapucaia do Sul sites, located in the middle and in the lower courses of the Sinos River, respectively. The Caraá site, located in the upper river reach, presented all the physicochemical parameters in accordance with the allowed limits in both sampling periods. Comet assay in fish revealed genotoxicity in water samples collected in the middle course site in summer and in the three sites in winter when compared to control group. Thus, the physicochemical parameters indicated that the water quality of the upper course complies with the limits set by the national guidelines, and the ecotoxicological assessment, however, indicated the presence of genotoxic agents. The present study highlights the importance of combining water physicochemical analysis and bioassays to river monitoring.

Genotoxic damage in auto body shop workers.

Some studies have shown increased DNA damage among car painters, but other professionals working in auto body and paint shops have not been extensively assessed. The aim of this study was to assess DNA damage in different types of auto body shop workers by measuring micronucleus (MN) levels in exfoliated buccal cells. The mean number of cells with MN per 2000 exfoliated buccal cells was analyzed in three groups of male workers: auto body repair technicians, painters, and office workers (control group). All participants answered a questionnaire inquiring about age, smoking habits, alcohol consumption, work practices, occupational exposure time, job activities, and use of protective equipment. The mean number of cells with MN was 3.50 ± 1.50 in auto body painters, 3.91 ± 2.10 in auto body repair technicians, and 0.80 ± 0.78 in office workers, with a significant difference between the control group and the two other groups (p = 0.0001). Age, occupational exposure time, use of protective masks, alcohol consumption, and smoking habit did not affect MN results. The findings indicate that technicians and painters working in auto body shops are at risk for genotoxic damage, while office workers seem to be protected.

Exposure to ractopamine hydrochloride induces changes in heart rate and behavior in zebrafish embryos and larvae.

Different veterinary drugs have been widely found in surface and groundwater, affecting non-target organisms. Ractopamine (RAC) is one of these drugs found in water bodies. It is a ß-adrenergic agonist used as a feed additive to modulate the metabolism, redirect nutrients from the adipose tissue towards muscles, and increase protein synthesis in swine, cattle, and turkeys. RAC shows toxicological potential, but there is no data about its impacts on the development of non-target organisms, such as zebrafish (Danio rerio). In this study, we evaluated the effect of the exposure to this feed additive on critical parameters (hatching, survival, spontaneous movement, heart rate, and exploratory and locomotor behavior) in zebrafish embryos and larvae. The animals were exposed to RAC hydrochloride at 0.1, 0.2, 0.85, 8.5, and 85 µg/L. Zebrafish exposed to the drug showed increased heart rate at all tested concentrations and alterations on locomotion and exploratory behavior at 85 µg/L. No changes were observed in the survival, hatching rate and spontaneous movement. Our results suggest that RAC present in the environment can induce disabling effects on non-target organisms and elicit an ecological imbalance by increasing the animals' vulnerability to predation due to greater visibility.

Oxidative state of the frugivorous bat Sturnira lilium (Chiroptera: Phyllostomidae) in agricultural and urban areas of southern Brazil.

Exposure to contaminants is one of the main threats to all living organisms. In this context, bats have been used to indicate environmental contaminants in urban and agricultural environments, since they are extremely sensitive to changes in the ecosystem and easily accumulate waste in their body tissues. Among bats, Sturnira lilium, is a frugivorous species widely distributed and abundant in Brazil that uses an extensive variety of habitats and shelters. In this study, we aimed to evaluate the oxidative state of S. lilium individuals in agricultural and urban areas in southern Brazil. Individuals were sampled in agricultural and urban areas from November 2017 to March 2018 through the mist-net method. Parameters of the superoxide dismutase (SOD) and catalase (CAT) enzyme activity, non-protein thiols (NPSH), and lipid peroxidation (TBARS) were determined based on liver tissue. A total of 46 individuals were captured, 29 of them in urban areas and 17 in agricultural areas. We found that S. lilium individuals from agricultural areas showed a significant increase in TBARS, NPSH, and SOD activity, compared to individuals from urban areas. The activity of the antioxidant enzyme CAT did not differ. The present findings suggest that the species S. lilium, which are widely distributed and abundant in Brazil in urban and agricultural areas, can usefully be employed in biomonitoring programs. Further studies are to be encouraged to refine our knowledge on the potential DNA damage caused by environmental contamination, as well as identify potential contaminants to bats.

Exposure to the herbicide 2,4-dichlorophenoxyacetic acid impairs mitochondrial function, oxidative status, and behavior in adult zebrafish.

2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the most commonly used herbicides worldwide. While the effects of 2,4-D in target organisms are well known, its consequences in nontarget organisms are not fully explained. Therefore, the purpose of this study was to investigate the effects of the herbicide on mitochondrial energy metabolism, oxidative status, and exploratory behavior in adult zebrafish. Animal exposure to 2,4-D increased cytochrome c oxidase and catalase activities and reduced SOD/CAT ratio, moreover, increased the total distance traveled and the number of crossings. Finally, animals exposed to 2,4-D spent more time in the upper zone of the tank and traveled a long distance in the upper zone. Overall, our results indicate the 2,4-D can provoke disabling effects in nontarget organisms. The obtained data showed that exposure to 2,4-D at environmentally relevant concentrations alters mitochondrial metabolism and antioxidant status and disturbs the zebrafish innate behavior.

Micronized resveratrol shows promising effects in a seizure model in zebrafish and signalizes an important advance in epilepsy treatment.

Resveratrol is a natural non-flavonoid polyphenolic that has been emerging in epilepsy treatment. Despite its pharmacological properties, the poor bioavailability of resveratrol has been an important barrier that hinders its application as an anticonvulsant. The aim of this work was to improve resveratrol's anticonvulsant effects by micronizing this compound through supercritical fluid micronization technology, which promotes an increase of the particles' surface area and allows significantly reduced particle size to be obtained. We obtained commercial and micronized resveratrol and investigated the anticonvulsant effects of resveratrol as commercially found and micronized resveratrol in a pentylenetetrazole-induced seizure model in zebrafish (Danio rerio) larvae. Diazepam was used as the positive control. Also, animals had their locomotor and exploratory activity analyzed 24 h after the seizure occurrence. The occurrence of the tonic-clonic seizure stage was only prevented by diazepam and micronized resveratrol, unlike the non-processed compound. The seizure development was significantly slowed by diazepam and micronized resveratrol, while non-micronized resveratrol was not able to increase the latency of seizure stages. In addition, diazepam and micronized resveratrol prevented the deleterious effects of pentylenetetrazole-induced seizures on animals' locomotor and exploratory behaviour. Obtained data demonstrates that the micronization process potentiates the anticonvulsant effect of resveratrol. Micronized resveratrol achieved a similar effect to the classical drug diazepam, with the benefit that it may be a safe drug candidate to be used during the neurodevelopmental stage.

Antinociceptive and anti-inflammatory activities of Philodendron bipinnatifidum Schott ex Endl (Araceae).

ETHNOPHARMACOLOGICAL RELEVANCE: Popular medicine use stems of Philodendron bipinnatifidum (Araceae) in inflammation cases, such as in erysipelas, as well as orchitis and rheumatism treatment. The present study, conducted for the first time in literature, investigate the antinociceptive and anti-inflammatory activities of P. bipinnatifidum stems ethyl acetate extract (EPB). MATERIALS AND METHODS: GC/MS and HPLC analysis were performed for EPB extract. We used EPB at 250, 375 and 500 mg/kg (oral route, p.o.) in male Swiss mice. The antinociceptive activity of the plant extract assessed by acetic acid induced writhing and formalin tests. To investigate the possible participation of opioid system in EPB-mediated effects, we previously administered naloxone to the mice. Anti-inflammatory activity was evaluated using carrageenan-induced paw oedema. The open-field test aimed to investigate the possible EPB effects on the locomotor and exploratory activities. To assess the protective role of EPB on carrageenan-induced oxidative stress, the levels of NPSH, TBARS, as well as SOD and CAT activities were evaluated in blood and paw tissue. The acute toxicity of the EPB was investigated using OECD 423 guideline. RESULTS: The EPB chemical analysis by GC/MS and HPLC revealed the presence of flavonoids (luteolin and quercetin) and phytosterols (ß-sitosterol and stigmasterol). The oral treatment with the EPB inhibited mice abdominal writhings (P < 0.01) at 375 and 500 mg/kg, and reduced the formalin effect at the first-phase (500 mg/kg, P < 0.05) and also at the second-phase (500 mg/kg, P < 0.001) of the test. EPB (375 and 500 mg/kg) did not alter spontaneous locomotion in open field test, however the number of fecal bolus was significantly lower for the EPB group at 500 mg/kg when compared to the vehicle group (P < 0.05). The pretreatment with naloxone caused significant inhibition of antinociceptive activity induced by EPB in the formalin test, revealing the possible involvement of opioid receptors. EPB extract administered at 500 mg/kg (p.o.) prevented carrageenan-induced paw oedema (P < 0.05 and 0.01) until 6 h after carragenan injection. Evaluation of TBARS and NPSH levels, SOD and CAT activities in the blood and paw tissue of animals submitted to the carrageenan assay suggested that the anti-inflammatory effect of EPB may be linked to oxidative stress inhibition. The acute administration of the EPB (2000 mg/kg, p.o.) caused no mortality, demonstrating low toxicity. CONCLUSIONS: The extract of P. bipinnatifidum displays antinociceptive and anti-inflammatory activities, causing no toxicological effects. The pharmacological activity of this vegetal species may be related to the presence of flavonoids and phytosterols. Our results support the ethnomedical use of this vegetal species as analgesic and anti-inflammatory agent.

Iron and manganese present in underground water promote biochemical, genotoxic, and behavioral alterations in zebrafish (Danio rerio).

Iron (Fe) and manganese (Mn) are metals commonly found at high concentrations in underground water. These metals are essential for the good functioning of living organisms, but high concentrations lead to imbalance, potentiating the appearance of pathologies. This study aimed to evaluate the effect of exposure to naturally occurring metals in groundwater, using zebrafish (Danio rerio) as an experimental model. Thus, zebrafish were exposed to Fe (0.8 and 1.3 mg/L), Mn (0.2 and 0.4 mg/L), and groundwater collected from deep tube wells with Fe and Mn (Fe 0.8/Mn 0.2 mg/L and Fe 1.3/Mn 0.4 mg/L) for 30 days. Bioaccumulation of these metals has been demonstrated in the livers and muscles of zebrafish. Acetylcholinesterase activity changed only in zebrafish muscles in all groups. Sulfhydryl levels changed mainly in the group Mn 0.4. SOD/CAT ratio decreased in the groups Fe 0.8 and 1.3, Mn 0.4, and Fe 0.8/Mn 0.4. An increase in the frequency of micronucleus in all groups was shown as a consequence of these changes. Behavioral parameters (time and distance traveled, mean speed, turn angle, latency, and number of crossings between compartments) have also changed, mainly in the groups Fe 1.3, Mn 0.4, and Fe 1.3/Mn 0.4. Therefore, long-term exposure to Fe and Mn, even at not so high concentrations, may cause biochemical, genotoxic, and behavioral changes in zebrafish.

Micronization potentiates curcumin's anti-seizure effect and brings an important advance in epilepsy treatment.

Epilepsy is one of the most common neurological diseases, and current antiepileptic drugs fail to suppress seizure occurrence in around one third of epileptic patients. Curcumin is a phytochemical with promising effects on epilepsy treatment. However, its application has been hindered by its low bioavailability. In order to improve curcumin's anti-seizure properties, increasing its bioavailability, here we proposed to micronize the compound through supercritical carbon dioxide processing, a suitable green chemistry technique to prepare and modify material properties. Here we investigated the anti-seizure potential of the classical antiepileptic drug valproate, curcumin in its natural state, and micronized curcumin in a PTZ-induced seizure model in zebrafish (Danio rerio). Concerning seizure development, valproate, curcumin and micronized curcumin showed protective effects, slowing seizure development both in larvae and adult animals. Nevertheless, considering the occurrence of the tonic-clonic seizure stage, only valproate and micronized curcumin reduced it, both in larvae and adult zebrafish, unlike non-processed curcumin. Our obtained results are very promising, since micronized curcumin showed effects that are similar to a classic antiepileptic drug, reducing seizure occurrence and slowing seizure progression.

Hydropower reservoirs: cytotoxic and genotoxic assessment using the Allium cepa root model.

Hydropower offers a reliable source of electricity in several countries, and Brazil supplies its energy needs almost entirely through hydropower plants. Nevertheless, hydropower plants comprise large buildings and water reservoirs and dams, resulting in huge ecological disruptions. Here, we analyzed the impact of four hydropower reservoirs construction in metals and pesticides incidence and the cytotoxic and genotoxic potential of sediment elutriate of rivers from southern Brazil. Our analyses have evidenced the elevated incidence of different metals (lead, iron, cadmium, and chrome) and pesticides (methyl parathion, atrazine, and 2,4-dichlorophenoxyacetic acid). We showed that Allium cepa exposed to sediment elutriates did not change the seed germination rate and mitotic index. However, roots from Allium cepa exposed to reservoirs sediment elutriates showed increased occurrence of chromosomal aberrations and nuclear abnormalities. Therefore, the results obtained in our study indicate that sediment from reservoirs present elevated concentration of metals and pesticides and a significant genotoxic potential. Taken together, our data support that hydropower reservoirs represent an environmental scenario that could impact surrounding wildlife and population.

Analysis of Extracellular Nucleotide Metabolism in Adult Zebrafish After Embryological Exposure to Valproic Acid.

Autism is a neurodevelopmental disorder characterized by symptoms related to stereotyped movements, deficits in social interaction, impaired communication, anxiety, hyperactivity, and the presence of restricted interests. Evidence indicates an important role of extracellular ATP and adenosine as signaling molecules in autism. ATP hydrolysis by ectonucleotidases is an important source of adenosine, and adenosine deaminase (ADA) contributes to the control of the nucleoside concentrations. Considering zebrafish is an animal model that may contribute towards to understanding the mechanisms that underlie social behavior, we investigated the purinergic signaling in a model of embryological exposure to valproic acid (VPA) that induces social interaction deficit in adult zebrafish. We demonstrated embryological exposure to VPA did not change ATP and ADP hydrolysis in zebrafish at 120 dpf, and the cytosolic (soluble) ADA activity was not altered. However, we observed an increase of AMP hydrolysis (12.5 %) whereas the ecto-ADA activity was decreased (19.2 %) in adult zebrafish submitted to embryological exposure to VPA. Quantitative reverse transcription PCR (RT-PCR) analysis showed changes on ntpd8, ADA 2.1, and A2a1 mRNA transcript levels. Brain ATP metabolism showed a rapid catabolism of ATP and ADP, whereas the extracellular metabolism of AMP and adenosine (ADO) occurred slowly. We demonstrated that embryological exposure to VPA altered biochemical and molecular parameters related to purinergic system in adult zebrafish. These findings indicate that the enzyme activities involved in the control of ATP and adenosine levels may be involved in the pathophysiological mechanisms of diseases related to the impairment of social interaction, such as autism.

Oxytocin reversed MK-801-induced social interaction and aggression deficits in zebrafish.

Changes in social behavior occur in several neuropsychiatric disorders such as schizophrenia and autism. The interaction between individuals is an essential aspect and an adaptive response of several species, among them the zebrafish. Oxytocin is a neuroendocrine hormone associated with social behavior. The aim of the present study was to investigate the effects of MK-801, a non-competitive antagonist of glutamate NMDA receptors, on social interaction and aggression in zebrafish. We also examined the modulation of those effects by oxytocin, the oxytocin receptor agonist carbetocin and the oxytocin receptor antagonist L-368,899. Our results showed that MK-801 induced a decrease in the time spent in the segment closest to the conspecific school and in the time spent in the segment nearest to the mirror image, suggesting an effect on social behavior. The treatment with oxytocin after the exposure to MK-801 was able to reestablish the time spent in the segment closest to the conspecific school, as well as the time spent in the segment nearest to the mirror image. In addition, in support of the role of the oxytocin pathway in modulating those responses, we showed that the oxytocin receptor agonist carbetocin reestablished the social and aggressive behavioral deficits induced by MK-801. However, the oxytocin receptor antagonist L-368,899 was not able to reverse the behavioral changes induced by MK-801. This study supports the critical role for NMDA receptors and the oxytocinergic system in the regulation of social behavior and aggression which may be relevant for the mechanisms associated to autism and schizophrenia.