Biology subjects

Maximino, C.

Publications and source records attributed to Maximino, C..

At least 19 recordsLinked to original sources

bioRxiv2026

The anxiolytic-like effect of the aqueous extract of Punica granatum depends on the stress level of fish and mice: Evidence of a homeostatic re-establishing effect

Pomegranate (Punica granatum) has shown potential anxiolytic and antidepressant effects in preclinical research, but its mechanisms remain unclear. Importantly, some evidence suggests that the effects of P. granatum depend on previous stress, suggesting an adaptogenic effect. This study aimed to evaluate the anxiolytic-like effects of an aqueous extract of P. granatum (AE-PG) on lambaris and zebrafish exposed to acute restraint stress (ARS) and female BALB/c mice exposed to unpredictable chronic mild stress (CUMS). In addition, we evaluated antidepressant-like effects in female BALB/c mice. Acute administration of AE-PG (1 mg/kg, i.p.) was tested in the novel tank test (NTT) in lambaris and zebrafish and in the light/dark test (LDT) in zebrafish, while chronic (7 days) administration of AE-PG (1 mg/kg, i.p.) was tested in the elevated plus-maze (EPM), open-field test (OFT), splash test (ST), and forced swim test (FST) in mice. ARS increased geotaxis and erratic swimming in the NTT, as well as scototaxis, risk assessment, and erratic swimming in the LDT. Acute pre-treatment with AE-PG blocked the effects of ARS on these anxiety-like endpoints in both lambaris and zebrafish. CUMS increased open arm avoidance in the EPM, thigmotaxis and horizontal and vertical exploration in the OFT, and immobility in the FST, and decreased grooming in the ST. Chronic treatment with AE-PG blocked the effects of CUMS on anxiety-like endpoints, and depression-like endpoints, in mice. An in silico analysis of the main compounds in AE-PG suggested a possible mechanism of action on a wide network of targets that converge on PI3K/Akt and show differential expression in brain regions associated with fear- and anxiety-like behavior. Molecular docking suggests that a compound from AE-PG, ellagic acid, is likely to act through estrogen receptors, which could help reestablish homeostatic balance in response to stress.

pharmacology and toxicology↗

bioRxiv2026

Unpredictable chronic stress produces a mixed depression/anxiety behavioral profile in zebrafish

Stress is a physiological, adaptive, and preliminary response of the organism to situations of threats and instability caused by environmental and psychological stressors. The chronicity and predictability of stressors are important variables in determining neurobehavioral outcomes. While unpredictable chronic stress (UCS) protocols typically induce depressive-like phenotypes in rodents, in zebrafish the effects of these protocols are assessed using anxiety-like outcomes. This study aimed to analyze the effects of an unpredictable UCS on depressive-type behavioral parameters and brain lipid peroxidation in zebrafish. A 14-day UCS protocol was used, with 10 different types of stressors administered twice daily in a random manner, using draws, for greater unpredictability. Animals underwent the Novel Tank Test (anxiety-like outcome) and the Social Preference Test (depressive-like outcome) 24 hours after the end of the UCS protocol. Biochemical data were collected using a thiobarbituric acid reactive substances (TBARS) assay to quantify malondialdehyde (MDA), an indicator of lipid peroxidation. The findings suggest that prolonged exposure to stressors causes damage to the organism, with increased anxiety and decreased social preference, highlighting zebrafish as an efficient model in the investigation of the neurobiological and neuropathological mechanisms of stress.

neuroscience↗

bioRxiv2025

Role of the 5HT2C receptor in anxiety-like behavior in zebrafish (Danio rerio)

The present study aims to describe the acute effects of 5-HT2C receptor agonists and antagonists in behavioral tests related to anxiety in adult zebrafish (Danio rerio). For this, three groups of fish (n = 12/group) were used: a group treated with the drug MK-212 (2 mg/kg), a 5-HT2C receptor agonist; another group treated with the drug RS-102221 (2 mg/kg), a 5-HT2C receptor antagonist; and a third group, the control group, using a vehicle solution. The three groups were exposed to two behavioral tests: novel tank test (NTT) and light-dark preference (LDT). MK-212 produced no effects on the NTT, while RS-102221 decreased geotaxis (d = 0.99, 95%CI[0.3, 1.7]) and erratic swimming (d = 0.87, 95%CI[0.18, 1.56]) in this test; these effects are consistent with a tonic facilitation of defensive behavior in the NTT. Conversely, in the LDT, MK-212 increased scototaxis (d = 0.96, 95%CI[0.25, 1.65]), risk assessment (d = -1.31, 95%CI[-2.02, -0.59]), and thigmotaxis (d = -1.48, 95%CI[-2.21, -0.75]), consistent with an anxiogenic-like effect of this drug. Thus, tonic and phasic effects of the activation of this receptor are observed depending on the type of behavioral test used.

neuroscience↗

bioRxiv2024

Flavonoids as anxiolytics in animal tests: Bibliometry and meta-analysis of the effects of flavonoids on anxiety-like behavior in animal tests

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=118 SRC="FIGDIR/small/596117v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@177bd39org.highwire.dtl.DTLVardef@27f63forg.highwire.dtl.DTLVardef@197a43aorg.highwire.dtl.DTLVardef@9f0ad0_HPS_FORMAT_FIGEXP M_FIG C_FIG Flavonoids are natural secondary compounds of plants with a basic composition derived from polyphenols that can produce a plethora of different neurochemical effects, some of which are relevant to anxiety disorders. As such, many flavonoids have been evaluated in behavioral screens in preclinical research on anxiolytics. Given the many different molecular subclasses of flavonoids, the many different molecular targets that have been proposed for these compounds, and the different research priorities that arise in preclinical research, we sought to map the potential of flavonoids as anxiolytics by bibliometric analysis and a meta-analysis of animal tests using these compounds. Bibliometric analysis suggest that the field is highly concentrated on few research groups that are mostly located in the Global South, suggesting the need to improve international collaborations. The themes which emerged in the bibliometric analysis are driven by the exploratory steps of pharmacological research, including finding anxioselective effects and looking for dose-response patterns; this suggests that the field, as a whole, could benefit from more mechanistic and confirmatory research. The meta-analysis showed strong evidence for an anxiolytic-like effect of flavonoids on animal tests, including assays made in rats, mice, and zebrafish (SMD = -1.4398, 95%CI[-1.7319, - 1.1477]). Subgroup analysis suggested that this effect is present in acute treatment (SMD = -1.14, 95%CI[-1.36, -0.93]), but not after chronic treatment (SMD = -1.96, 95%CI[-4.93; 1.01]). For all molecule subclasses included in the study, only isoflavones, glycoside derivatives, and flavanolignans did not show evidence of an anxiolytic-like effect, although the low number of studies including these subclasses is low. We finish with a set of recommendations for preclinical research on the anxiolytic potential of flavonoids.

pharmacology and toxicology↗

bioRxiv2024

Roles of the 5-HT1A receptor in zebrafish responses to potential threat and in sociality

Anxiety is a normal emotion representing a reaction to potential danger, whereas fear can be defined as a reaction to real, explicit danger. Anxiety-like behavior in animal models has been associated with differences in the serotonergic system. Treatment of zebrafish cohorts with 8-OH-DPAT, a full agonist at the 5-HT1A receptor, decreased anxiety-like behavior in the novel tank test, but increased it in the phototaxis (light-dark preference) assay, both considered assays for anxiety-like behavior for this species. The same treatment decreased social approach in both the social investigation and social novelty phases of the social preference test. Blocking the 5-HT1A receptor with WAY 100,635 shifted the dose-response curve for the novel tank test rightward. These effects suggest a participation of the 5-HT 1A heteroreceptors in zebrafish anxiety and social preference, increasing anxiety and decreasing sociality. Thus, the study of this receptor is important for a better understanding of anxiety-like behavior in zebrafish and its relationship with similar phenomena in vertebrates. Preprint: https://www.biorxiv.org/content/10.1101/2024.04.17.588464v1 Data: https://github.com/lanec-unifesspa/5HT/tree/main/5HT1A Lay summaryThis study looked at how a certain type of protein, the 5-HT1A receptor, affected anxiety in zebrafish. Its important to understand that anxiety is a normal feeling we all get when were worried or scared about something, while fear is a reaction to an immediate danger. The researchers wanted to see how a specific drug that activates the 5-HT1A receptor, 8-OH-DPAT, affected the behavior of the fish. They used different tests to see how the fish reacted in different situations. When the fish were given the drug, their anxiety-like behavior decreased in one test where they were put in a new tank. But in another test where they had to choose between light and dark areas, their anxiety-like behavior actually increased. It also made the fish less interested in being social with other fish. When a drug that blocks the 5-HT1A receptor, WAY 100,635, was give together with 8-OH-DPAT, evidence was found for a receptor reserve. The researchers found that this drug affected the way the fish behaved in these situations. It seemed to make them more anxious in some cases and less interested in being social. This tells us that the receptor has an impact on how the fish are feeling, which can help us learn more about anxiety in zebrafish and, potentially, in other animals too, including humans. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=150 SRC="FIGDIR/small/588464v3_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@14b3f13org.highwire.dtl.DTLVardef@11a2217org.highwire.dtl.DTLVardef@b42602org.highwire.dtl.DTLVardef@12b51c4_HPS_FORMAT_FIGEXP M_FIG C_FIG Significance statementThis research indicates that 5-HT1A heteroreceptors play a key role in increasing anxiety and decreasing sociality across vertebrates, shedding light on neural mechanisms that could inform treatments for anxiety-related disorders.

neuroscience↗

bioRxiv2024

Role of the NOS-cGMP pathways in time-dependent sensitization of behavioral responses in zebrafish

Nitric oxide (NO) is a molecule involved in plasticity across levels and systems. The role of NOergic pathways in time-dependent sensitization, a behavioral model of translational relevance to trauma and stress-related disorders, was assessed in adult zebrafish. In this model, adult zebrafish acutely exposed to a fear-inducing conspecific alarm substance (CAS) and left undisturbed for an incubation period show increased anxiety-like behavior 24 h after exposure. CAS increased forebrain glutamate immediately after stress and 30 min after stress, an effect that was accompanied by increased nitrite levels immediately after stress, 30 min after stress, 90 min after stress, and 24 h after stress. CAS also increased nitrite levels in the head kidney, where cortisol is produced in zebrafish. CAS-elicited nitrite responses in the forebrain 90 min (but not 30 min) after stress were prevented by a NOS-2 blocker. Blocking NOS-1 30 min after stress prevents TDS; blocking NOS-2 90 min after stress also prevents TDS, as does blocking calcium-activated potassium channels in this latter time window. TDS is also prevented by blocking guanylate cyclase activation in both time windows, and cGMP-dependent channel activation in the second time window. These results suggest that different NO-related pathways converge at different time windows of the incubation period to induce TDS.

neuroscience↗

bioRxiv2023

Serotonergic mediation of orienting and defensive responses in zebrafish

Serotonin (5-HT) is involved in arousal and defensive responses, both of which represent modulators of attention and orienting. Orienting responses (ORs), considered as a unit of attentional processing, are elicited by novel innocuous stimuli, differ from defense reflexes (DR)s, as the latter are elicited by painful and threatening stimuli. When zebrafish (Danio rerio) are exposed to a conspecific alarm substance (CAS), visual stimuli elicit a DR instead of ORs, suggesting a state of hypervigilance. CAS elicited an OR-to-DR shift, as shown both by the shift from an approach to an escape response when the stimulus was turned on and by the changes in directional focus. Both pCPA and 5-HTP attenuated the CAS-elicited OR-to-DR shift . While pCPA did not alter ORs in animals which were not exposed to CAS, 5-HTP abolished those responses, suggesting that the serotonergic tone is important in regulating the general arousal levels in zebrafish.

neuroscience↗

bioRxiv2023

Social status in zebrafish modulates the behavioral response to 5-HT2C receptor agonists and antagonists

The effects of previous social experiences on social behavior have been demonstrated across species both in cooperative and competitive contexts. In dominance-subordinate hierarchies, differences across social ranks have been observed in many different mechanisms. Dominance hierarchies interfere in defensive behavior, where subordinate animals present a greater defensive behavior, regarding potential threats ("anxiety-like behavior"), than dominant animals. The serotonergic system plays a key role in regulating and mediating threat responses, including 5-HT2 receptors in the types of proximal threat responses modulated by the stress of social defeat. We separated 148 adult zebrafish in pairs, and allowed to interact for five days; after that, the dominant-subordinate rank was determined, and animals were treated with a 5-HT2C receptor agonist (MK-212) or antagonist (RS-102221) before being observed in the novel tank test. While MK-212 increased bottom-dwelling, erratic swimming, and freezing across all statuses, RS-102221 decreased these variables in dominants but increased them in subordinates. Moreover, the effects of MK-212 were larger in subordinates than in controls or dominants, suggesting a sensitization of the 5-HT2C receptor.

neuroscience↗

bioRxiv2022

Social investigation and social novelty in zebrafish: Roles of salience and novelty

Social preference tests can be used to analyze variables that influence and modify social behaviors, and to investigate effects of substances such as medications, drugs, and hormones. They may become important tools for finding a valid model to study neuropsychiatric changes and to study human neurodevelopmental processes that have been impaired by social events. While a preference for conspecifics has been shown for different species, social novelty has been used as a model for anxiety-like behavior in rodents. The goal of this research was to understand the roles of stimulus salience (numerousness) and novelty in social investigation and social novelty tests in zebrafish (Danio rerio Hamilton 1822). We used a sequential design, in which animals are exposed first to a social investigation test (with dichotomous presentation of novel conspecifics vs. empty tank) and then to a social novelty test (with dichotomous presentation of the already known conspecific and a novel conspecific). In experiment 1, animals were presented to either 1 or 3 (vs. an empty tank) conspecifics as stimuli. In experiment 2, animals were presented to 1 vs. 3 conspecifics as stimuli. In experiment 3, animals were observed in the social investigation and social novelty tests for 3 consecutive days. The results showed equivalence between 1 or 3 conspecifics in the social investigation and social novelty tests, although animals were able to discriminate between different shoal sizes. These preferences do not change with repeated test exposure, suggesting novelty to be a minor contributor to social investigation and social novelty in zebrafish.

animal behavior and cognition↗

bioRxiv2022

Roles of the 5-HT2C receptor on zebrafish sociality

Serotonin (5-HT) receptors have been implicated in social behavior in vertebrates. Zebrafish (Danio rerio) have been increasingly being used behavioral neuroscience to study the neurobiological correlates of behavior, including sociality. Nonetheless, the role of 5-HT2C receptors in different social functions were not yet studied in this species. Zebrafish were treated with the agonist MK-212 (2 mg/kg) or the antagonist RS-102221 (2 mg/kg) and tested in the social interaction and social novelty tests, conditional approach test, or mirror-induced aggressive displays. MK-212 increased preference for an unknown conspecific in the social investigation test, but also increased preference for the known conspecific in the social novelty test; RS-102221, on the other hand, decreased preference in the social investigation test but increased preference for the novel conspecific in the social novelty test. MK-212 also decreased predator inspection in the conditional approach test. While RS-102221 decreased time in the display zone in the mirror-induced aggressive display test, it increased display duration. Overall, these results demonstrate the complex role of 5-HT2C receptors in different social contexts in zebrafish, revealing a participation in social plasticity in vertebrates.

neuroscience↗

bioRxiv2021

Decynium-22 affects behavior in the zebrafish light/dark test

Decynium-22 (D-22) is an inhibitor of the uptake2 system of monoamine clearance, resulting in increased levels of dopamine, norepinephrine, and serotonin in the nervous system and elsewhere. Uptake2 is mediated by low-affinity, high-capacity transporters that are inhibited by glucocorticoids, suggesting a mechanism of fast glugocorticoid-monoamine interaction in the brain. D-22 dose-dependently increased anxiety-like behavior in adult zebrafish exposed to the light/dark test, monotonically increasing scototaxis (dark preference), but affecting risk assessment with an inverted-U-shaped response. These results suggest that the uptake2 system has a role in defensive behavior in zebrafish, presenting a novel mechanism by which stress and glucocorticoids could produce fast neurobehavioral adjustments in vertebrates. Data: https://github.com/lanec-unifesspa/decynium22

neuroscience↗

bioRxiv2020

Role of 5-HT2C receptors in zebrafish alarm reactions and post-exposure behavior

Serotonin (5-HT) receptors have been implicated in responses to aversive stimuli in mammals and fish, but its precise role is still unknown. Moreover, since at least seven families of 5-HT receptors exist in vertebrates, the role of specific receptors is still debated. Aversive stimuli can be classified as indicators of proximal, distal, or potential threat, initiating responses that are appropriate for each of these threat levels. Responses to potential threat usually involve cautious exploration and increased alertness, while responses to distal and proximal threat involve a fight-flight-freeze reaction. We exposed adult zebrafish to a conspecific alarm substance (CAS) and observed behavior during (distal threat) and after (potential threat) exposure, and treated with the 5-HT2C receptor agonists MK-212 or WAY-161503 or with the antagonist RS-102221. The agonists blocked CAS-elicited defensive behavior (distal threat), but not post-exposure increases in defensive behavior (potential threat), suggesting inhibition of responses to distal threat. MK-212 blocked changes in freezing elicited by acute restraint stress, a model of proximal threat, while RS-102221 blocked changes in geotaxis elicited this stressor. We also found that RS-102221, a 5-HT2C receptor antagonist, produced small effect on behavior during and after exposure to CAS. Preprint: https://www.biorxiv.org/content/10.1101/2020.10.04.324202; Data and scripts: https://github.com/lanec-unifesspa/5-HT-CAS/tree/master/data/5HT2C

neuroscience↗

bioRxiv2020

EMBRYONIC DEVELOPMENT OF THE FIRE-EYE-TETRA Moenkhausia oligolepis (CHARACIFORMES: CHARACIDAE)

This study describes the embryonic development of Moenkhausia oligolepis in captive conditions. After fertilization, the embryos were collected every 10 min up to 2 h, every 20 min up to 4 h, and every 30 min until hatching. The fertilized eggs of M. oligolepis measured approximately 0.85 {+/-} 0.5 mm and have an adhesive surface. The embryonic development lasted 14 hours at 25{degrees}C, with the Zygote, Cleavage, Blastula, Gastrula, Neurula and Segmentation phases. The hatching occurred in embryos around the 30-somites stage. Our results bring only the second description of embryonic development to a species of Moenkhausia genus, the first for the refereed species. Such data are of paramount importance considering the current conflicting state of this genus phylogenetic classification and may help taxonomic studies. Understand the biology of a species that is easily handling in captive conditions and has an ornamental appeal may assist studies in its reproduction in order to both, supply the aquarium market and help the species conservation in nature. Moreover, our data enable the M. oligolepis to be used as a model species in biotechnological applications, such germ cell transplantation approach.

developmental biology↗

bioRxiv2019

A model to study orienting responses in zebrafish, and applications towards the emotion-cognition interaction

Orienting responses (ORs) are whole-organism reflexes that are elicited by innocuous stimuli, and which decrease in magnitude after stimulus repetition. ORs represent relatively simple responses that can be used to study attentional processes, and are modulated by the organism’s state, including arousal and activation levels, as well as by emotional processes. Here we describe a simple method to study ORs in zebrafish, a model organism increasingly being used in behavioural neuroscience. After presentation of a static visual stimulus, an OR is elicited, characterized by approaching the stimulus and orienting towards it. After repeated stimulation, OR decreases, suggesting habituation. These responses are qualitatively altered by exposure to a fear-eliciting alarm substance (i.e., derived from the skin of a conspecific), since exposed animals avoid the visual stimulus and orient either away from the stimulus or towards it, but at a distance. The protocol can be used to study orienting responses, as well as the impact of fear and arousal on these reflexes.Competing Interest StatementThe authors have declared no competing interest.View Full Text

animal behavior and cognition↗

bioRxiv2019

Phasic and tonic serotonin modulate alarm reactions and post-exposure behavior in zebrafish

Current theories on the role of serotonin (5-HT) in vertebrate defensive behavior suggest that this monoamine increases anxiety but decreases fear, by acting at different levels of the neuroaxis. This paradoxical, dual role of 5-HT suggests that a serotonergic tone inhibits fear responses, while an acute increase in 5-HT would produce anxiety-like behavior. However, so far no evidence for a serotonergic tone has been found. Using zebrafish alarm responses, we investigate the participation of phasic and tonic 5-HT levels in fear-like behavior, as well as in behavior after stimulation. Conspecific alarm substance (CAS) increased bottom-dwelling and erratic swimming, and animals transferred to a novel environment after CAS exposure (post-exposure behavior) showed increased bottom-dwelling and freezing. Clonazepam blocked CAS effects during and after exposure. Acute fluoxetine dose-dependently decreased fear-like behavior, but increased post-exposure freezing. Metergoline had no effect on fear-like behavior, but blocked the effects of CAS on post-exposure behavior; similar effects were observed with pCPA. Finally, CAS was shown to decrease the activity of monoamine oxidase in the zebrafish brain after exposure. These results suggest that phasic and tonic serotonin encode an aversive expectation value, switching behavior towards cautious exploration/risk assessment/anxiety when the aversive stimulus is no longer present.

neuroscience↗

bioRxiv2019

Zebrafish cooperate while inspecting predators: experimental evidence for conditional approach

Different fish species employ a conditional approach strategy during predator inspection; the risk of approaching a predator is distributed across all inspectors, but is not shared with the animals which keep its distance. Zebrafish, a highly social fish, is increasingly being used in behavioural neuroscience, but it is not known whether it displays conditional approach. In the predator inspection task, animals are observed in a tank with a refuge in one extremity, and an animated image of a predator in the other extremity, with a mirror positioned in parallel to the tank, simulating a perfectly reciprocating conspecific. In Experiment 1, animals spent more time in an inspection zone when the image was turned on, but also displayed more erratic swimming, suggesting cooperation under fear. In Experiment 2, animals spent more time inspecting predators when the mirror was parallel to the tank ("cooperating mirror") than when the mirror was in an angle ("defecting mirror"), suggesting retaliatory behaviour; in both conditions, animals displayed more freezing and erratic swimming. In Experiment 3, no changes in behaviour were observed, regardless of mirror position, when the image was turned off, suggesting that the choice of specific zones in Experiment 2 was not due to shoaling tendencies. These results suggest that predator inspection is associated with conditional approach, while at the same time inducing fear-like behaviour in the animal.

animal behavior and cognition↗

bioRxiv2019

Chrysin, but not the flavone backbone, decreases anxiety-like behavior in animal tests

Chrysin (5,7-dihydroxyflavone), a nutraceutical flavonoid present in diverse plants, has a backbone structure shared with the flavone backbone, with additional hydroxyl groups that confers its antioxidant properties and effects at the GABAA receptor complex. However, whether these effects are due to the hydroxyl groups is unknown. Here we report the effects of chrysin or the flavone backbone (1 mg/kg) in rats subjected to the elevated plus-maze and the locomotor activity test, as well as in the zebrafish evaluated in light/dark model. Chrysin, but not flavone, increased entries and time in the open arms of the elevated plus-maze, as well as time on white compartment of the light/dark model in zebrafish. These effects were comparable to diazepam, and were devoid of motor effects in both tests, as well as in the locomotor activity test. On the other hand, flavone decreased risk assessment in the light/dark test but increased rearing in the locomotor activity test in rats, suggesting effects threat information gathering; important species differences suggest new avenues of research. It is suggested that the specific effects of chrysin in relation to flavone include more of a mechanism of action in which in addition to its action at the GABAA/benzodiazepine receptor complex also could be involved its free radical scavenging abilities, which require specific research. Preprinthttps://doi.org/10.1101/575514; Data and scriptshttps://github.com/lanec-unifesspa/chrysin

pharmacology and toxicology↗

bioRxiv2018

Conditional approach as cooperation in predator inspection: a role for serotonin?

In guppies (Poecilia reticulata), a small number of individuals break away from a shoal and approach a potential predator, a behavior termed "predator inspection". These animals often employ a "conditional approach" strategy, in which an individual approaches the predator in the first move and subsequently approaches it only if a second individual swims even with it during inspection. This strategy is analogous to the "tit-for-tat" strategy of the Prisoners Dilemma, suggesting that it could be used to study cooperation. Serotonin is thought to mediate cooperative behavior in other fish species. Exposure to the animated image of a predator in a tank that contained a parallel mirror - mimicking an equally cooperating conspecific - promoted inspection and decreased refuge use, but increased freezing, suggesting that conditional approach is also associated with fear. To understand whether serotonin participates in conditional approach in guppies, we treated animals with either vehicle (Cortlands salt solution), fluoxetine (2.5 mg/kg) or metergoline (1 mg/kg), and tested then in a predator inspection paradigm. Fluoxetine increased the time the animal spent inspecting the predator image, while metergoline decreased it. Fluoxetine also decreased time spent avoiding the predator and increased freezing, while metergoline decreased freezing. These results suggest that phasic increases in serotonin levels promote conditional approach, suggesting a role for this neurotransmitter in cooperation. Preprint: https://doi.org/10.1101/436345; Data and scripts: https://github.com/lanec-unifesspa/TFT

animal behavior and cognition↗