Learning and memory are vital to an animal's survival, and numerous factors can disrupt cognitive... more 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.
Zebrafish have been successfully employed in the study of the behavioural and biological effects ... more Zebrafish have been successfully employed in the study of the behavioural and biological effects of ethanol. Like in mammals, low to moderate doses of ethanol induce motor hyperactivity in zebrafish, an effect that has been attributed to the activation of the dopaminergic system. Acute ethanol exposure increases dopamine (DA) in the zebrafish brain, and it has been suggested that tyrosine hydroxylase, the rate-limiting enzyme of DA synthesis, may be activated in response to ethanol via phosphorylation. The current study employed tetrahydropapaveroline (THP), a selective inhibitor of phosphorylated tyrosine hydroxylase, for the first time, in zebrafish. We treated zebrafish with a THP dose that did not alter baseline motor responses to examine whether it can attenuate or abolish the effects of acute exposure to alcohol (ethanol) on motor activity, on levels of DA, and on levels of dopamine's metabolite 3,4-dihydroxyphenylacetic acid (DOPAC). We found that 60-minute exposure to 1%...
Zebrafish have become a popular animal model for behavioral neuroscience with an increasing numbe... more Zebrafish have become a popular animal model for behavioral neuroscience with an increasing number of studies examining the effects of pharmacological compounds targeting the brain. Exposure to MK-801, a non-competitive N-methyl-d-aspartate receptor antagonist has been shown to increase locomotor activity in zebrafish. However, others have failed to replicate this finding as several contradicting studies report no changes in locomotor activity following exposure to similar doses. In the current study we reconcile these behavioral reports by demonstrating that zebrafish do not exhibit changes in locomotor activity during exposure to non-sedative doses of MK-801. Interestingly, zebrafish do exhibit significant increases in locomotion if pre-treated with MK-801 followed by subsequent testing in a novel environment, which suggests the effects of MK-801 are context-dependent. In addition, we examine the potential role of the dopaminergic system in mediating MK-801's locomotor stimulant effect by quantifying the levels of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in the brains of zebrafish following a 30min exposure to 10μM of MK-801 (the dose found to induce the largest increase in locomotor activity). Our findings indicate that the MK-801-induced increase in locomotor activity is not accompanied by changes in whole-brain levels of dopamine or DOPAC. Overall, our results suggest that MK-801's context-dependent locomotor stimulant effect may be independent of whole-brain dopaminergic activation.
Progress in Neuro-Psychopharmacology and Biological Psychiatry
Variation among individuals may arise for several reasons, and may have diverse underlying mechan... more Variation among individuals may arise for several reasons, and may have diverse underlying mechanisms. Individual differences have been studied in a variety of species, but recently a new model organism has emerged in this field that offers both sophistication in phenotypical characterization and powerful mechanistic analysis. Recently, zebrafish, one of the favorites of geneticists, have been shown to exhibit consistent individual differences in baseline locomotor activity. In the current study, we further explore this finding and examine whether individual differences in locomotor activity correlate with anxiety-like behavioral measures and with levels of dopamine, serotonin and the metabolites of these neurotransmitters. In addition, we examine whether individual differences in locomotor activity are also associated with reactivity to the locomotor stimulant effects of and neurochemical responses to acute ethanol exposure (30 min long, 1% v/v ethanol bath application). Principal ...
The zebrafish has become an increasingly popular animal model for investigating ethanol's act... more The zebrafish has become an increasingly popular animal model for investigating ethanol's actions in the brain and its effects on behavior. Acute exposure to ethanol in zebrafish has been shown to induce a dose-dependent increase of locomotor activity, to reduce fear- and anxiety-related behavioral responses, and to increase the levels of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC). The objective of the present study was to investigate the role of dopamine D1 receptors (D1-R) in ethanol-induced locomotor activity in zebrafish. Zebrafish were pre-treated with SCH-23390 (0 or 1 mg/L bath concentration), a D1-R antagonist, and subsequently exposed to ethanol (0, 0.25, 0.5, 1.0 % v/v). To explore potential underlying mechanisms, we quantified levels of dopamine, DOPAC, serotonin, and 5-HIAA from whole-brain tissue using high-precision liquid chromatography. We found pre-treatment with the D1-R antagonist to attenuate locomotor activity independent of ethanol c...
Progress in neuro-psychopharmacology & biological psychiatry, Jan 2, 2015
Chronic ethanol exposure paradigms have been successfully used in the past to induce behavioral a... more Chronic ethanol exposure paradigms have been successfully used in the past to induce behavioral and central nervous system related changes in zebrafish. However, it is currently unknown whether chronic ethanol exposure alters ethanol metabolism in adult zebrafish. In the current study we examine the effect of acute ethanol exposure on adult zebrafish behavioral responses, as well as alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) activity in the liver. We then examine how two different chronic ethanol exposure paradigms (continuous and repeated ethanol exposure) alter behavioral responses and liver enzyme activity during a subsequent acute ethanol challenge. Acute ethanol exposure increased locomotor activity in a dose-dependent manner. ADH activity was shown to exhibit an inverted U-shaped curve and ALDH activity was decreased by ethanol exposure at all doses. During the acute ethanol challenge, animals that were continuously housed in ethanol exhibited a significantl...
The zebrafish dopaminergic system is thought to be evolutionarily conserved and may be amenable t... more The zebrafish dopaminergic system is thought to be evolutionarily conserved and may be amenable to pharmacological manipulation using drugs developed for mammalian receptors. However, only few studies have examined the role of specific receptor subtypes in behaviour of adult zebrafish. The objectives of this study are to determine the translational relevance of the zebrafish and examine the psychopharmacology of specific dopamine receptors in this species. Using a behavioural pharmacological approach, we examine the effect of D1 and D2/3 receptor antagonisms on motor patterns of adult zebrafish during acute drug exposure and withdrawal. Acute exposure to SCH-23390 (D1 receptor antagonist) decreased total distance travelled in a dose-dependent manner. Exposure to amisulpride (D2/3 receptor antagonist) induced a biphasic dose-response in total distance travelled and in angular velocity. The results provide support for the existence of structurally and functionally conserved postsynaptic D1 and D2 receptors, as well as presynaptic D2 autoreceptors in the zebrafish brain. The behavioural effects of the employed antagonists did not persist following 30 min of withdrawal. The results suggest that zebrafish, a cheaper and simpler model organism compared to the rat and the mouse, may be an efficient translationally relevant tool for the analysis of the psychopharmacology of receptors of the vertebrate dopaminergic system.
Motor function and anxiety-like responses are easily quantifiable in zebrafish, a novel model org... more Motor function and anxiety-like responses are easily quantifiable in zebrafish, a novel model organism for behavioral pharmacology. Activation of serotonin receptors through the use of selective agonists has been shown to alter anxiety-like behaviors in zebrafish. However, few studies have examined the effect of blockade of specific serotonin receptors. In the current study, we examine the effect of 4 serotonin receptor antagonists selective for 5-HT1 A , 5-HT1 B/D , 5-HT 2 , and 5-HT 3 receptors on zebrafish motor and anxiety-like responses. Exposure to the receptor antagonists did not change baseline motor responses. However, when placed in a novel environment, zebrafish previously exposed to GR 55562 (5-HT1 B/D antagonist) exhibited reduced anxiety-like behavior, whereas zebrafish previously exposed to p-MPPF (5-HT1 A antagonist), Ketanserin (5-HT 2 antagonist), or Ondasetron (5-HT 3 antagonist) exhibited increased anxiety-like behaviors. These results show that drugs developed for mammalian serotonin receptors are efficacious in the zebrafish too, a finding that demonstrates evolutionary conservation of the serotoninergic system. The results also imply that zebrafish may be an appropriate animal model for examining the serotonergic neurotransmitter system in vertebrates.
Recent studies have started to examine the neurochemical and hormonal basis of behavior in zebraf... more Recent studies have started to examine the neurochemical and hormonal basis of behavior in zebrafish by examining biological correlates postmortem. However, it is unknown whether stress involved with experimental handling prior to euthanizing animals will have an impact on subsequent biological measures. In the current study, we expose zebrafish to a short net handling stressor (30 s) and examine the levels of monoamine neurotransmitters (dopamine, serotonin, and their metabolites) and whole-body cortisol at different intervals poststressor (0, 1, 5, 10, and 15 min). We report a time-dependent increase in the levels of cortisol, but no alterations in the levels of dopamine, DOPAC (dopamine's metabolite), serotonin, or 5HIAA (serotonin's metabolite) poststressor. The results demonstrate cortisol levels are more responsive to this type of stimulus compared with neurochemical measures.
Progress in Neuro-Psychopharmacology and Biological Psychiatry, 2014
Alcohol abuse and dependence are a rapidly growing problem with few treatment options available. ... more Alcohol abuse and dependence are a rapidly growing problem with few treatment options available. The zebrafish has become a popular animal model for behavioral neuroscience. This species may be appropriate for investigating the effects of alcohol on the vertebrate brain. In the current review, we examine the literature by discussing how alcohol alters behavior in zebrafish and how it may affect biological correlates. We focus on two phenomena that are often examined in the context of alcohol-induced neuroplasticity. Alcohol tolerance (a progressive decrease in the effect of alcohol over time) is often observed following continuous (chronic) exposure to low concentrations of alcohol. Alcohol sensitization also called reverse tolerance (a progressive increase in the effect of alcohol over time) is often observed following repeated discrete exposures to higher concentrations of alcohol. These two phenomena may underlie the development and maintenance of alcohol addiction. The phenotypical characterization of these responses in zebrafish may be the first important steps in establishing this species as a tool for the analysis of the molecular and neurobiological mechanisms underlying human alcohol addiction.
The zebrafish is emerging as a popular animal model for alcohol (ethanol or EtOH) addiction due t... more The zebrafish is emerging as a popular animal model for alcohol (ethanol or EtOH) addiction due to its simplicity and practical advantages. Two phenomena associated with ethanol addiction are the development of tolerance and withdrawal. Using a multi-level approach in the current study, we characterise ethanol tolerance and withdrawal in zebrafish. We first investigate the temporal trajectory of ethanol concentration in the zebrafish brain in response to an acute exposure and during withdrawal. We report that ethanol concentrations approach a steady state within 60 min of exposure to 0.50% and 1.00% v/v ethanol and rapidly decline and return to zero within 60 min following withdrawal from chronic ethanol exposure (0.50% v/v). We characterise the changes associated with ethanol tolerance and withdrawal in zebrafish by focusing on three domains relevant to ethanol addiction: motor patterns, physiological responses (i.e. cortisol levels), and neurochemical alterations. The use of multiple domains of investigation allowed an in-depth analysis of ethanol induced changes in zebrafish.
The zebrafish has been proposed for modeling fetal alcohol spectrum disorders (FASD). Previous FA... more The zebrafish has been proposed for modeling fetal alcohol spectrum disorders (FASD). Previous FASD research with zebrafish employed high concentrations of alcohol and/or long exposure periods. Here, we exposed zebrafish eggs to low doses of alcohol (0, 0.25, 0.50, 0.75 and 1.0% (vol/vol); external bath application of which 1/20th may reach the inside of the egg) at 16-h post-fertilization (hpf) and only for a short duration (2h) in the hope to avoid gross morphological aberrations and to mimic the more frequent FASD exposure levels. Upon reaching adulthood the exposed and control zebrafish were tested for their associative learning performance in a plus-maze. Embryonic alcohol exposure led to no gross anatomical abnormalities and did not increase mortality. Unexposed (control) zebrafish showed excellent acquisition of association between a conditioned visual stimulus (CS) and food reward, demonstrated by their preference for the target zone of the maze that contained the CS during a probe trial in the absence of reward. However, alcohol-exposed fish showed no such preference and performed indistinguishable from random chance. Locomotor activity during training and the probe trial or the amount of food consumed during training did not differ between the embryonic alcohol exposed and unexposed (control) fish, suggesting that the impaired learning performance found was unlikely to be caused by altered motivation or motor function. Our results suggest that even very small amounts of alcohol reaching the embryo for only a short duration of time may have long lasting deleterious effects on cognitive function in vertebrates.
The zebrafish has been proposed for the study of the effects of ethanol on the vertebrate brain. ... more The zebrafish has been proposed for the study of the effects of ethanol on the vertebrate brain. Behavioural tests have been successfully employed in the phenotypical characterization of these effects. However, the short scale (minute to minute) time course of ethanol induced changes of zebrafish behaviour has not been analyzed. The current study alleviates this need using a 2×3 chronic×acute ethanol exposure experimental design. We first expose zebrafish to ethanol chronically using a dose escalation procedure in which fish are kept in a final concentration of 0.5% vol/vol ethanol for 10 days while control fish receive identical dosing procedures but no ethanol. Subsequently, we expose zebrafish for 1h to an acute dose of ethanol (0.00, 0.50, or 1.00% vol/vol) and monitor their behaviour throughout this period. We quantify the mean and within-individual temporal variance of distance travelled, distance from bottom and angular velocity using video-tracking, and establish temporal trajectories of ethanol induced behavioural changes in zebrafish. For example, we find fish of the highest acute dose group previously not exposed to chronic ethanol to exhibit an inverted U shaped temporal trajectory in distance travelled (biphasic alcohol effect). We find this response to be blunted after chronic ethanol exposure (development of tolerance). We also describe an acute ethanol withdrawal induced increase in angular velocity. We conclude that temporal analysis of zebrafish behaviour is a sensitive method for the study of chronic and acute ethanol exposure induced functional changes in the vertebrate brain.
• Behavioural responses to acute alcohol exposure were compared between two strains. • A predator... more • Behavioural responses to acute alcohol exposure were compared between two strains. • A predator stimulus induced unexpected inspection response. • Significant alcohol dose and strain dependent effects were found.
Immediate early genes (IEGs) are transcription factors whose own transcription is initiated rapid... more Immediate early genes (IEGs) are transcription factors whose own transcription is initiated rapidly, for example, in the brain in response to environmental stimuli. c-fos is an IEG often used as a marker of neuronal activation. c-fos mRNA expression has started to be quantified and localized in the zebrafish brain following environmental manipulations but analysis of the expression of c-fos protein in the zebrafish brain has rarely been attempted. Here, we describe an immunofluorescence staining method for quantifying c-fos protein expression in different regions of the zebrafish brain. In addition, we expose zebrafish to caffeine, a positive control for c-fos activation in the brain. To confirm cell nucleus specific binding of the c-fos antibody, we counterstained brain sections with the nuclear fluorescent stain DAPI. Furthermore, we describe a method for reducing background autofluorescence often observed in zebrafish brain tissue. Our analysis showed that exposure to caffeine in...
Learning and memory are vital to an animal's survival, and numerous factors can disrupt cognitive... more 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.
Zebrafish have been successfully employed in the study of the behavioural and biological effects ... more Zebrafish have been successfully employed in the study of the behavioural and biological effects of ethanol. Like in mammals, low to moderate doses of ethanol induce motor hyperactivity in zebrafish, an effect that has been attributed to the activation of the dopaminergic system. Acute ethanol exposure increases dopamine (DA) in the zebrafish brain, and it has been suggested that tyrosine hydroxylase, the rate-limiting enzyme of DA synthesis, may be activated in response to ethanol via phosphorylation. The current study employed tetrahydropapaveroline (THP), a selective inhibitor of phosphorylated tyrosine hydroxylase, for the first time, in zebrafish. We treated zebrafish with a THP dose that did not alter baseline motor responses to examine whether it can attenuate or abolish the effects of acute exposure to alcohol (ethanol) on motor activity, on levels of DA, and on levels of dopamine's metabolite 3,4-dihydroxyphenylacetic acid (DOPAC). We found that 60-minute exposure to 1%...
Zebrafish have become a popular animal model for behavioral neuroscience with an increasing numbe... more Zebrafish have become a popular animal model for behavioral neuroscience with an increasing number of studies examining the effects of pharmacological compounds targeting the brain. Exposure to MK-801, a non-competitive N-methyl-d-aspartate receptor antagonist has been shown to increase locomotor activity in zebrafish. However, others have failed to replicate this finding as several contradicting studies report no changes in locomotor activity following exposure to similar doses. In the current study we reconcile these behavioral reports by demonstrating that zebrafish do not exhibit changes in locomotor activity during exposure to non-sedative doses of MK-801. Interestingly, zebrafish do exhibit significant increases in locomotion if pre-treated with MK-801 followed by subsequent testing in a novel environment, which suggests the effects of MK-801 are context-dependent. In addition, we examine the potential role of the dopaminergic system in mediating MK-801's locomotor stimulant effect by quantifying the levels of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in the brains of zebrafish following a 30min exposure to 10μM of MK-801 (the dose found to induce the largest increase in locomotor activity). Our findings indicate that the MK-801-induced increase in locomotor activity is not accompanied by changes in whole-brain levels of dopamine or DOPAC. Overall, our results suggest that MK-801's context-dependent locomotor stimulant effect may be independent of whole-brain dopaminergic activation.
Progress in Neuro-Psychopharmacology and Biological Psychiatry
Variation among individuals may arise for several reasons, and may have diverse underlying mechan... more Variation among individuals may arise for several reasons, and may have diverse underlying mechanisms. Individual differences have been studied in a variety of species, but recently a new model organism has emerged in this field that offers both sophistication in phenotypical characterization and powerful mechanistic analysis. Recently, zebrafish, one of the favorites of geneticists, have been shown to exhibit consistent individual differences in baseline locomotor activity. In the current study, we further explore this finding and examine whether individual differences in locomotor activity correlate with anxiety-like behavioral measures and with levels of dopamine, serotonin and the metabolites of these neurotransmitters. In addition, we examine whether individual differences in locomotor activity are also associated with reactivity to the locomotor stimulant effects of and neurochemical responses to acute ethanol exposure (30 min long, 1% v/v ethanol bath application). Principal ...
The zebrafish has become an increasingly popular animal model for investigating ethanol's act... more The zebrafish has become an increasingly popular animal model for investigating ethanol's actions in the brain and its effects on behavior. Acute exposure to ethanol in zebrafish has been shown to induce a dose-dependent increase of locomotor activity, to reduce fear- and anxiety-related behavioral responses, and to increase the levels of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC). The objective of the present study was to investigate the role of dopamine D1 receptors (D1-R) in ethanol-induced locomotor activity in zebrafish. Zebrafish were pre-treated with SCH-23390 (0 or 1 mg/L bath concentration), a D1-R antagonist, and subsequently exposed to ethanol (0, 0.25, 0.5, 1.0 % v/v). To explore potential underlying mechanisms, we quantified levels of dopamine, DOPAC, serotonin, and 5-HIAA from whole-brain tissue using high-precision liquid chromatography. We found pre-treatment with the D1-R antagonist to attenuate locomotor activity independent of ethanol c...
Progress in neuro-psychopharmacology & biological psychiatry, Jan 2, 2015
Chronic ethanol exposure paradigms have been successfully used in the past to induce behavioral a... more Chronic ethanol exposure paradigms have been successfully used in the past to induce behavioral and central nervous system related changes in zebrafish. However, it is currently unknown whether chronic ethanol exposure alters ethanol metabolism in adult zebrafish. In the current study we examine the effect of acute ethanol exposure on adult zebrafish behavioral responses, as well as alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) activity in the liver. We then examine how two different chronic ethanol exposure paradigms (continuous and repeated ethanol exposure) alter behavioral responses and liver enzyme activity during a subsequent acute ethanol challenge. Acute ethanol exposure increased locomotor activity in a dose-dependent manner. ADH activity was shown to exhibit an inverted U-shaped curve and ALDH activity was decreased by ethanol exposure at all doses. During the acute ethanol challenge, animals that were continuously housed in ethanol exhibited a significantl...
The zebrafish dopaminergic system is thought to be evolutionarily conserved and may be amenable t... more The zebrafish dopaminergic system is thought to be evolutionarily conserved and may be amenable to pharmacological manipulation using drugs developed for mammalian receptors. However, only few studies have examined the role of specific receptor subtypes in behaviour of adult zebrafish. The objectives of this study are to determine the translational relevance of the zebrafish and examine the psychopharmacology of specific dopamine receptors in this species. Using a behavioural pharmacological approach, we examine the effect of D1 and D2/3 receptor antagonisms on motor patterns of adult zebrafish during acute drug exposure and withdrawal. Acute exposure to SCH-23390 (D1 receptor antagonist) decreased total distance travelled in a dose-dependent manner. Exposure to amisulpride (D2/3 receptor antagonist) induced a biphasic dose-response in total distance travelled and in angular velocity. The results provide support for the existence of structurally and functionally conserved postsynaptic D1 and D2 receptors, as well as presynaptic D2 autoreceptors in the zebrafish brain. The behavioural effects of the employed antagonists did not persist following 30 min of withdrawal. The results suggest that zebrafish, a cheaper and simpler model organism compared to the rat and the mouse, may be an efficient translationally relevant tool for the analysis of the psychopharmacology of receptors of the vertebrate dopaminergic system.
Motor function and anxiety-like responses are easily quantifiable in zebrafish, a novel model org... more Motor function and anxiety-like responses are easily quantifiable in zebrafish, a novel model organism for behavioral pharmacology. Activation of serotonin receptors through the use of selective agonists has been shown to alter anxiety-like behaviors in zebrafish. However, few studies have examined the effect of blockade of specific serotonin receptors. In the current study, we examine the effect of 4 serotonin receptor antagonists selective for 5-HT1 A , 5-HT1 B/D , 5-HT 2 , and 5-HT 3 receptors on zebrafish motor and anxiety-like responses. Exposure to the receptor antagonists did not change baseline motor responses. However, when placed in a novel environment, zebrafish previously exposed to GR 55562 (5-HT1 B/D antagonist) exhibited reduced anxiety-like behavior, whereas zebrafish previously exposed to p-MPPF (5-HT1 A antagonist), Ketanserin (5-HT 2 antagonist), or Ondasetron (5-HT 3 antagonist) exhibited increased anxiety-like behaviors. These results show that drugs developed for mammalian serotonin receptors are efficacious in the zebrafish too, a finding that demonstrates evolutionary conservation of the serotoninergic system. The results also imply that zebrafish may be an appropriate animal model for examining the serotonergic neurotransmitter system in vertebrates.
Recent studies have started to examine the neurochemical and hormonal basis of behavior in zebraf... more Recent studies have started to examine the neurochemical and hormonal basis of behavior in zebrafish by examining biological correlates postmortem. However, it is unknown whether stress involved with experimental handling prior to euthanizing animals will have an impact on subsequent biological measures. In the current study, we expose zebrafish to a short net handling stressor (30 s) and examine the levels of monoamine neurotransmitters (dopamine, serotonin, and their metabolites) and whole-body cortisol at different intervals poststressor (0, 1, 5, 10, and 15 min). We report a time-dependent increase in the levels of cortisol, but no alterations in the levels of dopamine, DOPAC (dopamine's metabolite), serotonin, or 5HIAA (serotonin's metabolite) poststressor. The results demonstrate cortisol levels are more responsive to this type of stimulus compared with neurochemical measures.
Progress in Neuro-Psychopharmacology and Biological Psychiatry, 2014
Alcohol abuse and dependence are a rapidly growing problem with few treatment options available. ... more Alcohol abuse and dependence are a rapidly growing problem with few treatment options available. The zebrafish has become a popular animal model for behavioral neuroscience. This species may be appropriate for investigating the effects of alcohol on the vertebrate brain. In the current review, we examine the literature by discussing how alcohol alters behavior in zebrafish and how it may affect biological correlates. We focus on two phenomena that are often examined in the context of alcohol-induced neuroplasticity. Alcohol tolerance (a progressive decrease in the effect of alcohol over time) is often observed following continuous (chronic) exposure to low concentrations of alcohol. Alcohol sensitization also called reverse tolerance (a progressive increase in the effect of alcohol over time) is often observed following repeated discrete exposures to higher concentrations of alcohol. These two phenomena may underlie the development and maintenance of alcohol addiction. The phenotypical characterization of these responses in zebrafish may be the first important steps in establishing this species as a tool for the analysis of the molecular and neurobiological mechanisms underlying human alcohol addiction.
The zebrafish is emerging as a popular animal model for alcohol (ethanol or EtOH) addiction due t... more The zebrafish is emerging as a popular animal model for alcohol (ethanol or EtOH) addiction due to its simplicity and practical advantages. Two phenomena associated with ethanol addiction are the development of tolerance and withdrawal. Using a multi-level approach in the current study, we characterise ethanol tolerance and withdrawal in zebrafish. We first investigate the temporal trajectory of ethanol concentration in the zebrafish brain in response to an acute exposure and during withdrawal. We report that ethanol concentrations approach a steady state within 60 min of exposure to 0.50% and 1.00% v/v ethanol and rapidly decline and return to zero within 60 min following withdrawal from chronic ethanol exposure (0.50% v/v). We characterise the changes associated with ethanol tolerance and withdrawal in zebrafish by focusing on three domains relevant to ethanol addiction: motor patterns, physiological responses (i.e. cortisol levels), and neurochemical alterations. The use of multiple domains of investigation allowed an in-depth analysis of ethanol induced changes in zebrafish.
The zebrafish has been proposed for modeling fetal alcohol spectrum disorders (FASD). Previous FA... more The zebrafish has been proposed for modeling fetal alcohol spectrum disorders (FASD). Previous FASD research with zebrafish employed high concentrations of alcohol and/or long exposure periods. Here, we exposed zebrafish eggs to low doses of alcohol (0, 0.25, 0.50, 0.75 and 1.0% (vol/vol); external bath application of which 1/20th may reach the inside of the egg) at 16-h post-fertilization (hpf) and only for a short duration (2h) in the hope to avoid gross morphological aberrations and to mimic the more frequent FASD exposure levels. Upon reaching adulthood the exposed and control zebrafish were tested for their associative learning performance in a plus-maze. Embryonic alcohol exposure led to no gross anatomical abnormalities and did not increase mortality. Unexposed (control) zebrafish showed excellent acquisition of association between a conditioned visual stimulus (CS) and food reward, demonstrated by their preference for the target zone of the maze that contained the CS during a probe trial in the absence of reward. However, alcohol-exposed fish showed no such preference and performed indistinguishable from random chance. Locomotor activity during training and the probe trial or the amount of food consumed during training did not differ between the embryonic alcohol exposed and unexposed (control) fish, suggesting that the impaired learning performance found was unlikely to be caused by altered motivation or motor function. Our results suggest that even very small amounts of alcohol reaching the embryo for only a short duration of time may have long lasting deleterious effects on cognitive function in vertebrates.
The zebrafish has been proposed for the study of the effects of ethanol on the vertebrate brain. ... more The zebrafish has been proposed for the study of the effects of ethanol on the vertebrate brain. Behavioural tests have been successfully employed in the phenotypical characterization of these effects. However, the short scale (minute to minute) time course of ethanol induced changes of zebrafish behaviour has not been analyzed. The current study alleviates this need using a 2×3 chronic×acute ethanol exposure experimental design. We first expose zebrafish to ethanol chronically using a dose escalation procedure in which fish are kept in a final concentration of 0.5% vol/vol ethanol for 10 days while control fish receive identical dosing procedures but no ethanol. Subsequently, we expose zebrafish for 1h to an acute dose of ethanol (0.00, 0.50, or 1.00% vol/vol) and monitor their behaviour throughout this period. We quantify the mean and within-individual temporal variance of distance travelled, distance from bottom and angular velocity using video-tracking, and establish temporal trajectories of ethanol induced behavioural changes in zebrafish. For example, we find fish of the highest acute dose group previously not exposed to chronic ethanol to exhibit an inverted U shaped temporal trajectory in distance travelled (biphasic alcohol effect). We find this response to be blunted after chronic ethanol exposure (development of tolerance). We also describe an acute ethanol withdrawal induced increase in angular velocity. We conclude that temporal analysis of zebrafish behaviour is a sensitive method for the study of chronic and acute ethanol exposure induced functional changes in the vertebrate brain.
• Behavioural responses to acute alcohol exposure were compared between two strains. • A predator... more • Behavioural responses to acute alcohol exposure were compared between two strains. • A predator stimulus induced unexpected inspection response. • Significant alcohol dose and strain dependent effects were found.
Immediate early genes (IEGs) are transcription factors whose own transcription is initiated rapid... more Immediate early genes (IEGs) are transcription factors whose own transcription is initiated rapidly, for example, in the brain in response to environmental stimuli. c-fos is an IEG often used as a marker of neuronal activation. c-fos mRNA expression has started to be quantified and localized in the zebrafish brain following environmental manipulations but analysis of the expression of c-fos protein in the zebrafish brain has rarely been attempted. Here, we describe an immunofluorescence staining method for quantifying c-fos protein expression in different regions of the zebrafish brain. In addition, we expose zebrafish to caffeine, a positive control for c-fos activation in the brain. To confirm cell nucleus specific binding of the c-fos antibody, we counterstained brain sections with the nuclear fluorescent stain DAPI. Furthermore, we describe a method for reducing background autofluorescence often observed in zebrafish brain tissue. Our analysis showed that exposure to caffeine in...
Uploads
Papers by Steven Tran