Chronic Exposure to Low Concentration Lead Chloride-Induced Anxiety and Loss of Aggression and Memory in Zebrafish

Abstract

Lead and lead-derived compounds have been extensively utilized in industry, and their chronic toxicity towards aquatic animals has not been thoroughly addressed at a behavioral level. In this study, we assessed the risk of exposure to lead at a waterborne environmental concentration in adult zebrafish by behavioral and biochemical analyses. Nine tests, including three-dimension (3D) locomotion, novel tank exploration, mirror biting, predator avoidance, social interaction, shoaling, circadian rhythm locomotor activity, color preference, and a short-term memory test, were performed to assess the behavior of adult zebrafish after the exposure to 50 ppb PbCl 2 for one month. The brain tissues were dissected and subjected to biochemical assays to measure the relative expression of stress biomarkers and neurotransmitters to elucidate the underlying mechanisms for behavioral alterations. The results of the behavioral tests showed that chronic exposure to lead could elevate the stress and anxiety levels characterized by elevated freezing and reduced exploratory behaviors. The chronic exposure to PbCl 2 at a low concentration also induced a sharp reduction of aggressiveness and short-term memory. However, no significant change was found in predator avoidance, social interaction, shoaling, or color preference. The biochemical assays showed elevated cortisol and reduced serotonin and melatonin levels in the brain, thus, altering the behavior of the PbCl 2 -exposed zebrafish. In general, this study determined the potential ecotoxicity of long-term lead exposure in adult zebrafish through multiple behavioral assessments. The significant findings were that even at a low concentration, long-term exposure to lead could impair the memory and cause a decrease in the aggressiveness and exploratory activities of zebrafish, which may reduce their survival fitness.(EC10/NOEC-usually more than 14 days) on fish range from 18 to 1559 µg/L and 44 to 437 µg/L, respectively [3,4].More evidence has shown the detrimental impacts of lead on human health, especially at a neurobehavioral level. The neurotoxicity of chronic exposure to low concentrations of lead can impair cognitive performance in childhood through to adulthood [5][6][7][8][9]. Some studies demonstrated the correlation between the exposure to lead at low concentrations and attention-deficit/hyperactivity disorder (ADHD) in children [10]. The development of the central nervous system can be disrupted when children are exposed to low concentrations of lead for a long period of time (blood lead level below 10 mg/dL) [11]. Therefore, lead toxicity has become a serious issue for human health and environmental protection [6]. According to previous studies, the effect of lead on the nervous system includes the disruption of key molecules during neuronal migration and differentiation, interference with synapse formation mediated by a reduction in neuronal sialic acid production and premature differentiation of glial cells, interference with neurotransmitter release, and disruption of the...

Duplicated dnmt3aa and dnmt3ab DNA Methyltransferase Genes Play Essential and Non-Overlapped Functions on Modulating Behavioral Control in Zebrafish

“…Three repeated trials of training were conducted to build up the ability of zebrafish to learn and remember. The short-term memory test by passive avoidances was performed according to our previously published method reported by Bui et al [45].…”

Interspecies Behavioral Variability of Medaka Fish Assessed by Comparative Phenomics

“…This phenomenon could be related to the high level of serotonin and AChE measured in the fish. This speculation was taken since serotonin has been reported to play a positive role in regulating locomotor activity in many animals, while AChE is an enzyme responsible for the breakdown of acetylcholine, which plays an important role in modulating neuromuscular activity in neural synapses [72]. This trend is also observed in other medaka fishes.…”

In vivo Modelling of Toxicity of Eight Commercial Artificial Sweeteners in Daphnia Neonates and Zebrafish Embryos through Cardiac Performance Assessments

“…As part of our interests to provide in vivo models to study the effects of substances in a variety of disease model systems [31][32][33], zebrafish and daphnia were explored as animal host models to investigate cardiac performance after exposure to eight different artificial sweeteners by measuring different cardiac parameters such as the stroke volume, cardiac output, ejection fraction, and shortening fraction, along with heart rate, heartbeat interval, and heart rate variability.…”