It has been centuries since humans consume coffee and get the benefits of this bean. Many researches worldwide continue to show healthful properties of coffee, while others suggest a number of side effects. In fact, anything consumed in excess may cause disturbance of the body functioning, whereas caffeine is a central nervous system stimulant that increases focus and improves performance, its high concentration can cause insomnia, dizziness, and vomiting. Thus, the question is: which coffee dose promotes benefits and prevents risks? To answer it, we used the zebrafish, a popular animal model that is at the vanguard of psychopharmacological research due to its unique combination of complexity and simplicity, translational relevance and applicability to high throughput behavioral drug screens. In the current study, we examine time-course and dose-dependent changes in zebrafish following exposure to caffeine. Our data show an inverted U-shaped path for the locomotor parameters and crescent path for the anxiety-like parameters. High doses are harmful to the individual, because the stimulating effect disappears and anxiogenic effects take place. We conclude that temporal analysis of zebrafish behavior is a sensitive method for the study of acute caffeine exposure-induced functional changes in the vertebrate brain.
Many studies regarding the effects of drugs investigate the acute and chronic use of alcohol, but only a few address the effects of caffeine and alcohol combined to the performance of the zebrafish in cognitive tasks. The zebrafish is an important model for studying the effects of drugs on learning, because it has large genetic similarities to humans and the non-invasive administration of the substances favors translational bias of research. In this study, we observed the effects of alcohol and caffeine on zebrafish cognition through an object discrimination test. We noticed that animals subjected to acute alcohol dose and those under alcohol or caffeine withdrawal did not show discrimination. When fish were treated with associated alcohol and caffeine, those chronically treated with alcohol and subjected to moderate acute dose of caffeine showed learning of the task. Our results reinforce the harmful effects of the alcohol use on cognitive tasks, and suggest that continued use of high doses of caffeine cause cognitive impairment during withdrawal of the substance. However, the acute use of caffeine appears to reverse the harmful effects of alcohol withdrawal, allowing discriminative performance equivalent to control fish. Finally, we reiterate the use of zebrafish as a model for drug effects screening and search for active compounds that modulate the alcohol and caffeine effects.
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