Research Article: Individual differences in response to alcohol exposure in zebrafish (Danio rerio)

Date Published: June 7, 2018

Publisher: Public Library of Science

Author(s): Heloysa Araujo-Silva, Jaquelinne Pinheiro-da-Silva, Priscila F. Silva, Ana C. Luchiari, William HJ Norton.


Personality traits are related to many aspects of one’s life, including risk taking, sociability, and behavioral changes caused by psychoactive substances. This study aimed to investigate individual differences and behavioral changes due to alcohol exposure in zebrafish (Danio rerio). To that end, adult animals were separated into two behavioral profiles: bold and shy, according to their risk taking behavior in an emergence test. Bold and shy fish were allowed to explore a 5-chamber tank and were tested for exploration and sociability (shoaling behavior) following alcohol exposure. The acute drug exposure treatments were 0.0%, 0.1% and 0.5% (v/v%) alcohol. The behavioral parameters evaluated were average and maximum swimming speed, total distance traveled, total time spent immobile, and time spent near a shoal or exploring the tank. For the groups that received no alcohol (0.0% alcohol), shy individuals spent more time near the shoal than bold fish. However, 0.5% alcohol increased bold fish responsiveness to the shoal, while both 0.1% and 0.5% alcohol diminished shoaling in shy fish. Our results show that the behavioral profiles of zebrafish are affected differently by alcohol, with shy animals seemingly more sensitive to behavioral change due to drug exposure. Moreover, we confirm zebrafish as a model for alcohol induced functional (exploration and social behavior) changes that could be useful in high throughput drug screens.

Partial Text

A number of studies have investigated the relationship between behavioral characteristics and alcohol consumption [1–4], albeit with contradictory results. The literature is limited and reports on addiction and behavioral profiles remain scarce. It is known that alcohol is the most widely consumed addictive substance in the world, and alcoholism is one of the most serious social problems [5,6]. While the types of treatment against alcoholism are still restricted and considered inefficient [7], abusive long-term consumption of alcoholic beverages causes serious adverse effects on tissue and brain function, ranging from memory lapses to complete dementia [8–11].

Fig 2 depicts the time spent in the pathway (chambers 1, 2 and 3) and shoal areas (chambers 4 and 5) for zebrafish categorized as bold and shy, and exposed to 0.0, 0.1 or 0.5% alcohol. Time spent in tank areas of interest varied between groups because the animals’ latency to leave the starting box was not considered for this data set (some fish stayed in the starting area for longer). For the pathway areas, two-way ANOVA revealed no significant alcohol treatment (F2,78 = 1.51 p = 0.23) or profile effect (F1,78 = 0.004 p = 0.94), but the interaction between alcohol treatment and profile was statistically significant (F2,78 = 4.98 p = 0.009). The Student-Newman-Keuls test showed that the bold 0.5% and shy 0.0% groups spent less time in pathway areas than the other four groups (p<0.05). For the shoal areas, two-way ANOVA indicated no significant profile effect (F1,78 = 1.25 p = 0.26), but significant alcohol treatment (F2,78 = 9.38 p<0.001) and alcohol treatment vs. profile interaction effects (F2,78 = 3.52 p = 0.03). The Student-Newman-Keuls test revealed that the shy 0.0% alcohol group spent more time in the shoal areas than all the other groups (p<0.05). In the present study we observed the effects of alcohol exposure on exploration and social behavior in two zebrafish profiles: bold and shy. In both the laboratory and in nature, zebrafish display strong social behavior, recognized as aggregation, group formation or shoaling [46,47]. For this and other species, social behavior has high adaptive significance, such as increasing reproductive success, avoiding predators and improving foraging success [48–50]. Our results suggest that social and exploratory differences seem to be related to individual behavioral profiles; bold individuals explore more and are less inclined to shoal with a group, while shy zebrafish spend significantly more time shoaling than exploring the environment, corroborating other findings [51–53]. This response might be related to the value each animal attributes to the resource (social group), that is, social animals consider the shoal to be more valuable than less social animals.   Source:


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