Anandamide increases the physical activity of adult zebrafish (Danio rerio).

Anandamide (AEA) is a fatty acid neurotransmitter that binds to the CB1 and CB2 cannabinoid receptors in the central and peripheral nervous systems. AEA functions with the dopaminergic system and its expression has been shown to increase during activity. Cannabinoids have been used as treatments to reduce pain and discomfort, so an increase in AEA during activity may have a similar function. To determine the effects of AEA on energy expenditure, behavioral changes after exposure to AEA were observed in adult zebrafish (Danio rerio). The fish were separated into 4 groups: low dose AEA (10 µM), high dose AEA (100 µM), a purported positive control (0.5% ethanol), and a negative control (untreated). Activity was measured by counting the number of times an individual fish crossed a horizontal or vertical line drawn on the aquarium using 5-min recorded intervals (line breaks). Vertical line breaks were significantly different between the untreated group and both of the AEA-treated groups (p < 0.0001), however horizontal line breaks were not significantly different (p = 0.14). An increase in the number of vertical line crossings indicate that the fish in both AEA groups were swimming along the horizontal plane more often than the other groups, indicating an increase in physical activity. There was no difference in the activity of the ethanol-treated group compared to the untreated group. These results demonstrate that the administration of a cannabinoid agonist such as AEA may increase overall activity levels in adult zebrafish. [ABSTRACT FROM AUTHOR]