Fluoxetine effects on sheepshead minnow (Cyprinodon variegatus) locomotor activity

Abstract

Fluoxetine (FLX), a selective serotonin reuptake inhibitor, is among the top 100 drugs prescribed annually in the United States and the United Kingdom and is one of many pharmaceutical products that have been detected in global surface waters. Our study used sublethal concentrations to assess the impact of FLX exposure on sheepshead minnow (Cyprinodon variegatus) locomotor behavior. Exposures lasted for 56 hours, and fish were recorded for locomotor behavior assessment at six timepoints between 1–56 h post-dose. Behavior was recorded to quantify locomotor activity using line crossing counts. Animals treated with 300 μg L⁻¹ FLX exhibited reduced locomotor activity at 1, 25, 32, 49 and 56 h post-dose. An EC₂₅ value of 2 μg L⁻¹ (lower and upper 95 % confidence limits at 1.3, 43 μg L⁻¹, respectively) was determined for locomotor activity at 32 h of exposure. Changes in locomotor activity due to FLX exposure may have implications for the ecological response of populations to other natural and anthropogenic stressors.

Keywords:

• Fluoxetine
• locomotor activity
• pharmaceuticals
• serotonin
• sheepshead minnow

Acknowledgments

The authors thank National Ocean Service (NOS) personnel Heather Harper for assistance with behavioral assays and line count reliability and Yelena Sapnozhnikova for assistance with LC/MS/MS method development. Thanks to Marie DeLorenzo, Jennifer Hoguet and Jennifer Keller for review of earlier versions of this manuscript. All handling of and procedures involving live animals were approved by the College of Charleston Institutional Animal Care and Use Committee (Protocol No. IACUC-2006–013). TheNOS does not approve, recommend, or endorse any proprietary product or material mentioned in this publication.

Notes

^aUnable to calculate EC₅₀ because of a lack of a 50 % reduction in locomotor activity.

^bUnable to calculate confidence limits since they would exceed the highest test concentration.