Does fluoxetine exposure affect hypoxia tolerance in the Gulf toadfish, Opsanus beta?

Area of Science:

• Environmental toxicology
• Marine biology
• Pharmacology

Background:

• Pharmaceuticals, including selective serotonin reuptake inhibitors (SSRIs), are present in surface waters due to inadequate wastewater treatment.
• Understanding the impact of SSRIs on non-target marine organisms, especially with co-occurring stressors like hypoxia, is crucial for environmental risk assessment.

Purpose of the Study:

• To investigate the effects of acute and chronic exposure to the SSRI fluoxetine (FLX) on the metabolic hypoxia response in the Gulf toadfish (Opsanus beta).
• To determine if FLX exposure impacts serotonin transporter (SERT) mRNA expression and plasma serotonin concentrations in marine fish.

Main Methods:

• Acute intraperitoneal injection of FLX (50 μg/g) and chronic waterborne exposure to environmentally relevant (0.01 μg/L) and high (8.5 μg/L) FLX concentrations.
• Measurement of the metabolic regulation index, SERT mRNA expression in gill and heart tissues, and plasma serotonin concentrations.

Main Results:

• Acute FLX exposure significantly reduced the metabolic regulation index and SERT mRNA expression in specific gill arches.
• Chronic exposure to FLX, even at high concentrations, did not affect the metabolic regulation index or SERT mRNA expression in gill or heart tissues.
• High-concentration chronic FLX exposure led to elevated plasma serotonin levels, but did not impair hypoxia tolerance.

Conclusions:

• The 5-HT pathway is implicated in hypoxia tolerance in marine fish.
• Current environmental concentrations of FLX are insufficient to impair the metabolic hypoxia response in marine fish, despite potential acute effects at higher doses.