Combined Toxicity and Toxicity Persistence of Antidepressants Citalopram and Mirtazapine to Zooplankton Daphnia Magna

Abstract

Citalopram (CTP) and mirtazapine (MTP) are two typical psychoactive drugs used for the treatment of depression. As emerging pollutants, CTP and MTP are of widely concern because they are active substances for organisms. However, the studies about the toxicity potential of CTP/MTP pollution to aquatic organisms were limited. In the present study, the effects of CTP and MTP on the feeding behavior, heartbeat, nutritional enzymes and related gene expressions of Daphnia magna were investigated under single and mixed environmental stress. Meanwhile, the recovery of exposed D. magna was studied to analyze the toxic persistence of those pollutants. After 24 h of exposure, the ingestion rate decreased significantly under 1.45 mg/L of CTP. In the mixed treatment groups, no significant synergistic effect of CTM and MTP on daphnia’ feeding inhibition was found. After 24 h of recovery, the feeding behavior of D. magna was stimulated by compensatory stimulation. At exposure period, the heartbeat rate of exposed D. magna increased significantly, and was recovered during the recovery period. The activity of α-amylase (AMS) and trypsin, and their relative gene expression were significantly changed in most of the exposed daphnia, both in the exposure period and recovery period. But there were different responses between gene transcription with enzyme activity. In general, psychoactive drugs have an obvious toxic threat to aquatic organisms, and after acute exposure, the physiological function of D. magna could be recovered to a certain extent. The results were helpful to evaluate the ecological risk of psychotropic drugs in aquatic environments.