Bioconcentration and behavioral effects of four benzodiazepines and their environmentally relevant mixture in wild fish

Divergent perspectives on the synergistic impacts of thermal-chemical stress on aquatic biota within the framework of climate change scenarios

Climate change, including global warming, leads to rising temperatures in aquatic ecosystems, which is one of the numerous repercussions it brings. Furthermore, water warming can indirectly impact aquatic organisms by modifying the toxicity levels of pollutants. Nevertheless, numerous studies have explored the potential impacts of chemical stress on aquatic biota, but little is known about how such chemicals and toxins interact with climate change factors, especially elevated temperatures. As such, this review paper focuses on exploring the potential effects of thermochemical stress on a wide sector of aquatic organisms, including aquatic vertebrates and invertebrates, in various aquatic ecosystems (freshwater and marine systems). Herein, the objective of this study is to explore the most up-to-date the impact of water warming (without chemical stress) and thermochemical stress on various biochemical and physiological processes in aquatic fauna and how this greatly affects biodiversity and sustainability. Therefore, there is a growing need to understand and evaluate this synergistic mechanism and its potential hazardous impacts. However, we need further investigations and scientific reports to address this serious environmental issue in order to confront anthropogenic pollutants regarding climate change and chemical pollution risks in the near future and subsequently find sustainable solutions for them.

Flunitrazepam and its metabolites induced brain toxicity: Insights from molecular dynamics simulation and transcriptomic analysis

Psychoactive drugs frequently contaminate aquatic environments after human consumption, raising concerns about their residues and ecological harm. This study investigates the effects of flunitrazepam (FLZ) and its metabolite 7-aminoflunitrazepam (7-FLZ), benzodiazepine-class psychoactive drugs, on brain accumulation, blood-brain barrier (BBB), and neuroinflammation of the model organism zebrafish. Molecular dynamics simulation and transcriptome sequencing were used to uncover their toxic mechanisms. Results demonstrate that both FLZ and 7-FLZ can accumulate in the brain, increasing Evans blue levels by 3.4 and 0.8 times, respectively. This increase results from abnormal expression of tight junction proteins, particularly ZO-1 and Occludin, leading to elevated BBB permeability. Furthermore, FLZ and 7-FLZ can also induce neuroinflammation, upregulating TNFα by 91% and 39%, respectively, leading to pathological changes and disrupted intracellular ion balance. Molecular dynamics simulation reveals conformational changes in ZO-1 and Occludin proteins, with FLZ exhibiting stronger binding forces and greater toxicity. Weighted gene co-expression network analysis identifies four modules correlated with BBB permeability and neuroinflammation. KEGG enrichment analysis of genes within these modules reveals pathways like protein processing in the endoplasmic reticulum, NOD-like receptor signaling pathway, and arginine and proline metabolism. This study enhances understanding of FLZ and 7-FLZ neurotoxicity and assesses environmental risks of psychoactive substances. ENVIRONMENTAL IMPLICATION: With the increasing prevalence of mental disorders and the discharge of psychoactive drugs into water, even low drug concentrations (ng/L-μg/L) can pose neurological risks. This study, utilizing molecular dynamic (MD) simulations and transcriptome sequencing, investigate the neurotoxicity and mechanisms of flunitrazepam and 7-aminoflunitrazepam. It reveals that they disrupt the blood-brain barrier in zebrafish and induce neuroinflammation primarily by inducing conformational changes in tight junction proteins. MD simulations are valuable for understanding pollutant-protein interactions. This research offers invaluable insights for the environmental risk assessment of psychoactive drugs and informs the development of strategies aimed at prevention and mitigation.

Exposure to the pharmaceutical buspirone alters locomotor activity, anxiety-related behaviors, and transcripts related to serotonin signaling in larval zebrafish (Danio rerio)

Buspirone is a pharmaceutical used to treat general anxiety disorder by acting on the dopaminergic and serotoninergic system. Buspirone, like many human pharmaceuticals, has been detected in municipal wastewater; however, the environmental exposure risks are unknown for this psychoactive compound. We studied the effects of buspirone on the behavior of zebrafish, focusing on locomotor and anxiolytic behavior. We also measured transcripts associated with oxidative stress, neurotoxicity, and serotonin signaling to identify potential mechanisms underlying the behavioral changes. Concentrations ranged from environmentally relevant (nM) to physiologically active concentrations typical of human pharmaceuticals (μM). Buspirone treatment did not impact survival, nor did it induce deformities in zebrafish treated for 7 days up to 10 μM. There was a positive relationship between locomotor activity and buspirone concentration in dark periods of the visual motor response test. In the light-dark preference test, both the average time per visit to the dark zone and the percent cumulative duration in the dark zone were increased by 1 μM buspirone. Transcript levels of ache, manf, and mbp were decreased in larvae, while the expression of gap43 was increased following exposure to buspirone, indicating potential neurotoxic effects. There was also reduced expression of serotonin-related genes encoding receptors, transporters, and biosynthesis enzymes (i.e., 5ht1aa, sertb, and tph1a). These data increase understanding of the behavioral and molecular responses in zebrafish following waterborne exposure to neuroactive pharmaceuticals like buspirone.

Behavioral alterations and gills damage in Mytilus galloprovincialis exposed to an environmental concentration of delorazepam

Psychoactive compounds, and benzodiazepines (BZPs) in particular, represent an important class of emerging pollutants due to their large (ab)use and high resistance to degradation. Nowadays it is known that sewage treatment does not completely eliminate these substances and, therefore, BZPs and their metabolites reach concern levels in most aquatic environments all over Europe, ranging from µg/L to ng/L. In this study, we investigated the effects of delorazepam on Mytilus galloprovincialis, a model organism in toxicity testing and a key species in coastal marine ecosystems. Given its psychoactive activity, the study primarily addressed discovering the effects on behavior, by conventional valve opening and closure tests. Possible cytotoxic activity was also investigated by analyzing valve abductor muscles, gills histology, and correlated oxygen consumption. Results demonstrate negative effects on mussel behavior, interference with metabolism, and alteration of gill morphology and protein content. In conclusion, delorazepam confirms its toxicity to aquatic environments, highlighting the possibility that BZDs can ultimately affect the structure of the food web and the functions of the coastal ecosystems.

Environmental concentrations of a delorazepam-based drug impact on embryonic development of non-target Xenopus laevis

Benzodiazepines, psychotropics drugs used for treating sleep disorders, anxiety and epilepsy, represent a major class of emerging water pollutants. As occurs for other pharmaceutical residues, they are not efficiently degraded during sewage treatment and persist in effluent waters. Bioaccumulation is already reported in fish and small crustaceans, but the impact and consequences on other "non-target" aquatic species are still unclear and nowadays of great interest. In this study, we investigated the effects of a pharmaceutical preparation containing the benzodiazepine delorazepam on the embryogenesis of Xenopus laevis, amphibian model species, taxa at high risk of exposure to water contaminants. Environmental (1 μg/L) and two higher (5 and 10 μg/L) concentrations were tested on tadpoles up to stage 45/46. Results demonstrate that delorazepam interferes with embryo development and that the effects are prevalently dose-dependent. Delorazepam reduces vitality by decreasing heart rate and motility, induces marked cephalic and abdominal edema, as well as intestinal and retinal defects. At the molecular level, delorazepam increases ROS production, modifies the expression of some master developmental genes and pro-inflammatory cytokines. The resulting stress condition significantly affects embryos' development and threatens their survival. Similar effects should be expected as well in embryos belonging to other aquatic species that have not been yet considered targets for these pharmaceutical residues.

Environmentally relevant concentration of caffeine-effect on activity and circadian rhythm in wild perch

We studied the ecological consequences of widespread caffeine contamination by conducting an experiment focused on changes in the behavioral traits of wild perch (Perca fluviatilis) after waterborne exposure to 10 μg L^-1 of caffeine. We monitored fish swimming performance during both light and dark conditions to study the effect of caffeine on fish activity and circadian rhythm, using a novel three-dimensional tracking system that enabled positioning even in complete darkness. All individuals underwent three behavioral trials-before exposure, after 24 h of exposure, and after 5 days of exposure. We did not observe any effect of the given caffeine concentration on fish activity under light or dark conditions. Regardless of caffeine exposure, fish swimming performance was significantly affected by both the light-dark conditions and repeating of behavioral trials. Individuals in both treatments swam significantly more during the light condition and their activity increased with time as follows: before exposure < after 24 h of exposure < after 5 days of exposure. We confirmed that the three-dimensional automated tracking system based on infrared sensors was highly effective for conducting behavioral experiments under completely dark conditions.

Predicting the impacts of chemical pollutants on animal groups

Chemical pollution is among the fastest-growing agents of global change. Synthetic chemicals with diverse modes-of-action are being detected in the tissues of wildlife and pervade entire food webs. Although such pollutants can elicit a range of sublethal effects on individual organisms, research on how chemical pollutants affect animal groups is severely lacking. Here we synthesise research from two related, but largely segregated fields - ecotoxicology and behavioural ecology - to examine pathways by which chemical contaminants could disrupt processes that govern the emergence, self-organisation, and collective function of animal groups. Our review provides a roadmap for prioritising the study of chemical pollutants within the context of sociality and highlights important methodological advancements for future research.

Anxiety in Duckweed–Metabolism and Effect of Diazepam on Lemna minor

The fate of pharmaceuticals in the human body, from their absorption to excretion is well studied. However, medication often leaves the patient’s body in an unchanged or metabolised, yet still active, form. Diazepam and its metabolites, ranging up to 100 µg/L, have been detected in surface waters worldwide; therefore, the question of its influence on model aquatic plants, such as duckweed (Lemna minor), needs to be addressed. Lemna was cultivated in a Steinberg medium containing diazepam in three concentrations—0.2, 20, and 2000 µg/L. The activity of superoxide dismutase (SOD) and catalase (CAT), leaf count, mass, and the fluorescence quantum yield of photosynthesis were assessed. The medium was also analysed by LC-MS/MS to determine the concentration of diazepam metabolites. Our results show no negative impact of diazepam on Lemna minor, even in concentrations significantly higher than those that are ecotoxicologically relevant. On the contrary, the influence of diazepam on Lemna suggests growth stimulation and a similarity to the effect diazepam has on the human body. The comparison to the human body may be accurate because γ-Aminobutyric acid-like (GABA-like) receptors responsible for the effect in humans have also been recently described in plants. Therefore, our results can open an interesting scientific area, indicating that GABA receptors and interference with benzodiazepines are evolutionarily much older than previously anticipated. This could help to answer more questions related to the reaction of aquatic organisms to micropollutants such as psychopharmaceuticals.

Bioconcentration of neuroactive pharmaceuticals in fish: Relation to lipophilicity, experimental design and toxicity in the aquatic environment

Uptake of contaminants is linked to their toxicity and is usually estimated through their lipophilicity (logK_ow). Here, we review current literature regarding bioconcentration, i.e. uptake of contaminants from the external environment only, and the effects of exposure to neuroactive pharmaceuticals in fish. We aim to determine if lipophilicity is a suitable predictor of bioconcentration of these compounds in fish, to identify major drivers of bioconcentration and explore the link between bioconcentration potential and toxicity, focusing on survival, growth, condition, behaviour and reproduction endpoints. Additionally, we compare concentrations known to elicit significant effects in fish with current environmental concentrations, identifying exposure risk in ecosystems. The majority of studies have focused on antidepressants, mainly fluoxetine, and encompasses mostly freshwater species. Few studies determined pharmaceuticals bioconcentration, and even a smaller portion combined bioconcentration with other toxicity endpoints. Results show that lipophilicity isn't a good predictor of neuroactive pharmaceuticals' bioconcentration in fish, which in turn is highly influenced by experimental parameters, including abiotic conditions, species and life-stage. The need for increased standardization of experimental settings is key towards improving accuracy of environmental risk assessments and application in future regulatory schemes. Still, increased fish lethality was linked to increased bioconcentration, yet no other correlations were observed when considering effects on growth, condition, behaviour or reproduction, likely as a result of insufficient and variable data. In the context of current environmental concentrations, several neuroactive pharmaceuticals were found to be potentially threatening, while data on occurrence is lacking for some compounds, particularly in brackish/marine systems. Specifically, nine compounds (fluoxetine, citalopram, sertraline, amitriptyline, venlafaxine, clozapine, carbamazepine, metamfetamine and oxazepam) were found at concentrations either above or critically close to minimum response concentrations, thus likely to affect fish in freshwater and brackish or marine environments, which supports further exploration in risk management strategies and monitoring programs in aquatic environments.

Behavioral changes and neurochemical responses in Chinese rare minnow exposed to four psychoactive substances

With the increase use of psychoactive pharmaceuticals, these substances and their metabolites are frequently detected in aquatic environment. However, there is still a knowledge gap in the neurotoxicity of these pollutants on aquatic organisms as well as related behavioral effects. In this study, the effects of four psychoactive substances alprazolam (ALPZ), lorazepam (LORZ), codeine (COD) and morphine (MOR) were investigated on 23 neurochemicals and 5 behaviors in Chinese rare minnow (Gobiocypris rarus). The comprehensive neurotoxicity was then evaluated at three levels of neurochemical, neurotransmitter system and comprehensive index. The results indicated that ALPZ and LORZ not only increased serotonin and dopamine along with the decrease of glutamic acid, but also depressed the locomotory activity of Chinese rare minnow although without significance. Exposure to COD and MOR increased acetylcholine, dopamine and adrenaline, and significantly increased anxiety-related behaviors of Chinese rare minnow. Comprehensive evaluation showed that COD has the lowest neurotoxic effect on Chinese rare minnow. LORZ shows a stronger neurotoxicity at low concentration of exposure than the other three substances. MOR has the highest neurotoxic effect at high concentration of exposure among the four drugs. The findings revealed the comprehensive neurotoxicity of these psychoactive substances in fish and suggested ecological risks of these pollutants in aquatic environment.

Presence of pharmaceuticals and their metabolites in wild-living aquatic organisms - Current state of knowledge

In the last decades an increasing number of studies has been published concerning contamination of aquatic ecosystems with pharmaceuticals. Yet, the distribution of these chemical compounds in aquatic environments raises many questions and uncertainties. Data on the presence of selected pharmaceuticals in the same water bodies varies significantly between different studies. Therefore, since early 1990 s, wild organisms have been used in research on environmental contamination with pharmaceuticals. Indeed, pharmaceutical levels measured in biological matrices may better reflect their overall presence in the aquatic environments as such levels include not only direct exposure of a given organisms to a specific pollutant but also processes such as bioaccumulation and biomagnification. In the present paper, data concerning occurrence of pharmaceuticals in aquatic biota was reviewed. So far, pharmaceuticals have been studied mainly in fish and molluscs, with only a few papers available on crustaceans and macroalgae. The most commonly found pharmaceuticals both in freshwater and marine organisms are antibiotics, antidepressants and NSAIDS while there is no information about the presence of anticancer drugs in aquatic organisms. Furthermore, only single studies were conducted in Africa and Australia. Hence, systematization of up-to-date knowledge, the main aim of this review, is needed for further research targeting.

Water reuse for aquaculture: Comparative removal efficacy and aquatic hazard reduction of pharmaceuticals by a pond treatment system during a one year study

Aquaculture is increasing at the global scale, and beneficial reuse of wastewater is becoming crucial in some regions. Here we selected a unique tertiary treatment system for study over a one-year period. This experimental ecosystem-based approach to effluent management included a treated wastewater pond (TWP), which receives 100% effluent from a wastewater treatment plant, and an aquaculture pond (AP) that receives treated water from the TWP for fish production. We examined the fate of a wide range of pharmaceutically active compounds (PhACs) in this TWP-AP system and a control pond fed by river water using traditional grab sampling and passive samplers. We then employed probabilistic approaches to examine exposure hazards. Telmisartan, carbamazepine, diclofenac and venlafaxine, exceeded ecotoxicological predicted no effect concentrations in influent wastewater to the TWP, but these water quality hazards were consistently reduced following treatment in the TWP-AP system. In addition, both grab and passive sampling approaches resulted in similar occurrence patterns of studied compounds, which highlights the potential of POCIS use for water monitoring. Based on the approach taken here, the TWP-AP system appears useful as a tertiary treatment step to reduce PhACs and decrease ecotoxicological and antibiotic resistance water quality hazards prior to beneficial reuse in aquaculture.

In vivo exposure of marine mussels to venlafaxine: bioconcentration and metabolization

Pharmaceuticals are present in natural waters, thus contributing to the general exposure of aquatic organisms, but few data are available on the accumulation of these substances in marine organisms. The present study evaluated the in vivo bioconcentration of an antidepressant-venlafaxine (VLF)-in marine mussels (Mytilus galloprovincialis) during 7 days of exposure at nominal 10 μg/L concentration, followed by a 7-day depuration period. The bioconcentration factor (BCF) was 265 mL/g dry weight (dw). VLF accumulation reached an average tissue concentration of 2146 ± 156 ng/g dw within 7 days, showing a first-order kinetics process. N-desmethylvenlafaxine (N-VLF) and O-desmethylvenlafaxine (O-VLF) metabolites were quantified in mussel tissues, whereas N,N-didesmethylvenlafaxine (NN-VLF) was only recorded as being detected. These three metabolites were also quantified in water, indicating an active metabolism and VLF excretion in Mediterranean mussels. Complementary experiments conducted at nominal concentrations of 1, 10, and 100 μg/L for 7 days confirmed the VLF bioconcentration and metabolism and allowed us to quantify a supplementary metabolite, i.e., N,O-didesmethylvenlafaxine (NO-VLF), in mussel tissues. These results encourage further research on a more complete characterization of metabolism and on any disturbances linked to bioconcentration of VLF on bivalves.

Multigenerational effects of a complex urban contaminant mixture on the behavior of larval and adult fish in multiple fitness contexts

Agricultural and urban storm water runoffs can introduce chemicals of emerging concern (CECs) into waterways. These chemicals can be continually released, persist, or even accumulate over time, with adverse effects on the physiology and behavior of aquatic species. Most studies aimed at evaluating the intergenerational effects of CECs have focused exclusively on single chemicals. By comparison, little is known about the effects of complex CEC mixtures on the behavior of organisms, or how these effects might manifest in subsequent generations. In this study, we exposed three generations of fathead minnows (Pimephales promelas) to environmentally relevant concentrations of a complex CEC mixture representative of urban-impacted waterways and assessed the growth and behavior of larval and adult fish in life-stage-relevant fitness contexts (foraging, boldness, courtship). We found that (i) multigenerational exposure to a complex mixture of CECs altered the behavior of both larvae and adults in different fitness contexts; (ii) concentration-dependent patterns of behavioral impairment were consistent across fitness contexts and life stages; and (iii) the effects of exposure were magnified in the F₁ and F₂ generations. These results highlight the need for long-term, multigenerational assessments of CECs in affected waterways to robustly inform conservation practices aimed at managing aquatic systems.

Water temperature affects the biotransformation and accumulation of a psychoactive pharmaceutical and its metabolite in aquatic organisms

Pharmaceutically active compounds (PhACs) have been shown to accumulate in aquatic and riparian food-webs. Yet, our understanding of how temperature, a key environmental factor in nature, affects uptake, biotransformation, and the subsequent accumulation of PhACs in aquatic organisms is limited. In this study, we tested to what extent bioconcentration of an anxiolytic drugs (temazepam and oxazepam) is affected by two temperature regimes (10 and 20 °C) and how the temperature affects the temazepam biotransformation and subsequent accumulation of its metabolite (oxazepam) in aquatic organisms. We used European perch (Perca fluviatilis) and dragonfly larvae (Sympetrum sp.), which represent predator and prey species of high ecological relevance in food chains of boreal and temperate aquatic ecosystems. Experimental organisms were exposed to target pharmaceuticals at a range of concentrations (0.2-6 µg L^-1) to study concentration dependent differences in bioconcentration and biotransformation. We found that the bioconcentration of temazepam in perch was significantly reduced at higher temperatures. Also, temperature had a strong effect on temazepam biotransformation in the fish, with the production and subsequent accumulation of its metabolite (oxazepam) being two-fold higher at 20 °C compared to 10 °C. In contrast, we found no temperature dependency for temazepam bioconcentration in dragonfly larvae and no detectable biotransformation of the parent compound that would result in measurable concentrations of oxazepam in this organism. Our results highlight that while organisms may share the same aquatic ecosystem, their exposure to PhACs may change differently across temperature gradients in the environment.

Dosing the Coast: Leaking Sewage Infrastructure Delivers Large Annual Doses and Dynamic Mixtures of Pharmaceuticals to Urban Rivers

Pharmaceuticals are commonly detected at low concentrations in surface waters, where they disrupt biological and ecological processes. Despite their ubiquity, the annual mass of pharmaceuticals exported from watersheds is rarely quantified. We used liquid chromatography-mass spectroscopy to screen for 92 pharmaceuticals in weekly samples from an urban stream network in Baltimore, MD, USA, that lacks wastewater treatment effluents. Across the network, we detected 37 unique compounds, with higher concentrations and more compounds in streams with higher population densities. We also used concentrations and stream discharge to calculate annual pharmaceutical loads at the watershed outlet, which range from less than 1 kg to ∼15 kg and are equivalent to tens of thousands of human doses. By calculating annual watershed mass balances for eight compounds, we show that ∼0.05 to ∼42% of the pharmaceuticals consumed by humans in this watershed are released to surface waters, with the importance of different pathways (leaking sewage vs treated wastewater effluent) differing among compounds. These results demonstrate the importance of developing, maintaining, and improving sewage infrastructure to protect water resources from pharmaceutical contamination.

Exposure via biotransformation: Oxazepam reaches predicted pharmacological effect levels in European perch after exposure to temazepam

It is generally expected that biotransformation and excretion of pharmaceuticals occurs similarly in fish and mammals, despite significant physiological differences. Here, we exposed European perch (Perca fluviatilis) to the benzodiazepine drug temazepam at a nominal concentration of 2 µg L^-1 for 10 days. We collected samples of blood plasma, muscle, and brain in a time-dependent manner to assess its bioconcentration, biotransformation, and elimination over another 10 days of depuration in clean water. We observed rapid pharmacokinetics of temazepam during both the exposure and depuration periods. The steady state was reached within 24 h of exposure in most individuals, as was complete elimination of temazepam from tissues during depuration. Further, the biologically active metabolite oxazepam was produced via fish biotransformation, and accumulated significantly throughout the exposure period. In contrast to human patients, where a negligible amount of oxazepam is created by temazepam biotransformation, we observed a continuous increase of oxazepam concentrations in all fish tissues throughout exposure. Indeed, oxazepam accumulated more than its parent compound, did not reach a steady state during the exposure period, and was not completely eliminated even after 10 days of depuration, highlighting the importance of considering environmental hazards posed by pharmaceutical metabolites.

Gene alteration in zebrafish exposed to a mixture of substances of abuse

A recent surge in the use and abuse of diverse prescribed psychotic and illicit drugs necessitates the surveillance of drug residues in source water and the associated ecological impacts of chronic exposure to the aquatic organism. Thirty-six psychotic and illicit drug residues were determined in discharged wastewater from two centralized municipal wastewater treatment facilities and two wastewater receiving creeks for seven consecutive days in Kentucky. Zebrafish (Danio rerio) larvae were exposed to the environmental relevant mixtures of all drug residues, all illicit drugs, and all prescribed psychotic drugs. The extracted RNA from fish homogenates was sequenced, and differentially expressed sequences were analyzed for known or predicted nervous system expression, and screened annotated protein-coding genes to the true environmental cocktail mixture. Illicit stimulant (cocaine and one metabolite), opioids (methadone, methadone metabolite, and oxycodone), hallucinogen (MDA), benzodiazepine (oxazepam and temazepam), carbamazepine, and all target selective serotonin reuptake inhibitors including sertraline, fluoxetine, venlafaxine, and citalopram were quantified in 100% of collected samples from both creeks. The high dose cocktail mixture exposure group revealed the largest group of differentially expressed genes: 100 upregulated and 77 downregulated (p ≤ 0.05; q ≤ 0.05). The top 20 differentially expressed sequences in each exposure group comprise 82 unique transcripts corresponding to 74% annotated genes, 7% non-coding sequences, and 19% uncharacterized sequences. Among 61 differentially expressed sequences that corresponded to annotated protein-coding genes, 23 (38%) genes or their homologs are known to be expressed in the nervous system of fish or other organisms. Several of the differentially expressed sequences are associated primarily with the immune system, including several major histocompatibility complex class I and interferon-induced proteins. Interleukin-1 beta (downregulated in this study) abnormalities are considered a risk factor for psychosis. This is the first study to assess the contributions of multiple classes of psychotic and illicit drugs in combination with developmental gene expression.

Low concentrations of oxazepam induce feeding and molecular changes in Radix balthica juveniles

Psychotropics, especially benzodiazepines, are commonly prescribed worldwide. Poorly eliminated at wastewater treatment plants, they belong to a group of emerging contaminants. Due to their interaction with the GABA_A receptor, they may affect the function of the nervous system of non-target organisms, such as aquatic organisms. The toxicity of oxazepam, a very frequently detected benzodiazepine in continental freshwater, has been largely studied in aquatic vertebrates over the last decade. However, its effects on freshwater non-vertebrates have received much less attention. We aimed to evaluate the long-term effects of oxazepam on the juvenile stage of a freshwater gastropod widespread in Europe, Radix balthica. Juveniles were exposed for a month to environmentally-relevant concentrations of oxazepam found in rivers (0.8 μg/L) and effluents (10 μg/L). Three main physiological functions were studied: feeding, growth, and locomotion. Additionally, gene expression analysis was performed to provide insights into toxicity mechanisms. There was a strong short-term activation of the feeding rate at low concentration, whereas the high dose resulted in long-term inhibition of food intake. A significant decrease in mortality rate was observed in juveniles exposed to the lowest dose. Shell growth and locomotor activity did not appear to be affected by oxazepam. Transcriptomic analysis revealed global over-expression of genes involved in the nervous regulation of the feeding, digestive, and locomotion systems after oxazepam exposure. The molecular analysis also revealed a possible interference of animal manipulation with the molecular effects induced by oxazepam exposure. Overall, these results improve our understanding of the effects of the psychoactive drug oxazepam on an aquatic mollusc gastropod.