Toxicity and behavioral effects of dimethylsulfoxide in planaria

Planarian RNAi knockdown: feeding once might just be enough

RNA interference (RNAi) is a powerful tool to knock down the expression of genes of interests. In planarians, a popular animal model to study development and regeneration processes, RNAi is easily set up by feeding the animals double-stranded RNA (dsRNA). However, there is no consensus in the literature on the amount of dsRNA needed to efficiently knock down gene expression, nor on the lasting effect of this knockdown. Here, we exposed the worms to two RNAi protocols, either feeding them dsRNA only once or three times in the span of a week. To observe the gradual loss and retrieval of nociceptive phenotypes, we exposed the worms to Allyl Isothiocyanate (AITC), an irritant and TRPA1 receptor agonist, while we knocked down the expression of the TRPA1 receptor and performed behavioral assessments over 11 weeks. We showed that feeding planarians once was sufficient to induce similar phenotypes as feeding them three times, that also lasted as long. These insights are useful to refine RNAi protocol timelines and may save some valuable resources.

Cinnamaldehyde induces a TRPA1-mediated nociceptive behavior in planarians

Nociception is defined as "the neural process of encoding noxious stimuli" by the International Association for the Study of Pain (IASP). Nociception relies on detecting noxious stimuli arising from a potentially or actually tissue-damaging event via specialized cells called nociceptors. In planarians, nociceptive behavior is often indicated by a 'scrunching' gait, in contrast to the usual gliding behavior displayed in normal conditions. The present study extends our previous study Reho et al. (2024) by testing a new potentially irritant molecule, Cinnamaldehyde (CA), which could induce scrunching gaits. We reproduced the nociceptive chemical tests from our previous study using CA instead of Allyl isothiocyanate (AITC) on Girardia dorotocephala (Gd) implementing an open field behavioral analysis. CA induced a dose-dependent increase in scrunching gait similar to the action of AITC and was expectedly partially suppressed by morphine and meloxicam. Knocking down the expression of the Gd-TRPA1 ion channel by RNA interference also suppressed the behavioral reaction to the molecule. In conclusion, we demonstrated that CA induced a nociceptive behavior in planarians through an action on the ion channel TRPA1.

Cotinine influences the effect of high and low nicotine concentrations on planarian motility differently

Previous work from our laboratory showed that cotinine, a nicotine metabolite, reverses three nicotine-induced behavioral effects in freshwater planarians: motility decrease, seizure-like movements, and withdrawal-like behaviors. The present work explored whether cotinine, a nicotine metabolite, antagonized the nicotine-induced effects on planarian motility in a concentration-dependent manner. We found that nicotine decreased planarian motility at nicotine concentrations above 60 μM but increased planarian velocity at concentrations equal to or below 50 μM, in agreement with previous data. Cotinine did not affect planarian motility at a concentration range between 250 and 2750 μM. Furthermore, we found that cotinine alleviated the 100 μM nicotine-induced motility decrease in a concentration-dependent manner and reversed the low nicotine concentration motility increase, albeit in a concentration-independent manner. The apparent concentration-dependent alleviation of >60 μM nicotine-induced motility decrease by cotinine suggests an orthosteric relationship between nicotine and cotinine. On the other hand, the evident concentration-independent cotinine alleviation of the increase in motility induced by 50 μM nicotine suggests an allosteric relationship. Our data is consistent with the existing literature about the relationship between nicotine and cotinine in various models, reinforcing the case for the usefulness of the planarian model in pharmacological studies.

Schild Analysis of the Interaction between Parthenolide and Cocaine Suggests an Allosteric Relationship for Their Effects on Planarian Motility

The freshwater planarian is an emerging animal model in neuroscience due to its centralized nervous system that closely parallels closely parallels the nervous system of vertebrates. Cocaine, an abused drug, is the 'founding member' of the local anesthetic family. Parthenolide, a sesquiterpene lactone, acts as a behavioral and physiological antagonist of cocaine in planarians and rats, respectively. Previous work from our laboratory showed that both parthenolide and cocaine reduced planarian motility and that parthenolide reversed the cocaine-induced motility decrease at concentrations where parthenolide does not affect the movement of the worms. However, the exact mechanism of the cocaine/parthenolide antagonism is unknown. Here, we report the results of a Schild analysis to explore the parthenolide/cocaine relationship in the planarian Girardia tigrina. The Schild slopes of a family of concentration-response curves of parthenolide ± a single concentration of cocaine and vice versa were -0.55 and -0.36, respectively. These slopes were not statistically different from each other. Interestingly, the slope corresponding to the parthenolide ± cocaine (but not the cocaine ± parthenolide) data set was statistically different from -1. Our data suggest an allosteric relationship between cocaine and parthenolide for their effect on planarian motility. To the best of our knowledge, this is the first study about the mechanism of action of the antagonism between cocaine and parthenolide. Further studies are needed to determine the specific nature of the parthenolide/cocaine target(s) in this organism.

Exposure to polystyrene microplastics and perfluorooctane sulfonate disrupt the homeostasis of intact planarians and the growth of regenerating planarians

Microplastics (MPs) and perfluorinated compounds (PFAS) are widespread in the global ecosystem. MPs have the ability to adsorb organic contaminants such as perfluorooctane sulfonate (PFOS), leading to combined effects. The current work aims to explore the individual and combined toxicological effects of polystyrene (PS) and PFOS on the growth and nerves of the freshwater planarian (Dugesia japonica). The results showed that PS particles could adsorb PFOS. PS and PFOS impeded the regeneration of decapitated planarians eyespots, whereas the combined treatment increased the locomotor speed of intact planarians. PS and PFOS caused significant DNA damage, while co-treatment with different PS concentrations aggravated and attenuated DNA damage, respectively. Further studies at the molecular level have shown that PS and PFOS affect the proliferation and differentiation of neoblasts in both intact and regenerating planarians, alter the expression levels of neuronal genes, and impede the development of the nervous system. PS and PFOS not only disrupted the homeostasis of intact planarians, but also inhibited the regeneration of decapitated planarians. This study is the first to assess the multiple toxicity of PS and PFOS to planarians after combined exposure. It provides a basis for the environmental and human health risks of MPs and PFAS.

Behavioral and pharmacological characterization of planarian nociception

Introduction

Pain mostly arises because specialized cells called nociceptors detect harmful or potentially harmful stimuli. In lower animals with less convoluted nervous system, these responses are believed to be purely nociceptive. Amongst invertebrate animal models, planarians are becoming popular in a wide range of pharmacological and behavioral studies beyond the field of regeneration. Recent publications led the way on pain studies by focusing on nociceptive behaviors such as the 'scrunching' gait displayed under various noxious stimuli, as opposed to the 'gliding' gait planarians usually adopt in normal conditions.

Methods

In this study, we adapted commonly used nociceptive tests to further explore nociception in planarians of the species Girardia dorotocephala. By using behavioral analysis in open fields and place preferences, we managed to set up chemical, thermal and mechanical nociceptive tests. We also adapted RNA interference protocols and explored the effects of knocking down TRPA1 ion channels, one of the main effectors of chemically and thermally-induced nociceptive responses in vertebrates.

Results

Consequently, we demonstrated the reliability of the scrunching gait in this planarian species, which they displayed in a dose-dependent manner when exposed to the irritant AITC. We also showed that suppressing the expression of TRPA1 ion channels completely suppressed the scrunching gait, demonstrating the involvement of TRPA1 nociceptors in this nociceptive reaction. Besides, we also explored the effects of two common analgesics that both displayed strong antinociceptive properties. First, morphine reduced the chemically-induced nociceptive scrunching gaits by more than 20% and shifted the E C 50 of the dose-response curve by approximately 10 μM. Secondly, the NSAID meloxicam drastically reduced chemically-induced scrunching by up to 60% and reduced heat avoidance in place preference tests.

Discussion

Thus, we managed to characterize both behavioral and pharmacological aspects of G. dorotocephala's nociception, further developing the use of planarians as a replacement model in pain studies and more globally the study of invertebrate nociception.

How neurobehavior and brain development in alternative whole-organism models can contribute to prediction of developmental neurotoxicity

Developmental neurotoxicity (DNT) is not routinely evaluated in chemical risk assessment because current test paradigms for DNT require the use of mammalian models which are ethically controversial, expensive, and resource demanding. Consequently, efforts have focused on revolutionizing DNT testing through affordable novel alternative methods for risk assessment. The goal is to develop a DNT in vitro test battery amenable to high-throughput screening (HTS). Currently, the DNT in vitro test battery consists primarily of human cell-based assays because of their immediate relevance to human health. However, such cell-based assays alone are unable to capture the complexity of a developing nervous system. Whole organismal systems that qualify as 3 R (Replace, Reduce and Refine) models are urgently needed to complement cell-based DNT testing. These models can provide the necessary organismal context and be used to explore the impact of chemicals on brain function by linking molecular and/or cellular changes to behavioural readouts. The nematode Caenorhabditis elegans, the planarian Dugesia japonica, and embryos of the zebrafish Danio rerio are all suited to low-cost HTS and each has unique strengths for DNT testing. Here, we review the strengths and the complementarity of these organisms in a novel, integrative context and highlight how they can augment current cell-based assays for more comprehensive and robust DNT screening of chemicals. Considering the limitations of all in vitro test systems, we discuss how a smart combinatory use of these systems will contribute to a better human relevant risk assessment of chemicals that considers the complexity of the developing brain.

A broad-taxa approach as an important concept in ecotoxicological studies and pollution monitoring

Aquatic invertebrates play a pivotal role in (eco)toxicological assessments because they offer ethical, cost-effective and repeatable testing options. Additionally, their significance in the food chain and their ability to represent diverse aquatic ecosystems make them valuable subjects for (eco)toxicological studies. To ensure consistency and comparability across studies, international (eco)toxicology guidelines have been used to establish standardised methods and protocols for data collection, analysis and interpretation. However, the current standardised protocols primarily focus on a limited number of aquatic invertebrate species, mainly from Arthropoda, Mollusca and Annelida. These protocols are suitable for basic toxicity screening, effectively assessing the immediate and severe effects of toxic substances on organisms. For more comprehensive and ecologically relevant assessments, particularly those addressing long-term effects and ecosystem-wide impacts, we recommended the use of a broader diversity of species, since the present choice of taxa exacerbates the limited scope of basic ecotoxicological studies. This review provides a comprehensive overview of (eco)toxicological studies, focusing on major aquatic invertebrate taxa and how they are used to assess the impact of chemicals in diverse aquatic environments. The present work supports the use of a broad-taxa approach in basic environmental assessments, as it better represents the natural populations inhabiting various ecosystems. Advances in omics and other biochemical and computational techniques make the broad-taxa approach more feasible, enabling mechanistic studies on non-model organisms. By combining these approaches with in vitro techniques together with the broad-taxa approach, researchers can gain insights into less-explored impacts of pollution, such as changes in population diversity, the development of tolerance and transgenerational inheritance of pollution responses, the impact on organism phenotypic plasticity, biological invasion outcomes, social behaviour changes, metabolome changes, regeneration phenomena, disease susceptibility and tissue pathologies. This review also emphasises the need for harmonised data-reporting standards and minimum annotation checklists to ensure that research results are findable, accessible, interoperable and reusable (FAIR), maximising the use and reusability of data. The ultimate goal is to encourage integrated and holistic problem-focused collaboration between diverse scientific disciplines, international standardisation organisations and decision-making bodies, with a focus on transdisciplinary knowledge co-production for the One-Health approach.

Synthesis of Methacryloylated Hydroxyethylcellulose and Development of Mucoadhesive Wafers for Buccal Drug Delivery

Non-ionic hydroxyethylcellulose (HEC) has limited mucoadhesive properties for application in transmucosal drug delivery. In this study, HEC was chemically modified by reaction with glycidyl methacrylate. This allowed introducing the methacryloyl groups to HEC structure to make it capable of forming covalent bonds with the sulfhydryl groups present in the mucin glycoprotein to achieve enhanced mucoadhesive properties. The results showed a successful modification of HEC as confirmed by ¹H NMR and FTIR spectroscopies. The quantification of methacryloyl moieties was conducted using HPLC. The toxicity studies using in vivo planaria acute toxicity assay, in vivo planaria fluorescent test, and in vitro MTT assay with Caco-2 cell line confirmed that the chemical modification of HEC does not result in any toxicological effects. Mucoadhesive wafers were developed based on parent and modified HEC as a model dosage form for buccal delivery. The mucoadhesive properties of modified HEC assessed using a tensile test were found to be significantly better compared to unmodified HEC.

Differences in neurotoxic outcomes of organophosphorus pesticides revealed via multi-dimensional screening in adult and regenerating planarians

Organophosphorus pesticides (OPs) are a chemically diverse class of commonly used insecticides. Epidemiological studies suggest that low dose chronic prenatal and infant exposures can lead to life-long neurological damage and behavioral disorders. While inhibition of acetylcholinesterase (AChE) is the shared mechanism of acute OP neurotoxicity, OP-induced developmental neurotoxicity (DNT) can occur independently and/or in the absence of significant AChE inhibition, implying that OPs affect alternative targets. Moreover, different OPs can cause different adverse outcomes, suggesting that different OPs act through different mechanisms. These findings emphasize the importance of comparative studies of OP toxicity. Freshwater planarians are an invertebrate system that uniquely allows for automated, rapid and inexpensive testing of adult and developing organisms in parallel to differentiate neurotoxicity from DNT. Effects found only in regenerating planarians would be indicative of DNT, whereas shared effects may represent neurotoxicity. We leverage this unique feature of planarians to investigate potential differential effects of OPs on the adult and developing brain by performing a comparative screen to test 7 OPs (acephate, chlorpyrifos, dichlorvos, diazinon, malathion, parathion and profenofos) across 10 concentrations in quarter-log steps. Neurotoxicity was evaluated using a wide range of quantitative morphological and behavioral readouts. AChE activity was measured using an Ellman assay. The toxicological profiles of the 7 OPs differed across the OPs and between adult and regenerating planarians. Toxicological profiles were not correlated with levels of AChE inhibition. Twenty-two "mechanistic control compounds" known to target pathways suggested in the literature to be affected by OPs (cholinergic neurotransmission, serotonin neurotransmission, endocannabinoid system, cytoskeleton, adenyl cyclase and oxidative stress) and 2 negative controls were also screened. When compared with the mechanistic control compounds, the phenotypic profiles of the different OPs separated into distinct clusters. The phenotypic profiles of adult vs. regenerating planarians exposed to the OPs clustered differently, suggesting some developmental-specific mechanisms. These results further support findings in other systems that OPs cause different adverse outcomes in the (developing) brain and build the foundation for future comparative studies focused on delineating the mechanisms of OP neurotoxicity in planarians.

Natural and Synthetic Pyrethrins Act as Feeding Deterrents against the Black Blowfly, Phormia regina (Meigen)

Pyrethrum is a botanical insecticide derived from pyrethrum flowers. Feeding deterrence caused by pyrethrum has been reported in several sucking insects; however, there is no account of the cause of deterrence—whether from a single component or the combination of six active ingredients, called pyrethrins. We determined the feeding deterrence of natural pyrethrins, their two main components (pyrethrins I and II), and pyrethroid insecticides on the blowfly, Phormia regina. In a dual-choice feeding assay that minimized tarsal contact with food sources but allowed feeding through proboscises, natural pyrethrins, synthetic pyrethrins I/II, and allethrin were observed to induce deterrence at a concentration 16 times lower than the lowest concentration at which the knockdown rate increased. Feeding bouts were interrupted by intensive grooming of the proboscis at the deterring concentration, but no such grooming was observed to occur while feeding on the unpalatable tastants—NaCl, quinine, and tartaric acid. The underlying mode of action for the feeding deterrence of pyrethrins at sub-lethal concentrations probably occurs on the fly oral gustatory system, while differing from that of unpalatable tastants. The potent feeding deterrence of pyrethrins may provide effective protection for pyrethrum plants by rapidly deterring insects from feeding, before insecticidal activities occur.

Maternal Cigarette Smoke Exposure Exaggerates the Behavioral Defects and Neuronal Loss Caused by Hypoxic-Ischemic Brain Injury in Female Offspring

Objective

Hypoxic-ischemic encephalopathy affects ∼6 in 1,000 preterm neonates, leading to significant neurological sequela (e.g., cognitive deficits and cerebral palsy). Maternal smoke exposure (SE) is one of the common causes of neurological disorders; however, female offspring seems to be less affected than males in our previous study. We also showed that maternal SE exaggerated neurological disorders caused by neonatal hypoxic-ischemic brain injury in adolescent male offspring. Here, we aimed to examine whether female littermates of these males are protected from such insult.

Methods

BALB/c dams were exposed to cigarette smoke generated from 2 cigarettes twice daily for 6 weeks before mating, during gestation and lactation. To induce hypoxic-ischemic brain injury, half of the pups from each litter underwent left carotid artery occlusion, followed by exposure to 8% oxygen (92% nitrogen) at postnatal day (P) 10. Behavioral tests were performed at P40–44, and brain tissues were collected at P45.

Results

Maternal SE worsened the defects in short-term memory and motor function in females with hypoxic-ischemic injury; however, reduced anxiety due to injury was observed in the control offspring, but not the SE offspring. Both hypoxic-ischemic injury and maternal SE caused significant loss of neuronal cells and synaptic proteins, along with increased oxidative stress and inflammatory responses.

Conclusion

Oxidative stress and inflammatory response due to maternal SE may be the mechanism of worsened neurological outcomes by hypoxic-ischemic brain injury in females, which was similar to their male littermates shown in our previous study.

Larval cryopreservation as new management tool for threatened clam fisheries

Cryopreservation is the only reliable method for long-term storage of biological material that guarantees genetic stability. This technique can be extremely useful for the conservation of endangered species and restock natural populations for declining species. Many factors have negatively affected the populations of high economical value shellfish in Spain and, as a result, many are declining or threatened nowadays. This study was focused on early-life stages of Venerupis corrugata, Ruditapes decussatus and Ruditapes philippinarum to develop successful protocols to enhance the conservation effort and sustainable shellfishery resources. Firstly, common cryoprotecting agents (CPAs) were tested to select the suitable permeable CPA attending to toxicity. Cryopreservation success using different combinations of CPA solutions, increasing equilibrium times and larval stages was evaluated attending to survival and shell growth at 2 days post-thawing. Older clam development stages were more tolerant to CPA toxicity, being ethylene-glycol (EG) and Propylene-glycol (PG) the least toxic CPAs. CPA solution containing EG yielded the highest post-thawing survival rate and the increase of equilibration time was not beneficial for clam larvae. Cryopreservation of trochophores yielded around 50% survivorship, whereas over 80% of cryopreserved D-larvae were able to recover after thawing.

Behavioral responses of three freshwater planaria species to light, visual and olfactory stimuli: Setting the stage for further ecotoxicological studies

Planarians are freshwater flatworms commonly used as environmental bioindicator due to their sensitivity of response and their ease of culturing in lab. Nevertheless, to date, very few studies describing their behavior have been led. This work aims to fill the literature gap by providing preliminary results through six behavioral challenges (locomotion, exploration, light stress, planarian light/dark test, shoaling and foraging) conducted with three different species Dugesia tigrina, Schmidtea mediterranea and Schmidtea polychroa. The behavioral responses of every species in each of these six assays were recorded and differences between species were highlighted, depending on the assays and conditions. Schmidtea polychroa is less active than the two others and had the highest light aversion. Reactions observed in response to diverse and realistic stimuli helped us to select the most suitable tests and choose the species that seem the most appropriate for future ecotoxicological and neurophysiological tests. Four tests - out of the six tested- seem reliable in order to standardize planarian behavioral tests.

Neurotoxicity of perfluorooctanoic acid and post-exposure recovery due to blueberry anthocyanins in the planarians Dugesia japonica

Perfluorooctanoic acid (PFOA) is a widely used synthetic industrial chemical which accumulates in ecosystems and organisms. Our study have investigated the neurobehavioral effects of PFOA and the alleviation effects of PFOA-induced neurotoxicity by blueberry anthocyanins (ANT) in Dugesia japonica. The planarians were exposed to PFOA and ANT for ten days. Researchs showed that exposure to PFOA affected locomotor behavior and ANT significantly alleviated the reduction in locomotion induced by PFOA. The regeneration of eyespots and auricles was suppressed by PFOA and was promoted by ANT. Following exposure to PFOA, acetylcholinesterase activity continually decreased and was unaffected in the ANT group, but was elevated after combined administration of PFOA and ANT. Oxidative DNA damage was found in planarians exposed to PFOA and was attenuated after administration of ANT by the alkaline comet assay. Concentrations of three neurotransmitters increased following exposure to PFOA and decreased after administration of ANT. Furthermore, ANT promoted and PFOA inhibited neuronal regeneration. DjotxA, DjotxB, DjFoxG, DjFoxD and Djnlg associated with neural processes were up-regulated following exposure to PFOA. Our findings indicate that PFOA is a neurotoxicant while ANT can attenuate these detrimental effects.

Effects of Fe3+ on Acute Toxicity and Regeneration of Planarian (Dugesia japonica) at Different Temperatures

Objective

To investigate the effects of different concentrations of Fe³⁺ on the acute toxicity and regeneration of planarian at different temperatures.

Method

The planarians were treated with 40 mg/l, 50 mg/l, 60 mg/l, and 70 mg/l Fe³⁺ solution and placed in 15°C, 20°C, and 25°C, respectively, to observe the mortality and the poisoning pattern of the planarian. In addition, the planarians were cut into three parts of head, trunk, and tail, then placed in Fe³⁺ solution at concentrations of 10 mg/l, 15 mg/l, 20 mg/l, and 30 mg/l, and placed in 15°C, 20°C, and 25°C respectively, and the regeneration rate of the planarian was investigated.

Results

At the same temperature, in the concentration of Fe³⁺ from 40 mg/l to 70 mg/l, the mortality of the planarian increased with the increasing of the concentration of Fe³⁺; at the same concentration and different temperatures, the death speed of the planarian is the fastest at 20°C, the next at 25°C, and the lowest at 15°C, indicating that the toxic effect of Fe³⁺ can be accelerated at a suitable temperature of 20°C. At the same temperature, in the low concentration of Fe³⁺ from 10 mg/l to 30 mg/l, the regeneration rate of the planarian gradually decreased with the increasing of the concentration of Fe³⁺; at the same concentration and different temperature, the regeneration rate of planarian was faster at 20°C and 25°C, but the difference between 20°C and 25°C was small, and the slowest at 15°C, indicating that the low temperature significantly affects the planarian regeneration speed. The study also found the regeneration rates of the head, trunk, and tail of the planarian were different; the head regeneration was the fastest, the trunk was the second, and the tail was the slowest.

Conclusion

Fe³⁺ had obvious toxic effects on the survival and regeneration of planarian; the planarian is sensitive to Fe³⁺ and may be used to detect Fe³⁺ water pollution; in addition, temperature can affect the toxic effects of Fe³⁺ and thus affect the survival and regeneration of the planarian. Therefore, the temperature should be taken into consideration when detecting water Fe³⁺ pollution.

Toxicity tests of cryoprotecting agents for Mytilus galloprovincialis (Lamark, 1819) early developmental stages

Global aquaculture production of blue mussel has increased over last years. This work reaffirms the great potential of cryopreservation technique on mussel industry and overcome economic barriers a cause of a traditional and rudimentary management and continue growing. The aim of this work is to set some preliminary basis attending to toxicity of cryoprotecting agents (CPAs) on different development stages of Mytilus galloprovincialis as a start point to develop a stable cryopreservation protocol. Toxicity tests were carried out by using common CPAs (dimethyl-sulfoxide (Me₂SO), glycerol, (GLY), propylene glycol (PG) and ethylene glycol (EG)) in a range from 0.5 to 3 M on fertilized egg, trochophore larva, and D-larva of Mytilus galloprovincialis. Results evidenced more resistance of older development stages to toxicity. Of all CPAs tested, toxicity testing highlights PG or EG as suitable CPAs for cryopreservation of early development stages; whereas D-larva was unaffected by any of the CPAs tested. Preliminary cryopreservation trials were developed to obtain information into cell cryoprotection. Further research should be focused on membrane permeability and other parameters, such as the balance between toxicity and cryoprotective effect of CPAs.

The use of freshwater planarians in environmental toxicology studies: Advantages and potential

Regarding the humane use of animals in scientific research, invertebrates are often recommended in toxicological studies. "Freshwater planarians" refers to numerous free-living freshwater members of the Class "Turbellaria" of the phylum Platyhelminthes. This group of invertebrates has received extensive attention from biologists for many years because of their unique biological characteristics, such as the primitive form of the central nervous system and notable capability to regenerate tissues. Using freshwater planarians as test animals in chemical toxicity studies has grown in popularity since the 1960s. Results from various toxicological experiments have collectively suggested that freshwater planarians can serve as not only alternative models for chemical toxicity screenings in laboratories but also as potential bioindicators for the quality of freshwater environments. However, thus far, no standardized battery of tests for conducting toxicological studies that includes freshwater planarians has been proposed. This paper comprehensively reviews the toxicological information obtained from chemically exposed planarians and proposes practical factors for consideration in toxicity experiments with freshwater planarians as test organisms.

Effects of ethanol on negative phototaxis and motility in brown planarians (Dugesia tigrina)

The behavioral effects of ethanol in brown planarians were studied in four experiments. In the first two experiments, acute administrations of ethanol increased travel time in a dose-dependent fashion in individual planarians moving away from a light source. Orderly results were obtained using both within-subject and between-group designs. In a third experiment, ethanol dose was arranged by time rather than concentration. Ethanol increased travel time overall, but variability between subjects was considerable. In a final experiment, ethanol administration reduced motility and altered movement patterns in planarians in an open-field test. These experiments demonstrated that negative phototaxis by planarians may exhibit sufficient stability to allow for experimental determinations of dose-response curves utilizing both within-subject and between-subject designs.

Unsuitable use of DMSO for assessing behavioral endpoints in aquatic model species

Dimethyl sulfoxide (DMSO) is a universally used aprotic solvent with the ability to permeate biological membranes and thus is commonly used to achieve appropriate biological availability of hydrophobic toxicants. While DMSO as a carrier medium has a reportedly low toxicity and is routinely employed in ecotoxicology, very little is known about its effect on dynamic behavioral parameters. This study presents a comparative analysis of the lethal and behavioral effects of exposures to DMSO concentrations of 0.1-10% on several test species such as: neonates of the freshwater crustacean Daphnia magna, nauplii of the marine crustacean Artemia franciscana, the marine crustacean Allorchestes compressa, embryos and larvae of the freshwater fish Danio rerio. The results demonstrated that DMSO did not cause statistically significant mortality even at concentrations close to 1% but induced clear and significant behavioral abnormalities in response to sublethal concentrations on all test species. These included hypoactivity syndrome in A. franciscana, A. compressa, D. magna and zebrafish larvae while a slight time-dependent hyperactivity response was observed in zebrafish embryos. For the majority of test species, behavioral changes such as moving distance, acceleration and burst movement were often observed during the first hours of exposure. These results indicate that caution should be exercised when using DMSO as a carrier solvent in experiments assessing behavioral endpoints.

Planarian cholinesterase: molecular and functional characterization of an evolutionarily ancient enzyme to study organophosphorus pesticide toxicity

The asexual freshwater planarian Dugesia japonica has emerged as a medium-throughput alternative animal model for neurotoxicology. We have previously shown that D. japonica are sensitive to organophosphorus pesticides (OPs) and characterized the in vitro inhibition profile of planarian cholinesterase (DjChE) activity using irreversible and reversible inhibitors. We found that DjChE has intermediate features of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Here, we identify two candidate genes (Djche1 and Djche2) responsible for DjChE activity. Sequence alignment and structural homology modeling with representative vertebrate AChE and BChE sequences confirmed our structural predictions, and show that both DjChE enzymes have intermediate sized catalytic gorges and disrupted peripheral binding sites. Djche1 and Djche2 were both expressed in the planarian nervous system, as anticipated from previous activity staining, but with distinct expression profiles. To dissect how DjChE inhibition affects planarian behavior, we acutely inhibited DjChE activity by exposing animals to either an OP (diazinon) or carbamate (physostigmine) at 1 µM for 4 days. Both inhibitors delayed the reaction of planarians to heat stress. Simultaneous knockdown of both Djche genes by RNAi similarly resulted in a delayed heat stress response. Furthermore, chemical inhibition of DjChE activity increased the worms' ability to adhere to a substrate. However, increased substrate adhesion was not observed in Djche1/Djche2 (RNAi) animals or in inhibitor-treated day 11 regenerates, suggesting this phenotype may be modulated by other mechanisms besides ChE inhibition. Together, our study characterizes DjChE expression and function, providing the basis for future studies in this system to dissect alternative mechanisms of OP toxicity.

Planarian brain regeneration as a model system for developmental neurotoxicology

Freshwater planarians, famous for their regenerative prowess, have long been recognized as a valuable in vivo animal model to study the effects of chemical exposure. In this review, we summarize the current techniques and tools used in the literature to assess toxicity in the planarian system. We focus on the planarian's particular amenability for neurotoxicology and neuroregeneration studies, owing to the planarian's unique ability to regenerate a centralized nervous system. Zooming in from the organismal to the molecular level, we show that planarians offer a repertoire of morphological and behavioral readouts while also being amenable to mechanistic studies of compound toxicity. Finally, we discuss the open challenges and opportunities for planarian brain regeneration to become an important model system for modern toxicology.

Behavioural responses of freshwater planarians after short-term exposure to the insecticide chlorantraniliprole

Recent advances in video tracking technologies provide the tools for a sensitive and reproducible analysis of invertebrate activity under stressful conditions nurturing the field of behavioural ecotoxicology. This study aimed to evaluate behavioural responses of the freshwater planarian Dugesia subtentaculata exposed to a model compound, chlorantraniliprole (CAP). This compound is an anthranilic diamide insecticide and due to its neurotoxic action can, at low concentrations, impair behaviour of exposed organisms. Behavioural endpoints measured included feeding and locomotor activities. Feeding responses were based on planarian predatory behaviour using Chironomus riparius larvae as prey. Locomotion was measured by the traditional planarian locomotor velocity (pLMV) assay and additionally using an automated video tracking system using a Zebrabox(®) (Viewpoint, France) device. While feeding and pLMV were significantly impaired at 131.7μg/L CAP, the video tracking system showed that total distance covered by planarians was significantly reduced at concentrations as low as 26.2μg/L CAP. Our results show that more advanced automated video recording systems can be used in the development of sensitive bioassays allowing a reliable, time- and cost-effective quantification of behaviour in aquatic invertebrates. Due to their ecological relevance, behavioural responses should not be disregarded in risk assessment strategies and we advocate the suitability of planarians as suitable organisms for behavioural ecotoxicological studies.

Freshwater Planarians as an Alternative Animal Model for Neurotoxicology

Traditional toxicology testing has relied on low-throughput, expensive mammalian studies; however, timely testing of the large number of environmental toxicants requires new in vitro and in vivo platforms for inexpensive medium- to high-throughput screening. Herein, we describe the suitability of the asexual freshwater planarian Dugesia japonica as a new animal model for the study of developmental neurotoxicology. As these asexual animals reproduce by binary fission, followed by regeneration of missing body structures within approximately 1 week, development and regeneration occur through similar processes allowing us to induce neurodevelopment "at will" through amputation. This short time scale and the comparable sizes of full and regenerating animals enable parallel experiments in adults and developing worms to determine development-specific aspects of toxicity. Because the planarian brain, despite its simplicity, is structurally and molecularly similar to the mammalian brain, we are able to ascertain neurodevelopmental toxicity that is relevant to humans. As a proof of concept, we developed a 5-step semiautomatic screening platform to characterize the toxicity of 9 known neurotoxicants (consisting of common solvents, pesticides, and detergents) and a neutral agent, glucose, and quantified effects on viability, stimulated and unstimulated behavior, regeneration, and brain structure. Comparisons of our findings with other alternative toxicology animal models, such as zebrafish larvae and nematodes, demonstrated that planarians are comparably sensitive to the tested chemicals. In addition, we found that certain compounds induced adverse effects specifically in developing animals. We thus conclude that planarians offer new complementary opportunities for developmental neurotoxicology animal models.

Cadmium neurotoxicity to a freshwater planarian

Although freshwater planarians are evolutionarily primitive, they are some of the simplest bilateral animals possessing integrated neural networks similar to those in vertebrates. We attempted to develop planarian Dugesia japonica as a model for investigating the neurotoxicity of environmental pollutants such as cadmium (Cd). This study was therefore designed to study the effects of Cd on the locomotor activity, neurobehavior, and neurological enzymes of D. japonica. After planarians were exposed to Cd at high concentrations, altered neurobehavior was observed that exhibited concentration-dependent patterns. Morphological alterations in Cd-treated planarians included irregular shape, body elongation, screw-like hyperkinesia, and bridge-like position. To study the direct effects of Cd on neurological enzymes, tissue homogenates of planarians were incubated in vitro with Cd before their activity was measured. Results showed that acetylcholinesterase (AChE), adenosine triphosphatase (ATPase), and monoamine oxidase A (MAO-A) activities were inhibited in a concentration-dependent manner. MAO-B activity was significantly induced by Cd at low concentrations and inhibited at high concentrations. Changes in the in vivo activity of AChE and ATPase were also found after planarians were treated with Cd at a sublethal concentration (5.56 μM). These observations indicate that neurotransmission systems in planarians are disturbed after Cd exposure.

Flatworm models in pharmacological research: the importance of compound stability testing

Flatworms possess adult pluripotent stem cells, which make them extraordinary experimental model organisms to assess in vivo the undesirable effects of substances on stem cells. Currently, quality practices, implying evaluation of the stability of the test compound under the proposed experimental conditions, are uncommon in this research field. Nevertheless, performing a stability study during the rational design of in vivo assay protocols will result in more reliable assay results. To illustrate the influence of the stability of the test substance on the final experimental outcome, we performed a short-term International Conference on Harmonization (ICH)-based stability study of cyclophosphamide in the culture medium, to which a marine flatworm model Macrostomum lignano is exposed. Using a validated U(H)PLC method, it was demonstrated that the cyclophosphamide concentration in the culture medium at 20°C is lowered to 80% of the initial concentration after 21days. The multiwell plates, flatworms and diatoms, as well as light exposure, did not influence significantly the cyclophosphamide concentration in the medium. The results of the stability study have practical implications on the experimental set-up of the carcinogenicity assay like the frequency of medium renewal. This case study demonstrates the benefits of applying appropriate quality guidelines already during fundamental research increasing the credibility of the results.

Toxicity profiles and solvent-toxicant interference in the planarian Schmidtea mediterranea after dimethylsulfoxide (DMSO) exposure

To investigate hydrophobic test compounds in toxicological studies, solvents like dimethylsulfoxide (DMSO) are inevitable. However, using these solvents, the interpretation of test compound-induced responses can be biased. DMSO concentration guidelines are available, but are mostly based on acute exposures involving one specific toxicity endpoint. Hence, to avoid solvent-toxicant interference, we use multiple chronic test endpoints for additional interpretation of DMSO concentrations and propose a statistical model to assess possible synergistic, antagonistic or additive effects of test compounds and their solvents. In this study, the effects of both short- (1 day) and long-term (2 weeks) exposures to low DMSO concentrations (up to 1000 µl l(-1) ) were studied in the planarian Schmidtea mediterranea. We measured different biological levels in both fully developed and developing animals. In a long-term exposure set-up, a concentration of 500 µl l(-1) DMSO interfered with processes on different biological levels, e.g. behaviour, stem cell proliferation and gene expression profiles. After short exposure times, 500 µl l(-1) DMSO only affected motility, whereas the most significant changes on different parameters were observed at a concentration of 1000 µl l(-1) DMSO. As small sensitivity differences exist between biological levels and developmental stages, we advise the use of this solvent in concentrations below 500 µl l(-1) in this organism. In the second part of our study, we propose a statistical approach to account for solvent-toxicant interactions and discuss full-scale solvent toxicity studies. In conclusion, we reassessed DMSO concentration limits for different experimental endpoints in the planarian S. mediterranea.

Galantamine reverses scopolamine-induced behavioral alterations in Dugesia tigrina

In planaria (Dugesia tigrina), scopolamine, a nonselective muscarinic receptor antagonist, induced distinct behaviors of attenuated motility and C-like hyperactivity. Planarian locomotor velocity (pLMV) displayed a dose-dependent negative correlation with scopolamine concentrations from 0.001 to 1.0 mM, and a further increase in scopolamine concentration to 2.25 mM did not further decrease pLMV. Planarian hyperactivity counts was dose-dependently increased following pretreatment with scopolamine concentrations from 0.001 to 0.5 mM and then decreased for scopolamine concentrations ≥ 1 mM. Planarian learning and memory investigated using classical Pavlovian conditioning experiments demonstrated that scopolamine (1 mM) negatively influenced associative learning indicated by a significant decrease in % positive behaviors from 86 % (control) to 14 % (1 mM scopolamine) and similarly altered memory retention, which is indicated by a decrease in % positive behaviors from 69 % (control) to 27 % (1 mM scopolamine). Galantamine demonstrated a complex behavior in planarian motility experiments since co-application of low concentrations of galantamine (0.001 and 0.01 mM) protected planaria against 1 mM scopolamine-induced motility impairments; however, pLMV was significantly decreased when planaria were tested in the presence of 0.1 mM galantamine alone. Effects of co-treatment of scopolamine and galantamine on memory retention in planaria via classical Pavlovian conditioning experiments showed that galantamine (0.01 mM) partially reversed scopolamine (1 mM)-induced memory deficits in planaria as the % positive behaviors increased from 27 to 63 %. The results demonstrate, for the first time in planaria, scopolamine's effects in causing learning and memory impairments and galantamine's ability in reversing scopolamine-induced memory impairments.

An exploratory evaluation of tyrosine hydroxylase inhibition in planaria as a model for parkinsonism

Planaria are the simplest organisms with bilateral symmetry and a central nervous system (CNS) with cephalization; therefore, they could be useful as model organisms to investigate mechanistic aspects of parkinsonism and to screen potential therapeutic agents. Taking advantage of the organism’s anti-tropism towards light, we measured a significantly reduced locomotor velocity in planaria after exposure to 3-iodo-l-tyrosine, an inhibitor of tyrosine hydroxylase that is an enzyme catalyzing the first and rate-limiting step in the biosynthesis of catecholamines. A simple semi-automatic assay using videotaped experiments and subsequent evaluation by tracking software was also implemented to increase throughput. The dopaminergic regulation of locomotor velocity was confirmed by bromocriptine, a drug whose mechanisms of action to treat Parkinson’s disease is believed to be through the stimulation of nerves that control movement.

Riluzole attenuates the effects of chemoconvulsants acting on glutamatergic and GABAergic neurotransmission in the planarian Dugesia tigrina

Planarians, the non-parasitic flatworms, display dose-dependent, distinct (C-like and corkscrew-like) hyperkinesias upon exposure to 0.001-10 mM aqueous solutions of glutamatergic agonists (L-glutamate and N-methyl-D-aspartate (NMDA)) and 0.001-5 mM concentrations of the glutamate decarboxylase (GAD) inhibitor (semicarbazide). In the planarian seizure-like activity (PSLA) experiments the three chemoconvulsants displayed the following order of potency (EC50): L-glutamate (0.6mM)>NMDA (1.4 mM)>semicarbazide (4.5mM). Planarian hyperkinesias behavior counting experiments also revealed that riluzole (0.001 to 1mM), an anti-convulsive agent, displayed no significant behavioral activity by itself, but attenuated hyperkinesias elicited by the three chemoconvulsants targeting either glutamatergic or GABAergic neurotransmission with the following order of potency (IC50): NMDA (44.7 µM)>semicarbazide (88.3 µM)>L-glutamate (160 µM). Further, (+)-MK-801, a specific NMDA antagonist, alleviated 3mM NMDA (47%) or 3mM L-glutamate (27%) induced planarian hyperkinesias. The results provide pharmacological evidence for the presence of glutamatergic receptor-like and semicarbazide sensitive functional GAD enzyme-like proteins in planaria in addition to demonstrating, for the first time, the anti-convulsive effects of riluzole in an invertebrate model. High performance liquid chromatography coupled with fluorescence detection (HPLC-F) analysis performed on planarian extracts post no drug treatment (control) or treatment with 3mM semicarbazide, combination of 3mM semicarbazide and 0.1 mM riluzole, or 0.1 mM riluzole revealed that 3 mM semicarbazide induced 35% decrease in the GABA levels and a combination of 3mM semicarbazide and 0.1 mM riluzole induced 42% decrease in glutamate levels with respect to the control group.

Effects of N,N-dimethylformamide on behaviour and regeneration of planarian Dugesia japonica

In this study, the toxicity, behavioural and regeneration effects of dimethylformamide (DMF) on planarian Dugesia japonica were investigated. One control and six different concentrations of DMF (10 ppm, 100 ppm, 500 ppm, 1000 ppm, 5000 ppm and 10,000 ppm) were used in triplicate. The results showed that the mortality was directly proportional to the DMF concentration and planarian locomotor velocity (pLMV) was significantly reduced by increasing the exposure time and DMF concentration. pLMV of D. japonica was significantly reduced at a lower concentration of 10 ppm after 7 days of continuous exposure to DMF. The recovery of the motility of planarians pretreated with DMF was found to be time- and dose dependent, all planarians had complete recovery in their motility after 48 h. The appearance of auricles in regenerating animals was easily affected by DMF exposure in comparison with the appearance of eyespot. The present results suggest that the intact adult mobility in the aquatic planarian D. japonica is a more sensitive biomarker than mortality, and the appearance of auricles in regenerating animals is a more sensitive biomarker than eyespot.

Effects of dimethylsulfoxide on behavior and antioxidant enzymes response of planarian Dugesia japonica

In this study, the toxicity, behavioral and antioxidant activity effects of dimethylsulfoxide (DMSO) on planarian Dugesia japonica were investigated. The results showed that the mortality was directly proportional to the DMSO concentration, and planarian locomotor velocity decreased as the concentration of DMSO increased. The recovery of the motility for planarians pre-exposed to DMSO was found to be time- and dose-dependent, and only those pre-exposed to 0.1-3% DMSO resulted in full recovery. The antioxidant enzymes of planarians in response to long-term DMSO stress was also altered in a time- and dose-dependent manner. Planarians revealed more tolerance to DMSO toxicity at low DMSO (0.1%) level in short- and long-term DMSO stress, in which an efficient antioxidant system was involved and the motility was not affected.

Minimal structural requirements of alkyl γ-lactones capable of antagonizing the cocaine-induced motility decrease in planarians

We recently reported that the natural cyclic lactone, parthenolide, and related analogs prevent the expression of behavioral effects induced by cocaine in planarians and that parthenolide's γ-lactone ring is required for this effect. In the present work, we tested a series of alkyl γ-lactones with varying chain length (1-8 carbons) to determine their ability to antagonize the planarian motility decrease induced by 200 μM cocaine. Alkyl lactones with up to a 4-carbon alkyl chain did not affect planarian motility or antagonized the cocaine-induced motility decrease; only the compound γ-nonalactone (a γ-lactone with a 5-carbon chain) was able to prevent the cocaine-induced behavioral patterns, while alkyl lactones with longer carbon chains failed to prevent the cocaine-induced effects. Thus, we conclude that the optimal structural features of this family of compounds to antagonize cocaine's effect in this experimental system is a γ-lactone ring with at a 5-carbon long functional group.

Quantitative characterization of planarian wild-type behavior as a platform for screening locomotion phenotypes

Changes in animal behavior resulting from genetic or chemical intervention are frequently used for phenotype characterizations. The majority of these studies are qualitative in nature, especially in systems that go beyond the classical model organisms. Here, we introduce a quantitative method to characterize behavior in the freshwater planarian Schmidtea mediterranea. Wild-type locomotion in confinement was quantified using a wide set of parameters, and the influences of intrinsic intra-worm versus inter-worm variability on our measurements was studied. We also examined the effect of substrate, confinement geometry and the interactions with the boundary on planarian behavior. The method is based on a simple experimental setup, using automated center-of-mass tracking and image analysis, making it an easily implemented alternative to current methods for screening planarian locomotion phenotypes. As a proof of principle, two drug-induced behavioral phenotypes were generated to show the capacity of this method.

Developmental exposures to ethanol or dimethylsulfoxide at low concentrations alter locomotor activity in larval zebrafish: implications for behavioral toxicity bioassays

Ethanol and dimethylsulfoxide (DMSO) are commonly used as carrier solvents for lipophilic chemicals in aquatic toxicity bioassays. However, very little information has been reported on the behavioral effects of these solvents. In this study, we examined the effects of ethanol and DMSO on development and locomotor activity by a zebrafish embryo-larval bioassay. The zebrafish were exposed to different concentrations (control, 0.01, 0.1, and 1%) of ethanol or DMSO from blastula stage to 144 hour-post-fertilization (hpf). Hatchability, survival, and abnormalities were monitored every 12h, and locomotor activity of the larvae was analyzed at 144 hpf. Hatchability was not affected by the ethanol or DMSO treatments. No effect on survival was observed except the 1% ethanol group suffered 89% mortality during 108-120 hpf. No developmental defects were observed in any of the solvents at the 0.01 and 0.1% concentrations, but significantly higher deformity rates occurred with 1% ethanol and DMSO groups. Hyperactivity and less tortuous swimming paths were observed in all ethanol and DMSO concentrations. Based on this study, we suggest that data of behavioral toxicity bioassays using ethanol or DMSO as carrier solvents should be interpreted cautiously, because the solvents at low concentrations could alter locomotor activity of larval zebrafish without causing any observable developmental defects.

Cryopreservation of sea urchin embryos (Paracentrotus lividus) applied to marine ecotoxicological studies

Current strategies for marine pollution monitoring are based on the integration of chemical and biological techniques. The sea urchin embryo-larval bioassays are among the biological methods most widely used worldwide. Cryopreservation of early embryos of sea urchins could provide a useful tool to overcome one of the main limitations of such bioassays, the availability of high quality biological material all year round. The present study aimed to determine the suitability of several permeant (dimethyl sulfoxide, Me(2)SO; propylene glycol, PG; and ethylene glycol, EG) and non-permeant (trehalose, TRE; polyvinylpyrrolidone, PVP) cryoprotectant agents (CPAs) and their combination, for the cryopreservation of eggs and embryos of the sea urchin Paracentrotus lividus. On the basis of the CPAs toxicity, PG and EG, in combination with PVP, seem to be most suitable for the cryopreservation of P. lividus eggs and embryos. Several freezing procedures were also assayed. The most successful freezing regime consisted on cooling from 4 to -12 degrees C at 1 degrees C/min, holding for 2 min for seeding, cooling to -20 degrees C at 0.5 degrees C/min, and then cooling to -35 degrees C at 1 degrees C/min. Maximum normal larvae percentages of 41.5% and 68.5%, and maximum larval growth values of 42.9% and 60.5%, were obtained for frozen fertilized eggs and frozen blastulae, respectively.

A cembranoid from tobacco prevents the expression of nicotine-induced withdrawal behavior in planarian worms

Using an adaptation of published behavioral protocols, we determined that acute exposure to the cholinergic compounds nicotine and carbamylcholine decreased planarian motility in a concentration-dependent manner. A tobacco cembranoid (1S,2E,4R,6R,7E,11E)-cembra-2,7,11-triene-4,6-diol (4R-cembranoid), also decreased planarian motility. Experiments in the presence of 1 microM 4R-cembranoid did increase the IC50 for nicotine- but not carbamylcholine-induced decrease in planarian motility. When planarians were exposed for 24 h to either nicotine or carbamylcholine at concentrations near their respective IC50 values and then transferred to plain media, nicotine-exposed, but not carbamylcholine- or cembranoid-exposed worms displayed withdrawal-like distress behaviors. In experiments where planarians were pre-exposed to 100 microM nicotine for 24 h in the presence of 1 microM 4R-cembranoid, the withdrawal-like effects were significantly reduced. These results indicate that the 4R-cembranoid might have valuable applications for tobacco abuse research. This experimental approach using planarians is useful for the initial screening of compounds relevant to drug abuse and dependence.

Effects of nonionic and ionic surfactants on survival, oxidative stress, and cholinesterase activity of planarian

Eight widely used surfactants (cetyltrimethylammonium bromide; CTAB, benzethonium chloride; Hyamine 1622, 4-nonylphenol; NP, octylphenol ethoxylate; Triton X-100, dodecylbenzene sulfonate; LAS, lauryl sulfate; SDS, pentadecafluorooctanoic acid; PFOA, and perfluorooctane sulfonate; PFOS) were selected to examine their acute toxicities and effects on oxidative stress and cholinesterase (ChE) activities in Dugesia japonica. The differences in acute toxicity among eight surfactants to planarians were at least in the range of three orders of magnitudes. The toxicity rank of surfactants according to estimated 48-h LC(50) was SDS>NP>LAS>Hyamine 1622>CTAB>Triton X-100>PFOS>PFOA. The toxicity rank of surfactants according to 96-h LC(50) was as follows: SDS>CTAB>NP>LAS>Hyamine 1622>Triton X-100>PFOS>PFOA. There were significant increases in catalase activities in planarians exposed to LAS at nominal concentrations of 0.5 or 1 mgl(-1) and to PFOS at nominal concentrations of 5 or 10 mgl(-1) after 48-h exposure. Inhibitions of ChE activities were found in planarians exposed to Hyamine 1622 at all concentrations tested, to PFOS at nominal concentration of 10 mgl(-1), to PFOA at nominal concentrations of 50 or 100 mgl(-1) and to NP at nominal concentration of 0.5 mgl(-1). A significant increase in ChE activities was also observed in planarian exposed to Triton X-100 at nominal concentration of 5 mgl(-1). The implication of ChE inhibition by NP, PFOS and PFOA on neurological and behavioral effects in aquatic animals requires further investigation.

Parthenolide prevents the expression of cocaine-induced withdrawal behavior in planarians

We recently reported that parthenolide and related sesquiterpene lactones are able to prevent and reverse behavioral responses in planarian worms induced by acute cocaine exposure. Previous reports indicate that when planarians are chronically exposed to microM concentrations of cocaine, they display stereotypical withdrawal-like behaviors when the cocaine is removed. Here we report that parthenolide prevents this cocaine-induced expression of planarian withdrawal-like behaviors.

Reversal of cocaine-induced planarian behavior by parthenolide and related sesquiterpene lactones

Here we report the prevention and reversal of cocaine-induced behaviors in planarian worms by parthenolide and two related cyclic sesquiterpene lactones (SL), costunolide and santonin. Using established protocols, we studied two cocaine-induced behavioral effects in planaria; the induction of motility decrease and the induction of C-like hyperkinesia. Cocaine, parthenolide, costunolide, santonin, and a lactone-less cyclic sesquiterpene, beta-eudesmol, decreased planarian motility in a concentration-dependent manner. Only cocaine induced C-like hyperkinesia. At concentrations that did not show any motility decrease, parthenolide, costunolide and santonin, but not beta-eudesmol, significantly reduced the cocaine-induced motility decrease and C-like hyperkinesia, in a concentration-dependent manner. Furthermore, parthenolide, costunolide and santonin were able to rescue planaria from C-like hyperkinesia, after the worms were exposed to cocaine. Conversely, cocaine at a concentration that did not show any measurable effects (10 microM), was able to alleviate the SL-, but not the beta-eudesmol-induced motility decrease. Liquid Chromatography/Mass Spectrometry experiments demonstrated that cocaine does not interact directly with any of the cyclic sesquiterpenoids, which suggests specific biochemical targets for these compounds in planarians. Our data suggests a common binding site for cocaine and the sesquiterpene lactones in planarians.