Neuropharmacological effects of alfa-cypermethrin in rats

Morphometric Evaluation of the Recurrent Laryngeal Nerve of Wistar Rats Exposed to Pesticides

The literature has been shown that exposition by inhalation to chemical compounds can cause vocal disorders and dysphagia in humans, in addition to other symptoms that are manifested according to the type, concentration and duration of exposure to the substance. Cypermethrin and dichlorvos are pesticides widely used in agriculture, public health, veterinary, and home environments. Despite the scientific evidence that cypermethrin and dichlorvos can cause neurodegenerative damage and motor alterations, there are no studies evaluating the toxic effects of these pesticides on the morphology of structures responsible for vocal mobility, especially to the Recurrent Laryngeal Nerve (RLN). Considering the association between vocal disorders in humans and variations in RLN and morphometry, the aim of this study was to evaluate the possible alterations in the microstructure of RLN secondary to subchronic exposure to cypermethrin (pyrethroid) and dichlorvos (organophosphate) in Wistar rats. The experimental protocol (approved by CEUA-UFCSPA: 321/15 and 323/15) consisted of 15 male Wistar rats, allocated in 3 groups: Control (n = 5, exposed to water), Cypermethrin (n = 5, exposed to cypermethrin - 1/10 of the inhalation median lethal concentration [LC50] - 0.25 mg/L) and dichlorvos (n = 5, exposed to dichlorvos - 1/10 of the LC50 - 1.5 mg/L). Inhalation exposure was performed for 4 hours, 5 times per week, for 6 weeks. The nerves were collected, histologically processed and analyzed using morphometric parameters measured using ZEN 2.6 (Zeiss - Germany). The cypermethrin and dichlorvos groups showed significant changes (P < 0.001, ANOVA) in the g-ratio and in the thickness of the myelin sheath of the RLN when compared to the control animals, however, none of the other parameters evaluated showed statistically significant differences. These findings indicate that repeated inhalation exposure to commercial products of cypermethrin and dichlorvos is able to modify the structure of the RLN and possibly generating vocal changes and / or dysphagia.

Modelling the effects of the pyrethroid insecticide cypermethrin on the life cycle of the soil dwelling annelid Enchytraeus crypticus, an original experimental design to calibrate a DEB-TKTD model

The Dynamic Energy Budget theory (DEB) enables ecotoxicologists to model the effects of chemical stressors on organism life cycles through the coupling of toxicokinetic-toxicodynamic (TK-TD) models. While good progress has been made in the application of DEB-TKTD models for aquatic organisms, applications for soil fauna are scarce, due to the lack of dedicated experimental designs suitable for collecting the required time series effect data. Enchytraeids (Annelida: Clitellata) are model organisms in soil ecology and ecotoxicology. They are recognised as indicators of biological activity in soil, and chemical stress in terrestrial ecosystems. Despite this, the application of DEB-TKTD models to investigate the impact of chemicals has not yet been tested on this family. Here we assessed the impact of the pyrethroid insecticide cypermethrin on the life cycle of Enchytraeus crypticus. We developed an original experimental design to collect the data required for the calibration of a DEB-TKTD model for this species. E. crypticus presented a slow initial growth phase that has been successfully simulated with the addition of a size-dependent food limitation for juveniles in the DEB model. The DEB-TKTD model simulations successfully agreed with the data for all endpoints and treatments over time. The highlighted physiological mode of action (pMoA) for cypermethrin was an increase of the growth energy cost. The threshold for effects on survival was estimated at 73.14 mg kg^- 1, and the threshold for effects on energy budget (i.e., sublethal effects) at 19.21 mg kg^- 1. This study demonstrates that DEB-TKTD models can be successfully applied to E. crypticus as a representative soil species, and may improve the ecological risk assessment for terrestrial ecosystems, and our mechanistic understanding of chemical effects on non-target species.

Environmental Pyrethroid Exposure and Cognitive Dysfunction in U.S. Older Adults: The NHANES 2001-2002

Pyrethroid compounds are widely used in household insecticides and agricultural pesticides. Recent studies, however, report that pyrethroid exposures affect neurobehavioral function in animals and may be associated with adverse neurocognitive development in children. This study aimed to examine the association between pyrethroid exposure and cognitive dysfunction in older adults using a well-defined general population. We analyzed data from 336 individuals, aged 60–84 years, who participated in the National Health and Nutrition Examination Survey 2001–2002. We used urinary 3-phenoxybenzoic acid (3-PBA) concentration as a biomarker of pyrethroid exposures and assessed cognitive function with the digit–symbol coding test. The geometric means (±geometric standard errors) of creatinine-uncorrected and corrected urinary 3-PBA were 0.30 (±0.87) μg/L and 0.36 (±0.89) μg/g. After adjusting for sociodemographic factors, higher 3-PBA concentrations (> vs. ≤0.30 μg/g creatinine (median)) were associated with lower scores of cognitive function (−3.83 95% confidence interval: −7.11, −0.54). Significance was persistent after additionally adjusting for physical activity and smoking pack-year (−3.76 95% CI: −7.16, −0.36) and further adjusting for BMI and presence of hypertension and diabetes (−3.82 95% CI: −6.92, −0.71). Our findings suggest that pyrethroid exposure is associated with cognitive dysfunction in older adults.

Mitochondrial dysfunction and oxidative stress in liver of male albino rats after exposing to sub-chronic intoxication of chlorpyrifos, cypermethrin, and imidacloprid

The adverse effects of chlorpyrifos, cypermethrin, and imidacloprid on mitochondrial dysfunction and oxidative stress biomarkers were studied in rat liver. The liver deficiency was also confirmed by histological analysis and gel electrophoresis. Each insecticide was administered orally with five doses per week for 28 days to male albino rats at 1/50 of the LD₅₀ per insecticide. The results demonstrated that the mitochondrial dysfunction was confirmed by a significant decrease in NADH dehydrogenase and ATPase activities. Oxidative stress biomarkers include malondialdehyde (MDA), and protein carbonyl content (PCC) were significantly increased. However, superoxide dismutase (SOD) and glutathione S-transferase (GST) as antioxidant enzymes were significantly decreased in the mitochondria of the rat liver. HPLC analysis showed a significant increase of the 8-hydroxy-2'-deoxyguanosine (8-OH-2DG) as a biomarker of the DNA damage in rat liver. In addition, the residue levels of 0.96 and 0.29 μg/mL serum were found for cypermethrin and imidacloprid, respectively. However, chlorpyrifos not detected using the HPLC analysis. Blue native polyacrylamide gel electrophoresis (BN-PAGE) analysis showed a change in the pattern and sequence of complexions of the electron transport chain in liver mitochondria with treatment by such insecticides. The hepatic histological examination also showed symptoms of abnormalities after exposure to these insecticides.

Pyrethroid based pesticides - chemical and biological aspects

Human and animal welfare primarily depends on the availability of food and surrounding environment. Over a century and half, the quest to identify agents that can enhance food production and protection from vector borne diseases resulted in the identification and use of a variety of pesticides, of which the pyrethroid based ones emerged as the best choice. Pesticides while improved the quality of life, on the other hand caused enormous health risks. Because of their percolation into drinking water and food chain and usage in domestic settings, humans unintentionally get exposed to the pesticides on a daily basis. The health hazards of almost all known pesticides at a variety of doses and exposure times are reported. This review provides a comprehensive summation on the historical, epidemiological, chemical and biological (physiological, biochemical and molecular) aspects of pyrethroid based insecticides. An overview of the available knowledge suggests that the synthetic pyrethroids vary in their chemical and toxic nature and pose health hazards that range from simple nausea to cancers. Despite large number of reports, studies that focused on identifying the health hazards using doses that are equivalent or relevant to human exposure are lacking. It is high time such studies are conducted to provide concrete evidence on the hazards of consuming pesticide contaminated food. Policy decisions to decrease the residual levels of pesticides in agricultural products and also to encourage organic farming is suggested.

Acute Changes in Thyroid Hormone Levels among Thai Pesticide Sprayers

The objective of this study was to investigate the relationship of acute pesticide exposures and acute changes in thyroid hormones among Thai farmers. We recruited 78 farmers, who were scheduled to spray insecticides (chlorpyrifos and/or cypermethrin) or herbicides (paraquat and/or glyphosate). On the day before spraying, farmers collected their first morning void urine and went for blood collection. On the spray day, urine samples were collected at end of the spraying event and they were interviewed with questionnaires. The next morning, the first morning void urine and blood samples were collected. Blood samples were analyzed for thyroid hormones. Urine samples were analyzed for the metabolites of the pesticide sprayed. The results showed that the thyroid hormones, free triiodothyronine (FT3) and total triiodothyronine (T3) were significantly reduced as urinary chlorpyrifos metabolite increased the day after spraying. Total thyroxine (T4) significantly increased as cypermethrin metabolites increased the day after spraying. T4 significantly increased as urinary glyphosate levels increased; however, FT3 and T3 decreased significantly as urinary paraquat levels increased the day after spraying. These findings suggest that acute exposures to the pesticides chlorpyrifos, cypermethrin, paraquat and glyphosate can produce acute effects on the hypothalamic-pituitary-thyroid (HPT) axis, acutely altering thyroid hormone levels.

Co-exposure to deltamethrin and thiacloprid induces cytotoxicity and oxidative stress in human lung cells

Deltamethrin (DEL) and thiacloprid (THIA) are commonly used synthetic insecticides in agriculture either separately or in combination. There is limited information in human cells for the effects of the mixture of DEL + THIA on oxidative stress. Therefore, the present study was designed to examine the effects of the mixture on cell proliferation and oxidative stress in human lung fibroblast cells. Human telomerase reverse transcriptase (hTERT)-expressing human lung fibroblasts, WTHBF-6 cells, were treated with 2.5 + 37.5, 5 + 75, 12.5 + 187.5, and 25 +375 µM concentrations of DEL + THIA for the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and 5 + 75, 12.5 + 187.5, and 25 + 375 µM for lipid peroxidation and reduced glutathione (GSH) assays for 24, 48, and 72 h in the absence and presence of metabolizing fractions of the mammalian liver (S9 mixture). Both the mixture of DEL + THIA and their metabolites significantly reduced cell viability and induced cytotoxicity in WTHBF-6 cells, especially at higher concentrations. The mixture of DEL + THIA significantly decreased GSH levels at the highest concentration for all treatment times and at the highest two concentrations (12.5 + 187.5 and 25 + 375 µM) for 72 h in the presence of S9 mixture. The highest concentration of DEL + THIA mixture caused a significant increase in malondialdehyde (MDA) level at 72 h in the absence of S9 mixture. There were also significant increases in MDA levels at the highest concentration for 48-h and all concentrations of DEL + THIA for 72-h treatment in WTHBF-6 cell cultures with S9. These data showed that the mixture of DEL + THIA and their metabolites can induce cytotoxicity and oxidative stress in human lung fibroblasts.

Effects of ultraviolet photooxidation of cypermethrin on the activities of phosphatases and digestive enzymes, and intestinal histopathology in African catfish, Clarias gariepinus (Burchell, 1822)

The possibility of ultraviolet (UV) photooxidation of cypermethrin generating more toxic intermediates or isomers demands that studies that look at the effects of cypermethrin and UV irradiation under a coexposure scenario be carried out. In this study, juvenile African catfish (Clarias gariepinus) were exposed to 50 µg/L cypermethrin, 100 µg/L cypermethrin, UV, 50 µg/L cypermethrin + UV or 100 µg/L cypermethrin + UV, in a static renewal for 3 weeks. The control fish were maintained in uncontaminated water, and not exposed to UV radiation. After the exposure duration, the fish were killed, and the activities of acid phosphatase, alkaline phosphatase, amylase, protease, and lipase were determined in the liver or intestinal homogenates. Also, the histopathology of some sections of the intestine was performed. The results showed that the activities of the enzymes decreased significantly following exposure to cypermethrin while there was no change in the activities of the enzymes due to UV irradiation alone. The histopathological analyses indicated that exposure to cypermethrin caused alterations in the histoarchitecture of the fish such as severe erosion of the mucosa layer, faded lamina propria, and disintegration of the muscle layer. The exposure of fish to both cypermethrin and UV irradiation caused significant decrease in the activities of the enzymes. This could be an indication that UV irradiation has the tendency to potentiate cypermethrin-induced toxicity in fish.

Nano selenium ameliorates oxidative stress and inflammatory response associated with cypermethrin-induced neurotoxicity in rats

Cypermethrin (CYP), a class II synthetic pyrethroid, is used to control household insects. CYP can cross the blood-brain barrier to exert neurotoxicity through changes in sodium ion channels. Selenium is an essential component of glutathione peroxidise enzyme; in addition, it shows a potential anti-inflammatory property. The present study aimed to investigate the neuroprotective role of Nano-Se on CYP-induced neurotoxicity. Twenty-four adult male Wister rats were randomly divided into three groups: a) control, b) CYP (1mg/kg) administered orally for 21 days, c) CYP (1mg/kg) administered orally for 21 days and Nano-Se (2.5 mg/kg) given once a day three times a week for three weeks). Locomotor activity was assessed using open field test then rats were sacrificed under anaesthesia, and their brains were dissected out and processed for biochemical and histopathological studies. Histological examination of CYP-treated rats demonstrated some degenerative changes; besides, CYP affected rat locomotor activity. CYP-treated rats showed increased levels of malondialdehyde (MDA), TNF-α and IL-1β in addition to the reduction of glutathione (GSH) levels and gamma-Aminobutyric acid (GABA). Nano-Se restored normal behavioural function and significantly attenuated CYP-evoked degenerative changes. Nano-Se increased levels of GABA and glutathione; on the other hand, it significantly prevented the rise in the levels of MDA, TNF-α and IL-1β. Therefore, Nano-Se demonstrated both anti-oxidant and anti-inflammatory potential. Nano-Se may be suggested to be a prospective candidate to ameliorate CYP-induced neurotoxicity.

Haematological changes in rats exposed to insecticidal oils from the leaves of Cassia occidentalis and Euphorbia milii

This study analysed the effect of insecticidal oils obtained from the leaves of Cassia occidentalis and Euphorbia milii on haematological indices in rats. It also evaluated the extent ethyl ether anaesthesia affects the concentration of haematological indices in experimental rats. Oils were extracted from both plants via soxhlet and administered to Wistar rats orally once a week, for 2 weeks. Fifty-six rats were divided into two groups (28 rats each), these were further divided into seven (7) groups of four rats each. The control group (A) received feed and water only, Groups B1, B2, and B3 received 1500 mg/kg, 3000 mg/kg and 5000 mg/kg body weight of C. occidentalis oil extract, respectively, and similarly, groups C1, C2 and C3 received 1500 mg/kg, 3000 mg/kg and 5000 mg/kg body weight of E. milii oil extracts. The first set was sacrificed under mild ethyl ether anaesthesia, while the second set was sacrificed without any anaesthetic agent. Thereafter, whole blood was drawn and analysed for changes in haematological indices. Both oils caused a significant (P < 0.05) decrease in white blood cells (WBC) and platelet counts at 5000 mg/kg body weight relative to the control in both unanaesthetised and anaesthetised rats. In addition, a significant decrease in MCH, MCHC and in Red Blood Cell counts and Packed Cell Volume was also observed in unanaesthetised rats exposed to E. milii oil and C. occidentalis oil respectively at 5000 mg/kg body weight relative to the control. Since insecticides are usually applied at much lower concentrations, the plant oils may be considered safe for use as insecticidal agents.

Prooxidant effects of chronic exposure to deltamethrin in green toad Bufotes viridis

Pesticide-induced oxidative stress, as one of mechanism of toxicity, has been a focus of toxicological research. However, there is a lack of data for certain pesticides-oxidative stress effects especially on terrestrial amphibians. This study evaluates the prooxidative effects of orally administered insecticide deltamethrin (DM) in some tissues of the terrestrial toad Bufotes viridis. Toads were randomly divided and assigned to a control group and a test group that was orally exposed to the pesticide (5 mg/kg of body weight/daily) for 21 days. Animals were euthanized from each group on days 7, 14, and 21, and the liver, leg muscle, ventral skin, and gastrointestinal tissue (GIT) were dissected and used for analysis. From battery of investigated antioxidant components, superoxide dismutase (SOD) was the most differentiate parameter in all examined tissues. For the period of prolonged exposure to pesticide, antioxidative strategy of Bufotes viridis was based on SOD utilization in attempt to maintain the oxidative disbalance at acceptable level. The integrated biomarker response (IBR) as the measure of the overall biochemical response to DM exposure revealed that the group exposed for 21 days had the highest response. Our work has offered valuable data ensuring evidence that toads exposed to deltamethrin developed adaptive reactions that were tissue-specific and that DM-generated systemic toxicity was time-dependent. The present work showed that oxidative stress has significant role in pesticide-induced toxicity and contributes to better understanding of ecotoxicological risk in the terrestrial amphibians exposed to DM.

Current Research on the Safety of Pyrethroids Used as Insecticides

Pyrethroids are synthetic derivatives of natural pyrethrins extracted from Chrysanthemum cinerariaefolium. They are 2250 times more toxic to insects than to vertebrates due to insects' smaller size, lower body temperature and more sensitive sodium channels. In particular, three pyrethroid compounds, namely deltamethrin, permethrin, and alpha-cypermethrin, are commonly used as insecticides and are recommended for in-home insect control because they are considered to be relatively non-toxic to humans in all stages of life. However, recent data show that they are not completely harmless to human health as they may enter the body through skin contact, by inhalation and food or water, and absorption level depending on the type of food. Permethrin seems to have an adverse effect on fertility, the immune system, cardiovascular and hepatic metabolism as well as enzymatic activity. Deltamethrin induces inflammation, nephro- and hepatotoxicity and influences the activity of antioxidant enzymes in tissues. Alpha-cypermethrin may impair immunity and act to increase glucose and lipid levels in blood. The aim of the review is to provide comprehensive information on potential hazards associated to human exposure to deltamethrin, permethrin and alpha-cypermethrin. The results of presented studies prove that the insecticides must be used with great caution.

Urinary Metabolites of Organophosphate and Pyrethroid Pesticides and Neurobehavioral Effects in Chinese Children

Organophosphate (OP) and pyrethroid (PYR) pesticides are widely used in China. However, few studies have investigated the neurobehavioral outcomes of Chinese children exposed to low levels of OP and PYR. We investigated urinary metabolite levels and their association with exposure characteristics and the neurobehavior of children. For all children, biomarker measurements were made in the same interval relative to neurobehavioral testing. We analyzed the morning urine samples of 406 children aged 3-6 years from Nanjing, China. The Kruskal-Wallis and Wilcoxon rank sum tests were used to identify the associations between urinary metabolite levels and exposure characteristics. Multiple linear regression models were used to test the associations between urinary metabolite levels and neurobehavioral test scores after adjusting for covariates (e.g., sex, age, and education expense). The detection of 3,5,6-trichloropyridinol (TCP) and 3-phenoxybenzoic acid (3-PBA) in the urine was positively associated with living areas adjacent to agricultural fields and using indoor mosquito repellent incense. These two metabolites were negatively associated with the soaking time of fruits and vegetables. When treated as dichotomous variables, TCP was significantly associated with arithmetic test scores in adjusted models, and 3-PBA was significantly associated with the scores on the Chinese Binet and arithmetic tests. When treated as a continuous variable, higher urinary 3-PBA levels were significantly associated with lower cancellation test scores. Our findings suggest that exposure to organophosphate and pyrethroid pesticides may have a significant impact on children's working memory and verbal comprehension.

Identifying the metabolic perturbations in earthworm induced by cypermethrin using gas chromatography-mass spectrometry based metabolomics

Globally, cypermethrin is one of the most widely used synthetic pyrethroid for agricultural and domestic purposes. Most part of the pesticides used in the agriculture ends up as residues in the soil, making soil dwelling organisms, especially earthworms more susceptible to pesticide intoxication. Cypermethrin is known to be a neurotoxicant to many model organisms, including mammals and insects, but such type of toxicity evidence is not available for invertebrate systems like earthworms. In the present work, metabolomics based approach was utilized to identify the toxic mechanism of action of cypermethrin on earthworm (Metaphire posthuma) and these were exposed to sub-lethal concentrations of cypermethrin such as 2.5 mg/kg, 5 mg/kg, 10 mg/kg and 20 mg/kg (1/40^th, 1/20^th, 1/10^th and 1/5^th of LC₅₀, respectively) for fourteen days. The results revealed that 22 metabolites (mainly fatty acids, sugars and amino acids) were shown significant responses in the exposed earthworms and these responses are dose dependent. It is proposed that mainly carbohydrate and fatty acids in neural system metabolism was disturbed. Overall, the results provided that metabolomics can be an effective tool to understand the effects of cypermethrin on the metabolic responses of earthworm Metaphire posthuma.

Protective Effect of Ethanolic Extract of Grape Pomace against the Adverse Effects of Cypermethrin on Weanling Female Rats

The adverse effect of cypermethrin on the liver and kidney of weanling female rats and the protective effect of ethanolic extract of grape pomace were investigated in the present study. Weanling female rats were given cypermethrin oral at a dose of 25 mg kg⁻¹ body weight for 28 consecutive days. An additional two Cyp-trated groups received extract at a dose of 100 and 200 mg kg⁻¹ body weight, respectively, throughout the experimental duration. Three groups more served as extract and control groups. Administration of Cyp resulted in a significant increase in serum marker enzymes, for example, aminotransferases (AST and ALT), alkaline phosphatase (ALP), and gamma-glutamyl transferase (GGT), and increases the level of urea nitrogen and creatinine. In contrast, Cyp caused significant decrease in levels of total protein and albumin and caused histopathological alterations in liver and kidneys of female rats. Coadministration of the extract to Cyp-treated female rats restored most of these biochemical parameters to within normal levels especially at high dose of extract. However, extract administration to Cyp-treated rats resulted in overall improvement in liver and kidney damage. This study demonstrated the adverse biohistological effects of Cyp on the liver and kidney of weanling female rats. The grape pomace extract administration prevented the toxic effect of Cyp on the above serum parameters. The present study concludes that grape pomace extract has significant antioxidant and hepatorenal protective activity.

Ameliorative effect of N-acetyl cysteine on alpha-cypermethrin-induced pulmonary toxicity in male rats

Alpha-cypermethrin (α-CYP) is one of the most widely used insecticides. It may become an air pollutant and adversely affect the health. The present study was designed to determine whether treatment with N-acetyl cysteine (NAC), a well-known antioxidant, can be useful for the management of the deleterious effects of α-CYP on lung tissues. For this purpose, thirty two male rats were divided into four different groups (eight rats for each). Group (I) gavaged with corn oil (control group), group (II) gavaged daily with NAC (150 mg kg(-1) body weight), group (III) gavaged with α-CYP (14.5 mg kg(-1) body weight/day, dissolved in corn oil), group (IV) gavaged with NAC then with α-CYP 2 h later for 12 weeks. α-CYP significantly increased serum lactate dehydrogenase (LDH) and pulmonary malondialdehyde (MDA) levels, while decreased the activities of catalase (CAT) and superoxide dismutase (SOD) as well as reduced glutathione (GSH) content in lung. It also provoked higher levels of serum nitric oxide (NO), lung interleukin-1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), hydroxyproline (Hyp) as well as heme oxygenase-1 (HO-1), inducible nitric oxide synthase (iNOS) and nuclear factor-kappa B (NF-К B) gene expression in lung tissues. Histopathological alterations in lung with congestion, cellular infiltration, necrotic changes and thickening of inter-alveolar septa were observed following α-CYP administration. NAC reduced the adverse effects of α-CYP on lung tissues and improved the histological architecture of lung since it showed antioxidant, anti-inflammatory and antifibrotic effects on lung tissues. Our results indicate that NAC exerts a potent protective effect against α-CYP-induced oxidative damage and inflammation in lung tissues.

Effect of repeated oral administration of bifenthrin on lipid peroxidation and anti-oxidant parameters in Wistar rats

The oxidative stress-inducing potential of the pyrethroid insecticide, bifenthrin, was evaluated in rats at 5.8 mg/kg body weight once daily for 20 or 30 days. Bifenthrin treated animals showed significantly increased lipid peroxidation, evidenced by increased blood malondialdehyde levels. Blood glutathione levels and activities of catalase and glutathione peroxidase decreased significantly in the bifenthrin treated animals after both 20 and 30 days of treatment, whereas, the activities of superoxide dismutase and glutathione S-transferase decreased significantly only on the 30th day. In conclusion, bifenthrin has a potential to induce severe oxidative stress in rats exposed to sublethal concentrations.

Long term exposure to cypermethrin induces nigrostriatal dopaminergic neurodegeneration in adult rats: postnatal exposure enhances the susceptibility during adulthood

The study aimed to investigate the effects of cypermethrin on biochemical, histopathological, and motor behavioral indices of the nigrostriatal dopaminergic system in adult rats treated with or without cypermethrin (1/10 adult dose) during postnatal days 5-19. Spontaneous locomotor activity (SLA) and rotarod tests were performed to assess motor behavior. Levels of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the striatum, and tyrosine hydroxylase (TH) immunoreactivity and 4',6-diamidino-2-phenylindole (DAPI)/Fluoro-Jade B staining in the substantia nigra were measured to assess dopaminergic neurodegeneration. Postnatal treated animals did not exhibit significant changes in any measured parameters. The significant reduction in the time of stay on rotarod, spontaneous locomotor activity, dopamine, 3,4-dihydroxyphenylacetic acid, and tyrosine hydroxylase immunoreactivity while an increase in homovanillic acid level and Fluoro-Jade B-positive cells were observed in cypermethrin treated adult rats. These changes were more pronounced in the animals treated with cypermethrin during postnatal days followed by adulthood compared with adulthood alone. The results obtained thus demonstrate that exposure to cypermethrin during adulthood induces dopaminergic neurodegeneration in rats and postnatal exposure enhances the susceptibility of animals to dopaminergic neurodegeneration if rechallenged during adulthood.

Neurobehavioral toxicology of pyrethroid insecticides in adult animals: a critical review

Pyrethroids are pesticides with high selectivity for insects. In order to identify strengths and gaps in the database for pyrethroid neurobehavioral toxicology, we have critically analyzed the data from peer-reviewed literature. This review includes dose-response data that have been recently generated demonstrating consistent findings for low-dose, acute, oral exposure to pyrethroids in small rodents. All pyrethroids tested (i.e., about twenty compounds), regardless of structure, produce a decrease in motor activity in a variety of test protocols. The range of relative potencies varies more than two orders of magnitude, and thresholds for motor activity were found well below doses that produce overt signs of poisoning. Six compounds (allethrin, permethrin, cis-permethrin, deltamethrin, cypermethrin, and fenvalerate) impair schedule-controlled operant responding, seven compounds (pyrethrum, bifenthrin, S-bioallethrin, permethrin, beta-cyfluthrin, cypermethrin, and deltamethrin) decrease grip strength, and two compounds (deltamethrin and alpha-cypermethrin) produce incoordination using the rotarod. In addition, while compounds lacking an alpha-cyano group (e.g., cismethrin, permethrin, bifenthrin) induce an increase in acoustic-evoked startle response amplitude, cyano compounds (e.g., deltamethrin, cypermethrin, cyfluthrin) produce the opposite outcome. Other endpoints (e.g., tremor intensity, sensory response) have been only occasionally explored. A synthesis of the neurobehavioral evidence relating to the action of pyrethroids indicates that some differences in the experimental findings across compounds are also present in the low-effective dose range. For risk assessment purposes, a strategy that takes into account data from an array of neurobehavioral endpoints is needed to capture the heterogeneity of pyrethroid-induced adverse effects and accurately inform policy decisions.

Biochemical effects of chlorpyrifos and deltamethrin on altered antioxidative defense mechanisms and lipid peroxidation in rat liver

Pesticides such as organophosphorus and organochlorine compounds commonly used in agriculture for achieving better quality products are toxic substances and lead to generation of reactive oxygen species (ROS) which have harmful effects on human health. While pyrethroid pesticides are used in preference to organophosphates and organochlorines due to their high effectiveness, low toxicity to non-target organisms and easy biodegradability, they may also produce oxidative stress. Thus, we investigated the effects of chlorpyrifos (CP, an organophosphate) and deltamethrin (DM, a pyrethroid pesticide) treatments at low and high doses on lipid peroxidation (LPO) and antioxidant enzyme activities such as SOD, GSH-Px and CAT in rat liver following 16 weeks exposure. Antioxidative defence mechanisms and lipid peroxidation in rat liver tissues display different responses depending on different pesticide treatments and doses. Biochemical analysis showed that administrations of the chlorpyrifos and deltamethrin cause liver damage. In the present study, we observed that lipid peroxidation levels are higher at high doses than at low doses, but DM caused more pronounced increase than CP. Experimentally, we have also observed that oxidant-antioxidant balance is more affected by deltamethrin treatment than by chlorpyrifos.

Neuropharmacological effects of deltamethrin in rats

This study examined the effect of deltamethrin on some of the neuropharmacological paradigms in a rat brain such as the motor co-ordination test using a rotarod, the pentobarbitone-induced sleeping time and pentylenetetrazole (PTZ)-induced convulsion as well as the gamma aminobutyric acid (GABA) level. Albino Wistar rats were used as the experimental animals. Different neuropharmacological paradigms such as the motor co-ordination by the rotarod, pentobarbitone-induced sleeping time and the PTZ-induced convulsion were examined after administering deltamethrin orally at two doses, 150 mg/kg (LD₅₀) and 15 mg/kg (1/10 LD₅₀). The GABA level in the rat brain was estimated by HPLC after a single oral dose of 150mg/kg deltamethrin. Deltamethrin significantly reduced the motor coordination, decreased the onset time and increased the sleeping time duration induced by pentobarbitone. In addition, it also decreased the onset time and increased the duration of convulsions induced by PTZ at 150 mg/kg (LD₅₀) and 15 mg/kg (1/10 LD₅₀), respectively. Further deltamethrin administration decreased the GABA levels in the cerebellum as well as in the whole brain (except the cerebellum) significantly at the LD₅₀ dose level. There was some correlation between the effect of deltamethrin on the central GABA levels and its neuropharmacological effects.