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PubMed1996

Comparison of different insecticides and fabrics for anti-mosquito bednets and curtains.

Various formulations of six insecticides (a carbamate and five pyrethroids), were impregnated into bednets and curtains made from cotton, polyester, polyethylene or polypropylene fabric. For bioassays of insecticidal efficacy, female Anopheles gambiae mosquitoes were made to walk on the fabrics for 3 min and mortality was scored after 24 h. The main concentrations tested were: bendiocarb 400 mg/m2, cyfluthrin 30-50 mg/m2, deltamethrin 15-25 mg/m2, etofenprox 200 mg/m2, lambda-cyhalothrin 5-15 mg/m2 and permethrin 200-500 mg/m2. Field trials in Tanzania used experimental huts (fitted with verandah traps) entered by wild free-flying Anopheles gambiae, An.funestus and Culex quinquefasciatus mosquitoes. Results of testing the impregnated fabrics in experimental huts showed better personal protection provided by bednets than by curtains. Permethrin cis:trans isomer ratios 25:75 and 40:60 were equally effective, and the permethrin rate of 200 mg/m2 performed as well as 500 mg/m2. Bioassay data emphasized the prolonged insecticidal efficacy of lambda-cyhalothrin deposits, except on polyethylene netting. Most of the impregnated nets (including the 'Olyset' net with permethrin incorporated during manufacture of the polyethylene fibre) and an untreated intact net performed well in preventing both Anopheles and Culex mosquitoes from feeding on people using them overnight in the experimental huts. Anopheles showed high mortality rates in response to pyrethroid-treated nets, but only bendiocarb treated curtains killed many Culex. Holed nets treated with either cyfluthrin (5 EW formulation applied at the rate of 50 mg a.i./m2) or lambda-cyhalothrin (2.5 CS formulation at 10 mg a.i./m2) performed well after 15 months of domestic use. Treatment with deltamethrin SC or lambda-cyhalothrin CS at the very low rate of 3 mg/m2 gave good results, including after washing and re-treatment.

Animals↗

PubMed1997

Activities of an Environmental Analysis Van in the German Federal State Schleswig-Holstein.

A cooperation was started between the Union of Physicians of Schleswig-Holstein (Bad Segeberg, Germany) and an environmental engineer in 1992. A mobile unit for environmental analysis was set up, the Environmental analysis Van (EAV) or mobile umweltambulanz. Inspection of sites and collection of air and dust/material samples for analysis of xenobiotics were performed on request. The results of this cooperation were evaluated to show which sources of indoor pollutants could be particularly relevant to human health impairment. During a 30-month period form July 1993 to December 1995, 1793 site inspections wer conducted. Xenobiotic analysis and subsequent advising was performed in 1318 cases; enhanced concentrations of one or more toxic substances (mainly biocides such a pentachlorophenol, permethrin, and/or hexachlorocyclohexane) were found in 71% of the sites analyzed. Formaldehyde, volatile organic compounds, and contamination by molds were also documented. A follow-up was done on 80 clients of the Environmental Analysis Van, which had detected elevated concentrations of permethrin because of pyrethroid-treated carpeting. The effect of removing all contaminated carpeting on health improvement in comparison with nonremoval was statistically significant (p<0.0001). Pyrethroid-treated carpeting, which was already 5, 7 and 10 years old, revealed permethrin concentrations of 115, 100, and 150 mg/kg dust. This result indicates that indoor contamination of permethrin is highly persistent and may be the cause of adverse health effects.

Air Pollution, Indoor↗

PubMed2001

Effect of insecticides used in corn, sorghum, and alfalfa on the predator Orius insidiosus (Hemiptera: Anthocoridae).

Orius insidoisus (Say) is an important predator in corn, sorghum, and alfalfa. Foliar insecticides commonly used on corn (permethrin, bifenthrin, and fipronil); sorghum (chlorpyrifos, carbofuran, dimethoate, and cyfluthrin); and both crops (A-cyhalothrin and ethyl parathion) were evaluated in 1998 and 1999 for their residual effects on O. insidiosus by caging adults on treated plants at several time intervals: at application (day 0) and 2, 3, and 6 d after application. In addition, imidacloprid, fipronil, and thiamethoxam used as seed treatments on corn and sorghum were tested for their effects on O. insidiosus by caging adults on plants in the presence and absence of greenbugs, Schizaphis graminum (Rondani). Finally, six of the same insecticides that also are used on alfalfa were evaluated in the field for their effects on O. insidiosus and other insects. On day 0, ethyl parathion. bifenthrin, and [lambda]-cyhalothrin on corn caused significantly higher mortality to O. insidiosus than permethrin and fipronil. Ethyl parathion and carbofuran on sorghum caused significantly higher mortality than chlorpyrifos, dimethoate, and A-cyhalothrin, which differed significantly from the control. Mortality with cyfluthrin did not differ significantly from that in the control. Insecticides had no significant effects on O. insidiosus 3 and 6 d after application in 1998 with the exception of permethrin on day 3. Similar patterns of mortality were observed in 1999 experiments. No significant differences in mortality of adults occurred with fipronil and thiamethoxam in the presence and absence of greenbugs. Imidachloprid caused significantly higher mortality to O. insidiosus adults than thiamethoxam or fipronil in some instances when greenbugs were not supplied as food. In alfalfa, the insecticides caused significant mortality to most of the insects evaluated. Ethyl parathion, permethrin, chlorpyrifos, and cyfluthrin caused significantly higher mortality to O. insidiosus than carbofuran and A-cyhalothrin, which differed significantly from the control in 1998. In 1999, all treatments significantly reduced O. insidiosus numbers and did not differ significantly from each other.

Animals↗

PubMed1999

[Resistance of malaria vectors to pyrethrins used for impregnating mosquito nets in Benin, West Africa].

Impregnated bednets can be considered a major tool for reducing Anopheles bites, malaria morbidity and overall mortality. The resistance of Anopheles gambiae to pyrethroids used to impregnate bednets and curtains has already been noted in the urban area of Cotonou in Benin (18, 21). In this study, we wished to find out if the resistance observed in Cotonou is localized only in this town or is already extensive throughout Benin. In this case, such resistance would be a handicap to the promotion of impregnated bednets in Benin. The study was carried out in 15 localities throughout the different ecological zones of Benin. The study has also taken into account environmental factors favouring the emergence of resistance. We did susceptibility tests with WHO test kits for adult mosquitoes using impregnated papers. The papers were impregnated with permethrin 0.25%, deltamethrin 0.025% and lambdacyhalothrin 0.1%. We also tested DDT 4% to find out if there was a cross resistance between DDT and the pyrethroids. Two mosquito species were tested: An. gambiae and An melas. In northern Benin, where farmers use insecticides against cotton pests, vectors are susceptible to deltamethrin and lambdacyhalothrin and resistant to permethrin. In the south, An. gambiae is resistant to deltamethrin and permethrin. This resistance is high in the urban zone of Cotonou, in the coastal and lagoon areas and at Kraké, a frontier viliage with Nigeria. The resistance observed in southern Benin is confirmed by the lengthening of the knock-down time of mosquitoes which were exposed for 1 hour to insecticide in impregnated WHO test tubes, and by a reduction of permethrin and deltamethrin remanence effect.

Animals↗

PubMed2000

Correlation between toxic natures of pyrethroid and behavioral response of desert locusts.

Optomotor normal visual response of the locust Schistocerca gregaria was compared when injected (between 1st and 2nd thoracic segments) with 10, 5, 2.5 and 1.25 microg/g body weight doses of Permethrin after different intervals of time (just after injection, 10 and 20 minutes). LD50 value for Permethrin was calculated to be 3.0 microg/g. Results are analyzed statistically by t. test and ANOVA technique. It was noticed that there was a significant decrease of vision (P<0.005, Table II) in treated locusts and at the same time Permethrine effect is significantly time related (P<0.05, ANOVA, table III). Correlation between increasing age, weight and increasing toxicity has also been established. The inhibition of neural enzyme Cholinesterase with Permethrin and as a result more accumulation of acetylcholine at nerve junctions and less passage of the transmission of impulses thus less response from the locusts has also been explored and discussed.

Journal Article↗

PubMed2001

Laboratory evaluation of fipronil, a phenylpyrazole insecticide, against adult Anopheles (Diptera: Culicidae) and investigation of its possible cross-resistance with dieldrin in Anopheles stephensi.

Adult mosquitoes from two strains of Anopheles gambiae and from three strains of Anopheles stephensi were exposed to 0.25% fipronil-treated papers in WHO test kits or to 500 mg fipronil m-2 impregnated mosquito netting in bioassay spheres. For comparison, tests were also carried out with the pyrethroid permethrin, using the same methods and doses, and on papers treated with 0.4 and 4% of the cyclodiene insecticide dieldrin. Compared with the same doses of permethrin, fipronil showed less and delayed activity. Two of the An stephensi strains were resistant to fipronil and dieldrin. To investigate whether this was due to a resistance mechanism in the An stephensi strains acting against both insecticides, the most fipronil- and dieldrin-tolerant strain was further selected in two separate lines with one of the insecticides, followed by tests with the insecticide that the line had not been selected with. This indicated a concomitant rise of resistance to dieldrin in the fipronil-selected line and vice versa. Repeated back-crossing of the two lines with a susceptible strain and re-selection with either dieldrin or fipronil gave evidence for the involvement of a single resistance mechanisms to both insecticides. Permethrin resistance in both lines declined with selection for dieldrin or fipronil and confirms the absence of cross-resistance between fipronil and pyrethroids.

Animals↗

PubMed2005

Can agrobiont spiders (Araneae) avoid a surface with pesticide residues?

Integrated pest management includes the use of various pesticides that can have a detrimental effect on spiders. A pesticide can express its activity directly or via residues. Most of the attention paid to the impact of pesticides on spiders has investigated the effects of direct exposure. Our aim in this study was to investigate the residual activity (repellency and toxicity) of selected pesticides on six principal species of spider occurring in an apple orchard. Four of these species (Clubiona spp., Pardosa spp., Philodromus spp., Xysticus spp.) are hunting spiders, and two species (Dictyna spp., Theridion spp.) are web-building. We were interested to see whether these spiders could avoid a surface with residues and to examine their susceptibilities to fresh and 1-day-old residues. For this purpose we conducted laboratory experiments using three types of pesticide, an organophosphate, phosalone (Zolone), a pyrethroid, permethrin (Ambush) and Bacillus thuringiensis (Bt; Novodor), which were applied to paper discs or branches. Spiders could choose to stay on any treated paper/branch within a dish. Except for Theridion spp., all species were repelled by fresh residues but not by 1-day-old residues. Clubiona spp., Dictyna spp., Pardosa spp. and Xysticus spp were repelled by phosalone and permethrin residues only, whereas Philodromus spp. specimens were repelled also by Bt residues. Theridion spp. avoided contact with residues by making a web on any available branch. Regarding toxicity, neither fresh nor 1-day-old residues of phosalone or Bt caused significant mortality to any spider species. In contrast, both fresh and 1-day-old residues of permethrin caused significant mortality to all species except for Theridion spp. In conclusion, spiders can recognise and avoid only fresh residues, although older residues might still be toxic to them.

Animals↗

PubMed2007

Lack of cross-resistance to indoxacarb in insecticide-resistant Spodoptera frugiperda (Lepidoptera: Noctuidae) and Plutella xylostella (Lepidoptera: Yponomeutidae).

Two field strains of the fall armyworm, Spodoptera frugiperda (JE Smith), collected from corn in north Florida showed high resistance to carbaryl (626- and 1159-fold) and moderate resistance to parathion-methyl (30- and 39-fold) as compared with a laboratory susceptible strain. A field strain of the diamondback moth, Plutella xylostella (L.) collected from cabbage in north Florida and selected for 20 generations with permethrin showed high resistance to permethrin (987-fold) as compared with a susceptible strain. However, in all instances, no cross-resistance to indoxacarb, a novel oxidiazine insecticide, was observed in these two species. Biochemical studies revealed that, in S. frugiperda, activities of detoxification enzymes (microsomal oxidase, glutathione S-transferase and general esterase) were significantly higher in the field strains than in the susceptible strain, indicating that these detoxification enzymes were not actively involved in the resistance to indoxacarb. The lack of cross-resistance between indoxacarb and permethrin in P. xylostella further supports the notion that the mode of action of these insecticides on the insect sodium channel is different.

Animals↗

PubMed2002

Long-term effectiveness of grain protectants and structural treatments against Liposcelis decolor (Pearman) (Psocoptera: Liposcelididae), a pest of stored products.

Numerous strains of the psocid pest, Liposcelis decolor (Pearman) were collected from farms and central storages and interbred to form three representative strains from three major grain-growing states of Australia: Queensland, South Australia and New South Wales. These were tested against the grain protectants and structural treatments currently registered for use in Australia. Recently, L decolor has become an important pest of stored grain in Australia, particularly in the eastern and southern parts. There is no published information available on management of this pest and the current pest-management strategy, based predominantly on phosphine fumigation, has failed to control infestations of this pest in numerous grain storages in Australia. Alternative methods of control such as use of contact insecticides were explored in the present work to supplement phosphine fumigation to manage this new pest. From eight grain protectants tested as admixtures, only chlorpyrifos-methyl, bioresmethrin plus piperonyl butoxide, and fenitrothion were found to provide long term (3-9 months) protection against all three strains of L decolor. Chlorpyrifos-methyl gave the best protection, providing a minimum of 7.5 to a maximum of 9 months protection, depending on the strains tested. Three structural treatments, azamethiphos, azamethiphos plus carbaryl and permethrin provided long-term control (8-9 months) of all three strains of L decolor on galvanised steel surfaces, with permethrin delivering 9 months protection against all strains. However, all of these treatments failed to provide long-term control of any strains on concrete surfaces. We conclude that chlorpyrifos-methyl as a grain admixture can be incorporated into fumigation strategies to optimise the control of L decolor infestations. Structural treatments, such as permethrin can be used to support a fumigation strategy in storages made of galvanised steel.

Animals↗

PubMed2006

A new shampoo based on neem (Azadirachta indica) is highly effective against head lice in vitro.

Because topical compounds based on insecticidal chemicals are the mainstay of head lice treatment, but resistance is increasing, alternatives, such as herbs and oils are being sold to treat head lice. To test a commercial shampoo based on seed extract of Azadirachta indica (neem tree) for its in vitro effect, head lice (n=17) were collected from school children in Australia and immersed in Wash-Away Louse shampoo (Alpha-Biocare GmbH, Germany). Vitality was evaluated for more than 3 h by examination under a dissecting microscope. Positive and negative controls were a commercially available head lice treatment containing permethrin 1% (n=19) and no treatment (n=14). All lice treated with the neem shampoo did not show any vital signs from the initial examination after immersion at 5-30 min; after 3 h, only a single louse showed minor signs of life, indicated by gut movements, a mortality of 94%. In the permethrin group, mortality was 20% at 5 min, 50% at 15 min, and 74% after 3 h. All 14 head lice of the negative control group survived during the observation period. Our data show that Wash-Away Louse is highly effective in vitro against head lice. The neem shampoo was more effective than the permethrin-based product. We speculate that complex plant-based compounds will replace the well-defined chemical pediculicides if resistance to the commonly used products further increases.

Animals↗

PubMed1984

Hydrolysis of pyrethroid insecticides by soluble mouse brain esterases.

trans-Permethrin, a pyrethroid insecticide, was hydrolyzed by one or more carboxylesterases located in the soluble fraction of mouse brain homogenates. The apparent affinity of this activity for trans-permethrin was greater than that reported for mouse hepatic carboxylesterase activity, but the apparent maximum velocity was considerably lower than that of the hepatic activity. Soluble brain esterases also hydrolyzed several other pyrethroid esters with a substrate specificity different from that of the hepatic esterases. In particular, alpha-cyano-3-phenoxybenzyl esters of noncyclopropane acids (e.g., fenvalerate and fluvalinate) were hydrolyzed by brain esterases at rates equal to or greater than that measured for trans-permethrin. These results suggest that hydrolysis in the brain may contribute to the detoxication of some pyrethroids in mammals.

Animals↗

PubMed1986

Clinical evaluation of insecticide-impregnated tags attached to chains and used as backrubbers for control of Haematobia irritans.

Fenvalerate and permethrin insecticide tags were tested for horn fly (Haemotobia irritans) control. Three fenvalerate-impregnated ear tags attached to a chain and used as a backrubber controlled horn flies on steers for 8 weeks, and six tags provided 18 weeks control. Ten tags impregnated with permethrin failed to control horn flies. The choice of insecticide in tags attached to chains and used as backrubbers for horn fly control may be important, as fenvalerate and permethrin (both pyrethroids) varied in effectiveness.

Animals↗

PubMed2006

A new clothing impregnation method for personal protection against ticks and biting insects.

The efficacy and residual activity of a factory-based, permethrin-impregnated military battle dress uniform (BDU) using a new polymer-coating technique has been evaluated by laboratory and field testing during deployment to Afghanistan and compared with two commercially available, widely used dipping methods. Residual permethrin concentrations and remaining contact toxicities on treated fabrics before laundering, after up to 100 launderings as well as after being worn-out during deployment were tested against Aedes aegypti (L.) and Ixodes ricinus (L.). The residual amount of permethrin was considerably higher with the polymer-coating technique with 280mg/m(2) remaining after 100 launderings. Polymer-coated BDUs collected for disposal after being worn-out during military deployment showed equivalent or better residual knockdown efficacy against test arthropods when compared with the results obtained with the US Army IDA (Illinois Department of Agriculture)-Kit after 50 launderings, which represent the recommended baseline for re-impregantion or disposal of the impregnated fabric. BDUs impregnated by the polymer-coating method were found to be effective throughout the lifetime of the uniform, ensuring protection of soldiers in the field from arthropod vectors, while simultaneously decreasing logistical constraints and occupational health threats.

Aedes↗

PubMed2005

Additional repression of activity-dependent c-fos and BDNF mRNA expression by lipophilic compounds accompanying a decrease in Ca2+ influx into neurons.

Recently, it has been proposed that a variety of environmental disruptors (EDs) disturb the neonatal development of the brain in mammals because of their lipophilic characteristics. Therefore, the synergism of these lipophilic compounds is important when evaluating the risk from EDs. In mouse cerebellar granule cells (CGCs), the activity-dependent expression of the brain-derived neurotrophic factor (BDNF) gene is activated through an influx of calcium ions (Ca2+) into CGCs caused by membrane depolarization, which is involved in the activity-dependent development of not only the cerebellum but also other regions of the brain after birth. In our previous study, we reported that permethrin and some other pyrethroid insecticides, which are suspected of being EDs, repressed the induction of c-fos and BDNF mRNA expression, accompanying a reduction of Ca2+ influx at doses non-toxic to CGCs. In the present study, we investigated whether other lipophilic compounds influenced the Ca2+ signal-induced expression of both genes as permethrin did and, if so, whether these effects were synergistic or additional. Pretreatment with p,p'-DDT, diethylstilbestrol (DES) or bisphenol A dose-dependently repressed the induction of both genes as well as the increase in the uptake of Ca2+ by CGCs. Simultaneous exposure of CGCs with permethrin, p,p'-DDT and DES, in addition, revealed an additional repression on the induction of the genes and the Ca2+ uptake. These results suggest that toxic effects of EDs might, at least additionally, occur in the brain even if the concentration of each compound is lower than the effective dose for humans.

Animals↗

PubMed2005

Pyrethroid pesticide-induced alterations in dopamine transporter function.

Parkinson's disease (PD) is a progressive neurodegenerative disease affecting the nigrostriatal dopaminergic pathway. Several epidemiological studies have demonstrated an association between pesticide exposure and the incidence of PD. Studies from our laboratory and others have demonstrated that certain pesticides increase levels of the dopamine transporter (DAT), an integral component of dopaminergic neurotransmission and a gateway for dopaminergic neurotoxins. Here, we report that repeated exposure (3 injections over 2 weeks) of mice to two commonly used pyrethroid pesticides, deltamethrin (3 mg/kg) and permethrin (0.8 mg/kg), increases DAT-mediated dopamine uptake by 31 and 28%, respectively. Using cells stably expressing DAT, we determined that exposure (10 min) to deltamethrin and permethrin (1 nM-100 microM) had no effect on DAT-mediated dopamine uptake. Extending exposures to both pesticides for 30 min (10 microM) or 24 h (1, 5, and 10 microM) resulted in significant decrease in dopamine uptake. This reduction was not the result of competitive inhibition, loss of DAT protein, or cytotoxicity. However, there was an increase in DNA fragmentation, an index of apoptosis, in cells exhibiting reduced uptake at 30 min and 24 h. These data suggest that up-regulation of DAT by in vivo pyrethroid exposure is an indirect effect and that longer-term exposure of cells results in apoptosis. Since DAT can greatly affect the vulnerability of dopamine neurons to neurotoxicants, up-regulation of DAT by deltamethrin and permethrin may increase the susceptibility of dopamine neurons to toxic insult, which may provide insight into the association between pesticide exposure and PD.

Animals↗

PubMed2006

Dopaminergic system modulation, behavioral changes, and oxidative stress after neonatal administration of pyrethroids.

Pyrethroids are a class of insecticides involved in different neurological disorders. They cross the blood-brain barrier and exert their effect on dopaminergic system, contributing to the burden of oxidative stress in Parkinson's disease through several pathways. The aim of the present study was to evaluate the effect of neonatal exposition to permethrin and cypermethrin (1/10 of DL(50)) in rats from the eighth to the fifteenth day of life. Open-field studies showed increased spontaneous locomotor activity in the groups treated with permethrin and the one treated with cypermethrin, while a higher number of center entries and time spent in the center was observed for the cypermethrin-treated group. Lower dopamine and higher homovanillic acid levels were measured in the striatum from both treated groups. A reduction of blood glutathione peroxidase content was measured, while no change in blood superoxide dismutase was observed. Carbonyl group formation increased in striatum, but not in erythrocytes. Lipid peroxidation occurred in erythrocytes, but not in striatum. No changes in fluidity at different depths of plasma membrane were measured in striatum or erythrocytes. The activation of monocyte NADPH oxidase by phorbol esters (PMA) shows that superoxide anion production was reduced in the pyrethroid-treated groups compared to the control group. Our studies suggest that neonatal exposition to permethrin or cypermethrin induces long-lasting effects after developmental exposure giving changes in open-field behaviors, striatal monoamine level, and increased oxidative stress. Although the action of pyrethroids on various target cells is different, a preferential interaction with the extracellular side of plasma membrane proteins can be observed.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2005

Efficacy of a combination of imidacloprid 10%/permethrin 50% versus fipronil 10%/(S)-methoprene 12%, against ticks in naturally infected dogs.

Preventing tick bites is a fundamental step towards reducing the impact of tick-borne protozoal, bacterial and viral diseases (TBDs) in humans and animals. The aim of this study was to evaluate the efficacy of a combination of imidacloprid 10%/permethrin 50% and of fipronil 10%/S-methoprene 12% against ticks in naturally infected dogs and to assess methodological parameters to calculate drug efficacy on tick immature stages. From July to August 2004, 45 privately owned dogs of various sexes, ages, breeds, coat length and habits were enrolled in a trial carried out in an area (radius approximately 50km) in Southern Italy. Three homogeneous groups (both for dog population and tick population) were formed: 15 dogs treated with imidacloprid 10% and permethrin 50% spot-on (group A), 15 dogs treated with fipronil 10% and methoprene 12% spot-on (group B) and 15 untreated dogs (group C). The dogs in each group were then sub-grouped according to their age and weight. Two different treatments were administered (time 0 and +28 days) to groups A and B, and the dogs were checked weekly for tick infestation until day +56 post-treatment (p.t.). Twenty-four areas distributed on the whole body surface were examined for ticks at each follow-up, while only at time 0 and at day +56 p.t., ticks were collected from the dogs and identified. For the immature stages a semi-quantitative method was adopted and the load of immature stages was evaluated and grouped into four classes up to day +56 p.t. when the mean number of immature ticks (MIT) for each infection class was evaluated. All the adult ticks collected were identified as brown dog ticks (Rhipicephalus sanguineus). Immature stages were first compared at day +28 p.t.. The efficacy of both products used in groups A and B on adult ticks was high and generally very similar. Conversely, the efficacy of imidacloprid 10% and permethrin 50% against immatures was higher than that of fipronil 10% and methoprene 12% throughout the observation period with statistically significant differences (p<0.05) at day +28 p.t. (i.e. group A=98.52%, group B=72.40%). On the whole, in analysing the efficacy of both products against adult plus immature ticks, it was found that the combination of imidacloprid 10% and permethrin 50% was more effective than fipronil 10% and methoprene 12%, with the differences being statistically significant at day +28 p.t. (group A=98.43%, group B=77.56%).

Animals↗

PubMed2002

Selective effects of insecticides on nigrostriatal dopaminergic nerve pathways.

A degeneration of the nigrostriatal pathway is a primary component of Parkinson's disease (PD), and we have investigated the actions of insecticides on this pathway. For in vivo exposures, C57BL/6 mice were treated three times over a 2-week period with heptachlor, the pyrethroids deltamethrin and permethrin, or chlorpyrifos. One day after the last treatment, we observed that heptachlor and the pyrethroids increased maximal [3H]dopamine uptake in striatal synaptosomes from treated mice, with dose-dependent changes in Vmax displaying a bell-shaped curve. Western blot analysis confirmed increased levels of dopamine transporter (DAT) protein in the striatum of mice treated with heptachlor and permethrin. In contrast, we observed a small, but statistically significant decrease in dopamine uptake by 100 mg/kg chlorpyrifos. For heptachlor, doses that upregulated DAT expression had little or no effect on serotonin transport. Permethrin did cause an upregulation of serotonin transport, but required a 30-fold greater dose than that effective on dopamine uptake. Other evidence of specificity was found in transmitter release assays, where heptachlor and deltamethrin released dopamine from striatal terminals with greater potency than other transmitter types. These findings confirm that insecticides possess specificity for effects on striatal dopaminergic neurotransmission.

Animals↗