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1.
The reactivation of the rat brain muscarinic acetylcholine receptor (mACh-R) binding with dimercaptosuccinic acid (DMSA) after in vitro and in vivo inhibition by mercuric chloride (HgCl2) and methylmercuric chloride (MeHg) was investigated. Receptor binding was estimated by the potent and specific antagonist l-[3H]quinuclidinyl benzilate ([3H]QNB). Rat brain synaptosomal membranes were exposed to HgCl2 and MeHg. At 1 × 10?4M. HgCl2 caused complete inhibition of the [3H]QNB binding. The inhibition of [3H]QNB binding by HgCl2 was still higher than 50% at 1 × 10?8M. MeHg caused less inhibition of [3H]QNB binding than HgCl2. The inhibited receptors showed a significant degree of reactivation when treated with DMSA. The recovery was almost complete after MeHg inhibition or with the lower HgCl2 concentrations. Generally, the reactivation was dependent on the concentration of DMSA. When rats injected with either early or delayed doses of DMSA following administration with five consecutive daily doses (8 mg/kg body wt, Gavage method) of MeHg or HgCl2, the inhibition of [3H]QNB binding was less than untreated ones. The early treatment with DMSA decreased the inhibition of [3H]QNB binding due to MeHg or HgCl2 intoxication. However, DMSA was more effective in reducing HgCl2 inhibition than MeHg either in vitro or in vivo treatment. The ability of DMSA to reactivate the mACh-R after inhibition with the mercurials emphasizes the involvement of essential sulfhydryl groups in [3H]QNB binding sites, and also shows that these sulfhydryl groups are the primary target for the MeHg and HgCl2 inhibition of the rat brain muscarinic receptors.  相似文献   

2.
[3H]Flunitrazepam ([3H]Flu) was used to identify benzodiazepine binding sites in house fly thorax muscle membranes using a filter assay. [3H]Flu bound to a finite number of sites in a concentration- and time-dependent manner, reaching equilibrium in 10 min. Scatchard plots of the binding indicated a high-affinity site at 0.2 pmol/mg protein (Kd 24.3 nM) and a low-affinity site at 8.2 pmol/mg protein (Kd994nM). Binding of [3H]Flu to the high-affinity binding site was inhibited by several benzodiazepine analogs, with Flu, diazepam, and Ro 5-4864 being more potent than β-CCE, Ro 5-3027, and Ro 5-2180. Clonazepam was least potent in inhibiting [3H]Flu binding. Thus, the drug specificity of these insect muscle benzodiazepine binding sites was quite different from both the mammalian central and peripheral benzodiazepine receptor sites, though closer to the peripheral ones. GABA (γ-aminobutyric acid) and its agonists enhanced the specific binding of [3H]Flu in a dose-dependent manner, and this effect was inhibited with the GABA antagonist bicuculline. The effect was biphasic since at high GABA concentrations this stimulation was reduced. The data suggest that house fly muscles have benzodiazepine receptors, which are coupled allosterically to GABA receptors, analogous to the GABA/benzodiazepine receptors of vertebrates, but with some differences in their drug specificities.  相似文献   

3.
A muscarinic acetylcholine receptor (mAChR) has been demonstrated and partially characterized in larvae of the cattle tick Boophilus microplus. Its properties are compared with mAChR from an epithelial cell line from the dipteran insect Chironomus tentans. Competition studies with cholinergic ligands of different specificity revealed the muscarinic nature of the cholinergic receptors investigated in both species. In homogenates from tick larvae, specific binding sites for [3H]quinuclidinyl benzilate (QNB) with high affinity (1·2±(0·13) nM ; Bmax 22·5 pmol mg protein−1) were detected that do not bind nicotinic compounds specifically. The estimated IC50 values for nicotine, imidacloprid and α-bungarotoxin were all in the mM range. Additionally, with tick larvae, high-affinity nicotinic binding sites were detected with [3H]nicotine which could be displaced by high concentrations of imidacloprid or QNB. The estimated IC50 values for nicotine, α-bungarotoxin, imidacloprid and QNB were 43(±8) nM , 0·8(±0·2) μM , 2·8(±0·6) μM and 78(±1·9) μM , respectively. With homogenates of the non-neuronal insect cell line from C. tentans, only high-affinity binding sites for [3H]QNB were found. Muscarinic antagonists selectively displaced [3H]quinuclidinyl benzilate (QNB) binding to tick larvae homogenates. The mAChR of B. microplus preferred pirenzepine (IC50 2·13(±1·02) μM ) among different subtype-specific mAChR antagonists (4-DAMP had IC50 49·9(±9·13) μM and methoctramine had IC50 121(±14·2) μM ) indicating a type of binding site similar to the vertebrate M1 mAChR subtype. The tick muscarinic receptor seems to be a G-protein-coupled receptor, as concluded from the 4·8-fold reduction in receptor affinity for binding of the muscarinic agonist oxotremorine M upon treatment with the non-hydrolysable GTP-analogue γ-S-GTP. Binding data for the agonists oxotremorine M (IC50 71·3(±19·6) μM ) and carbachol (IC50 253(±87·1) μM ) parallel the biological efficacy of these compounds, in that, while oxotremorine M showed some activity against ticks, carbachol was ineffective.  相似文献   

4.
Monoterpenoids and their derivatives from plant essential oils showed good insecticidal activities in previous studies, but the mechanisms of their action as natural insecticides are not known yet. In the present work, we evaluated the pharmacological action of five monoterpenoids (α-terpineol, carvacrol, linalool, pulegone, and thymol) on native insect GABA receptors from house flies and American cockroaches using radiotracer methods. In the [3H]-TBOB binding assay, carvacrol, pulegone, and thymol all enhanced the [3H]-TBOB binding to membrane preparation of house fly heads with EC50 values of 48 μM, 432 μM, and 6 mM, respectively. Moreover, these three monoterpenoids at concentrations of 500 μM and 1 mM also significantly increased the 36Cl− uptake induced by GABA in membrane microsacs prepared from American cockroach ventral nerve cords. These results revealed that carvacrol, pulegone, and thymol are all positive allosteric modulators at insect GABA receptors. The other two monoterpenoids that were tested, α-terpineol and linalool, showed little or no effect in both the [3H]-TBOB binding and 36Cl− uptake assays.  相似文献   

5.
A series of known agonists of the mammalian muscarinic receptor were prepared and evaluated for their insecticidal potential. It was discovered that pests such as Nilaparvata lugens (brown planthopper), Nephotettix cincticeps (green leafhopper), Tetranychus urticae (two-spotted spider mite) and Aphis gossypii (cotton aphid) were particularly sensitive to most of these compounds. Several analogs proved to be extremely active, surpassing commercial standards in some of the laboratory bioassays. These compounds exhibited a range of potencies for the insect (Musca) muscarinic receptor. Addition of GTP significantly reduced the affinity of the most potent analog for the Musca mAChR, indicating the compound functions as an agonist in insect tissue. Regression analysis indicated that significant relationships exist between displacement of [3H]QNB at the Musca muscarinic receptor and whole organism toxicity to three insect and one mite species. The results suggested that the insect muscarinic receptor represents a viable target site for insecticidal action. © 1997 SCI.  相似文献   

6.
Repeated exposures to anti-cholinesterase compounds induce profound enzyme inhibition and consequent neurotransmitter perturbations. When the result of exposure is an accumulation of neurotransmitter, as it is in the case of exposure to soman, target receptors may respond by compensating for the imbalance by regulating either their number or binding affinity. Recovery of function may further include alterations in receptor systems not themselves a direct target of the toxic compound. Rats were injected with soman (50 μg/kg, sc) three times weekly for 4 weeks and decapitated at intervals ranging from 1 hr to 6 days after the final injection. Synaptic membranes were prepared from hippocampus (HIP), striatum (STR), and cortex (COR) and kinetics of muscarinic cholinergic and GABAergic binding were assessed using [3H]QNB and [3H]muscimol, respectively, as ligands. Soman induced large and persistent decreases in the number of muscarinic receptors in HIP and COR with the surviving receptors being of higher affinity. The number of high affinity GABA receptors decreased in all three regions but returned to near baseline within 3 days after the final soman exposure. These effects are due either to a direct action of soman on the receptors, or a diaschitic response of the receptors to cholinergic excess. Muscarinic cholinergic receptors exhibit a persistent down regulation, and GABA receptors a transient response, to soman administration.  相似文献   

7.
The mode of action of DDT and pyrethroids was investigated in the house fly, Musca domestica L, using drug:receptor binding techniques. Both in vivo and in vitro binding studies demonstrated the existence of membrane receptors which bind specifically to [14C]DDT and [14C]cis-permethrin. The receptors show properties to be expected of a critical target site of these insecticides. These include negative temperature correlation with binding, relatively nonsensitivity to DDE, and sensitivity to Ca2+. The receptor sites are readily saturated at 45–90 nM [14C]DDT and have an apparent disassociation constant (Kd) of 12.2 nM. The maximum number of binding sites was estimated to be 17 pmol DDT/mg membrane protein (0.34 pmol/house fly head). Competition studies showed DDT, cis-permethrin, and cypermethrin bind to the same receptor but not at precisely the same site. The addition of Ca2+ to the incubation buffer significantly inhibited the binding of both [14C]DDT and [14C]cis-permethrin, suggesting the receptor binding is Ca2+ sensitive and may have a role in ion conductance.  相似文献   

8.
Anthranilic and phthalic diamides exemplified by chlorantraniliprole (Chlo) or cyantraniliprole (Cyan) and flubendiamide (Flu), respectively, are the newest major chemotype of insecticides with outstanding potency, little or no cross resistance with other classes and low mammalian toxicity. They are activators of the ryanodine (Ry) receptor (RyR)-Ca2+ channel, based on Ca2+ flux and electrophysiology investigations. The goal of this study is to define species differences in the degree and mechanisms of diamide selective action by radioligand specific binding studies at the [3H]Ry, [3H]Chlo and [3H]Flu sites. The [3H]Ry site is observed in muscle of lobster, rabbit and four insect species (Musca domestica, Apis mellifera, Heliothis virescens and Agrotis ipsilon) whereas the [3H]Chlo site is evident in the four insects and the [3H]Flu site in only the two lepidoptera (Agrotis and Heliothis). [3H]Ry binding is significantly stimulated by Chlo, Cyan and Flu with the insects (except Flu with Musca) but not the lobster and rabbit. [3H]Chlo binding is stimulated by Ry and Flu in Musca and Apis but not in the lepidoptera, while Flu and Cyan are inhibitory. [3H]Flu binding is strongly inhibited by Chlo and Cyan in Agrotis and Heliothis. [3H]Chlo and [3H]Flu binding are not dependent on added Ca2+ or ATP in Heliothis and Agrotis whereas the other radioligand-receptor combinations are usually enhanced by Ca2+ and ATP. More generally, there are species differences in the Ry, Chlo and Flu binding sites of the RyR that may confer selective toxicity and determine target site cross resistance mechanisms.  相似文献   

9.
The ability of spinosyn A to either enhance or displace binding to selected insecticidally-relevant receptors was investigated using a number of radioligands including, [3H]imidacloprid and [3H]ivermectin in tissues from the ventral nerve cord (VNC) membranes of the American cockroach, Periplaneta americana and head membranes from the housefly, Musca domestica. In these insect neural tissues, spinosyn A does not appear to alter the binding of a number of radioligands suggesting that spinosyn A does not interact directly with a variety of known receptors, including nicotinic or γ-aminobutyric acid (GABA)-based insecticidal target sites. However, available data are consistent with spinosyn A interacting with a site distinct from currently known insecticidal target sites, thus supporting a novel insecticidal mechanism of action for the spinosyns.  相似文献   

10.
γ-Aminobutyric acid (GABA) receptors (GABARs) are an important target for existing insecticides such as fiproles. These insecticides act as noncompetitive antagonists (channel blockers) for insect GABARs by binding to a site within the intrinsic channel of the GABAR. Recently, a novel class of insecticides, 3-benzamido-N-phenylbenzamides (BPBs), was shown to inhibit GABARs by binding to a site distinct from the site for fiproles. We examined the binding site of BPBs in the adult housefly by means of radioligand-binding and electrophysiological experiments. 3-Benzamido-N-(2,6-dimethyl-4-perfluoroisopropylphenyl)-2-fluorobenzamide (BPB 1) (the N-demethyl BPB) was a partial, but potent, inhibitor of [3H]4′-ethynyl-4-n-propylbicycloorthobenzoate (GABA channel blocker) binding to housefly head membranes, whereas the 3-(N-methyl)benzamido congener (the N-methyl BPB) had low or little activity. A total of 15 BPB analogs were tested for their abilities to inhibit [3H]BPB 1 binding to the head membranes. The N-demethyl analogs, known to be highly effective insecticides, potently inhibited the [3H]BPB 1 binding, but the N-methyl analogs did not even though they, too, are considered highly effective. [3H]BPB 1 equally bound to the head membranes from wild-type and dieldrin-resistant (rdl mutant) houseflies. GABA allosterically inhibited [3H]BPB 1 binding. By contrast, channel blocker-type antagonists enhanced [3H]BPB 1 binding to housefly head membranes by increasing the affinity of BPB 1. Antiparasitic macrolides, such as ivermectin B1a, were potent inhibitors of [3H]BPB 1 binding. BPB 1 inhibited GABA-induced currents in housefly GABARs expressed in Xenopus oocytes, whereas it failed to inhibit l-glutamate-induced currents in inhibitory l-glutamate receptors. Overall, these findings indicate that BPBs act at a novel allosteric site that is different from the site for channel blocker-type antagonists and that is probably overlapped with the site for macrolides in insect GABARs.  相似文献   

11.
The interactions of natural pyrethrins and nine pyrethroids with the nicotinic acetylcholine (ACh) receptor/channel complex of Torpedo electric organ membranes were studied. None caused significant reduction in [3H]ACh binding to the receptor sites, but all inhibited [3H]perhydrohistrionicotoxin ([3H]H12-HTX) binding to the channel sites in presence of carbamylcholine. Allethrin inhibited [3H]H12-HTX binding noncompetitively, but [3H]imipramine binding competitively, suggesting that allethrin binds to the receptor's channel sites that bind imipramine. The pyrethroids were divided into two types according to their actions: type I, which included pyrethrins, allethrin, bioallethrin, resmethrin, and tetramethrin, was more potent in inhibiting [3H]H12-HTX binding and acted more rapidly (i.e., in <30 sec). Type II, which included permethrin, fluvalinate, cypermethrin and fenvalerate, was less potent and their potency increased slowly with time. Also, inhibition of the initial rate of [3H]H12-HTX binding by type I compounds increased greatly by the presence of the agonist carbamylcholine, but this was not so with type II compounds. The receptor-regulated 45Ca2+ flux into Torpedo microsacs was inhibited by pyrethrins and pyrethroids, suggesting that their action on this receptor function is inhibitory. There was very poor correlation between the potencies of pyrethrins and pyrethroids in inhibiting [3H]H12-HTX binding and their toxicities to house flies, mosquitoes, and the American cockroach. However, the high affinities that several pyrethroids have for this nicotinic ACh receptor suggest that pyrethroids may have a synaptic site of action in addition to their well known effects on the axonal channels.  相似文献   

12.
Desnitroimidacloprid (desnitro-IMI) is proposed to be a bioactivation product of imidacloprid and to bind at the same site as [3H]nicotine in the nicotinic acetylcholine receptor (nAChR) of mouse brain membranes. The α4β2 nAChR subtype accounts for >90% of the binding sites for nicotine in rat brain. This study further characterizes the binding site for [3]desnitro-IMI and [3H]nicotine in rat recombinant α4β2 nAChR using receptor expressed in Sf9 insect cells so that the assays involved no other receptor subtypes or interference from metabolic activation and detoxification systems. The two radioligands gave the same Bmax of 7.5 pmol/mg protein and apparent Kd values of 3.3 nM for nicotine and 8.9 nM for desnitro-IMI by Scatchard analysis at 22°C. However, at 4°C, the observed apparent association rate is slower and dissociation rate is faster for [3H]desnitro-IMI than for [3H]nicotine and due to the rapid rate of dissociation of [3H]desnitro-IMI the Kd calculated from the determined association and dissociation rates more closely approximates 1.0 for both ligands. Eight cholinergic agents and nine nicotinoids are equipotent in displacing [3H]desnitro-IMI and [3H]nicotine, with IC50 values (nM) of 0.5 for epibatidine, 1 for cytisine, 4–6 for nicotine and desnitro-IMI, 15 for acetylcholine, and 155 for imidacloprid, with an overall correlation for inhibitor potencies of r2 = 0.99 (n = 17). This correlation of binding site properties extends to [3H]nicotine in the recombinant α4β2 receptor and rat brain membranes (r2 = 0.99, n = 12). Thus, desnitro-IMI and nicotine bind with high affinity to the same site in rat recombinant α4β2 neuronal nAChR. This recombinant receptor can be generated in sufficient quantities for high-throughput target site screening and structural analysis of the binding site.  相似文献   

13.
5-tert-Butyl-2-(4-ethynylphenyl)pyrimidine and the corresponding 2,5-disubstituted-4H-1,3-thiazine block the GABA-gated chloride channel at c.20and c.200 nm , respectively, measured as 50% inhibition of the binding of 1-(4-ethynylphenyl)-4-[3H]propyl-2,6,7-trioxabicyclo[2.2.2]octane (4′-ethynyl-4-n-[3H]propylbicycloorthobenzoate; [3H]EBOB) in house fly and mouse brain membranes, and they are also toxic to topically-treated flies with LD50 values of 6–27 μg g−1 alone and 2–6 μg g−1 with piperonyl butoxide (PB) as synergist. In the pyrimidine series, the general pattern of effectiveness of substituents in the 5-position is tert-butyl>isopropyl≈cyclohexyl≈cyclopropyl>methyl, phenyl and 3- and 4-fluorophenyl, and in the 2-position is 4-ethynylphenyl≪4-bromophenyl. These planar pyrimidines and nearly-planar 4H-1,3-thiazines with 2-ethynylphenyl or 2-bromophenyl and 5-tert-butyl or 5-isopropyl substituents are more effective than the corresponding 6H-1,3-thiazine, 6-oxo-1,3-thiazines and 4,6-dioxo-1,3-thiazine examined, but they are less active than the analogous conformationally flexible trans-1,3-dioxanes and -1,3-dithianes. The heterocyclic moiety confers a region of high electron density and positions the 2- and 5-substituents in a linear or parallel relationship for optimal affinity at the receptor. Two observations indicate that the new pyrimidines and thiazines probably act as chloride channel blockers. First, the poisoning signs are identical to those of EBOB in both mice and house flies. Second, each of the pyrimidines, thiazines and dioxanes falls on the same correlation line for inhibition of [3H]EBOB binding and toxicity to house flies (with PB) as that obtained earlier for EBOB analogs, dithianes and polychlorocycloalkanes, suggesting that they all act at the same or closely coupled binding sites in the GABA-gated chloride channel.  相似文献   

14.
House fly (Musca domestica L.) microsomes prepared from larvae, pupae, or adults contain three enzyme system which can metabolize juvenile hormone I: an esterase, an oxidase, and epoxide hydrase. The presence of the oxidase is indicated by the increased metabolism when microsomes are supplemented with NADPH and by the occurrence of additional metabolites tentatively identified as products arising from oxidation of the 6, 7 double bond. Additional evidence of the activity of the oxidase system is the increased metabolism of juvenile hormone I by the NADPH-dependent system from phenobarbital-induced insects, by inhibition of the oxidation by piperonyl butoxide and carbon monoxide, and by the greater metabolism of the hormone by microsomes from insecticide-resistant (high oxidase) strains. In vivo studies of house fly adults treated with 3H-labeled juvenile hormone I reveal a pattern of metabolism similar to that seen during NADPH-supplemented in vitro metabolism. The three enzymes have somewhat different patterns of activity during the larval stage of the house fly, juvenile hormone esterase and epoxide hydrase beginning at a high level of activity in the young larvae while the juvenile hormone oxidase is low at this stage. In the late larval stage all three enzymes show increased activity followed by declines during the pupal stage and further increases in the adult stage. Comparison of in vitro enzyme levels of the house fly, flesh fly (Sarcophaga bullata Parker), and blow fly [Phormia regina (Meigen)] showed that, although the enzymes were present in the latter two species, their activity on a per insect basis was considerably less than that of the house fly.  相似文献   

15.
BACKGROUND: Bicyclophosphorothionates (2,6,7‐trioxa‐1‐phosphabicyclo[2.2.2]octane‐1‐sulfides) are blockers (or non‐competitive antagonists) of γ‐aminobutyric acid (GABA) receptor channels. Twenty‐two bicyclophosphorothionates with different 3‐ and 4‐substituents were synthesised, and [3H]4′‐ethynyl‐4‐n‐propylbicycloorthobenzoate (EBOB) binding assays were performed to evaluate their affinities for housefly and rat GABA receptors. RESULTS: Introduction of an isopropyl group at the 3‐position enhanced the affinity of bicyclophosphorothionates for housefly GABA receptors and reduced the affinity towards rat GABA receptors. The 4‐isopentyl‐3‐isopropylbicyclophosphorothionate showed the highest affinity for housefly GABA receptors (IC50 = 103 nM ) among the analogues tested, while the 4‐cyclohexylbicyclophosphorothionate showed the highest affinity for rat GABA receptors (IC50 = 125 nM ). Among the bicyclophosphorothionates synthesised to date, the former analogue exhibited the highest selectivity for housefly GABA receptors, with an IC50rat/IC50fly ratio of approximately 97. Three‐dimensional GABA receptor models successfully explained the structure–activity relationships of the bicyclophosphorothionates. CONCLUSION: The results indicate that minor structural modifications of blockers can change their selectivity for insect versus mammalian GABA receptors. The substituent at the 3‐position of the bicyclophosphorothionates dictates selectivity for housefly versus rat GABA receptors. This information should prove useful for the design of safer insecticides and parasiticides. Copyright © 2010 Society of Chemical Industry  相似文献   

16.
Conventional film autoradiography was used at the light microscopic level for the localization and quantization of 4-aminobutyric acid (GABA) receptors in the locust brain (Schistocerca americana). Localization of the receptor site was achieved via binding with the receptor-ligand probe [3 H]muscimol. Frozen sections were cut and subsequently incubated either in 40 nM [3H]muscimol or by coincubating sections with [3H]muscimol and one of the following: GABA (50 μM)], a receptor specific agonist [muscimol (1 μM) or isoguvacine (1 μM)], an uptake inhibitor [nipecotic acid (50 μM)], or a noncompetitive channel modulator [avermectin B1a, (1 μM) or aldrin (50 μM)]. Through computer image enhancement and densitometric analysis of the optical density of [3H]muscimol binding sites, the interaction of the above compounds with the putative GABA receptor was determined for various anatomical regions of the locust brain. By comparing the differently treated, but adjacent sections, GABA receptor distribution was quantitated and mapped. Receptor sites were found distributed in the antennal lobes, central body, β-lobe and β-lobe of the corpus pedunculatum, protocerebral bridge, and calyx as well as the optic lobe regions.  相似文献   

17.
A series of 14 new 3-[4(3H)-quinazolinone-2-(yl)thiomethyl]-1,2,4-triazoles were prepared and characterized by elemental analyses, IR, [1H] NMR and mass spectral data. Four of the compounds showed insecticidal activity equivalent to that of malathion against the adult stage of the blow fly (Chrysomyia albiceps). However, their activity against the larval stages of this insect species was considerably weaker.  相似文献   

18.
The release of [3H]neurotransmitters was used as a functional assay to assess the actions of selected neurotoxins on the synaptosomal membranes prepared from the invertebrate nervous systems of squid and house fly. A reproducible release of [3]neurotransmitter was evoked by pulsed-depolarization in the presence of elevated K+ or of veratridine. Pretreatment with deltamethrin resulted in a substantial enhancement of [3H]neuro-transmitter release during pulsed-depolarization. This enhanced neurotransmitter release was greatly reduced or absent when synaptosomes of knockdown-resistant house flies were examined. No enhanced neurotransmitter release due to deltamethrin pretreatment was apparent from any synaptosomal preparation under non-depolarizing conditions. Under similar conditions, collaborative experiments demonstrated that deltamethrin causes a significant change in protein phosphorylation activities which follow depolarization. The most significant change caused by deltamethrin was the prolonged elevation of the level of phosphorylation on a number of key synaptic proteins beyond the normal time of their recovery to the dephosphorylated state. The most notable protein reacting to deltamethrin in this manner was calcium-cadlmodulin-dependent protein kinase.  相似文献   

19.
The sulfoximines, as exemplified by sulfoxaflor ([N-[methyloxido[1-[6-(trifluoromethyl)-3-pyridinyl]ethyl]-λ4-sulfanylidene] cyanamide] represent a new class of insecticides. Sulfoxaflor exhibits a high degree of efficacy against a wide range of sap-feeding insects, including those resistant to neonicotinoids and other insecticides. Sulfoxaflor is an agonist at insect nicotinic acetylcholine receptors (nAChRs) and functions in a manner distinct from other insecticides acting at nAChRs. The sulfoximines also exhibit structure activity relationships (SAR) that are different from other nAChR agonists such as the neonicotinoids. This review summarizes the sulfoximine SAR, mode of action and the biochemistry underlying the observed efficacy on resistant insect pests, with a particular focus on sulfoxaflor.  相似文献   

20.
The nature of target site or knockdown resistance (kdr) to DDT and pyrethroids was studied by investigating specific binding of [14C] DDT and [14C] cis-permethrin to the previously established membrane receptors from the heads of susceptible (sbo) and resistant (kdr) strains of the house fly, Musca domestica L. In vivo studies showed the heads from sbo flies bound two to three times more DDT than those from kdr flies at all doses tested. Reduced binding was also observed in kdr flies in in vitro [14C] DDT binding assays. Scatchard analysis indicated that kdr flies have the same affinity but fewer receptors per milligram protein in the CNS than sbo flies. Assays with [14C] cis-permethrin also showed binding was much reduced in kdr flies in comparison with sbo flies. Based on these results, the nature of the target site insensitivity of kdr flies may relate to their having a reduced number of receptors for the insecticides.  相似文献   

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