The activity of some pyrethroids against Periplaneta americana and Blattella germanica

The knockdown and contact killing actions of various pyrethroids were compared using Blattella germanica and Periplaneta americana. A wide range of knockdown activity was found; 5-benzyl-3-furylmethyl (1R)-cis-3-(dihydro-2-oxo-3-thienylidenemethyl)-2,2-dimethylcyclopropanecarboxylate (RU 15525) acted fastest, more rapidly than pyrethrins, against B. germanica as well as having a low LD₅₀ value. Topical application and direct spray tests showed that (S)-α-cyano-3-phenoxybenzyl (1R)-cir-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate (NRDC 161) was more active as a killing agent, by an order of magnitude, than cismethrin, the next most active compound, and also had considerable knockdown activity. Piperonyl butoxide generally had little synergist effect. Female P. americana were over three times more tolerant than males to a range of insecticides applied topically. Residual knockdown action in the WHO resistance test was observed to provide baseline data. There was little overlap in speed of action between pyrethroids and other insecticides among the compounds tested.     

Comparative activity of tralomethrin and deltamethrin on Periplaneta americana

Tralomethrin, a tetrabromopyrethroid pesticide, is sometimes considered as owing its activity only to its degradation into deltamethrin. This work provides new results showing the activity of tralomethrin itself on Periplaneta americana. Behavioral study during tarsal contact shows that at low doses, tralomethrin is more potent than deltamethrin. Residue analysis shows that after topical application, the observed activity cannot be explained by the residues of deltamethrin present with tralomethrin. We also show that under our conditions, there is no degradation of tralomethrin on the insects' cuticle and the toxic effect cannot be explained by the quantities of deltamethrin found inside the intoxicated insects.     

Actions of quinolizidine alkaloids on Periplaneta americana nicotinic acetylcholine receptors

BACKGROUND: Botanical insecticides do not play a major role as crop protectants, but they are beneficial in some applications. The authors investigated the actions of naturally occurring alkaloids on insect nicotinic acetylcholine (ACh) receptors (nAChRs) by evaluating their abilities to inhibit specific binding of [³H]imidacloprid (IMI) to nerve‐cord membranes from Periplaneta americana L. Two alkaloids were also tested for their actions on nAChRs expressed by cockroach neurons using patch‐clamp electrophysiology. RESULTS: Four natural quinolizidine alkaloids (matrine, sophocarpine, cytisine and aloperine) exhibited more than 50% inhibition of [³H]IMI binding at 10 µM , although other compounds were found to have no or low inhibitory activity. The rank order of potency based on concentration–inhibition curves was cytisine > sophocarpine ≥ aloperine ≥ matrine. Patch‐clamp analysis indicated that sophocarpine and aloperine were not agonists of nAChRs expressed in P. americana neurons, yet, at 10 µM , aloperine, but not sophocarpine, suppressed ACh‐induced inward currents significantly. CONCLUSION: Three of the four natural alkaloids tested possess structural moieties that are necessary for interaction with P. americana nAChRs. Aloperine, which possesses a unique structure and showed a distinctive dose–response curve, was found to act as an antagonist. Appropriate modifications of these alkaloids might result in novel insecticidal nAChR ligands. Copyright © 2008 Society of Chemical Industry     

Actions of isothiocyanates on the central nervous system of Periplaneta americana

A simple sucrose-gap method for determining the effects of neurotoxicants on the insect central nervous system is used to investigate the mode of action of various isothiocyanates which are known potent inhibitors of insect choline acetyltransferase. The application of 2-isothiocyanatoethyltrimethylammonium iodide to desheathed sixth abdominal ganglia of Periplaneta americana produces rapid effects on synaptic transmission at the cercal-nerve, giant-fibre synapses. Monitoring effects on the excitatory postsynaptic potential (EPSP) and changes of resistance and potential of the postsynaptic membrane indicate that this compound acts primarily on the postsynaptic membrane. Similar actions are noted for other isothiocyanates investigated.     

The neuroexcitatory,convulsive and lethal effects of lindane analogs on Periplaneta americana (L.)

Lindane analogs, in which one or two chlorine atoms are replaced by various substituents, exhibit convulsive and lethal effects on Periplaneta americana (L.). Some analogs are as active as lindane. These effects are well related to the neuroexcitatory action which produces after-discharges in the central nervous system. Carbamate insecticides have potent convulsive and lethal effects on P. americana, which are also related to after-discharges produced in nerve cords. Convulsion caused by lindane analogs and carbamates is solely attributable to their neuroexcitatory effects on the nervous system, in spite of the difference in their ultimate modes of action.     

Quantitative structure—activity studies of some octopaminergic agonists against Periplaneta americana

The quantitative relationship between the structure of 2-(arylimino) thiazolidines (AITs), arylethanolamines (AEAs) and 2-(arylalkylamino)-2-thi-azolines (AATs) and their octopamine (OA)-agonist activities against the ventral nerve cord of American cockroach, Periplaneta americana L., was analysed using reported physicochemical parameters and regression analysis. The electronic nature of a substituent was the most important factor for AAT, followed by the hydrophobic effects: the more electron-donating and the more hydrophobic the substituent, the greater the activity. The hydrophobic nature of a substituent in AEA was the most important factor, followed by the steric effects: the more hydrophobic the substituent, the greater the activity. The more electron-donating the substituent of AIT, the greater the activity.     

Pharmacokinetic behavior of enantiomeric pyrethroid esters in the cockroach,Periplaneta americana L

The potent pyrethroid insecticide NRDC 157 (I; 3-phenoxybenzyl (1R, cis)-3 - (2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate) and its insecticidally inactive 1S, cis enantiomer (II) have similar cuticular penetration rates and are detectable in the hemolymph, nerve cord, fat body, and midgut of the American cockroach, Periplaneta americana, within 2 hr of topical application at 0.17 μg/g, a just-lethal dose of I. At this dose, both enantiomers show similar distribution patterns in these tissues, but symptoms of intoxication are seen only with I. Steady state concentrations of both enantiomers in the hemolymph and nerve cord are between 1.2 × 10^?7 and 1.7 × 10^?7M. I and II are not detectably hydrolyzed by fat body, nerve cord, and hemolymph preparations and are not detectably oxidized by fat body preparations in vitro, but a very low oxidation rate is measured for II, but not I, in nerve cord preparations. These results do not demonstrate a pharmacokinetic basis for the difference in insecticidal activity between enantiomers and therefore it is likely that the site of pyrethroid action is stereospecific. The use of the inactive enantiomer II as a model to study the effects of dose on penetration and distribution in the absence of symptoms is explored.     

Toxicity and electrophysiological effects of Spilanthes amella Murr. extracts on Periplaneta americana L.

The potential insecticidal activity of Spilanthes acmella Murr. (Compositae) extracts was assessed in this study. The extracts were shown to be toxic against adults of American cockroach, Periplaneta americana L. The active component in S. acmella extract was isolated and identified as N-isobutyl-2,6,8-decatrienamide (spilanthol). The results from topical application of spilanthol show that it has a high acute toxicity and spilanthol was the most potent compound when compared to three conventional insecticides. The potency was found to be 1.3, 2.6 and 3.8 times more toxic than carbaryl, bioresmethrin and lindane, respectively. Electrophysiological studies indicated immediate hyperexcitation followed by complete inhibition of the cockroach cercal nerve activity.     

Electrophysiological effects of paraoxon on the giant interneurons in the American cockroach,Periplaneta americana

Effects of the organophosphate insecticide, paraoxon, on the ventral grant interneurons of the American cockroach (Periplaneta americana) were studied by using intracellular microelectrodes. Within 5 min after paraoxon treatment, the efficacy of transmission at the cercal-to-giant interneuron synapse was markedly reduced or blocked, and alternating waves of depolarization and repolarization were initiated in the giant interneurons. Superimposed on these waves were high-frequency bursts of overshooting and nonovershooting spikes. Comparisons of paraoxon-induced activity in the cell body and at sites along the axon of the giant interneurons indicated that the cyclical waves, as well as high-frequency spikes, originated in the sixth abdominal ganglion rather than at more anterior sites. The effects of paraoxon were not mimicked by the application of exogenous acetylcholine, the latter causing a sustained depolarization and repetitive spiking of giant interneurons but not cyclical bursting or alternations in membrane potential. Although the precise origin of the paraoxon-induced activity is not known, several lines of evidence (e.g., results from chronic deafferentation experiments) suggest that cholinergic inputs from cercal afferent fibers are not involved in initiating the bursting.     

美洲大蠊和东亚飞蝗的耐缺氧力及其比较

研究并比较了美洲大蠊和东亚飞蝗在接近真空和充满CO2的环境下的耐缺氧力。结果表明：美洲大蠊和东亚飞蝗在0.06pa的真空泵中都能存活,在2～10min后其生理活动会不断减弱,直到假死或静止不动,但不会死亡,90～120min后两者的生理活动逐渐恢复,但都比正常状态下弱,生理活动都呈现反抛物线的规律,且在同一时间东亚飞蝗比美洲大蠊的生理活动要弱;美洲大蠊在充满CO2的密闭瓶中存活的时间比东亚飞蝗要长,将不同程度缺氧处理后的试虫置于空气中后,美洲大蠊恢复正常生理活动的能力和恢复后的活动强度明显比东亚飞蝗强。说明美洲大蠊和东亚飞蝗都有较强的耐缺氧力,但美洲大蠊的耐缺氧力更强。     

The toxicity of mptp (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) to Periplaneta americana l. and its effects on dopamine in the cerebral ganglia

MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and MPP⁺ (1-methyl-4-phenylpyridinium ion) are potent dopaminergic neurotoxins in mammals. The mammalian toxicity of MPTP depends on its conversion, by monoamine oxidase, to MPP⁺. MPTP is toxic to cockroaches (LD₅₀ 720 μg gm^?1) and the results suggest that MPTP toxicity depends on monoamine oxidase activity at a site outside the nervous system. MPTP depletes dopamine from cockroach cerebral ganglia and MPP⁺ inhibits cockroach mitochondrial respiration. While the biochemistry of MPTP toxicity appears to be the same as in mammals it seems that insects are unable to detoxify MPTP before its action has fatal consequences outside the nervous system.     

Cholinergic properties of pinched-off synaptic nerve endings from the central nervous system of the cockroach Periplaneta americana

The preparation and cholinergic properties of a subcellular fraction, enriched in pinched-off nerve-endings (synaptosomes) from the central nervous system of the cockroach Periplaneta americana, are described. The endings retained their cytoplasmic components, as shown by the presence of marker enzymes and by ultrastructural examination. A carrier-mediated, high-affinity uptake of [³H] choline into the synaptosomes was demonstrated, and this uptake was saturable, depended on a Na⁺-gradient, and was inhibited by hemicholinium-3. It had an apparent K_m value of 0.6 (±0.1) μM, and a V_max of 20.5 (±2.5) pmol min^?1 per mg of protein. The high-affinity [³H]choline uptake was associated with the synthesis of [³H]phosphocholine and [³H]O-acetylcholine. The rate of [³H]choline uptake in synaptosomes was increased by DDT [1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane] at 100 nM concentration, and this increase was inhibited by tetrodotoxin, while neostigmine appeared to be a potent inhibitor (I₅₀ = 10 pM) of the DDT-activated uptake of [³H]choline. The site of action of the insecticides was specifically on the pre-synaptic nerve terminals because the synaptosomes preparation did not retain the post-synaptic membrane of the original nerve-endings. Cockroach synaptosomes provided a useful in-vitro preparation for studying the effects of insecticides on the pre-synaptic nerve endings.     

美洲大蠊Na~ -K~ -ATPase作为筛选靶标的初步研究

以美洲大蠊 (Periplanata americana)雄性成虫的中枢神经系统为试材 ,对 Na -K - ATPase作为农药筛选靶标进行了初步研究 ,表明 Na - K - ATPase活力测定的最适反应条件是 :酶源蛋白浓度 8.5μg/ m L,温度 30℃ ,p H7.4 ,反应时间 15min。同时以最佳反应系统初步研究了几种拟除虫菊酯 (南开菊酯、氯氰菊酯、溴灭菊酯、氰戊菊酯、二氯苯醚菊酯、胺菊酯 )对 Na - K - ATPase离体活性的影响 ,结果显示出不同程度的抑制作用。并对其用作农药筛选靶标的可能性进行了探讨。     

Interaction of formamidines with octopamine-, dopamine-and 5-hydroxytryptamine-sensitive adenylate cyclase in the nerve cord of Periplaneta americana

The interaction of chlordimeform, N¹-demethylchlordimeform [N²-(4-chloro-o-tolyl)-N¹-methylformamidine], BTS-27271 [N¹-methyl-N²-(2,4-xylyl)formamidine, the 2,4-xylyl analogue of N¹-demethylformamidine], and amitraz with octopamine-, dopamine-, and 5-hydroxytryptamine-mediated enhancement of cyclic-AMP production was investigated in nerve cord homogenates of the American cockroach Periplaneta americana. N¹-Demethylchlordimeform, BTS-27271 and amitraz simulated the actions of the monoamines in enhancing cyclic-AMP production, whereas chlordimeform showed no such agonism. Additivity studies indicated that these formamidine derivatives were interacting with dopamine- and 5-hydroxytryptamine-sensitive sites, in addition to their known interaction with octopamine-sensitive adenylate cyclase. N¹-Demethylchlordimeform (Ki= 0.2μM) and amitraz (Ki=0.5μM) inhibited the dopamine-mediated response, but only N¹-demethylchlordimeform (Ki=2μM) effected appreciable inhibition of the octopamine-response. Pharmacological characterisation of the formamidineinduced elevation of cyclic-AMP production indicated that the agonistic effects of formamidines are expressed primarily through the octopamine-sensitive adenylate cyclase, rather than the dopamine- or 5-hydroxytryptamine-sensitive sites. The results are discussed in the light of the proposal that the behavioural changes, associated with formamidine poisoning, reflect the cumulative effects of octopamine-agonism, and antagonism of the dopamine- and 5-hydroxytryptaminemediated processes.     

Inhibitors of juvenile hormone biosynthesis in corpora allata of the cockroach Periplaneta americana (L.) in vitro

The spontaneous biosynthesis of methyl (2E,6E)-(10R)-10,11-epoxy-3,7,11-trimethyldodeca-2,6-dienoate (juvenile hormone III; JH III) in excised corpora allata of Periplaneta americana was inhibited by a number of synthetic prop-2-ynyl ethers and 1,3-benzodioxole derivatives. One structurally diverse group of compounds inhibited only the final biosynthetic enzyme methyl farnesoate epoxidase (EC.1.14.14.–) at low to moderate concentrations, but at higher concentrations, also inhibited methyl farnesoate (MF) formation, causing an accumulation of MF in the concentration range 10 to 100 μM. For a second, more limited, group of compounds, there was close congruence between the inhibition of JH III biosynthesis and that of total ester (MF plus JH III) biosynthesis over their effective inhibitory concentration ranges. In contrast to the first group, there was no accumulation of MF and these compounds evidently inhibited JH III biosynthesis, at the level of either farnesoic acid esterification by O-methyl transferase (EC.2.1.1.–), or at an earlier step in the biosynthetic pathway that remains to be elucidated.     

Pharmacological properties of presynaptic muscarinic receptors in the sixth abdominal ganglion of the cockroach,Periplaneta americana L.

The effects of muscarinic agonists on acetylcholine (ACh) release in the cercal-afferent giant-interneuron synapses of the cockroach have been studied using the single-fibre oil-gap method. Decrease in amplitude of the cEPSP was induced by pressure ejection of arecoline (ARE), carbachol (CCh) and oxotremorine free base (OXO) within the sixth abdominal (A6) ganglion. This depressive effect was dose-dependent without any effect at the post-synaptic site in the range of concentrations used. The concentration for 50% of cEPSP inhibition of the most commonly used muscarinic agonists was determined. The rank order of potencies was: ARE > CCh > OXO > McN-A-343 > bethanechol (BET). Plateau levels of 56%, 54% and 68% were reached when increasing the concentration of ARE, CCh and OXO respectively. McN-A-343 and BET had an inhibitory effect on ACh release but higher doses also acted at the postsynaptic level. Furthermore, muscarinic agonists were able to evoke uIPSP and a smaller inhibitory effect of ARE and OXO was observed in presence of picrotoxin. It is concluded that the ACh release in the cockroach A6 ganglion is modulated by presynaptic muscarinic receptors which are possible target sites for insecticides. The presence of putative muscarinic receptors on inhibitory GABAergic interneurons, involved in pre- and postsynaptic inhibition is suspected.     

Effect of substituents at the 5-position of the pyridine ring of imidacloprid on insecticidal activity against Periplaneta americana

The insecticidal activities of imidacloprid derivatives with a wide range of substituents at the 5-position on the pyridine ring against American cockroaches, Periplaneta americana (L.), were measured by injection with and without synergists propyl 2-propynyl phenylphosphonate and piperonyl butoxide. The log(1/MLD) value (MLD = minimal lethal dose in mol) without synergists was 7.96 for the methyl derivative, and the values were lower for other derivatives. Synergists enhanced the potencies of all the compounds tested. Considering these compounds and those with other substituents at this position, the region for maximum activity was predicted to be in the conjunction of the pyridyl 6-chlorine atom with a lipophilic small group in the 5-position.     

Effects of topical application of three pyrethroid insecticides on spontaneous activity in sensory nerves of Periplaneta americana and Blabera craniifer

Electrophysiological techniques were used to analyse the effects, on the activity in the sensory nerves of Periplaneta americana and Blabera craniifer, after topical applications of three different pyrethroid insecticides: deltamethrin, (1R)-tetramethrin, and 5-benzyl-3-furylmethyl (E)-(1R)-cis-2,2-dimethyl-3-(2-oxothiolan-3-ylidenemethyl)cyclopropanecarboxylate (RU-15525; ‘Kadethrin’). The insecticides were applied: (a) to the cercus, and the activity was recorded on the cercal nerve and on the central nervous connectives; or (b) to the last segments of the metathoracic leg, and the corresponding activity was recorded on the crural nerve. In both cases, several categories of receptor were affected but the major part of the recorded activity came from the mechanoreceptors, the functional properties of which were monitored throughout the experiments. In most cases, topical application of small amounts of pyrethroid were found to induce an increase in the spontaneous activity, followed by decrease in excitability. Characteristic differences were, however, found between the three compounds and the effects were concentration- and solvent-dependent. The results were consistent with those obtained from experiments on the sense organs of vertebrates but did not support the idea that the effectiveness of pyrethroid insecticides with an α-cyanobenzyl group, compared with those without an α-cyanobenzyl group, originates from a greater effect on the peripheral sensory receptors.     

Insecticidal and repellent properties of nine volatile constituents of essential oils against the American cockroach,Periplaneta americana (L.)

The toxic and repellent properties of nine major constituents of essential oils, comprising benzene derivatives and terpenes, were evaluated against Periplaneta americana (L.). Contact and fumigant toxicities to adult females and repellency to nymphs were determined. The decreasing order of knockdown activity via contact was methyl-eugenol>isosafrole=eugenol>safrole. The killing effect via contact was in the order eugenol=methyl-eugenol=isosafrole>safrole. Fumigant toxicity was only observed for safrole and isosafrole, with safrole being the more potent. Isoeugenol and the tested terpenes had neither contact nor fumigant toxic effect. The decreasing order of repellency to nymphs was safrole>isosafrole>methyl-eugenol=α-pinene> eugenol>isoeugenol. The benzene derivatives were generally more toxic and repellent to P. americana than the terpenes. The distance of the side chain double bond from the aromatic ring and the substitution of a methoxy group to these compounds appeared to be important determinants of their toxicity and repellency. © 1998 Society of Chemical Industry