Modulation of the Ca(2+) signaling pathway by celangulin I in the central neurons of Spodoptera exigua.

Celangulin I is an insecticidal component isolated from Chinese bittersweet Celastrus angulatus. The present study explored the possible effects of celangulin I on the calcium signaling pathway, especially on the L-type Ca(2+) channel and the calcium channels in the endoplasmic reticulum in the central neurons isolated from the third instar larvae of Spodoptera exigua using whole-cell patch-clamp and calcium imaging technique. The results showed that celangulin I could activate the high voltage-gated calcium channel at the concentration of 150µM. The peak currents were increased by 17% of the initial value at the end of the 10-min recording after treated with celangulin I. The rises of intracellular calcium ion concentration ([Ca(2+)]i) in neurons treated by celangulin I showed that the effects of celangulin I were concentration-dependent. Activation of the RyRs by ryanodine decreased the calcium release induced by celangulin I, indicating that celangulin I exerts effect on insect RyRs. Furthermore, we also provided evidence for the first time that celangulin I activates inositol 1,4,5-trisphosphate (IP3) sensitive intracellular calcium release channels in the endoplasmic reticulum third instar larvae neurons of S. exigua. Plausibly, these experimental results can explain the characteristic symptoms of anesthesia and paralysis in celangulin I treated insects.

Synthesis and biological activities of 2,3-dihydro-1,3,4-oxadiazole compounds and its derivatives as potential activator of ryanodine receptors.

A series of novel 2,3-dihydro-1,3,4-oxadiazoles containing N-pyridylpyrazole carboxamides moieties were obtained by applying a new synthetic route. Their insecticidal tests against oriental armyworm (Mythimna separata) and diamondback moth (Plutella xylostella) indicated that most of the compounds showed moderate to excellent activities at the testing concentrations. In particular, compound 6a showed 40% larvicidal activities against oriental armyworm at 1mg/L, while 7a against diamondback was 100% at 0.01mg/L. Calcium imaging results demonstrated that 6a, 6d and 7a stimulated a transient elevation in [Ca(2+)]i in the absence of external calcium after the central neurons dye loading with fluo-3 AM, implying that these novel compounds were potential activators of the ligand-gated calcium channel on the endoplasmic reticulum.

Synthesis and insecticidal activities of 2,3-dihydroquinazolin-4(1H)-one derivatives targeting calcium channel.

A series of compounds containing dihydroquinazolinone moiety was designed and synthesized. Amine bridge part was changed in comparison with known anthranilic diamides insecticides. Their insecticidal activities against oriental armyworm (Mythimna separata) indicated that most of the compounds showed moderate to high activities at the tested concentrations. In particular, compounds 5a and 5k showed 80% larvicidal activities against oriental armyworm at the concentration of 5mg/L. The present study also explored the possible effects of target compounds on the high voltage-gated calcium channel and the calcium channels in the endoplasmic reticulum in the central neurons isolated from the third instar larvae of Spodoptera exigua using whole-cell patch clamp and calcium imaging technique. The results showed that compound 5a activated the high voltage-gated calcium channel in the central neurons of S. exigua weakly. The peak currents only increased by 6% of the initial value at the end of the 10-min recording after treated with 0.22µM 5a, while chlorantraniliprole has an opposite effect. The effects of 5a on the intracellular calcium ion concentration ([Ca(2+)]i) in neurons were well investigated. The experimental results indicated that these novel compounds have different mechanism compared with chlorantraniliprole.

Synthesis and insecticidal evaluation of novel N-pyridylpyrazolecarboxamides containing an amino acid methyl ester and their analogues.

On the basis of the commercial insecticide chlorantraniliprole, a series of novel N-pyridylpyrazolecarboxamides containing an amino acid methyl ester and their analogues were designed and synthesized. Their chemical structures were established on the basis of corresponding (1) H NMR spectroscopy, (13)C NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction analysis. The insecticidal activities of the new compounds against oriental armyworm ( Mythimna separata ) and diamondback moth ( Plutella xylostella ) were evaluated. The results of bioassays indicated that most of the compounds showed moderate to high activities at the tested concentration, of which the compounds 6 containing a methyl acrylate substructure had excellent larvicidal activity; for example, 6a displayed 100% larvicidal activity against P. xylostella at the concentration of 0.005 mg/L, whereas the activities of both compounds 6g and 6h against M. separata were 100% at 2.5 mg/L. The calcium imaging technique experiment results showed that novel compound 6 could elevate the calcium concentration in the cytoplasm. Furthermore, this study also provided evidence that compound 6h activates inositol 1,4,5-trisphosphate (IP3) sensitive intracellular calcium release channels in the endoplasmic reticulum of Spodoptera exigua third-instar larva neurons.