Effects of mating on host selection by female small white butterflies Pieris rapae (Lepidoptera: Pieridae).

Mating might significantly affect the host selection behaviors of phytophagous insects. Here, we investigated the post-mating changes in behavioral and antennal responses of Pieris rapae (Lepidoptera: Pieridae) females to host plant volatiles. In two-choice bioassays using artificial plant models, mated females visited the model scented with synthetic blends (15-, 9-, or 6-components) of cabbage plant volatiles more frequently than the unscented control, whereas virgin females did not exhibit this preference. Because single compounds and the 3-component blend did not induce preferential visiting, mated females apparently utilized complex odor blends as their host-finding cue. Moreover, 2- to 4-day-old mated females visited the models, scented and unscented, more frequently than did their virgin counterparts. Therefore, mating enhanced the host-finding behavior of young females and their responsiveness to plant volatiles. Gas chromatography-electroantennographic detector analysis revealed that eight of the 15 compounds in the cabbage plant volatiles elicited responses from female antennae. However, post-mating and age-dependent changes in antennal responses were not detected. Because female peripheral (antennal) sensitivity to volatiles remained practically unchanged after emergence, post-mating changes in host selection might be attributed to changes in the central nervous system.

Adiposity suppression effect in mice due to black pepper and its main pungent component, piperine.

We investigated energy metabolism enhancement by pepper by examining suppression of body fat accumulation in mice due to piperine (PIP) and black pepper (BP) intake. To induce adiposity, mice were fed a high-fat, high-sucrose (HFS) diet as a control diet for 4 weeks. Visceral fat weights decreased significantly in the mice fed diets of 0.03% and of 0.05% PIP. Body weight in the 0.05% PIP group also decreased significantly. In the mice fed a diet of 1.0% BP, body weight and visceral fat weights decreased significantly. For all parameters tested, the 1.0% BP group tended to show values slightly lower than those of the 0.03% PIP group. Expression of thermogenic protein uncoupling protein 1 tended to increase in the mice on the 1.0% BP diet. These results indicate that BP suppresses the effect of body fat accumulation mainly through the action of PIP.

Activation of TRPV1 and TRPA1 by black pepper components.

We searched in this study for novel agonists of transient receptor potential cation channel, subfamily V, member 1 (TRPV1) and transient receptor potential cation channel, subfamily A, member 1 (TRPA1) in pepper, focusing attention on 19 compounds contained in black pepper. Almost all the compounds in HEK cells heterogeneously expressed TRPV1 or TRPA1, increased the intracellular Ca(2+) concentration ([Ca(2+)](i)) in a concentration-dependent manner. Among these, piperine, isopiperine, isochavicine, piperanine, pipernonaline, dehydropipernonaline, retrofractamide C, piperolein A, and piperolein B relatively strongly activated TRPV1. The EC(50) values of these compounds for TRPV1 were 0.6-128 microM. Piperine, isopiperine, isochavicine, piperanine, piperolein A, piperolein B, and N-isobutyl-(2E,4E)-tetradeca-2,4-diamide also relatively strongly activated TRPA1, the EC(50) values of these compounds for TRPA1 were 7.8-148 microM. The Ca(2+) responses of these compounds for TRPV1 and TRPA1 were significantly suppressed by co-applying each antagonist. We identified in this study new transient receptor potential (TRP) agonists present in black pepper and found that piperine, isopiperine, isochavicine, piperanine, piperolein A, and piperolein B activated both TRPV1 and TRPA1.

Miogadial and miogatrial with alpha,beta-unsaturated 1,4-dialdehyde moieties--novel and potent TRPA1 agonists.

AIMS: Most of the terpenoids with an alpha,beta-unsaturated 1,4-dialdehyde moiety, which are found in plants, fungi, and insects, have a pungent taste. However, the neural receptors responsible for the pungency of these terpenoids have not been identified yet. The transient receptor potential ankyrin 1 (TRPA1) and transient receptor potential vanilloid 1 (TRPV1), which are expressed in the nociceptive neurons, induce a sensation of heat on activation by some pungent ingredients in food. In this study, we selected miogadial (MD), miogatrial (MT), and polygodial (PG) from the terpenoids with an alpha,beta-unsaturated 1,4-dialdehyde moiety and examined the effects of these 3 terpenoids on TRPA1 or TRPV1. MAIN METHODS: TRPV1 and TRPA1 activity by 3 terpenoids were evaluated using Ca(2+) imaging and patch-clamp methods in mammalian cells that express TRP heterologously and mouse sensory neurons. KEY FINDINGS: The 3 terpenoids activated TRPA1 that was heterologously expressed in HEK293 or CHO cells. The potencies of activation by the 3 terpenoids were equal and almost 10 times stronger than that of allyl isothiocyanate (AITC), which is known as the most potent TRPA1 agonist among all natural products. Moreover, these 3 terpenoids exhibited increased intracellular Ca(2+) concentration in mouse sensory neuron cells compared to AITC. High concentrations of the 3 terpenoids also activated TRPV1 that was heterologously expressed in HEK293 cells. SIGNIFICANCE: These results indicated that MD, MT, and PG were more potent in activating TRPA1 than TRPV1, and suggested that they primarily activate TRPA1 to induce pungency.