Two biogenic monoamines, octopamine and 5-hydroxytryptamine (5-HT), are known to play immune mediators in insects. They induce hemocyte behaviors by stimulating cytoskeleton rearrangement. However,it is not clear how they activate the hemocytes in terms of intracellular signal transduction. This study analyzed their interactions with signal pathways implicated in nodule formation via eicosanoids or hemocyte locomotory behavior via a small GTPase. Both octopamine and 5-HT increased hemocytic nodule formation in response to bacterial challenge in the beet armyworm, Spodoptera exigua. However, their immune mediation was inhibited by a treatment of dexamethasone (a specific inhibitor to phospholipase A2). In the presence of phentolamine (a specific antoganist to octopamine) or ketanserin (a specific antoganist to 5-HT), the inhibitory activity of dexamethasone was rescued by adding arachidonic acid (a precursor of eicosanoid biosynthesis). These results suggest that the mediation of nodule formation by the two monoamines is followed by eicosanoid signaling. Two monoamines also induced up-regulation of circulating hemocyte counts in S. exigua. This increase of hemocyte counts was not explained by de novo production of hemopoietic organ because even ligation between thorax and abdomenin order to block hemolymph circulation did not inhibit the increase of circulating hemocyte counts by octopamine.A small GTPase, Rac1, appeared to be involved in this hemocyte mobilization from a sessile compartment in S. exigua. Inhibition of Rac1 activity significantly suppressed hemocyte spreading behavior and the hemocyte mobilization. In summary, octopamine and 5-HT mediate cellular immune responses of S. exigua via eicosanoid signal or independently by activating Rac1 following increase of cAMP in the hemocytes.

Analytical method for synephrine and octopamine in citrus fruits, drinks containing citrus fruit, and human urine was developed using gas chromatography / mass spectrometry(GC/MS). Silylation with MSTFA, acetylation with MBTFA, and trimethylailylation with MSTFA followed by tritluoroacetylation with MBTFA were compared. The selective derivatization of aynephrine and octopamine was optimized with two derivatizing reagents ; MSTFA and MBTFA. The ion at mlz 267 was monitored to characterize the benzyl group of the both compounds. Synephrine was detected in the concentrations of 0.46-1.88 ug/g for citrus fruits and 1.2-8.1 ug/ml for drinks. The urinary excretion data of aynephrine showed the highest concentration at the period of 8-20 hours after drinking orange juices and total amounts of its urinary excretion calculated as a parent compound was 11-14% of a dose during 48 hours. Octopamine was not detected in citrus fruits, drinks, and human urine.