Octopamine mediates sugar relief from a chronic-stress-induced depression-like state in Drosophila

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Coordination and Integration of Metabolism in Insect Flight*

Insect flight is the most energy-demanding activity of animals. It requires the coordination and cooperation of many tissues, with the nervous system and neurohormones controlling the performance and energy metabolism of muscles, and of the fat body, ensuring that the muscles and nerves are supplied with essential fuels throughout flight. Muscle metabolism can be based on several different fuels, the proportions of which vary according to the insect species and the stage in flight activity. Octopamine, which acts as neurotransmitter, neuromodulator or neurohormone in insects, has a central role in flight. It is present in brain, ventral ganglia and nerves, supplying peripheral tissues such as the flight muscles, and its concentration in hemolymph increases during flight. Octopamine has multiple effects during flight in coordinating and stimulating muscle contraction and also energy metabolism partly by activating phosphofructokinase via the glycolytic activator, fructose 2,6-bisphosphate. One important muscle fuel is trehalose, synthesized by the fat body from a variety of precursors, a process that is regulated by neuropeptide hormones. Other fuels for flight include proline, glycerol and ketone bodies. The roles of these and possible regulation in some insect species are discussed.     

Octopamine and cooperation: octopamine regulates the disappearance of cooperative behaviours between genetically unrelated founding queens in the ant

We investigated whether octopamine (OA) is associated with the disappearance of cooperation in Polyrhachis moesta ant queens. Queens of P. moesta facultatively found the colony with genetically unrelated queens. The founding queens perform frequent food exchange with these non-related queens and partake in cooperative brood rearing, whereas single colony queens exclude non-related queens via aggressive behaviour. Thus, aggression is a factor that reduces cooperation. Given that aggression is generally associated with brain OA in insects, we hypothesized that OA controls the behavioural change in cooperation in the ant queen, via an increase in aggression. To test this hypothesis, we compared the amounts of OA and related substances in the brain between founding and colony queens, and observed the interaction of founding queens following oral OA administration. The brain OA levels in colony queens were significantly higher than those in founding queens. Oral administration of OA to founding queens caused significantly less trophallaxis and allogrooming behaviour than in the control founding queens, but with no significant increase in aggression. These results suggest that OA promotes the disappearance of cooperation in founding queens of P. moesta. This is the first study to reveal the neuroendocrine mechanism of cooperation in ant queens.     

Superextension and supercontraction in locust ovipositor muscles

A ten times elongation of certain abdominal intersegmental muscles occurs in female locusts during digging prior to oviposition. During and after oviposition the muscles contract, shortening by up to 90% or more, restoring the resting positions of the abdominal segments.Discontinuous Z-discs permit supercontraction at the resting length and then fragment into Z-bodies when the muscle is stretched, so enabling it to superextend without loss of the contractile property. In this superextended state the fibres resemble smooth muscles. After oviposition, the muscle fibres contract but the sarcomeres are not restored completely, some of the Z-bodies being unevenly distributed in the recontracted fibres. Locust ovipositor muscle has the most extreme example of Z-disc disagregation known from the insects and is the insect muscle which approaches most closely the smooth muscle condition.Two types of motor nerve innervate this muscle, one is ordinary and the other, containing granules, resembles an octopaminergic fibre possibly involved in regulating a catch mechanism in the muscle.The physiological requirements for egg-laying with an extensible ovipositor, which is also part of the normally functioning abdomen, are well met by the ultrastructural specializations of locust ovipositor muscles.     

Sublethal effects of neuroactive compounds on pheromone response thresholds in male oriental fruit moths

The pheromone-mediated flight behavior of male Oriental fruit moths in a sustained-flight tunnel was observed after males were treated topically with sublethal concentrations of permethrin, carbaryl, chlordimeform, dieldrin, octopamine, serotonin, yohimbine, and cyproheptadine. With the exception of serotonin all compounds were found to disrupt one or more specific elements of the male precopulatory flight sequence. Among the insecticides, dieldrin was least active, whereas permethrin, carbaryl, and chlordimeform induced unique effects at specific phases of the sequence. Octopamine induced a hypersensitivity to the olfactory signal and mimicked one of the effects observed with chlordimeform. Yohimbine and cyproheptadine significantly decreased moth activation to the chemical signal but did not alter flight performance in responding moths. Yohimbine and cyproheptadine also reversed the effects induced by octopamine. The results of our study show that the complex precopulatory sequence of behaviors exhibited by males is very sensitive to sublethal concentrations of a range of neuroactive compounds.     

Synergic effects of exercise training and octopamine on peroxisome proliferator-activated receptor-gamma coactivator -1a and uncoupling protein 1 mRNA in heart tissue of rat treated with deep frying oil

Octopamine (OCT) have an adverse effect on heart function. One of the positive effects of exercise training is improving cardiac function and cardiomyocytes signaling, which along with herbal supplements can have better effects on the heart tissue. Therefore, the aim of this study was to evaluate the effects of exercise training and OCT on changes of PGC1α and UCP1 expression in heart tissue of rat treated with deep frying oil (DFO). In this study, 45 male wistar rats were divided into 5 groups (n = 9 in each): I) control (Co), II) DFO, III) DFO + exercise, IV) DFO + OCT, and V) DFO + OCT + exercise. The quantification of apoptotic effects of DFO in heart tissue was assessed by TUNEL assay. Masson's trichrome stain applied to study cardiomyocytic fibers. Moreover, PGC1α and UCP1 genes and proteins expression in all groups were investigated using quantitative real-time PCR and immunohistochemical method. A significant increase in apoptotic cells was observed in the DFO-treated group (p < 0.05). In Masson's Trichrome stain study, more cardiomyocytic fibers were observed and some lymphocytic cells were present in some fibers. Also, the expression of PGC1α and UCP1 was significantly increase in DFO + exercise group, DFO + OCT group, and DFO + OCT + exercise group compare to DFO group (p < 0.05). Based on these findings, exercise and octopamine can be considered as factors affecting the expression of PGC1α genes and UCP1 as well as drug poisoning.     

Correlation between octopaminergic signalling and foraging task specialisation in honeybees

Regulation of pollen and nectar foraging in honeybees is linked to differences in the sensitivity to the reward. Octopamine (OA) participates in the processing of reward-related information in the bee brain, being a candidate to mediate and modulate the division of labour among pollen and nectar foragers. Here we tested the hypothesis that OA affects the resource preferences of foragers. We first investigated whether oral administration of OA is involved in the transition from nectar to pollen foraging. We quantified the percentage of OA-treated bees that switched from a sucrose solution to a pollen feeder when the sugar concentration was decreased experimentally. We also evaluated if feeding the colonies sucrose solution containing OA increases the rate of bees collecting pollen. Finally, we quantified OA and tyramine (TYR) receptor genes expression of pollen and nectar foragers in different parts of the brain, as a putative mechanism that affects the decision-making process regarding the resource type collected. Adding OA in the food modified the probability that foragers switch from nectar to pollen collection. The proportion of pollen foragers also increased after feeding colonies with OA-containing food. Furthermore, the expression level of the AmoctαR1 was upregulated in foragers arriving at pollen sources compared with those arriving at sugar-water feeders. Using age-matched pollen and nectar foragers that returned to the hive, we detected an upregulated expression of a TYR receptor gene in the suboesophageal ganglia. These findings support our prediction that OA signalling affects the decision in honeybee foragers to collect pollen or nectar.     

Flexible reprogramming of Pristionchus pacificus motivation for attacking Caenorhabditis elegans in predator-prey competition

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Does the solitary parasitoid Microplitis pennatulae use a combinatorial approach to manipulate its host?

Host manipulation is a strategy used by some parasites to enhance their transmission. These parasites use a combination of neuropharmacological, psychoneuroimmunological, genomic/proteomic, or symbiont-mediated mechanisms to manipulate their hosts. Bodyguard manipulation occurs when parasitized hosts guard parasitoid pupae to protect them from their natural enemies. Bodyguard-manipulated hosts exhibit altered behaviours only after the egression of parasitoid prepupae. Behavioural changes in post-parasitoid egressed hosts could have resulted from their altered physiology. Previous studies have shown that gregarious manipulative parasitoids induce multiple physiological changes in their host, but the physiological changes induced by solitary manipulative parasitoids are unknown. Microplitis pennatulae Ranjith & Rajesh (Hymenoptera: Braconidae) is a larval parasitoid of Psalis pennatula Fabricius (Lepidoptera: Erebidae). After the egression of parasitoid prepupae, P. pennatula stops its routine activities and protects the parasitoid pupa from hyperparasitoids by body thrashes. In this study, we looked into the physiological changes induced by the solitary manipulative parasitoid, M. pennatulae, in its host, P. pennatula, during various stages of parasitization. We considered octopamine concentration and phenoloxidase (PO) activity as biomarkers of physiological change. We also examined whether M. pennatulae has a symbiotic virus and whether the wasp transfers it to the host during parasitization. We found that octopamine concentration was low in the pre-parasitoid egressed host, but it was elevated after the parasitoid egressed. Phenoloxidase activity was lower in the pre- and post-parasitoid egressed host than in the unparasitized host. We also detected symbiotic bracovirus (BV) in the wasp ovaries and isolated the BV virulence gene from the parasitised host. Our study suggests that solitary parasitoids also induce multiple physiological changes to influence the host behaviour to their advantage, as is the case with the gregarious parasitoids.