Differential effects of octopamine and tyramine on the central pattern generator for <Emphasis Type="Italic">Manduca</Emphasis> flight |
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Authors: | R Vierk H J Pflueger C Duch |
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Institution: | (1) Institute of Biology/Neurobiology, Free University of Berlin, 14195 Berlin, Germany;(2) School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA |
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Abstract: | The biogenic amine, octopamine, modulates a variety of aspects of insect motor behavior, including direct action on the flight
central pattern generator. A number of recent studies demonstrate that tyramine, the biological precursor of octopamine, also
affects invertebrate locomotor behaviors, including insect flight. However, it is not clear whether the central pattern generating
networks are directly affected by both amines, octopamine and tyramine. In this study, we tested whether tyramine affected
the central pattern generator for flight in the moth, Manduca sexta. Fictive flight was induced in an isolated ventral nerve cord preparation by bath application of the octopamine agonist,
chlordimeform, to test potential effects of tyramine on the flight central pattern generator by pharmacological manipulations.
The results demonstrate that octopamine but not tyramine is sufficient to induce fictive flight in the isolated ventral nerve
cord. During chlordimeform induced fictive flight, bath application of tyramine selectively increases synaptic drive to depressor
motoneurons, increases the number of depressor spikes during each cycle and decreases the depressor phase. Conversely, blocking
tyramine receptors selectively reduces depressor motoneuron activity, but does not affect cycle by cycle elevator motoneuron
spiking. Therefore, octopamine and tyramine exert distinct effects on the flight central pattern generating network. |
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Keywords: | Insect Flight Locomotion Modulation Biogenic amine |
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