Detailed analysis of leucokinin-expressing neurons and their candidate functions in the Drosophila nervous system
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The distribution of leucokinin (LK) neurons in the central nervous system (CNS) of Drosophila melanogaster was described by immunolabelling many years ago. However, no detailed underlying information of the input or output connections of their neurites was then available. Here, we provide a more accurate morphological description by employing a novel LK-specific GAL4 line that recapitulates LK expression. In order to analyse the possible afferent and efferent neural candidates of LK neurons, we used this lk-GAL4 line together with other CNS-Gal4 lines, combined with antisera against various neuropeptides or neurotransmitters. We found four kinds of LK neurons in the brain. (1) The lateral horn neurons connect the antennal glomerula to the mushroom bodies. (2) The suboesophageal neurons connect the gustatory receptors to the suboesophageal ganglia and ventral nerve cord. (3) The anterior neurons innervate the corpus cardiacum of the ring gland but LK expression is surprisingly not detectable from the third instar onwards in these neurons. (4) A set of abdominal ganglion neurons connect to the dorsal median tract in larvae and send their axons to a segmental muscle 8. Thus, the methods employed in our study can be used to identify individual neuropeptidergic neurons and thereby characterize functional cues or developmental transformations in their differentiation.
KeywordsNeuropeptidergic characterization Nervous system Leucokinin Drosophila melanogaster
We are grateful to Reinhard Stocker, Manolo Calleja, Angel Acebes, Hermann Aberle, Laura Torroja and Richard Axel for kindly providing the fly stocks and to Hermann Aberlee for generously providing V-Glut antisera. We thank Laura Torroja and Isabel Molina for their technical assistance with the transgenic constructs and histological muscle preparations from larvae, Cristina Nuñez de Arce for her help in the laboratory and Carlos Sánchez, Verónica Labrador and Angeles Muñoz for their help with the confocal microscopy. We also thank Phil Mason for improving the English language of the manuscript.
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