Detailed analysis of leucokinin-expressing neurons and their candidate functions in the Drosophila nervous system

Abstract

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.

Postprandial sleep mechanics in Drosophila

“…Subsets of Lk neurons have been found in the lateral horn, with the diffuse puncta in close proximity to the cell bodies of the Lkr neurons, suggesting a neuromodulatory connection between these cells (Al-Anzi et al, 2010; de Haro et al, 2010; Cavey et al, 2016). Recent findings also show that incubating Lkr neurons with Lk inhibits their response to the cholinergic agonist carbachol, suggesting that Lk inhibits Lkr neuronal activity (Cavey et al, 2016).…”

translin Is Required for Metabolic Regulation of Sleep

“…We identified the Leucokinin (LK) neurons, where knockdown of trsn reduced sleep modulation in response to starvation. LK has been implicated in a host of fly behaviors including feeding and water homeostasis, locomotion, and olfactory behavior [37, 38]. Driving membrane tethered CD8::GFP with LK-GAL4 labeled a single large neuron in the lateral horn and three pairs of neurons in the subesophageal zone ([38]; Figure 4A).…”

Peptidergic control of food intake and digestion in insects1This review is part of a virtual symposium on recent advances in understanding a variety of complex regulatory processes in insect physiology and endocrinology, including development, metabolism, cold hardiness, food intake and digestion, and diuresis, through the use of omics technologies in the postgenomic era.

“…Insect kinins are localized throughout the CNS and in the digestive system (Nässel and Lundquist 1991;Te Brugge et al 2001;de Haro et al 2010). A detailed localization study in R. prolixus showed kinin-like immunostaining in neurons innervating the hindgut and lower posterior midgut, as well as in endocrine midgut cells (Te Brugge et al 2001).…”