Organization of descending neurons in Drosophila melanogaster

Abstract

Neural processing in the brain controls behavior through descending neurons (DNs) - neurons which carry signals from the brain to the spinal cord (or thoracic ganglia in insects). Because DNs arise from multiple circuits in the brain, the numerical simplicity and availability of genetic tools make Drosophila a tractable model for understanding descending motor control. As a first step towards a comprehensive study of descending motor control, here we estimate the number and distribution of DNs in the Drosophila brain. We labeled DNs by backfilling them with dextran dye applied to the neck connective and estimated that there are ~1100 DNs distributed in 6 clusters in Drosophila. To assess the distribution of DNs by neurotransmitters, we labeled DNs in flies in which neurons expressing the major neurotransmitters were also labeled. We found DNs belonging to every neurotransmitter class we tested: acetylcholine, GABA, glutamate, serotonin, dopamine and octopamine. Both the major excitatory neurotransmitter (acetylcholine) and the major inhibitory neurotransmitter (GABA) are employed equally; this stands in contrast to vertebrate DNs which are predominantly excitatory. By comparing the distribution of DNs in Drosophila to those reported previously in other insects, we conclude that the organization of DNs in insects is highly conserved.

Opposite effects of 5-HT/AKH and octopamine on the crop contractions in adult Drosophila melanogaster: Evidence of a double brain-gut serotonergic circuitry

“…The present experiments provide further support for the generality of feeding control systems between insects and mammals [27,28]. Serotonin and octopamine were investigated as possible modulatory neurohormones based on a recent paper of Hsu and Bhandawat [29] on the organization of descending neurons in Drosophila melanogaster . The brain–gut axis is an essential part of the feeding control circuit in both mammals [2,30] and insects [8], especially when it comes to nutrient sensing [17,31].…”

“…Thus, D . melanogaster possesses a complex serotonergic system featuring all major genes for 5-HT synthesis, metabolism and signaling [29] and provides a good model to test the effect of 5-HT on this important organ system.…”

A Descending Neuron Correlated with the Rapid Steering Maneuvers of Flying Drosophila

“…Aside from these cells, little is known of the roughly 1100 cells descending from the brain to the VNC [30]. Two noteworthy exceptions are the so-called “moonwalker neuron”, which elicits backward walking [31] and the giant fiber neuron, which triggers evasive take-offs [16].…”

Spatial distribution of intermingling pools of projection neurons with distinct targets: A 3D analysis of the commissural ganglia in Cancer borealis

“…Similar to other motor control centers (Jefferis et al, 2007;Tanaka, Awasaki, Shimada, & Ito, 2004;Travagli, Hermann, Browning, & Rogers, 2006), the CoGs integrate sensory information from various modalities, including mechanoand proprioceptive sensory structures Smarandache & Stein, 2007), and descending command signals from the brain (Hedrich & Stein, 2008). This is in contrast to many sensory neuropils and motor centers, which have rather consistent anatomical features across individuals of the same species or even between related species (Brandt et al, 2005;Burrows, 1996;Hsu & Bhandawat, 2016). This is in contrast to many sensory neuropils and motor centers, which have rather consistent anatomical features across individuals of the same species or even between related species (Brandt et al, 2005;Burrows, 1996;Hsu & Bhandawat, 2016).…”

“…In some invertebrates, this applies even to the level of individual cells, providing detailed maps of the locations of identified neurons or classes of neurons and how they are clustered (Borst, 2014;Brandt et al, 2005;Burrows, 1996;Busch, Selcho, Ito, & Tanimoto, 2009;Hsu & Bhandawat, 2016;Jefferis et al, 2007;Wolff, Iyer, & Rubin, 2015). Analyses of neuropilar projection patterns and soma locations in a number of systems have demonstrated that sensory and motor structures in the brain are highly organized, and preserved across individuals of a given species.…”