Morphological identification of the motor neurons innervating the dorsal longitudinal flight muscle of Drosophila melanogaster

Abstract

The dorsal longitudinal flight muscle (DLM) of Drosophila is composed of six muscle fibers (DLM1-6 from ventral to dorsal) and innervated by five motor neurons (MNs), DLM1-4 being innervated singly by MN1-4, and DLM5 and 6 being jointly innervated by MN5. This study identifies and describes the five motor neurons that innervate these six muscle fibers. Horseradish peroxidase (HRP) applied intracellularly to single identified DLM fibers resulted in the labeling of the single motor neuron innervating that muscle fiber by retrograde transsynaptic transport. This method allowed positive identification of the motor neuron innervating a particular muscle fiber, since only the innervating neuron was labeled. The axonal pathway, soma, and dendritic distribution of each labeled motor neuron was traced in the thoracic ganglion, and their relative positions were determined. The somata of MN1-4 lie in a cluster located near the lateral surface of the thoracic ganglion at the border of the pro- and mesothoracic regions, ipsilateral to the muscle fibers innervated. The somata of MN1 and 2 lie side by side in a horizontal plane with MN1 in a more anterior position. Those of MN3 and 4 lie ventrally to those of MN1 and 2 in a horizontal plane with MN3 in the more anterior position. The soma of MN5 is located contralaterally to the muscle fiber it innervates, lying in the dorsal outermost layer of the thoracic ganglion next to the midline at the border of the pro- and mesothoracic regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular mechanisms determining conserved properties of short-term synaptic depression revealed in NSF and SNAP-25 conditional mutants

“…In the present study, comparison of glutamatergic DLM neuromuscular synapses and cerebellar CF-PC synapses revealed a surprising degree of conservation in the detailed properties of synaptic function. These synapses exhibit morphological similarities as well, including extensive branching of axons and spatial isolation of active zones (34,52,53). Initial characterization of short-term depression at CF-PC synapses has been followed by a series of studies progressively defining the underlying factors in greater detail (7,9,10).…”

Loss of Flight and Associated Neuronal Rhythmicity in Inositol 1,4,5-Trisphosphate Receptor Mutants ofDrosophila

“…8G-I ). Cell bodies of the flight motor neurons innervating the DLMs were identified by their position and axonal projections, as described by Ikeda and Koenig (1988b).…”

Tiling among stereotyped dendritic branches in an identified Drosophila motoneuron

“…Metric dendritic architecture parameters of an identified motoneuron are tightly regulated across animals MN5 is a flight motoneuron innervating the two most dorsal fibers of the dorsal longitudinal wing depressor muscle (DLM, Ikeda and Koenig 1988;Consoulas et al, 2002). As described previously (Duch et al, 2008), MN5 is a large monopolar motoneuron with its soma located in the mesothoracic neuromere of the ventral nerve cord (VNC) on the contralateral side with respect to its target muscle (Fig.…”

“…Therefore, this study provides a quantitative analysis of the natural variability of metric and topological dendritic architecture of an identified adult Drosophila motoneuron, MN5. MN5 is a monopolar flight motoneuron that innervates the dorsal longitudinal flight muscle (Ikeda and Koenig, 1988;Consoulas et al, 2000). It exhibits a complex dendritic architecture with more than 6 mm of dendrites and roughly 4,000 branches.…”