DAn is a set of nine motoneurons that innervate dorsal muscles and have cell bodies in the
ventral cord. A typical DAn (e.g. DA3 (e)) has an exclusively postsynaptic, anteriorly directed
process in the ventral cord that runs in the ventral regions of the cord. It receives synaptic input
from AVA (*d) and AVD (*c); in addition, DA1-DA4 receive synaptic input from AVE (*d), DA8 receives input from DVB and DA9 from PHC (*a). There are gap junctions to AVA (c)
and occasional gap junctions to VAn. DA1 and DA2 also have gap junctions to SAB and DA9 to PHC (d). A posteriorly directed process from DAn leaves the ventral cord and runs round
to the dorsal cord. All except those from DA2 and DA9 go round as a left-hand commissure,
passing through the ventral hypodermal ridge (b). The process of DAn runs anteriorly in the
dorsal cord with the proximal regions of the process running adjacent to the basal lamina.
There are many NMJs in this region, which are nearly all dyadic, with VDn as the corecipient
(a). The distal regions of the dorsal DAn processes are generally not adjacent to the basal
lamina and have few, if any, synaptic contacts.
Magnifications: (a-d) x 25500.
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