FATE OF ABDOMINAL VENTRAL UNPAIRED MEDIAN CELLS DURING METAMORPHOSIS OF THE HAWKMOTH, MANDUCA-SEXTA

Each of the unfused abdominal ganglia in the larval, pupal, and adult stages of the hawkmoth, Manduca sexta, has two large ventral median ne urons with axons that bifurcate to innervate targets on both sides of the abdomen. Although the dendritic structures of the two neurons are similar, their axons branch to innervate distinct sets of target muscl es. During metamorphosis both neurons undergo dendritic regression, fo llowed by growth of new arborizations during adult development. The ne urons must innervate different targets in the larva and adult, since m any larval muscles degenerate and are replaced during metamorphosis. B oth neurons were reactive with an antibody to the neuromodulatory comp ound, octopamine, in the larval and adult stages. Pairwise intracellul ar recordings in isolated nerve cords revealed spontaneous excitatory synaptic potentials that occurred in the ventral median neurons of eac h ganglion in an anterior-to-posterior sequence. The synaptic potentia ls were eliminated when the interganglionic connective was interrupted posterior to the subesophageal ganglion. The ventral median neurons w ere also excited by tactile stimulation of the body surface in larvae, pupae and adults. (C) 1993 Wiley-Liss, Inc.