A motoneuron spared from steroid‐activated developmental death by removal of descending neural inputs exhibits stable electrophysiological properties and morphology

Neurons die during the development of nervous systems. The death of specific, idenified motoneuros during metamorphosis of the tobacco hornworm, Manduca sexta, provides an accessible model system in which to study the regulation of postembryonic neuronal death. Hormones and descending neural inputs have been shown toinfluence the survival of abdominal motoneurons during the first few days of adult life in this insect. Motoneurons prevented from undergoing the normal process of developmental degeneration by removal of neural inputs were examined at the physiological and structural levels using several cell imaging techniques. Although these neurons lost their muscle targets and experienced the endocrine cue that normally triggers death, they showed no overt electrophysiological or morphological signs of degeneration. Thus, by appropriate intervention, the MN‐12 motoneuron can be spared from developmental neuronal death and remain as a functioning supernumerary element in the mature nervous system. © 1995 John Wiley & Sons, Inc.