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 sp ecific, identified motoneurons during metamorphosis of the tobacco hor nworm Manduca sexta, provides an accessible model system in which to s tudy the regulation of postembryonic neuronal death, Hormones and desc ending neural inputs have been shown to influence tile survival of abd ominal motoneurons during the first few days of adult life in this ins ect, Motoneurons prevented from undergoing the normal process of devel opmental degeneration by removal of neural inputs were examined at the physiological and structural levels using several cell imaging techni ques, 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 deve lopmental neuronal death and remain as a functioning supernumerary ele ment in the mature nervous system. (C) 1995 John Wiley & Sons, Inc.