Deafferentation Increases the Intracellular Calcium of Cochlear Nucleus Neurons in the Embryonic Chick. Zirpel, Lance, Edward A. Lachica, and William R. Lippe. Department of Physiology & Biophysics, SJ-40, School of Medicine, University of Washington, Seattle, WA 98195, Virginia Merrill Bloedel Hearing Research Center, RL-30, University of Washington, Seattle, WA 98195.
APStracts 2:0185N, 1995.
Summary and Conclusions 1. Ratiometric fura-2 imaging was used to measure the intracellular calcium concentration ([Ca 2+ ] i ) of neurons in the embryonic avian cochlear nucleus, nucleus magnocellularis (NM), following an in ovo unilateral cochlea removal (deafferentation). 2. The mean [Ca 2+ ] i of NM neurons receiving normal input was 113 nM. 3. Deafferentation increased the mean [Ca 2+ ] i of NM neurons to 247 nM, 311 nM, 339 nM and 314 nM at 1, 3, 6 and 12 hours after cochlea removal, respectively. These values did not differ significantly. 4. The percent frequency distribution of deafferented NM neuron [Ca 2+ ] i shifts away from normative levels toward higher [Ca 2+ ] i at 1 and 3 hours after cochlea removal, but shifts back toward normative levels at 6 and 12 hours after cochlea removal. 5. This increased [Ca 2+ ] i following cochlea removal temporally coincides with well characterized changes in NM neurons following activity deprivation. 6. These data suggest that deregulation of [Ca 2+ ] i homeostasis plays a key role in NM neuron degeneration and death following activity deprivation. 

Received 22 May 1995; accepted in final form 21 June 1995.
APS Manuscript Number J337-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.