The dendritic arbor of locus coeruleus neurons contributes to opioid inhibition. Travagli, R. Alberto, Martin Wessendorf and John T. Williams. Vollum Institute, L474, Oregon Health Sciences University, 3181 Sam Jackson Park Road, Portland, OR 97201, Department of Cell Biology and Neuroanatomy, University of Minnesota, 4-135 Jackson Hall, 321 Church Street S.E., Minneapolis, MN 55455.
APStracts 2:0330N, 1995.
SUMMARY AND CONCLUSIONS
1. The nucleus locus coeruleus (LC) is made up of noradrenergic cells all of which are hyperpolarized by opioids. Recent work has shown that the reversal potential of the opioid induced current is more negative than the potassium equilibrium potential. The aim of the present study was to determine if the extent of the dendritic field could contribute to the very negative opioid reversal potential. 2. Individual LC cells were labeled in the brain slice preparation. The number of dendrites found on cells in slices sectioned in the horizontal plane was greater than cells in coronal slices. However, the dimensions of the cell bodies slices from each plane was not significantly different. 3. The resting conductance of neurons from slices cut in the horizontal plane was significantly larger than in cells from coronal plane. 4. The amplitude of the outward current induced by ME was larger in cells from horizontal slices and the reversal potential was more negative than cells in coronal slices. 5. The results show that the plane of section influences the membrane properties and opioid actions of LC neurons in vitro and suggests that these differences correlate with the numbers of dendrites. The results suggest that in vivo in addition to intrinsic membrane properties and synaptic inputs, the structural makeup of the nucleus is an important factor in determining the activity. 

Received 10 July 1995; accepted in final form 1 November 1995.
APS Manuscript Number J436-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95