FIGURE 8. 
SOURCE: 
This bright-field photomicrograph illustrates Fos-immunoreactive 
and retrogradely labeled neurons in a 40-pm thick horizontal 
section through lamina I of the lumbar dorsal horn. The 
retrograde tracer WGAapoHRP-AU was injected into the 
contralateral brain stem and thalamus. Fos-positive cells 
have a uniformly stained nucleus (>). Projection neurons 
contain punctate cytoplasmic label that results from silver 
intensification of the colloidal gold in the tracer; the nuclei 
of single-labeled projection neurons are unstained (o>). 
Double-labeled cells (->) have a densely stained nucleus 
and cytoplasmic silver precipitate. 
Men&rey, D.; Gannon, A.; Levine, J.D.; and Basbaum, A.I. 1989. 
Journal of Comparative Neurology. Copyright © 1 989 by Wiley- 
Liss. Reprinted by permission of Wiley-Liss, a division of John 
Wiley and Sons, Inc. 
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