control 
A B 
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S 
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O 
o 
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c 
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CL 
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FIGURE 4. Autoradiograms showing regulation of Fos mRNA in the LC in 
response to acute and chronic morphine treatment and opiate 
withdrawal. A: Control, subcutaneous (SC) administration of 
normal saline to control rats; tolerant, SC administration of saline 
to morphine-tolerant rats; and withdrawal, SC administration of 
naltrexone to morphine-tolerant rats. Animals were sacrificed 1 
hour after the injections. B: Control, SC administration of normal 
saline to control rats and acute, SC administration of morphine 
to control rats. Animals were sacrificed 90 minutes after the 
injections, and levels of Fos mRNA were analyzed (using 5 mg 
of total RNA) by Northern blotting. 
SOURCE: Hayward et al. 1990. Copyright 1990 by Elsevier Science 
Publishers (Amsterdam). 
105 
