Caudate Hippocampus 
i ii 1 
28S — ► 
Preprodynorphin -► 
18S-* 
Dose of 
cocaine o 5 10 20 40 0 5 10 20 40 
(mg/kg ip) I II I 
Caudate Hippocampus 
FIGURE 2. Upper panel: Dose-response ofc-fos mRNA increase assessed 
30 minutes after IP injection of cocaine at doses between 5 and 
40 mg/kg. The increase is regionally selective, occurring in 
striatum but not in hippocampus. Increases over control were 
detected at all doses of cocaine. Lower panel: The blot was 
reprobed for preprodynorphin mRNA. No change was seen in 
the amount of this transcript at 30 minutes after cocaine in either 
caudate or hippocampus. The blot was probed a third time for 
fi-actin (not shown), which demonstrated that the amount loaded 
was very similar across the 10 lanes. 
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