c-fos mRNA — 
Hours after 
injection 
I I I I I h 
0.5 2 6 24 48 0.5 
Saline 
Scan of ethidium 
bromide-stained 
RNA gel 
FIGURE 1 . Time course of increase in striatal c-fos mRNA. Rats were 
administered 40 mg/kg of cocaine IP. The main increase 
(eightfold to tenfold) occurred at 30 minutes. The autoradiogram 
is overexposed to show that only minor elevations of c-fos 
transcript were detected between 2 and 48 hours compared 
with saline (last lane). Densitometric scan of the corresponding 
ethidium bromide-stained RNA gel is placed at the bottom and 
indicates that the amount of RNA loaded in each lane is similar. 
186 
