Cocaine-Induced lEGs: P15 
o 
c 
• ■M 
CO 
< n 
c/5 
c 
o 
• ■Hi 
o 
3 
■o 
C 
2 
o 
Cortex Striatum 
■ c -fos 
0 c-jun 
□ zif/268 
FIGURE 2. Graph depicting induction (vs. saline) ofc-fos, c-jun , and zif/268 
mRNA in cortex and striatum of 15-day-old rat pups sacrificed 45 
minutes after IP injection of cocaine , 40 mg/kg. All three lEGs are 
induced in cortex and striatum. 
To characterize the consequences of cocaine-induced striatal IEG activation, 
the authors first performed gel-shift assays. We examined changes in the 
level of AP-1 DNA binding activity evident in striata of animals at different 
ages (P28 and adults) 2 hours after injection with cocaine, 30 mg/kg/I P. 
Striatal tissue suspended in buffer was homogenized, and protein was isolated 
as previously described (Nguyen et al., in press). Protein was quantitated and 
samples preincubated on ice for 15 minutes with poly (dl-dC), with or without 
cold competitor (100 ng). Samples were then incubated at room temperature 
for 15 minutes with 1 to 1.5 ng of P 32 -end-labeled double-stranded 
oligonucleotide probe and electrophoresed through a 4-percent nondenaturing 
polyacrylamide gel. On day P28 (figure 5) and in the adult (figure 6), extracts 
prepared from saline-treated animals demonstrated basal levels of binding 
activity to the AP-1 DNA sequence. However, cocaine administration 
augmented AP-1 DNA binding activity 2- to 2.5-fold on day 28 and 3- to 
3.5-fold in the adult (representing the average of two samples per condition). 
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