which IEG is activated in which brain area at what point in development. At the 
earliest age examined (figure 1 , P8), IEG activation is limited to the striatum, 
where c -fos and z/^268 are induced. By PI 5 (figure 2) and thereafter (P28, 
figure 3; adult, figure 4) all three lEGs are induced in striatum and cortex. The 
elevation of c -jun and z/7/268 in cortex and striatum at these ages was modest 
(1 .2 to 2.2x) but consistent. C -fos induction was more significant in cortex (1 .8 
to 2. lx) and was dramatically increased in striatum (4.6 to 6.6x). At all ages 
examined, striatal c -fos demonstrated the most significant cocaine-induced 
IEG elevation. In cerebellum, c -jun and ziU 268 were not induced at any age 
examined. At this dose, but not at 30 mg/kg, c-fos was induced in cerebellum, 
but only on or after PI 5 (data not shown). 
Cocaine-Induced lEGs: P8 
5 
<D 
C 
Striatum 
■ c -fos 
□ z/7/268 
FIGURE 1. Induction ofc-fos mRNA (4.2-fold) and zif/268 mRNA (1.8-fold) in 
striatum of P8 rats treated with cocaine, 40 mg/kg/intraperitoneal 
(IP), vs. saline. Rats were sacrificed 45 minutes after injection. 
At this age, changes in striatal c-jun were not evident, nor was 
induction of c-fos, c-jun, or zif/268 evident in neocortex or 
cerebellum. 
164 
