Number of IR Cells Number of IR Cells 
IP 0.3 3 10 30 
Saline 
Cocaine (mg/kg) 
FIGURE 7. Time course and dose response of the increase in Fos- 
immunoreactive (IR) cell nuclei following cocaine 30 mg/kg IP. 
Upper panel: The peak elevation of Fos-immunoreactive proteins 
is seen between 2 and 4 hours and returns to control over 
approximately the next 24 hours. This contrasts with the increase 
in c-fos mRNA, which peaked sharply at 30 minutes. Lower 
panel: The increase in Fos-immunoreactive protein staining 
occurred over the same dose increase in mRNA. Data were 
collected 2 hours after injection. Stained nuclei were counted 
regardless of intensity. However, the intensity increased 
progressively, especially between 10 and 30 mg/kg. At the latter 
dose many neurons were very dark brown, almost black, in color. 
*p<0.05, **p<0.01. 
SOURCE: Young et al. 1991 
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