Fig. 2.

Effect of vaccination with M-KLH or OXY-KLH on opioid concentrations after intravenous administration of low or high heroin or oxycodone doses. Plasma (A) and brain (B) samples were collected 4 minutes following the end of 1-minute infusion of heroin, and serum (C) and brain (D) samples were collected 4 minutes following the end of 1-minute infusion of oxycodone. Plasma and brain drug concentrations after heroin administration represent total opioid (heroin + 6-AM + morphine); converted data from Fig. 1 and presented here for comparison. *P < 0.05; **P < 0.01; ***P < 0.001 for the difference between vaccinated rats and KLH controls. Numbers above bars represent the percentage of difference from controls. Unpaired t tests with Welch’s correction were used to compare groups. Mean ± S.D., n = 8/group.