Figure 3

Cross tolerance between amphetamine and pseudoephedrine. Western blot analysis was used to measure the level of cross-tolerance between pseudoephedrine and amphetamine to drug induced c-Fos expression in striatum (n = 3) and nucleus accumbens (n = 3) in chronically treated rats. A: acute response to amphetamine in rats chronically treated with saline, amphetamine and pseudoephedrine (8 day treatment of drug twice a day with an increasing dose schedule; rats were killed 1.5 h after 40 mg/kg, i.p pseudoephedrine injection). There was no significant difference in the acute response to amphetamine between rats chronically treated with amphetamine or pseudoephedrine. B: acute response to pseudoephedrine in rats chronically treated with saline, pseudoephedrine and amphetamine (8 day treatment of drug twice a day with an increasing dose schedule, rats were killed 1.5 h after 40 mg/kg, i.p pseudoephedrine injection). There was no significant difference in the acute response to pseudoephedrine between rats treated with amphetamine or pseudoephedrine. The data are expressed as percentage of c-Fos value of control animals injected with saline. Values are mean ± S.E.M. a indicates significantly different from control and chronic; b indicates significantly different from acute, p < 0.05.