Fig. 1.

Effect of modafinil andd-amphetamine on wakefulness and caudate DA efflux in narcoleptic hypocretin receptor 2 mutant dogs. Systemic administration of modafinil (5 mg/kg, i.v.) and d-amphetamine (0.1 mg/kg, i.v.) equipotently increased time spent awake. The most pronounced effect on wakefulness was observed during the first hour after injection [inset; *p < 0.01 for both treatments compared with the respective vehicle treatment (white bars) by Student's t test;n = 4 per group; mean ± SEM]. Microdialysis experiments demonstrated that administration of amphetamine and modafinil significantly increased extracellular DA levels (p < 0.05;d-amphetamine or modafinil relative to vehicle treatment; repeated-measures ANOVA with Bonferroni's–Dunn'spost hoc comparisons; n = 4 per group; mean ± SEM). The baseline DA concentrations (at time 0) for modafinil and d-amphetamine sessions were 17.2 ± 3.1 and 17.6 ± 3.5 nm (mean ± SEM), respectively, and did not differ statistically among treatments.VEH, 1 ml of 100% DMSO; d-AMP,d-amphetamine.