Influence of MDL 100,907 (MDL) or SB 206553 (SB) pretreatment on DOI regulation of BDNF mRNA. Rats were pretreated (30 min) with vehicle, MDL 100,907 (1 mg/kg), or SB 206553 (15 mg/kg) before administration of DOI (2 mg/kg), and levels of BDNF mRNA were determined 2 hr later by in situ hybridization. In a separate experiment, rats were administered vehicle, MDL 100,907, and SB 206553, and levels of BDNF mRNA were determined 2 hr later. Results are expressed as percent of vehicle and are the mean ± SEM (n = 4). *p < 0.05 compared with vehicle (ANOVA; Newmann–Keuls post hoc test).