(A, C) Effects of PYT HCl, PIT HCl, DBT HCl, and 2-MT HCl treatment in the head-twitch response (HTR) and the mRNA expression levels of 5-HTR2a in the mouse prefrontal cortex during 7 days of treatment and on the day of challenge. (B) Another cohort of mice were used to examine the effect of ketanserin pretreatment (0.1 mg/kg) 10 min prior to treatment with PYT HCl, PIT HCl, DBT HCl, or 2-MT HCl during the HTR assay. Mice were treated with vehicle, PYT HCl (3 mg/kg), PIT HCl (3 mg/kg), DBT HCl (3 mg/kg), and 2-MT HCl (3 mg/kg) repeatedly for 7 days, and then challenged with the same drug and dose following a 7-day withdrawal period. HTRs and 5-HTR2a mRNA expression levels were assessed on the 1st and 7th day of treatment and on the challenge day. Values are mean ± S.E.M. n=5–6 animals per group. *p<0.05, **p<0.01, ***p<0.001 significantly different from the veh, †p<0.05, ††p<0.01, †††p<0.001 compared to acute treatment; #p<0.05, ###p<0.001 compared to PYT HCl, PIT HCl, DBT HCl, or 2-MT HCl pretreated with veh (Bonferroni’s posttest).