Effects of 8-OH-DPAT (250 μg/kg, s.c.) and WAY-100135 (10 mg/kg, i.p.) on startle amplitude and %PPI in rats after 14 days of either control diet (TR+) or TRP-poor (TR−) diet. n=8–10/group. Treatment and diet conditions are indicated below the horizontal axis. Results are expressed as mean ± SEM. **,p < .01; ***, p < .001, main effects for diet; ^^^, p < .001, main effects for pre-treatment. §§§, p < .001, in comparison with rats treated with SAL + SAL (pre-treatment x treatment interaction); †††, p < .001, in comparison with rats treated with SAL + 8-OH-DPAT (pre-treatment x treatment interaction). For further details, see text.