Percentage change of test R2 responses induced by SCH23390 + eticlopride, SCH23390, and eticlopride. Conditioning facilitation was decreased by either the combination of SCH23390 + eticlopride (A, *P < 0.05, n = 10) or the SCH23390 alone (B, *P < 0.05, n = 10) at 2,000-ms ISI. Conditioning suppression was increased by the SCH23390 + eticlopride at 250- and 500-ms ISIs (B). No effects on conditioning changes were found in eticlopride administration group (C) at any ISIs (n = 10).