Effects of the 5-HT6 receptor antagonist Ro 04-6790 on learning consolidation

The 5-HT6 receptor antagonist Ro-04-6790 or 8-OH-DPAT injection improved learning consolidation on an autoshaping task, while mCPP, scopolamine and dizocilpine decreased the performance. The effect induced by scopolamine, but not that induced by mCPP, was reversed completely by Ro-04-6790, while dizocilpine effect was antagonized partially. Nevertheless, ritanserin or WAY 100635. but not Ro 04-6790. antagonized the 8-OH-DPAT facilitatory effects on learning consolidation. As WAY 100635 did not modify the Ro 04-6790 facilitatory effect, hence 5-HT1A, and/or 5-HT7, but not 5-HT6, receptors might mediate the 8-OH-DPAT facilitatory effect on learning consolidation. Since, the Ro 04-6790 facilitatory effect was unaffected by 5-HT1A, 5-HT2A/2B/2C, 5-HT3 or 5-HT4 receptor blockade, thereby, the facilitatory effect induced by Ro 04-6790 involved specifically 5-HT6 receptors. Indeed, the present data provide further support to the notion that, 5-HT6 receptors play a significant part in the learning consolidation under normal and dysfunctional memory conditions. (C) 2001 Elsevier Science B.V. All rights reserved.