Two novel 5-HT6 receptor antagonists ameliorate scopolamine-induced memory deficits in the object recognition and object location tasks in Wistar rats

► CMP X and CMP Y are two novel and highly selective 5-HT6 receptor antagonists. ► CMP X and CMP Y improved scopolamine-induced deficits in tests for episodic memory. ► Donepezil and reference 5-HT6 antagonist GSK-742457 also improved performance. ► Co-adm. of CMP X, CMP Y with donepezil resulted in additive cogn. enhancing effects. ► 5-HT6 antagonists could have potential as adjunctive therapy to donepezil.