tokens: The present study sought to characterize the cognitive - enhancing effects of the 5-HT ( 6 ) antagonist Ro4368554 ( 3-benzenesulfonyl-7-(4-methyl-piperazin-1-yl)1H-indole ) in a rat object recognition task employing a cholinergic ( scopolamine pretreatment ) and a serotonergic -( tryptophan ( TRP ) depletion ) deficient model , and compared its pattern of action with that of the acetylcholinesterase inhibitor metrifonate .