In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

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