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 was designed to evaluate two endogenous and one synthetic neuroactive steroid that positively modulate the gamma - aminobutyric acid ( GABA ( A ) ) receptor against the increase in sensitivity to the convulsant effects of cocaine engendered by repeated cocaine administration ( seizure kindling ) .
### Output Text:
The present study was designed to evaluate two endogenous and one synthetic neuroactive <span class="chemical">steroid</span> that positively modulate the <span class="chemical">gamma - aminobutyric acid</span> ( <span class="chemical">GABA</span> ( A ) ) receptor against the increase in sensitivity to the convulsant effects of <span class="chemical">cocaine</span> engendered by repeated <span class="chemical">cocaine</span> administration ( seizure kindling ) . 