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: Pharmacology of gamma - aminobutyric acidA receptor complex after the in vivo administration of the anxioselective and anticonvulsant beta - carboline derivative abecarnil .
### Output Text:
Pharmacology of <span class="chemical">gamma - aminobutyric acidA</span> receptor complex after the in vivo administration of the anxioselective and anticonvulsant <span class="chemical">beta - carboline</span> derivative <span class="chemical">abecarnil</span> . 