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 antinociception produced by ( + / - ) - PG - 9 was prevented by the unselective muscarinic antagonist atropine , the M1 - selective antagonists pirenzepine and dicyclomine and the acetylcholine depletor hemicholinium - 3 , but not by the opioid antagonist naloxone , the gamma - aminobutyric acidB antagonist 3 - aminopropyl - diethoxy - methyl - phosphinic acid , the H3 agonist R - ( alpha ) - methylhistamine , the D2 antagonist quinpirole , the 5 - hydroxytryptamine4 antagonist 2 - methoxy - 4 - amino - 5 - chlorobenzoic acid 2 - ( diethylamino ) ethyl ester hydrochloride , the 5 - hydroxytryptamin1A antagonist 1 - ( 2 - methoxyphenyl ) - 4 - [ 4 - ( 2 - phthalimido ) butyl ] piperazine hydrobromide and the polyamines depletor reserpine .
### Output Text:
The antinociception produced by ( + / - ) - <span class="chemical">PG - 9</span> was prevented by the unselective muscarinic antagonist <span class="chemical">atropine</span> , the M1 - selective antagonists <span class="chemical">pirenzepine</span> and <span class="chemical">dicyclomine</span> and the <span class="chemical">acetylcholine</span> depletor <span class="chemical">hemicholinium - 3</span> , but not by the opioid antagonist <span class="chemical">naloxone</span> , the <span class="chemical">gamma - aminobutyric acidB</span> antagonist <span class="chemical">3 - aminopropyl - diethoxy - methyl - phosphinic acid</span> , the H3 agonist <span class="chemical">R - ( alpha ) - methylhistamine</span> , the D2 antagonist <span class="chemical">quinpirole</span> , the <span class="chemical">5 - hydroxytryptamine4</span> antagonist <span class="chemical">2 - methoxy - 4 - amino - 5 - chlorobenzoic acid 2 - ( diethylamino ) ethyl ester</span> hydrochloride , the <span class="chemical">5 - hydroxytryptamin1A</span> antagonist <span class="chemical">1 - ( 2 - methoxyphenyl ) - 4 - [ 4 - ( 2 - phthalimido ) butyl ] piperazine</span> hydrobromide and the polyamines depletor <span class="chemical">reserpine</span> . 