2066
The stimulant action of nicotine was blocked by the central nicotinic antagonist mecamylamine but not by the peripheral nicotinic blocker hexamethonium , indicating that the response is probably mediated by central nicotinic receptors .
 nicotine, mecamylamine, hexamethonium
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 nicotine, mecamylamine, hexamethonium