2955
Systemic pretreatment with ketanserin , a relatively specific type - 2 serotonin receptor antagonist , significantly attenuated the muscle rigidity produced in rats by the potent short - acting opiate agonist alfentanil .
 Chemical: ketanserin; Chemical: serotonin; Disease: muscle rigidity; Chemical: alfentanil
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 Chemical: ketanserin; Chemical: serotonin; Disease: muscle rigidity; Chemical: alfentanil