3778
Mutants of GPR18 , designed to constitutively activate receptors , did not tonically inhibit calcium currents , indicating a lack of GPR18 activation or coupling to endogenous G proteins .
 Chemical: calcium
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: calcium