"Studies with 16 arylguanidines found that their functional activity spanned a broad spectrum from superagonist to full agonist partial agonist and antagonist at 5-HT3 receptors; results confirm the utility of phenylguanidine as an extremely versatile scaffold in the design of 5-HT3 ligands with a "tunable" level of agonist or antagonist activity"xsd:string