Acylguanidines as Bioisosteres of Guanidines: <i>N</i><sup>G</sup>-Acylated Imidazolylpropylguanidines, a New Class of Histamine H<sub>2</sub> Receptor Agonists
demonstrated by HPLC-MS, the acylguanidines (bioisosteres of the alkylguanidines) were absorbed from the gut of mice and detected in brain. In GTPase assays using recombinant receptors, acylguanidines were more potent at the guineapig than at the human H2R. At the hH1R and hH3R, the compounds were weak to moderate antagonists or partial agonists. Moreover, potent partial hH4R agonists were identified. Receptor