Clonidine has various clinical effects mediated by agonism of α 1 - or α 2 -adrenoceptors and the blocking of hyperpolarization-activated-nucleotide-gated pacemaker channels (HCN). It is unknown whether clonidine can also stimulate human cardiac histamine H 2 receptors (hH 2 Rs). We used isolated electrically stimulated left and spontaneously beating right atrial preparations from mice overexpressing the hH 2 R specifically in...

Ergometrine (6a R ,9 R )- N -(( S )-1-hydroxypropan-2-yl)-7-methyl-4,6,6a,7,8,9-hexa-hydro-indolo-[4,3- fg ]chinolin-9-carboxamide or lysergide acid β-ethanolamide or ergonovine) activates several types of serotonin and histamine receptors in the animal heart. We thus examined whether ergometrine can activate human serotonin 5-HT 4 receptors (h5-HT 4 R) and/or human histamine H 2 receptors (hH 2 R) in the heart of transgenic m...