Liberation of histamine by compound 48/80, tolazoline, betahistine and burimamide from isolated spontaneously beating guinea pig and rabbit atrial pairs.

Tolazoline, betahistine, burimamide and compound 48/80 release histamine from isolated guinea pig atria resulting in histamine concentrations that stimulate H2-receptors. Tolazoline, burimamide and 48/80 also release histamine from rabbit atria but do not result in histamine concentrations that will stimulate either H1- or H2-receptors. However, betahistine (which does not release histamine from rabbit atria) and tolazoline stimulate the rabbit atrial chronotropic response by releasing catecholamines.