Effects of clonidine and other imidazole-receptor binding agents on second messenger systems and calcium influx in bovine adrenal chromaffin cells.

摘要: Clonidine and related imidazoline compounds bind to alpha 2-adrenergic as well newly described non-adrenergic imidazole/imidazoline receptors in brain peripheral tissues. The present study was undertaken identify the signal transduction mechanism coupled this new class of (imidazole receptors) using bovine adrenal chromaffin cells. did not modify basal or forskolin-stimulated production cyclic AMP (cAMP), suggesting absence functionally active also failed GTP gamma S- carbachol-stimulated increase phosphoinositide hydrolysis. However, clonidine increased significantly GMP (cGMP) uptake 45Ca2+. cGMP response slower (peak at 15 min) smaller (only about 50% over control) than acetylcholine shared by other agents that imidazole receptors. In contrast, all influx 45Ca2+ into It is concluded (a) are distinct linked different mechanisms; (b) classical G-protein soluble second messenger systems receptors; (c) may a non-receptor-mediated intracellular action; (d) regulate calcium levels through an ion regulating system be from channels.