Vasorelaxant effects of Cerebralcare Granule® are mediated by NO/cGMP pathway, potassium channel opening and calcium channel blockade in isolated rat thoracic aorta

Abstract

Ethnopharmacological relevanceCerebralcare Granule (CG), one of the famous classical recipes in traditional Chinese medicine, is developed from the “Decoction of Four Drugs”. It has been used for treatment of cerebrovascular related diseases, such as hypertension. It is well known that vasodilatation plays a very important role in hypertensive. Despite the popular medicinal use of CG, little data was available to its activity and mechanism involved in vasodilatation. Therefore, we aimed to investigate the vasorelaxant effects of CG on isolated rat thoracic aorta so as to assess some of the possible mechanisms. The present study was performed to examine the vasodilative activity of CG and its mechanisms in isolated rat thoracic aorta. Materials and methodsCG was studied on isolated rat thoracic aorta in vitro, including endothelium-intact and endothelium-denuded aortic rings. In present study, specific inhibitors including NO synthase inhibitor NG-nitro-l-arginine methyl ester (l-NAME), cyclooxygenase (COX) inhibitor indomethacin (INDO), non-selective K+ channel inhibitor tetraethylammonium chloride (TEA), Kir channel inhibitor BaCl2, KATP channel inhibitor Glibenclamide (Gli) and cholinergic receptor antagonist atropine were used, they were added 20min before NE contraction and then added CG-induced vasodilation. ResultsRemoval of endothelium or pretreatment of aortic rings (intact endothelium) with l-NAME (0.1mM) or INDO (0.01mM) significantly blocked the CG induced relaxation. Pretreatment with the non-selective K+ channel inhibitor TEA (1mM), or the Kir channel inhibitor BaCl2 (0.1mM), neither of them had no influence on the CG-induced response (p>0.05). However, pretreatment with the KATP channel inhibitor Gli (0.01mM) produced significant inhibition on the CG-induced response (p<0.01). Besides, CG also inhibited the contraction triggered by NE in endothelium-denuded rings in Ca2+-free medium. CG (0.4, 0.8 and 3.2mg/mL) produced rightward parallel displacement of CaCl2 curves and reduced the maximum contraction induced by 30mM CaCl2 to 31.1±9.3%, 18.8±6.9% and 9.4±4.5%, respectively. The relaxation, induced by CG on endothelium-intact rat aortic rings pre-contracted with NE, was significantly attenuated in the presence of atropine (EC50=3.7mg/mL, p<0.01). ConclusionsOur results suggest that CG induces relaxation in rat aortic rings through an endothelium-dependent pathway mediated by NO/cGMP pathway and an endothelium-independent pathway involving blockade of Ca2+ channels, inhibition of Ca2+ mobilization from intracellular stores, opening of KATP channel. In addition, the muscarinic receptor stimulation is also one of the vasorelaxant mechanisms.