Phenylephrine-Induced Contraction in Guinea Pig Thoracic Aorta Is Triggered by Stimulation of α-Adrenoceptors Functionally Coupled with Store-Operated Ca Channels and Voltage-Dependent Ca Channels.

We examined whether the α-adrenoceptor (AR), which shows low affinity (pA < 9) for prazosin (an α-AR antagonist) and high affinity (pA ≈ 10) for tamsulosin/silodosin (α-AR antagonists), is involved in phenylephrine-induced contractions in the guinea pig (GP) thoracic aorta (TA). Intracellular signaling induced by α-AR activation was also examined by focusing on Ca influx pathways. Tension changes of endothelium-denuded TAs were isometrically recorded and mRNA encoding α-ARs/Ca channels and their related molecules were measured using RT-quantitative PCR.