Stimulation of cyclic AMP‐dependent protein kinase in rat atria by (–;)‐CGP 12177 through an atypical β‐adrenoceptor

Abstract

Mammalian hearts possess an atypical β‐adrenoceptor (non‐β₁, non‐β₂, non‐β₃) through which (–)‐4‐(3‐t‐butylamino‐2‐hydroxypropoxy)benzimidazol‐2‐one ((–)‐CGP 12177) causes cardiostimulant effects. Here we showed that (–)‐CGP 12177 increased the activity of adenosine 3′ : 5′‐cyclic monophosphate (cyclic AMP)‐dependent protein kinase in the presence of 200 nm (–)‐propranolol in rat atria at a concentration (10 μm) that elicits maximum positive chronotropic and inotropic effects. The phosphodiesterase inhibitor 3‐isobutyl‐l‐methylxanthine (IBMX) potentiated the positive chronotropic and inotropic effects of (–)‐CGP 12177. We suggest that the atypical β‐adrenoceptor is coupled positively to the Gs protein‐adenylyl cyclase system.British Journal of Pharmacology (1997) 120, 1187–1189; doi:10.1038/sj.bjp.0701053