CHRNA4 and cystic fibrosis: Since our in vitro data strongly suggest a significant role of ACh–α7 nAChR signaling in causing CF proliferation and collagen synthesis, we next investigated the role of ACh–α7 nAChR signaling in PH-induced RV dysfunction in vivo by treating PH rats (SuHx model) with nAChR antagonist Mec (20 mg/kg/d i.p. for 3 weeks, Figure 7A).