Heterodimerization of β1- and β2-adrenergic receptor subtypes optimizes β-adrenergic modulation of cardiac contractility - Wei-Zhong Zhu; Khalid Chakir; Shengjun Zhang; Dongmei Yang; Catherine Lavoie; Michel Bouvier; Terence E. Hébert; Edward G. Lakatta; Heping Cheng; Rui-Ping Xiao (Circulation Research, 2005)