2.1. Animals
All experiments were approved by the appropriate Committee on Animal
Care and Use. Male C57BL/6J mice (7–8 weeks old) were purchased from
SPF Biotechnology Co., Ltd (Beijing, China).
βarr2−/− mice
were kindly gifted by Professor Ma Lan of Fudan University. This strain
was generated by the laboratory of R. J. Lefkowitz (Duke University
Medical Center, Durham, NC, USA) and backcrossed onto a C57BL/6J
background. The animals used in the present study were wild-type,
βarr2−/−, or βarr2+/− littermates
resulting from heterozygous breeding, and the descendants of mice
separately bred as homozygous wild-type, βarr2−/−, or
βarr2+/− mice after the initial backcrossing.
βarr2−/− mice were backcrossed onto the C57BL/6J
background every six generations. All mice were housed in groups of 5–6
mice per cage and maintained on a 12-h/12-h light/dark cycle with food
and water available ad libitum. All animals were adapted for at least 2
days before experimentation.