In vivo, the administration of a β2-AR agonist to rats with adjuvant-induced arthritis prior to or at the time of adjuvant challenge (Coderre et al., 1990) resulted in disease exacerbation, while β2-AR agonist treatment at or after disease onset reduced disease severity (Malfait et al., 1999; Lubahn et al., 2004). This evidence concerns the gene ADRB2 and Arthritis.