Figure 5: Effect of high sympathetic reactivity or β 2 -AR treatment on inflammatory arthritis in rodent models. In both the collagen-induced and adjuvant-induced animal models of RA, treatments that mimic increasing sympathetic nerve activity (e.g., administration of β2-AR agonists) have differential effects on disease severity depending upon the timing of the treatment relative to disease onset. Treatment with β2-AR agonists at the time of the disease-inducing challenge to disease onset increases the severity of disease at the time when disease becomes apparent and as the disease progresses from severe to chronic stages. In contrast, when β2-AR agonists are administered beginning at disease onset, disease severity, including extent of joint inflammation and progressive joint destruction, is significantly reduced. Tx: treatment.