Fig. 3. Mean cardiovascular variables at rest and while swimming at 1 and 2 BL s^-1 in the sea bass, Dicentrarchus labrax. Solid lines represent untreated fish (N=8-9) and hatched lines (N=7) represent fish after treatment with prazosin (1 mg kg^-1 M_b). The measured and calculated variables are (A) dorsal aortic pressure (PDA); (B) central venous pressure (PCV); (C) cardiac output (); (D) heart rate (fH); (E) stroke volume (V_s) and (F) systemic resistance (R_sys) All values are means ± S.E.M. ^*Statistically significant difference (P0.05) from the resting values within a treatment group, and statistically significant difference (P0.05) between the values before and after prazosin treatment.