Effects of prazosin (A-a; Group 9, n=5), prazosin plus rauwolscine (A-b; Group 10, n=6), and prazosin plus GABA (C; Group 11, n=6) on the renal nerve stimulation (RNS)-induced changes in perfusion pressure (PP), and effects of GABA (B; Group 12, n=5) on exogenous noradrenaline (NA)-induced changes in PP in the isolated pump-perfused rat kidney. Δ, changes from basal values in response to RNS or exogenous noradrenaline (NA). Prazosin (Group 9, 10 and 30 nM), Groups 10 and 11, 10 nM), rauwolscine (10 nM) and GABA (Group 11, 10 μM; Group 12, 3 and 10 μM) were infused into the perfusate at 0.05 ml min−1. *P<0.01 compared with the control value.