Dopamine-1 (DA-1) receptor antagonist SCH23390 and agonist Fenoldopam (F) are infused individually and combined intrarenally in doses confined to the kidney and different parameters of renal function will be measured. Time control study will be done where vehicle (V) alone will be given. Studies are done on same group of dogs on different days according to the following protocol: period: 1:V 2:V 3:V 4:V 5:V 6:V period: 1:V 2:V 3:V 4:V 5:SCH23390 6:V