Selective alpha-adrenoceptor and calcium antagonists have been used to determine both the alpha 1-adrenoceptor subtype and the extracellular calcium requirement for renal nerve-mediated antinatriuresis and antidiuresis in deoxycorticosterone acetate (DOCA)-salt and two-kidney, one clip (2K1C) Goldblatt hypertensive rats. Stimulation of the renal nerves at low frequencies reduced urine flow and absolute and fractional sodium excretions by 40-60% in pentobarbitone anaesthetized control, sham-operated, DOCA-salt and 2K1C Goldblatt hypertensive rats. Administration of prazosin, but not idazoxan, inhibited the renal nerve-induced excretory responses in both models of hypertension, a result compatible with the involvement of alpha 1-adrenoceptors. By contrast, the calcium antagonist inhibited the renal nerve-dependent antinatriuresis and antidiuresis in DOCA-salt but not 2K1C Goldblatt hypertensive rats. These results showed that the renal nerves mediated their action via alpha 1-adrenoceptors, but that the postreceptor responses were dependent on extracellular calcium in DOCA-salt but not 2K1C Goldblatt rats.