Transmural electrical stimulation (ES; A) or acetylcholine infusion (ACh; B) was applied to the adrenal gland in the absence (control, •) or presence of nifedipine (0.3 μm, ^; 1 μm, ▵; 3 μm, □). Symbols and vertical bars represent means ±s.e.m. * P < 0.05, ** P < 0.01 compared with corresponding control response obtained before nifedipine treatment.