Fig. 1. Ca²⁺ oscillations evoked by acetylcholine (ACh) in duodenum myocytes. Dependence on M2 muscarinic receptors and ryanodine receptors. (A) Typical Ca²⁺ oscillations induced by 1 µM ACh in an intact cell and a cell permeabilized with 10 µg/ml saponin. (B) Compiled data from intact cells showing the effects of ryanodine (10 µM, 30 minutes), thapsigargin (50 nM, 1 minute), RU360 (1 µM, 30 minutes) and of a superfusion with a Ca²⁺-free EGTA-containing solution (30 seconds) on the amplitude of the first Ca²⁺ peak (left) and the percentage of oscillating cells (right). (C) Compiled data from intact cells showing the effects of methoctramine (1 and 10 µM, 10 minutes) and 4-DAMP (0.1 and 1 nM, 10 minutes) on the amplitude of the first Ca²⁺ peak (left) and the percentage of oscillating cells (right). (D) Compiled data from permeabilized cells showing the effect of heparin (1 mg/ml), and heparin in presence of 10 µM methoctramine or 10 nM 4DAMP on the amplitude of the first Ca²⁺ peak (left) and the percentage of oscillating cells (right). F/F₀ is the fluorescence ratio during a response to that at rest. Heparin was applied 5 minutes before ACh application. Data are means ± s.e.m. with the number of tested cells indicated in parentheses. Myocytes were loaded with 2 µM Fluo4-AM (stars indicate P<0.05).