system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Nine healthy subjects participate in a study of gastric secretions. Subjects are asked to eat a meal at hour 0, at which time the pH of stomach contents and rate of stomach acid secretions are measured over the next 4 hours. Results of the study are shown. Which of the following mediators is most active at point A in the graph?
assistant
Acetylcholine