Muscarinic blockade inhibits gastric emptying of mixed-nutrient meal: effects of weight and gender.

We compared the vagal contribution to gastric emptying in lean and obese subjects by monitoring gastric emptying of a meal during muscarinic blockade. Lean ( n = 6) and obese subjects ( n = 6) underwent two treatments: 1) saline infusion and 2) atropine infusion [0.4 mg/m2 bolus, 0.4 mg ⋅ (m2)-1 ⋅ h-1] for 2 h, initiated 30 min before ingestion of a 600-kcal breakfast (64% carbohydrate, 23% fat, 13% protein) composed of orange juice (labeled with Indium-111), egg sandwich (labeled with Technetium-99m), cereal, milk, and banana. Anterior and posterior images were taken every 90 s for 90 min using a dual-headed camera. Atropine significantly delayed emptying of both solid ( P < 0.007) and liquid ( P < 0.002). Obese subjects exhibited a greater delay in liquid emptying during muscarinic blockade compared with lean subjects ( P < 0.02). Female subjects exhibited a slower rate of gastric emptying and were less sensitive to atropine. These data suggest that obese subjects exhibit altered gastric cholinergic activity compared with lean subjects and that gender differences in gastric emptying rate may be due to differences in autonomic tone.