Normal Gastric Emptying After a Meal
Placeholder: stomach fills, antral pump pushes chyme through pylorus at baseline rate.
- ~28%/hr: Baseline emptying rate (placeholder half-emptying pace)
- ~90 min: Half-emptying time (placeholder typical meal)
- Open/closed cycling: Pyloric sphincter (placeholder gating rhythm)
- ~3/min: Antral contractions (placeholder pacesetter rate)
Antral pump and pyloric gating
Placeholder: antrum contracts rhythmically, pylorus regulates chyme release downstream.
GLP-1 Agonist Acts on Gastric Smooth Muscle
Placeholder: agonist binds GLP-1 receptors on antral and pyloric smooth muscle.
- GLP-1R: Receptor target (placeholder smooth muscle site)
- Minutes–hours: Onset of motility effect (placeholder dose dependent)
- Increased: Pyloric tone (placeholder sphincter narrowing)
- Suppressed: Antral motility (placeholder reduced contractions)
Receptor binding and motility suppression
Placeholder: agonist raises pyloric tone and dampens antral contraction strength.
Emptying Rate Falls — Stomach Stays Distended
Placeholder: chyme lingers, gastric wall stretch and distension persist longer.
- Up to 70%: Emptying slowdown (placeholder at high dose)
- Extended: Distension duration (placeholder longer than baseline)
- Elevated: Wall stretch (placeholder mechanoreceptor load)
- Prolonged: Bolus residence time (placeholder hours not minutes)
Distension kinetics under slowed emptying
Placeholder: slower outflow keeps volume and wall tension high for longer.
Stretch Receptors Signal the Brainstem via Vagus
Placeholder: mechanoreceptors fire, vagal afferents carry fullness signal upward.
- Vagal afferents: Signal pathway (placeholder gut-to-brain route)
- NTS (brainstem): Target nucleus (placeholder relay center)
- Increased: Firing rate (placeholder with distension)
- With CCK, PYY: Signal integration (placeholder co-signals)
Vagal relay to brainstem satiety centers
Placeholder: nucleus tractus solitarius integrates stretch signal into fullness perception.
Prolonged Fullness, Smaller Meals, Nausea Risk
Placeholder: sustained distension reduces intake but risks delayed-emptying side effects.
- Up to ~30%: Meal size reduction (placeholder at high dose)
- Reduced: Meal frequency (placeholder fewer eating episodes)
- Dose dependent: Nausea risk (placeholder high-dose side effect)
- Gradual dose ramp: Titration strategy (placeholder tolerance building)
Balancing satiety benefit against GI side effects
Placeholder: clinicians titrate dose slowly to limit nausea while preserving satiety gain.
Placeholder: excess delay in emptying can tip benefit into nausea and discomfort.