Electroacupuncture at leg point ST36 increases stomach motility mainly through vagal pathways, while sympathetic signalling causes an initial temporary delay.
Researchers measured stomach contractions in anaesthetised rats using a pressure balloon, recorded activity in vagal and sympathetic nerves, and monitored neurons in the brainstem vagal motor nucleus. They compared intact animals with animals undergoing vagal or sympathetic nerve interruption, tested brainstem injections of glutamate or gamma-aminobutyric acid, and used genetically modified mice lacking selected muscarinic or beta-adrenergic receptors.
Electroacupuncture increased activity in both vagal and sympathetic nerves, but vagal activation was stronger and was essential for enhanced stomach motility. Removing sympathetic input eliminated the early delay in the response but reduced later stimulation, indicating that sympathetic signalling shapes the timing of the effect. Brainstem recordings and chemical injections supported involvement of vagal motor neurons, while receptor-deficient mice showed that muscarinic receptors support vagal stimulation and beta-adrenergic receptors mediate sympathetic influences.
