Motilin Response To Dilatation Of The Stomach Of Rat Arcuate Nucleus Neuronal Firing Activity And Gastric Motility,

Objective:The study aims to observe the effect of motilin on neuronal activity of gastric distension responsive neurons in Arc; and to explore whether motilin can activate pathways in the rat Arc to stimulate gastric motility.Methods:-Single unit discharges in the Arc were recorded extracellularly by means of four-barrel glass micropipettes in anesthetized rats and the effect of motilin on gastric motility by implantation of a force transducer into the stomach in conscious rats. The expression of motilin immunoreactive (MTL-IR) neurons in hypothalamus Arc was observed by fluo-immunohistochemistry staining.Results:65.5% of neurons in the Arc responded to GD,55.6% of which showed excitation (GD-E), and 44.4% showed inhibition (GD-I). After gastric distension, the firing rate of the GD-E neurons increased from 3.18±1.01 Hz to 5.62±1.22 Hz (P<0.01), and the firing rate of the GD-I neurons decreased from 3.21±0.68 Hz to 1.24±0.31 Hz. The GD-E neurons in the Arc examined for response to motilin,70% was activated, 17.5% were depressed, and the firing rate increased from 3.46±1.59 Hz to 8.83±2.25 Hz (P<0.05) after the administration of motilin.65.6% GD-I neurons were excited by motilin, their firing rates increased from 3.34±0.63 Hz to 6.17±0.97 Hz (P<0.05). The motilin-induced responses were abolished by the pretreatment with motilin receptor antagonist GM109. The frequency and amplitude of the gastric contractions increased by 22.69±10.52% and 50.12±13.77%(P<0.05) respectively.However, administration of GM109 abolished the excitatory effect-induced by motilin. Motilin immunoreactive (MTL-IR) neurons were detected in the Arc and increased staining (10.92±0.48 cells/mm2 vs 43.68±0.44 cells/mm2) was found with gastric distention in Arc (P<0.05).Conclusion:Our findings suggest that motilin neurons in Arc may accept peripheral somatosensory afferent inputs from gastric mechanoreceptors of the stomach, and also may acts as a stimulatory factor in Arc to regulate gastric motility via some inferior nucleus relay pathway.After gastric distention, motilin immunoreactive neurons were increased.The results provide insight into the role of Arc in the control of digestion mediated via motilin.