Amygdala Motilin On Gastric Motility Of The Central Regulatory Role

Object: To explore the effect and mechanism of Motilin in Amygdala on gastric motility. Motilin is a polypeptide composed of 22 amino acid, and secreted by endocrine cells of upper intestine mucosa. Motilin can contract gastric smooth muscle in vitro and regulate gastric contraction of phaseⅢ during the interdigestive state in vivo. It has been proved that motilin-immunoreactive substances and its receptors are wildly distributed in CNS such as cortex, cerebellum, thalamus, hypothalamus, limbic system and so on. Motilin coexists with some other gut peptides in CNS. Amygdala is one important part of limbic system and involved in many physiological function including emotional modulation, endocrine and gastrointestinal function. It has been suggested that CCK-8 in amygdala can inhibit gastric motility but, until now, the effect of motilin in amygdala on gastric motility has not been reported.Methods: 1. The curve of gastric motility in conscious rats was recorded before and after microinjection of solution (NS, motilin, motilin antagonist GM-109, mixture of motilin and GM-109) into bilateral BMA. 2. GDSNs in BMA of urathane-anesthesized rats were identified through gastric distention (GD) and record with microelectrode the firing of GDSNs before and after i.c.v microinjection of motilin or GM-109 .Results: 1. The amplitude of gastric motility in conscious rats were dose-dependently increased by microinjection of motilin in BMA after a latency of 5 min. The duration of excitorary effect was 5min ,10min and 15 min respectively in 0.2(g, 1(g, and 5(g motilin groups; The amplitude were decreased by microinjection of GM-109 in BMA with a latency of 5 min, too. The dutation of inhibitory effect was 20 min in 1(g GM-109 group. Either excitorary or inhibitory effect reduced by single motilin or GM-109 was minimized by microinjection of mixture solution composed of 1(g motilin and 1(g GM-109. 2. 105 neurons of spontaneous discharge were recorded in 56 rats with three types of patterns: phasic, continuous and single firing which can be classified as high, intermediate and low frenquency groups. 66 neurons responded to GD including 31(31/66, 47%) GD-EXC neurons and 35 (35/66, 53%) GD-INH neurons. In general, GD-EXC neurons were mainly inhibited by motilin (5/8, 62.5%) through i.c.v microinjection but could be excited by GM-109 (7/10, 70%). On the contrary, GD-INH neurons were mainly excited by motilin (9/11, 81.83%) but could be inhibited by GM-109 (6/11, 54.55%).Conclusion: Exotic motilin in amygdala can strengthen gastric motility dose-dependently and the effect can be eliminated by GM-109; GM-109 can inhibit gastric motility so that motilin in amygdala may have a continuous effect of tension on gaster; Both motilin and GM-109 can change the firing frenquency of GDSNs in BMA. So motilin in BMA can excite gastric motility by way of binding with motilin-receptors and change the discharge of GDSNs in BMA.