| The dorsal vagal complex (DVC) is composed of the dorsal motor nucleus of vagus (DMV), the nucleus of solitary tract (NTS) and the area postrema (AP). It is a parasympathetic preganglionic centre of gastric function, especially gastric motility. Other laboratories and our laboratory have reported the effects of electrical and chemical stimulation of DMV and NTS on the gastric motility in rats. All correlative papers published up to now indicated that the excitation of NTS inhibited the gastric motility, but some researches showed that the excitation of DMV enhanced the gastric motility while others, reduced the gastric motility. But, the effects of excitation of AP on gastric motility have not been reported so far. In this study, we observed the effects of chemical stimulation and electrical stimulation of AP on gastric motility and the efferent nervous pathway was probed.In the chemical stimulation experiment, 0.2μl of 0.1mol/L, 0.2mol/L, 0.5mol/L L-Glutamine solution were respectively microinjected into AP. Physiological saline was microinjected into AP in the control group. Gastric motility curves were recorded with water-filled balloons placed into stomach and two-lead physiological recorder. The frequency, duration, amplitude and motility index of gastric contractive waves within 5 min before and after microinjection were analyzed. The results showed that all the three kinds of concentration of L-Glu led to significant inhibitory effects on gastric motility. Moreover, the inhibitory extent was enhanced with the increase of L-Glu concentration. The inhibitory rates of gastric motility index were: 36.03%, 72.09%, 96.91%, respectively. Meanwhile, no obvious influence was observed after physiological saline was microinjected into AP. Respiration and heart rate were recorded at the same time. It showed that chemical stimulations inhibited heart rate while respiration did not show obvious change.In the electrical stimulation experiment, BL-420 was used to give electrical stimulus. The simulation parameters were: 30Hz, 0.15mA, 0.3ms.The stimulation lasted for 5 min. The second stimulation was performed after an interval of 15mins in order to relieve the effect of the first stimulation. Results: the inhibitory rates of gastric motility index by two stimulations were 52.44%, 57.50% respectively. It showed that electrical stimulation of AP led to significant inhibition on gastric motility. Similar to the effects of chemical stimulation, electrical stimulation had no effects on respiration but did inhibit heart rate.The results mentioned above suggested that the excitation of AP inhibited gastric motility.The gastric motility was not significant changed during stimulating AP after the vagus nerves beneath diaphragma were cut. The results showed that the inhibitory effects of AP on gastric motility were withdrawn by the vagus nerves vagotomy beneath diaphragma. The results indicate that the efferent nerve pathway of AP inhibiting gastric motility is vagus in rats.
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