Ghrelin accelerates gastric emptying via early manifestation of antro-pyloric coordination in conscious rats

Ghrelin is known to enhance gastric motility and accelerate gastric emptying of liquid and solid food in rats. As solid gastric emptying is regulated by the coordinated motor pattern between the antrum and pylorus (antro-pyloric coordination), we studied the correlation between solid gastric emptying and antro-pyloric coordination in response to ghrelin. Rats were given 1.5 g of solid food after a 24-h fasting. Immediately after the ingestion, ghrelin (0.4–8.0 μg/kg) or saline was administered by intraperitoneal (IP) injection. Ninety minutes after the feeding, rats were euthanized and gastric content was removed to calculate gastric emptying. To evaluate the antro-pyloric coordination, strain gauge transducers were sutured on the antrum and pylorus. The incidence of postprandial antro-pyloric coordination was compared between ghrelin-and saline-injected rats. In saline-injected rats, gastric emptying was 58.3 ± 3.7% (n = 6). Ghrelin (4.0–8.0 μg/kg), accelerated gastric emptying. Maximum effect was obtained by ghrelin (4.0 μg/kg), which significantly accelerated gastric emptying to 77.4 ± 3.7% (n = 6, p < 0.05). The number of antro-pyloric coordination 20–40 min after feeding was significantly increased in ghrelin-injected rats, compared to that of saline-injected rats (n = 4, p < 0.05). It is suggested that enhanced antro-pyloric coordination play an important role in accelerated solid gastric emptying induced by ghrelin.