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Since no previous studies have reported dual measurements of stomach and duodenal motility in conscious mice, we developed a manometric method to measure the gastroduodenal motility in the physiological fed and fasted states of conscious mice. By this method we measured, for the first time, the gastroduodenal motility in Y2 knockout mice and analyzed the effects of ghrelin on the gastroduodenal motility in conscious mice. To evaluate this new method, we provide the comparison on the effects of CCK-8 examined by present and previous methods. In the fasted state of mice, phase III-like contractions with frequencies of 7.8 ± 0.5 contractions/h in the antrum and 6.6 ± 0.7 contractions/h in the duodenum were observed. This fasted pattern was disrupted and replaced by the fed pattern after feeding, with an increase of the motor index (MI) immediately after feeding. Intravenous injection of ghrelin induced the fasted pattern in the duodenum when injected in the fed state and increased %MI (114.3 ± 9.8%) compared with saline-injected controls (64.4 ± 9.6%) in the antrum. Intravenous injection of CCK-8 disrupted phase III-like contractions in both antrum and duodenum, which were replaced by fed-like motor patterns accompanied with the elevation of baseline pressure. In Y2 knockout mice, the frequency of phase III-like contractions was decreased in the antrum compared with wild-type mice and the immediate increase of MI after feeding seen in wild-type mice was disrupted in Y2 knockout mice. Our model provides a new method for studies of gastrointestinal motility in various mouse models, including transgenic and knockout ones.

Acyl ghrelin has a 28-amino acid sequence with O-n-octanoyl acid modification at the serine 3 position, whereas des-acyl ghrelin has no octanoyl acid modification. Although these peptides exert different physiological functions, no previous studies have shown the different localization of acyl ghrelin and des-acyl ghrelin in the stomach. Here we have developed an antibody specific for des-acyl ghrelin that does not crossreact with acyl ghrelin. Both acyl ghrelin- and des-acyl ghrelin-immunoreactive cells were distributed in the oxyntic and antral mucosa of the rat stomach, with higher density in the antral mucosa than oxyntic mucosa. Immunofluorescence double staining showed that acyl ghrelin- and des-acyl ghrelin-positive reactions overlapped in closed-type round cells, whereas des-acyl ghrelin-positive reaction was found in open-type cells in which acyl ghrelin was negative. Acyl ghrelin-/des-acyl ghrelin-positive closed-type cells contain obestatin; on the other hand, des-acyl ghrelin-positive open-type cells contain somatostatin. We measured the release of acyl ghrelin and des-acyl ghrelin in vascularly perfused rat stomach by ELISA, and the effects of different intragastric pH levels on the release of each peptide were examined. The release of des-acyl ghrelin from the perfused stomach was greater at pH 2 than at pH 4; however, the release of acyl ghrelin was not affected by intragastric pH. The present study demonstrated the differential localization of acyl ghrelin and des-acyl ghrelin in the rat stomach and their different responses to the intragastric pH.

Neuromedin S (NMS) was recently identified as an endogenous ligand for the FM-4/TGR-1 receptor in the rat hypothalamus. No previous studies have examined the effect of NMS on gut motility. We examined the effects of intracerebroventricular administration of NMS on food intake in food-deprived and free-feeding mice, and on gastroduodenal motility by using a manometric method, and gastric emptying in mice. We found that NMS decreased food intake and the gastric emptying rate. It also disrupted the motor activity in the antrum and duodenum of conscious food-deprived mice. These results suggest that NMS influences gut motility as well as feeding behavior.

For several years, a new population of microglia derived from bone marrow has been described in multiple settings such as infection, trauma, and neurodegenerative disease. The aim of this study was to investigate the migration of bone marrow-derived cells to the brain parenchyma after stress exposure. Stress exposure was performed in mice that had received bone marrow transplantation from GFP mice, allowing identification of blood-derived elements within the brain. Electric foot-shock exposure was chosen because of its ability to serve as fundamental and physical stress in mice. Bone marrow-derived GFP(+) cells migrated to the ventral part of the hippocampus and acquired a ramified microglia-like morphology. Microglia marker Iba1 was expressed by 100% of the ramified cells, whereas ramified cells were negative for the astrocyte marker GFAP. Compared with the case in the control group, ramified cells significantly increased after chronic exposure to stress (5 days). One month after 5 days of stress exposure, ramified cells significantly decreased in ventral hippocampus compared with the group examined immediately after the last stress exposure. We report for the first time the migration of bone marrow-derived cells to the ventral hippocampus after stress exposure. These cells have the characteristics of microglia. Mechanisms responsible for this migration and their roles in the brain remain to be determined.